# Bus Batteries?!?!?!?!



## Flatstone (Sep 14, 2017)

Hi,

This is my first post, so sorry if this has been covered. I have searched and I'm going around in circles.

So I'm getting close to converting my 1972 VW Bus. I'll be using a conversion kit from EV West, with AC-50 motor and Curtis controller. I'm fairly happy with the system, it's just the batteries I'm having issues with.


My first option would be 30 x 3.2 Lifepo04 100ah (30s1p) wired up to a BMS. This seems to be a safe option and looking at other project should get me 30-40 mile range. If I have the room I would ideally like to get it too 200AH so 32s2p.

The second option, which I'm just a bit jittery about, is going the 18650 option. I have no intention of using old laptop batteries, all cells would be new. I could make 48v 50Ah battery pack myself, or buy the same spec E-Bike batteries (from Aliexpress etc heres one on eBay http://www.ebay.co.uk/itm/48V-50AH-rechargeable-Battery-Pack-Lithium-li-ion-ebike-EVs-BMS-20A-max-charge-/263205445934?hash=item3d4844612e:g:BKsAAOSw42dZN2XG ) and then connect them together, 2s2p, or budget willing 2s4p giving me 200Ah. They would all have there own charger, and have BMS's Would the premade E-Bike batteries standup to be using in this way. The gauge of the wire seems quite small, and would it be pushing to many amps through the batteries in series? 

This area is such a black hole to me, and I'm very aware of how much of a fire risk it is, so I'd like to get it right. Not to mention the money involved!

Any ideas?


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## john61ct (Feb 25, 2017)

Buy big prismatics. 

You already have enough to worry about, DIY at that level is nuts to me if you can afford CALB or Winston cells.


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## aquabiologist (Sep 8, 2017)

Hi
Excellent!!! Got a vw 1971 bus i like to convert, so i am super interested in your project.

I was looking at bike batteries as well: http://www.diyelectriccar.com/forums/showthread.php?t=188106

Those bike batteries are much lighter and way cheaper than lifepo4.

Does not seem to me to be more diy than lifepo4. Especially as they come packaged with bms already. 

So from paper specs seems a good choice. Or not?

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## john61ct (Feb 25, 2017)

You need many hundreds of AH, a 4.4AH pack is irrelevant.

There are some chemistries lighter per AH than LFP but they're more costly not cheaper, and much more dangerous.


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## Duncan (Dec 8, 2008)

Those are all very expensive and relatively low performance options
These days the best option is a battery pack from a wrecked EV
Chevy Volt (I use one of these)
Nissan Leaf
Tesla

Much cheaper and much higher quality


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## Flatstone (Sep 14, 2017)

There doesn’t seem to be much of a secondhand market in the UK yet for salvage EV’s. Most EV cars (Zoe,Leaf) are sold with battery leases so I guess these remain property of the manufacture.

I’ve done some (back of a *** packet) calculations and the E-Bike packs are coming out too good to be true in terms of size, price, and weight.

So just as a base line I’ve speced up a 96v 100ah pack (ultimately I’d like a 200 or 300ah pack)

*Prismatic 3.2v 100ah Cells*

30 cells (@ £115 per cell) needed (s30p1) Total cost with BMS = Approx *£3,500*
Total weight = 110kg
Total Volume = 0.07m3


*DIY 18650 3.7v 3ah Cells*

884 cells (@ £4 per cell) needed (s26p34) Total cost with BMS = Approx *£4000*
Total weight = 44kg
Total Volume = 0.02m3

*E-Bike 48v 50ah Pack using 26650 Cells inside built in BMS*

4 cells (@ £540 per cell) needed (s2p2) Total = Approx *£2160*
Total weight = 52kg
Total Volume = 0.027m3


This is the spec of the E-Bike battery. Am I missing something really import as they seem spot on.

Battery Model
48v 50ah
Nominal Voltage (V)
48v
Nominal Capacity (AH)
50ah
Source Resistance (mΩ)
about 40
Cell Specification
3.7V 5.0AH
Cell Combination
10-parallel 13-series
Cell Size
3.7v 5.0ah 26650
Cell Quantity (parallel*series)
130pcs
Discharge Cutoff Voltage (V)
41+/- 1V
Charge Cutoff Voltage (V)
54.6v
Rated Discharge Current (A)
50A
instantaneous Maximum Discharge Current (A)
150A
Maximum Continuous Discharge Current (A)
50A
Maximum Continuous Charge Current (A)
5A
Charge Mode
CC-CV
Standard Charge Current (A)
2A
Charge Time under Standard Charge Current
12hours
Fast Charge Current (A)
5A
Charge Time under Fast Charge Current
6hours
Charge Temperature Range
-20-55°C
Cell Size (L*W*T )
360*270*70mm
Battery Weight
About 13KG
Battery Power
2000W


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## Duncan (Dec 8, 2008)

Look a bit further - there are over 20,000 leafs and over 100,000 EV's in the UK

Something in the order of 1 in 80 will be written off - They will be there! - you just got to find them


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## Flatstone (Sep 14, 2017)

I've just had a look (have to admit never occurred to me to look before), and there are 2 Leaf batteries packs for sale on Ebay uk, for £3500-£4000. 

That works out a little bit more money to make the 96v 100am pack and weights more than the Prismatic option. Plus you have to take it apart, put it back together, etc etc. Secondhand batteries doesn't look that good to me. Might as well go down the Prismatic route.


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## john61ct (Feb 25, 2017)

Not to mention dealing with voltages, complex electronics, signaling, all proprietary. 

Buy a Leaf and tow it as a battery pack maybe. . .


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## Flatstone (Sep 14, 2017)

Might as well tow a generator. 

But good point, digging about in Nissan or Renaults electronics doesn't appeal, especially in a car thats written off in some way.

So that brings me back to the E-bike battery. What am I missing as they seem ideal, cheap(er), light, and much smaller. 

Prismatic seems to be the first step away from lead acid, but still bulky and expensive, I can't imagine having 90 of them in the van to get to 300ah (and still have room for 3 kids in the back). And I'm not keen on creating my own "Tesla" style battery.


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## john61ct (Feb 25, 2017)

Flatstone said:


> Might as well tow a generator.


Hybrids actually work well as both, seen a big Expedition rig dolly a Prius.


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## john61ct (Feb 25, 2017)

Flatstone said:


> Might as well tow a generator.
> 
> But good point, digging about in Nissan or Renaults electronics doesn't appeal, especially in a car thats written off in some way.
> 
> ...


Let's see, 300AH cells * 90, you really need 288V?

There are 12V units available, but lower AH, and you don't want drop-in with built-in BMS.

Unfortunately the physics doesn't go away, AH per kg vs fire risk.

The smaller the cell the more of them you need, hassles of interconnect, more points of failure.

I'd say lower your voltage requirement, you're going to need the AH if you want to go farther than around the block.


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## Flatstone (Sep 14, 2017)

Sorry that was my fault, I should of specified 90 prismatic would be in s30p3, so the volts would remain at 96v but I would have 300ah.

But practically 90 prismatic cell just wouldn't work. It would just be one VW Bus shaped battery on wheels.

Hence, if the 48v 50ah e-bike batteries aren't going to create a massive Nov 5th (read July 4th in the US) display, I could get to the goal of 96v 300AH with 2s6p each pack with it's own BMS and charger.


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## john61ct (Feb 25, 2017)

Flatstone said:


> My first option would be 30 x 3.2 Lifepo04 100ah (30s1p) wired up to a BMS. This seems to be a safe option and looking at other project should get me 30-40 mile range. If I have the room I would ideally like to get it too 200AH so 32s2p.


I thought you were just talking 300AH cells?

The above implies you only need 96-102V.

2P does give some redundancy, but I don't think 150AH is available.

I'd start with a string of 200AH, then later double that for good range.


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## Flatstone (Sep 14, 2017)

I think something getting lost in translation. I'm happy with the prismatic setup, it's a well trodden route.

My question is around the E-bike packs (48v 50h), and connecting them in s2p2 to make a 96v 100ah system (and then later adding more s2sp2's to increase the AH). See post 6 for the details.


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## john61ct (Feb 25, 2017)

Flatstone said:


> Hence, if the 48v 50ah e-bike batteries aren't going to create a massive Nov 5th (read July 4th in the US) display, I could get to the goal of 96v 300AH with 2s6p each pack with it's own BMS and charger.


Fewer parallel fewer problems, if true LiFePO4 little fire risk, but I've seen pretty authoritative sources say don't go past 3 maybe 4P, which implies go with at least 100AH cells.

IMO
30*200AH, later doubled, or 30*300AH

Advantage of standard 3.2V cells is you can always drop in a good BMS if one you like later comes on the market.

Plus CALB, Sinopoly, GBS or Winston known good quality. . .


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## john61ct (Feb 25, 2017)

Just build a special bench seat for the kids, under-dimensions just right for 30-32 cells.

Weight will be between the axles, maybe toward the back.

Or maybe even (mostly) fit with the motor in the very back, you'll be messing with the "frame" there anyway.


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## rmay635703 (Oct 23, 2008)

Ebike packs are notoriously unreliable


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## john61ct (Feb 25, 2017)

LiCo02? greater fire risk?

FYI, maybe be worth talking to this seller

Look at this on eBay http://www.ebay.com/itm/112562977502


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## aquabiologist (Sep 8, 2017)

Did some digging on the fire/safety issue
Here's a link that explains the different chemistries in detail: 
http://batteryuniversity.com/learn/article/types_of_lithium_ion

And here's is one with the battery codes for the 18650 battery cells*often used in e-bike packs:
https://batterybro.com/blogs/18650-.../18880255-battery-chemistry-finally-explained

So it seems that the 'cheap' e-bike packs use LiCo chemistry = the fire risk chemistry 

Leaf and volt batteries use NMC chemistry = safe with bms

Tesla uses NCA chemistry = safe with bms

Diy ev builders recommend LFP = lifepo4 = safe even without bms, no fire risk whatsoever

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## Flatstone (Sep 14, 2017)

That's is brilliant. Exactly the info and reasoning I was looking for. 

Thanks a lot!


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## brian_ (Feb 7, 2017)

Flatstone said:


> Prismatic seems to be the first step away from lead acid, but still bulky and expensive, I can't imagine having 90 of them in the van to get to 300ah (and still have room for 3 kids in the back).


Zelectric does conversions of air-cooled Volkswagens, using 37 180Ah LiFePO4 prismatic cells. I assume that those cells would occupy at least 140 litres of volume, and judging from their photos the cells are not in the original fuel tank location, so I asked them where they put them...



john61ct said:


> Just build a special bench seat for the kids, under-dimensions just right for 30-32 cells.
> 
> Weight will be between the axles, maybe toward the back.


The bench is the solution used by Zelectric. They apparently build a battery box which acts as the base for a new middle seat.

I would have thought that a rear seat base box would be a better location, but the wall between the interior and the engine compartment is sloped, making fit awkward. The original fuel tank location is another obvious target, for some of the cells.

Zelectric did say that they are planning to transition to Tesla battery modules.


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## Flatstone (Sep 14, 2017)

I think it has to be the route I have to go. It's my first conversion and I don't want to push the current chemistry. If I can get 50-65 miles in 180ah that's spot on for my needs. 

Maybe do a tesla type battery on the next convers 

By the way did you see the prices on their conversions. Wow! I might change my job!

Thanks again for the info.


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## brian_ (Feb 7, 2017)

Flatstone said:


> By the way did you see the prices on their conversions. Wow! I might change my job!


Zelectric is certainly going for the market of people who have more money than they know what to do with. The restored air-cooled VW market is already at prices out of the reach of average people. Zelectric has apparently found that some people want the novelty of electric drive without being so common as a Tesla, and the fashionable appeal of old VWs, at a price high enough to keep commoners from buying the same thing. 

But seriously, it does look like they do tidy work, and they keep the body intact so its value isn't reduced. They probably spend a fortune on body parts and labour, and it shows in the result.


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## john61ct (Feb 25, 2017)

aquabiologist said:


> Did some digging on the fire/safety issue


nice digging there, thanks!


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## Karter2 (Nov 17, 2011)

No such thing as a "safe" battery of any chemistry.
Even those little 9v alkaline batteries have been known to start fires.
Ask Jack at EVTV if modern commercial EV packs are totally fire safe.
..or Boeing too..they have expensive experience !
Any unit containing significant energy can be dangerous and many battery associated fires are actually started by wiring shorts...especially on DIY assembled and installed packs.
Never assume you are using a "Safe" battery.


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## john61ct (Feb 25, 2017)

Same can be said for any source of concentrated energy. 

However, there are significant inherent differences in thermal runaway risk during normal operation between battery types. 

Trying to discourage discussion of the different chemistries by such a general statement is IMO not constructive. 

Here's one data point: out of all non-lead chemistries (not just the lithium family) only LiFePO4 is widely used on boats, where instances of fire can very easily become fatal. 

The ABYC sets electrical standards for US boats, compliance being a major factor in getting insurance, and the relevant committee is finalizing their LFP requirements. 

They're not even considering allowing any other non-lead chemistry.


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## Karter2 (Nov 17, 2011)

So the ABYC is now the gold standard for battery knowledge and safety advice ?
Somebody should tell the FAA.
Who has the most to lose from battery selection, a Yachting association , a commercial aircraft builder, or a market leading EV manufacturer ?.
In order of potential commercial and reputation risk, i suspect the Yachting accociation is not top of that list.
Who has the most experience and research into battery safety...? Again not the ABYC.
What is the most common Li chemistry in commercial EV use ? ...not LiFePo.
There is nothing wrong with using LiFePo for a diy EV, its just not the best choice.
There are good reasons for all the above.
...and i certainly wouldnt trust a large capacity pack from an Alibaba site !


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## john61ct (Feb 25, 2017)

I never advocated LFP as the best for EV. Just within the context of LFP, advocating factory prismatics over the DIY cylindricals. 

Then I was just clarifying some over-generalizations regarding fire safety.

Finally I will repeat the point that commercial high value use cases (like EV and Aviation) can make anything very safe with expensively engineered infrastructure. 

LFP is inherently (relatively) safe as a chemistry, which is an advantage to low-end consumer uses like House banks and DIY projects.


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## Karter2 (Nov 17, 2011)

As i said, most battery associated fires are infact external to the cell ( hence the chemistry is not relavent) usually a connection short , failed insulation, etc, resulting in high current arcing .
Infact , Nissan who have probably made more large lithium (NMC?) packs than anyone else over the last 10 years (Leaf etc) have stated that they have never had a internal initiated cell fire.
Safety focus should be on the integrity of the manufacturer, assembly of the pack interconnects, and monitoring systems...Not an ideal area for inexperienced , untrained, amatures, to learn!
Packs for house storage , stationary projects, even boats, where weight is not a consideration... Have a very different set of issues to consider than a high voltage , high capacity, pack for an EV.


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## john61ct (Feb 25, 2017)

Yes. No disagreement here. Topic was buying bare cells, not packaged systems.


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## Solarsail (Jul 22, 2017)

I am in the process of building 18650 power packs. I am building 13s10p 18650 packs, and have ordered Panasonic 3.4 Ah cells at $3.25 each through Alibaba.

Lead Acid may be cheaper by about 50% at this time, but they are heavy and bulky, and do not cycle as many times as Li-ion. Lead Acid, for the same energy storage, are 10 to 12 times larger than 18650 packs, and 10 to 12 times heavier than 18650. I don't think anyone would recommend them.

LiFePO4 is also bulkier, as it packs less energy per unit volume and weight, and costs a lot more, maybe twice, than 18650.

For 18650, you can pack up to 540 Wh in a liter, with a 2mm separation between the cells. So if you need 6 kWh, that is about 12 liters (12"x16"x4"). Unit weight is 240 Wh per kg, not including packaging, cabling, and balance, protection, charging boards.


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## Solarsail (Jul 22, 2017)

Flatstone said:


> (from Aliexpress etc heres one on eBay



I am not convinced that 18650s are a safety issue. In particular if they are from Panasonic, LG, or Samsung. A hundred million laptops carry these batteries, and there has not been too many horror stories, except for the incident with Sony batteries a long time ago. How many Teslas are catching fire?

Please note that the above link to eBay appears to be a mislabelled product. It claims to use 5.0Ah 18650 cells. But such a cell cannot exceed 3.4Ah, except for those supplied by Chinese distributors that lie about the capacity.

It is also too expensive. On Alibaba you can find the 3.4Ah cells for $3.25 a piece. So if you build the pack yourself it would cost about $260/kWh. Add another $10 for balancer and $10 for charger. You can also find on Alibaba 48V 34Ah ready made packs with balancer/protector that cost a little more.


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## john61ct (Feb 25, 2017)

Exactly which LI chemistry are 18650?

Or does this vary by vendor?


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## Flatstone (Sep 14, 2017)

I double took at the 5AH as well, but the pack is made with 26650 cell and not 18650 cell so 5ah are realistic.

I've decided to go down the well trodden path of Lifepo4 prismatic 3.2 cell. 100ah or 180ah is still to be decided (on the basis of budget). And either s32p1 or s37p1 again dependant on budget, the controller should be able to handle either.

I'd love to go down the 18560 route, but for my first project simplicity is probably best!


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## Karter2 (Nov 17, 2011)

john61ct said:


> Exactly which LI chemistry are 18650?
> 
> Or does this vary by vendor?


 It varies a lot !
Most chemistries from LiFePo4, LiCo, NMC, NCA, etc etc


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## Solarsail (Jul 22, 2017)

john61ct said:


> Exactly which LI chemistry are 18650?
> 
> Or does this vary by vendor?


Generally 18650s are known as Lico (lithium cobalt). Then there are several subvarieties - LCO, LMN (does not contain much or any cobalt), NMC, etc. They are all at about 3.6V nominal and at 4.2V are 100% charged. But on the retail market from Chinese suppliers supplying Panasonic (Sharp), LG, and Samsung they all seem to be LCO. LCO has the highest energy capacity, but behaves the worst upon impact, internal short, penetration, etc. All 3.4Ah are LCO, as that is the highest energy storage you can get with 18650 form factor. LMN and NMC, NMA have about 10% less storage capacity. And they are probably more expensive as they don't have the economies of scale as LCO. I believe all laptop batteries are LCO. Panasonic, LG, Samsung do produce LMN, NMC, etc. but I don't see them on eBay or Alibaba. The other chemistry LiFePO4 does not seem to come in 18650 -- usually prismatic or 26650, and has much less storage per unit weight or volume, and more expensive per unit storage.

If Tesla can use LCOs, and laptops all use LCOs, then I will use LCOs.

Compared to Panasonic LCO 18650, LiFePO4 is 3.5 times larger, twice heavier, and 38% more expensive


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## rmay635703 (Oct 23, 2008)

Solarsail said:


> If Tesla can use LCOs, and laptops all use LCOs, then I will use LCOs.


Unless you are using TSLA LCOs you will likely be dissatisfied with the lifespan and durability of using something akin to AA batteries in your conversion.


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## john61ct (Feb 25, 2017)

And for me cobbling together the BMS functionality, I like the safety aspect of LFP prismatics.


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## Solarsail (Jul 22, 2017)

Flatstone said:


> I double took at the 5AH as well, but the pack is made with 26650 cell and not 18650 cell so 5ah are realistic.
> 
> I've decided to go down the well trodden path of Lifepo4 prismatic 3.2 cell. 100ah or 180ah is still to be decided (on the basis of budget). And either s32p1 or s37p1 again dependant on budget, the controller should be able to handle either.
> 
> I'd love to go down the 18560 route, but for my first project simplicity is probably best!


How will you balance 32S? Are there boards that can do LiFePO4 32S?

You can buy ready made 18650 LCO packs such as 13s10p from Alibaba containing balancing and protection and PVC or ABS packaging. The price is just a little over individual cells. I would go this route. I have not done any business with this place www.ayaatech.com, but the prices are fantastic - but check out their reputation, if any. They use 3.4Ah LG cells. And they will package with balance/protection for about $3.10 per LG cell. They don't do Panasonic, which are about 10% more expensive.

LCO Panasonic 18650 vs. LiFePO4

Cost per cell $3.28 - $120
V 3.6 - 3.2
Ah 3.4 - 100
Unit volume L/kWh 1.6 - 6.0
Unit weight kg/kWh 4.2 - 8.9
Unit price $/kWh 272 - 375

LiFePO4 is 3.5 times larger, twice heavier, and 38% more expensive.

Note: the packing for the 18650 is assumed to be tightest possible. If you go standard packing (square with 2mm separation) then unit volume increases to 1.9 L/kWh.


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## Flatstone (Sep 14, 2017)

Has anyone got any experience and using salvaged Tesla battery packs? I notice that EVWest sell them so I guess someone out there are putting them together in diy conversions.


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## Karter2 (Nov 17, 2011)

Solarsail said:


> ....The other chemistry LiFePO4 does not seem to come in 18650 --


 Actually there are several suppliers of 18650 LiFePO4 cells...
....not least of which is A123 whose M1b cell has one of the best reputations for power, performance, and durability, in battery storage. It has been used to power several record setting vehicles and a direct derivative is used in some F1 hybrid power packs 
Certainly it is low capacity at 1.3 AHr and 3.4 volts, but it is rated for 30 amp discharge with 10sec power over 60 amps..
Infact , most of the A123 LiFePO4 cells, cans and pouches , have very high discharge C ratings.
http://www.a123systems.com/Collateral/Documents/English-US/18650_2017_2 page.pdf


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## Karter2 (Nov 17, 2011)

Flatstone said:


> Has anyone got any experience and using salvaged Tesla battery packs? I notice that EVWest sell them so I guess someone out there are putting them together in diy conversions.


Just run a forum search for "Tesla packs", you will find several.


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## Solarsail (Jul 22, 2017)

Flatstone said:


> *Prismatic 3.2v 100ah Cells*
> 
> 30 cells (@ £115 per cell) needed (s30p1) Total cost with BMS = Approx *£3,500*
> Total weight = 110kg
> ...


@Flatstone - there are a couple of problems with this. Your price for 18650 3Ah cells is way too high at US$ 5.40 each. I am getting the best 18650 cells available - Panasonic NCR18650B Grade A (i.e. not seconds or capacity rejects) with 3.4Ah at a cost of $3.28 or £2.43 each.

The other problem is that your 3rd option is a 26650 cell which must be Chinese made and should not be trusted. I do not believe Panasonic, LG or Samsung have 26650s on the market. So its rating of 5Ah is quite arbitrary, and the quality will not meet Japanese or Korean cells. I think these should be avoided, especially that option #2 is cheaper than #3 with the correct price.

Salvaged autopacks like what Duncan has done, Volt or Leaf, etc. is another good option. But in terms of density and price when new, nothing can beat the 3.4Ah LCO 18650. I will run some comparisons in my spreadsheet below.


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## Solarsail (Jul 22, 2017)

Flatstone said:


> I’ve done some (back of a *** packet) calculations and the E-Bike packs are coming out too good to be true in terms of size, price, and weight.


I have entered your data in the spreadsheet, along with LG and Panasonic.

As can be seen from the red rows, the 26650 is not as dense as LG or Pana, and is about 20% more expensive than the LG. The LFP was far out of contention in density and quite more expensive.

The 26650 has the same density as a 2.5Ah 18650 cell. This would be at the limit of what the Chinese can deliver in terms of energy density.

I have discounted the cost of 26650 for the BMS it contains. What I have not done is to discount it for the labour, parts, and materials included in packaging the cells. My understanding, and I could be wrong, is that the cost of packaging adds about 10% to the cost of the cells - and should be added to columns 1 and 2.


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## Karter2 (Nov 17, 2011)

There are many reputable manufacturers of 26650 cells as i have mentioned.
Certainly Panasonic , Sony etc have produced them .
Capacities up to 5200mAh have been tested 
http://www.dampfakkus.de/akku_liste-nach-groesse.php
But i would not trust a Chinese Alibaba seller unless i had tested some cells first.
However, a couple of points to add.
The 18650 solution and costs ..884 cells ..+ BMS, @ $4k ,..does not make any allowance for assembly of the pack, enclosures , etc etc. 
That would be very resource intensive , tricky, and time consuming, with plenty of oportunity for a screw up !
Special equipment (pulse welder) , and skills would also be required.
Not a task for a first time battery builder.
Conversly, if thise pre assembled 50 Ahr Ebike packs are genuine, then putting a full 100Ah pack together would be very simple as all the tricky , specialist work is done. Just a 2x2 harness being required.
....but again , quality is unknown unless you can positively identify the cells and ideally test results.


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## Duncan (Dec 8, 2008)

I will echo Karter2's remark about trusting the label!

I would be very skeptical until I had tested a fair few units - my 15 Ah Headway cells ranged from 12 Ah to 14.7 Ah
And I had a random failure rate of about 5%


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## Solarsail (Jul 22, 2017)

rmay635703 said:


> Ebike packs are notoriously unreliable


Hi rmay -

In what way are they unreliable? I have not worked with them.


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## Solarsail (Jul 22, 2017)

Take a look at this one from Headway (Duncan is familiar with the company).

This cell is 18500. and 1.4 Ah. Lots of cells to weld.

It is the NMC chemistry for those who feel LCO is too risky. Compared to Panasonic LCO, the safest LCO:

3 vs 1.6 L/kWh (88% higher)

6.9 vs. 4 kg/kWh (72% higher)

222 vs. 272 $/kWh (-18% less)

Although bulkier and heavier, it is cheaper.

Also another one from Headway - NMC chemistry 22650, 2.0Ah. Heavier, bulkier, but cheaper: 184 $/kWh, -32% less than Panasonic

https://www.alibaba.com/product-det...m=a2700.7724838.2017115.21.3699fb49N9wlA0&s=p

https://www.alibaba.com/product-det...spm=a2700.details.maylikehoz.3.7815ba8aQFeRns


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## Solarsail (Jul 22, 2017)

Karter2 said:


> However, a couple of points to add.
> The 18650 solution and costs ..884 cells ..+ BMS, @ $4k ,..does not make any allowance for assembly of the pack, enclosures , etc etc.
> That would be very resource intensive , tricky, and time consuming, with plenty of oportunity for a screw up !
> Special equipment (pulse welder) , and skills would also be required.
> Not a task for a first time battery builder.


Chinese made packs are generally 10% to 20% more than the bare cells. So the difference is not that much.

However, there are reasons to build one's own pack. One of my projects requires 1.2 kWh of cells to fit a difficult space, and there is no way that can be described or made by another party as there will be trial and errors. Another project is to add 16 kWh to my 2011 Leaf to bring it to 40 kWh. But before I go ordering 16 kWh of power packs 96s14p, about $5,000 for grade A 18650 cells, I need to see if the idea is feasible. There does not seem to be too many people doing this and I am afraid that the system controller may barf if the power line is tapped. It will certainly get confused. So the plan is to build 96s1p, test the thing, try to charge it via the vehicle charger, and assure that it makes sense before ordering $5,000 worth of packs. But there is no way to buy a 96s1p pack. You have to make it yourself.

Building a pack is not so difficult I believe, and even not so time consuming. As long as one knows what to do with the electronics and has access to a spot welder. If you open up an e-bike pack, there is very little to it.

It is a good skill to have, especially if one needs to make custom packs.


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## Duncan (Dec 8, 2008)

The problem with building a pack is what happens when you get failures?
And how much capacity do they actually have

I took my 16 Ah (I miss-typed before) to 80% - that is 12.8 Ah - and some failed!
So I tested them and I got from 12 Ah to 14.7 Ah - NOT the 16 Ah !

I also had some random failures - and one cell failing can take it's brothers with it

Headway were very good about replacing the cells and those cells are now long obsolete

But if you are going to use lots of small cells you need to test each one and try and arrange it so that a single failure does not destroy a number of cells


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## Solarsail (Jul 22, 2017)

Good points. One mode of failure for power packs is an internal short. This will destroy the cell and all others in its group (the cells that are parallel with it). And if it results in a fire, it will destroy the whole pack.

There will be a "micro fuse" on the positive of each cell. This is just a 28 ga wire that will blow up at 10 A. So if there is an internal short in a cell, the brothers in a group will be spared.

If the cell loses charge and its capacity drops to 80% or less, then the group will lose a small fraction of its capacity, and the module of 13s10p becomes unbalanced. So once in a while when the groups are in full discharge, the 13 groups are measured and if an anomaly is detected, then the easiest way to fix that is to soldier a spare 11th cell to the group of 10. The pack should have space for spares. A $3 solution. Fast and effective.

Of course with an Arduino based BMS, this can be automated, and the group monitoring and reporting can be made automatic. The BMS can provide a state of health indicator and help predict if some groups are going bad.

If a cell completely fails, like it would be an open circuit (e.g. micro-fuse blown), then the balancer kicks in and upon charge or discharge, it will shut down power if that group is lagging badly behind the rest of the groups in the module. This saves the other cells in the group. A BMS can easily detect this condition, but is not absolutely necessary to have. The balancer and protector will save the day. Total pack capacity comes down and that is when each module is measured and then each group in the bad module should be measured.

So a single cell failure cannot damage the pack, and depending on the mode of failure, can only cut its capacity. Routine maintenance will identify this, and an 11th cell in parallel will restore the capacity. If it is imperative to identify the failed cell and remove it, first identify the module, then the group, then all ten microfuses can be cut, and the ten cells measured, and the failed cell identified.


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## Flatstone (Sep 14, 2017)

What happens when you have to packs with bms say 2x 13s10p in series. So the positive from the bms on pack one to the neg of the bms on pack two, effectively creating a 26s10p. How do the bms cope with the increased voltage in use. I assume you would charge each pack separately so that doesn?t change. 

it?s the discharge I can?t get my head around. Do I double the amount of amps I can pull? When I?ve looked at some bms the amp ratinging is way to small to drive a car, but I guess they are designed for push bike so it?s only to be expected. I have seen some 32s 200amp bms for forked lift truck which look suitable.


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## Solarsail (Jul 22, 2017)

If you take two modules each 13s10p and put them in series, you get 2s1p13s10p. This is slightly different from one larger module of 26s10p. Although the voltage is the same and Ah and continuous discharge A are all the same, 26s10p (or more correctly 1s1p26s10p) implies you are balancing and protecting 26 x 10 cells. This is tough to do - too many cells in series. On the other hand 2s1p13s10p implies you have two balancer-protectors, one for each module of 13s10p, and that is a lot easier. And yes, having two 54.6V chargers one each for 13s10p is a lot easier and safer than one huge 109.2V charger for 26s10p. In fact you need only one charger for 2s1p13s10p, and can share it between the two modules. 

I think the trick is to break down the pack to modules of about 48V (13s) each, as that is a standard adopted by motor makers - a multiple of 48V. Some motors are 96V (two 13s modules) and some are 144 volts (3 modules in series). However when you go to HV such as Leaf, i3, Volt, Tesla, the standard changes from 13s to 12s. The Leaf and Volt are 96s2p. The Tesla S100 is 16s1p6s86p. The new Tesla 3 low range is 4s1p24s31p and long range is 4s1p24s46p. 

The amps you pull depends on the p number while volt depends on the s number. By putting two 13s10p in series, you cannot pull any more amps. However, what you pull is at twice the voltage. So the power is now twice. If you have two motors of the same wattage, one is 48V for 13s and the other 96V for 26s, the 2nd motor will be drawing half the amperage as the first motor.

If your motor is 48V but the power is doubled, then you need double discharge amps and therefore 13s20p. So you can take your two modules and tie them in parallel: 1s2p13s10p. Your balancer, protector, and charger does not change. That is why it is better to construct a large number of smaller modules and tie them together in the manner that best satisfies the controller and motor.

Tesla plays the trick that the module tray is built for 24s46p. For the longer range T3, it fills them all out. But for the shorter range T3, it only puts 31 cells in the group of 46, with 15 spaces empty. This allows it to use the same tray, BMS and charger, heating and cooling, and module safety mechanisms for both cars.


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## Flatstone (Sep 14, 2017)

What an amazing post. Tons of information and really well written. This is my first step in converting a car to electric and it?s post like yours that really make a difference to my understanding of a new (to me) world. 

I haven?t even started converting the bus and I?m already lining up new projects.

Thanks again for a brill post.


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## Solarsail (Jul 22, 2017)

Thanks for your kind words Flatstone.

For a VW bus, you may choose 96V or 144V. Of course this depends on the controller and motor. I would avoid anything less than 96 (not efficient) and over 144 (not safe). But if you plan to put the battery in a used EV such as a used Leaf, then you should go 12s instead of 13s. I am pretty sure a 144 (39s) motor/controller for the bus can handle 133V (36s). 

Then you need to figure total storage capacity. Assume a unit range of 6km/kWh (Leaf is 6.07, while T3 is 6.79). So if you wish to travel 100 km, then you need 18 kWh. At 2s1p13sXp, that would be 192 Ah, and if you are using Panasonic 3.4Ah cells, then that is X = 56 cells in parallel, or 2s1p13s56p. I would divide 56p into four, as protector boards have a limit and standard boards probably will not be able to handle 56p. So it becomes 2s4p13s14p. That is 8 modules of 13s14p. Tie 4 in parallel to get a bank. And then tie two banks in series. Each module now has 182 cells and thus weighs 9 kg which is manageable. The volume of each module is 3.5L. And the storage per module is 2.2 kWh nominal. You can use one charger 13x4.2 = 54.6V charger to charge all 8 modules by rotation, or if you have enough power available, then put one charger on each module and you can charge 8 times faster.

You can custom order 13s14p modules from China (should cost about $3.6 per cell), or you can get the raw cells and build the modules (which is what I am doing), at about $3.3 a cell. Or as Duncan has done, you can get used Leaf or Volt or Tesla packs and modify them to your requirements. As safety is a concern, I am going with new Panasonic 'B', LG 'F1L', or Samsung '32A' Grade AAA raw cells, so I can test them individually before assembly. If I order modules, it would be very difficult to test the cells.


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## Solarsail (Jul 22, 2017)

As far as power (torque) is concerned, I do not think you will have an issue for a VW bus. The power available to drive a motor depends on two measures. 1- the discharge C factor for the cell, and 2- the total storage capacity. Thus pack power is:

P(max continuous) = C * kWh. 

The C for a Pana 'B' cell (3.4 Ah) is 1.5 (maximum continuous discharge current). Therefore 1.5*3.4 = 5.1A is the most you want to draw continuously from a cell.

Thus the maximum continuous power you can get out of the pack of 18 kWh will be 1.5*18 = 27 kW. Not too bad for a VW bus. IMO that is ample acceleration and hill climbing. 

If your module is 13s14p, then Imc = 14*1.5*3.4 = 72A. Just make sure your balancer-protection board can handle this current. Charging is usually 0.5C, so that wil be 14*0.5*3.4 = 24A. Make sure the board and the charger can handle this. If you are not in a rush, try charging at 0.2C. You can tell a CCCV charger what rate you wish to charge the module. It will automatically adjust the voltage to give you 24A constant if that is what you want. As the cells fill up, the voltage of the charger rises, but then you tell the charger to limit at 13*4.2 = 54.6V. When the charger approaches 54.6, it should not be supplying more than 100 mA per cell or 1.4A to the module. I believe that at 13*4.0 = 52V, and depending on the charger, it would stop pushing 24A and gradually decrease it to 1.4A. Once it hits 54.6V it should stop increasing the voltage. For longevity, program it to stop at 13*4.15 = 54V. You will be at 98% of capacity, but your cells will live longer.

Upon discharge, I would stop at 3.15V, even though you could go as far as 2.5V. A balancer-protector I have worked with cuts off at 2.8V. The amount of storage left below 3.15V is not more than 2%. If you go below 3V, then you have to slow charge the cell until it comes back up to 3 or 3.2V, and then you can charge it at full 0.5C. A hassle you want to avoid.


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## Duncan (Dec 8, 2008)

Hi Flatstone

144v is the very minimum for a roadable conversion - higher is better and NO it is not "unsafe" anything over 50v can kill you 400v does not kill you any deader

As far as batteries are concerned you need batteries from a scrapped EV - a Leaf or Tesla or Volt....

They will work out a fraction of the cost of doing it yourselves and they will work much better 
They are designed to work in a car - 

Do NOT believe the specifications on cells you get cheap! - or even the labels on them - your cells may say "Panasonic" but that may just mean that somebody has stuck some labels that say "Panasonic" on them
Be paranoid - they are out to get you! - or at least your money


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## Solarsail (Jul 22, 2017)

How would you know that the scrapped batteries were not involved in an accident and not shorted or discharged? Li-ion can discharge to 1V or even 0V, but regain their 4.2V standing upon charge. But the cell is internally damaged and holds very little charge and can potentially be unsafe? This would be most pronounced with a Leaf or a Volt where if a pouch cell goes, it would not be easy to find an exact replacement. With a Tesla module, I guess it can be opened up and cells swapped -- but with a lot of effort.

Regarding the authenticity of the brand-name cells, it should be said that the company that will sell you 1,500 cells, and warranties the cells, and carries a reputation is not going to send you fakes knowingly. And of course they should be tested (charge-discharge) individually upon reception, and returned if necessary.

The wholesale price of top brand large storage cells such as the Pany 3.4Ah is below $3 a cell. If you buy 1,500 of these cells at $3.30, there is a decent profit in the transaction and no reason for the seller to mix fakes with the shipment. Wholesale prices are about $200/kWh for the brand names. Tesla has claimed that it will reach $140/kWh with the Gigafactory, and the future will see $100/kWh prices. At $3.30 a cell, the cost is $275/kWh, way above the wholesale price. Long gone are those days that you paid $15.99 for a couple of brand name 2200 mAh 18650s.


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## Duncan (Dec 8, 2008)

Hi Solar
Look on the e-bike sites lots and lots of cells for sale 
And most of them simply don't perform as advertised

Lots of people on this site have started off making their packs from individual small cells
I don't remember any of them actually getting anything on the road


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## Solarsail (Jul 22, 2017)

The batch of 100 Pany 3.4 I have ordered is to arrive any day now. I have set up a test rig. Charge to 4.2, and then discharge through 7.5 ohm to 3, and count the mAh. If necessary, repeat. It does up to 8 cells at a time. We will have some empirical knowledge pretty soon, I guess.

Did you measure your 192 Volt cells when they arrived? What sort of results did you get? Or maybe you have measured them recently?


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## Duncan (Dec 8, 2008)

Hi Solar
The Volt pack has 288 cells in sets of three - 3P96S
I could not fit one of the modules so I used 252 cells in 3P84

I tested the voltage on arrival - and then after about 10 months when i got the car all together

I am not using a BMS - I should be - but I am using a Batt Bridge to check for inbalance


Then - from my thread

I have been driving with the Volt battery for about 5 months - including some driving on the track
I don't have a BMS - but I do have a Batt Bridge - everything looks OK

So time for my manual battery check
I drove until I got the battery down to my minimum voltage -295v 
Then started disassembling 
( I have to take a few bits out of the way to get to all my cells)
Friday Voltage - 295v (measured by CA)
Saturday - voltage had gone up to 296.9v (measured by CA)

Voltmeter on both sides of pack - both 149.7v (added together 299.4v)

Using my Celllog 8M I checked all of the cells 
max - 3.548v
min - 3.536v
range 12mv
Looking good!

So I charged it
341.6v on the CA
Voltmeter on both sides of pack - both 172.1v - 172.2v (added together 344.3v)

Using my Celllog 8M I checked all of the cells 
max - 4.078v
min - 4.064v
range 14mv

So all looking good!

That was about 6 months ago 

I am risking it a bit without a BMS - and I am also overloading the cells more than slightly!
My controller is set to 1200 amps - but I only hit that at the battery for a second or two


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## Solarsail (Jul 22, 2017)

1200A -- heh heh, you need one of those pyrotechnic fuses! How about 10x 120A normally closed latching contactors in parallel? It should be relatively easy taking a N.C. contactor and installing a mechanical latch in them. Actually what you need is 2x 400A fuse and 2x 200A latching contactors in parallel. As soon as the two contactors open, the fuses are sure to blowup without delay.

Looks like very good numbers.

Your discharge ended at 3.54V (relaxed). According to my chart, you still have 22% useful SoC remaining. You can take it down to 3.3V (unrelaxed) and get 18% back.

Also stopping charge at 4.07 rather than 4.15 leaves 6% unused. So you are using only 75% of the capacity and can increase your range by 1/3 without any or very little impact on the cells.

Balancing is not a problem it seems. But lack of a Mosfet gate per module leaves your modules unprotected. Do the modules have over charge and under charge and thermal protection?


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## Duncan (Dec 8, 2008)

Hi Solar
It is usual to use 80% of a batteries capacity

For me I have enough capacity for several days use around town or trailering to an event - but I don't have anywhere near enough capacity for trips to Invercargill or Dunedin

I have 60 km range (easy) - which covers usual trips
But Invercargill needs 160 km and Dunedin needs 300 km

So there is no point in pushing the range to get 75 Km instead of 60 km


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## Karter2 (Nov 17, 2011)

Solarsail said:


> Building a pack is not so difficult I believe, and even not so time consuming. .....


 Brave words,..... before the act !
Let us know how you go with those 884 cells, when you get it done !


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## Solarsail (Jul 22, 2017)

Would you rather buy packs from China when you have no idea what kind of cells they have put in? Fake cells mixed with good cells? Please read what Duncan says about fake cells.

My first project is 13s8p - 104 cells in an unusual layout. No pouch cells will fit the thing.


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## Karter2 (Nov 17, 2011)

I dont buy packs or cells from china, too risky.
Time yourself building that 13s 8p pack, including testing and matching the cells. Also monitor the amount of wireing , link strips balance cables etc etc, so you can estimate what it is going to take to build that 884 cell pack.
Anything beyond a 1-2 kWh pack can get very messy very quickly with 18650s
For larger packs, Leaf or Volt cells make much more sense and simplify the build.


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## Solarsail (Jul 22, 2017)

I do get the point. That is why I am starting with 104 cells for the first project (1.2 kWh) and not 1040 cells (12 kWh). The Leaf pouches are too large - the minimum 48V pack will be 1.6 kWh. With the Volt pouches I still have to distribute them out to the shape of the device, and then protect them individually or in groups of 2 or 4 with metal enclosures. This is not possible. The 18650s provide a modest form of mechanical protection and can be laid out to fit the device geometry.

As you and Duncan have recommended, I will seriously consider using Leaf pouches for the 12 kWh project. However note that 2170s are on their way and probably larger cylindricals after that. If they reach the same capacity as a Volt pouch cell (16 Ah), there will be no reason to use pouches anymore.

Balancing pouches is the same as balancing groups of 18650s. Protection and charging is the same. BMS is the same. So all you save timewise is the spot welding, which I understand is not a herculean task. Testing the cells 8 or 16 at a time is as fast as testing a pouch cell. What you gain is more control over the purity of your banks as underperforming cells can be identified and replaced more easily. I rather start with new cells than with cells with an unknown history. They could be sitting in the wreck for ages, discharged to near zero, and then recharged for sale. What would a salvage yard know about preserving lithium-ion in a wreck? The cells may have lost all their charge by the time they get to the yard. A fire in one 35 Ah Leaf pouch cell can easily result in a conflagration as it spreads, while one shorted 3.4 Ah 18650 will result in a venting event and some hot gases.

With proper and continuous intelligent BMS microcontroller monitoring of groups, problem cells or groups can be identified in advance of problems.


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## Duncan (Dec 8, 2008)

Hi Solar

How much space do you have?
The Volt battery starts as a T shaped lump - not much use

It can very easily be split into 7 off 2 Kwh modules and 2 off 1 Kwhr modules roughly 24 v and 48 v modules

Going down below that level is difficult - you need to cut things - but working at the module level is dead easy


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## Karter2 (Nov 17, 2011)

Solarsail said:


> . A fire in one 35 Ah Leaf pouch cell can easily result in a conflagration as it spreads, while one shorted 3.4 Ah 18650 will result in a venting event and some hot gases......


 Just an FYI...
Nissan Leaf cells have been commercial for near 10 years.
There has never been a reported incident of a fire initiated in a cell in all that time .
There have been many fires involving 18650 cells , (remember the laptops) for various reasons, in that same time frame. 
Check for videos of shorted cells in an 18650 pack,.. it rapidly becomes an explosive fireball.
Obviously there are many times more cells and varied uses for 18650s, but you cannot take fire safety for granted with any battery.


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## Solarsail (Jul 22, 2017)

Hi Duncan, space is extremely tight. There are several configurations for the 1.2 kWh pack (13s8p). At this point it will be two bays, each about 3 x 7 x 54 cm. This would be the optimal configuration. Anything else and there will be compromises topology-wise.


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## Solarsail (Jul 22, 2017)

Karter2, yes agreed. The Pany 3.4 Ah is an NCA or NMC cell, and their own report says that when they cook or internally short these cells, they vent and reach 170C but no explosion or fire.

BTW, 18650s have five levels of protection built into the cell that pouches do not have: Steel case, internal fuse, CID, PTC, and venting. And then externally there are four more levels added: cell micro fuse, balancing, protection (for 6 different events), and CCCV charging. That is a total of 14 levels of protection per cell. Then on top of that comes intelligent BMS. How much more nannying do we need? Lithium-ion contains only 2% of the energy of gasoline, per weight. God forbid when we get metal-air rechargeable cells which will be 200% the energy density of gasoline! 

My second project will be 8 modules of 1.5 kWh each. I will just throw them in the back of my Leaf. That is all. I have reserved active fire suppression for my third project - 100 kWh for a sailboat. The enclosure will be flushed with seawater!


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## Karter2 (Nov 17, 2011)

Not all cells have all the protection systems, and a simple short can bypass most of them..


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## brian_ (Feb 7, 2017)

Solarsail said:


> ... note that 2170s are on their way and probably larger cylindricals after that. If they reach the same capacity as a Volt pouch cell (16 Ah), there will be no reason to use pouches anymore.


A cylindrical cell with the capacity of a rectangular "pouch" cell will have at least the same volume, but in a shape which packs less efficiently into a box, so it will be harder to build a usable pack with cylindrical cells than pouch cells. I don't see how it would ever make sense to make very large cylindrical cells, although of course the 18650 size is not the ideal (it's just the size that was already in production for laptops when Tesla needed cells).


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## WolfTronix (Feb 8, 2016)

Solarsail said:


> 100 kWh for a sailboat.


For your sail boat, make sure you can do a system with regenerative braking...

Use the wind energy to move the boat, spin the prop, and charge the batteries.


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## Solarsail (Jul 22, 2017)

The essence of the cylindrical cell is the extra protection you get by casing the lithium-ion sandwich in a steel shell. If you include all the metal casing needed to enclose a pouch cell, the efficiency drops below that of a cylindrical cell. In fact today, the highest energy densities both by volume and weight are held by the 18650 (and 2170), and not by unprotected pouches. I think it is obvious that the pouch cell is not as safe as the cylindrical, except for the chemistry used. Being in a steel case allows the manufacturer to tweak the chemistry for more energy and power.

Automotive pouch cells are extremely inefficient in volumetric density. That is why Tesla can hit 100 kWh per vehicle, while the pouchies (only Bolt which is a limited-volume car) has hit 60 kWh. It is not the case that pouch cells are more efficient because they don't carry the steel case. It is the contrary. Even unprotected pouch cells are not as efficient volumetrically as the 18650 because their chemistry holds less energy.

Note that due to the extra surface area of a pouch cell, and its much larger size and energy storage (35 Ah for Leaf vs. 3.4 Ah), it can be a lot more destructive than an 18650.


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## Solarsail (Jul 22, 2017)

WolfTronix said:


> For your sail boat, make sure you can do a system with regenerative braking...
> 
> Use the wind energy to move the boat, spin the prop, and charge the batteries.


Exactly. You get that for almost free with an e-drive. You can also buy stand-alone hydro-generators that will capture power from the flow.

But the sailboat will have 20 kW of solar panels, so no need for hydro-generation unless you want to visit the arctic!


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## Solarsail (Jul 22, 2017)

Karter2 said:


> Not all cells have all the protection systems, and a simple short can bypass most of them..


These UltraFire cells are notorious for being rubbish. They are made in China and lack some of the protection mechanisms that Japanese and Korean cells have. And what the UltraFire has, does not work. As you can see from the video, the PCB internal board did not work. Neither did the internal fuse work. And neither did the CID or PTC work. It most probably did not have some of these mechanisms. And the 4000 mAh is a lie. It is at most 2000 mAh.

Please do not confuse this with a Panasonic NCR 'B' or a LG INR 'MJ1' or a Samsung INR '30Q', at 5 times the price.


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## Karter2 (Nov 17, 2011)

The video was just an example of what an 18650 can do if something goes wrong. That type of can shorting is very common.
You do know that the Panasonic 18650B is available as "protected" and " unprotected" versions ?....most being unprotected without all those internal safety features , Which version are you getting ?
Also, price is not an indication of a genuine cell...
....be aware, the Panasonic 18650B is one of the most "faked" cells on the market with multiple sellers stocking re-wrapped reject, and sub standard, cheap cells , in Panasonic wrappers. Hard to tell if genuine without extensive testing.
, .


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## Solarsail (Jul 22, 2017)

Of course I am getting the unprotected version. The protected version is a bit longer or less in capacity. And it cuts off the current at a low threshold that I would not be able to get 3C out of it. It also has a higher internal impedance.

And I don't need it because the external balancer-protection board will do the same job for the module which is 13s. The external board has two Mosfets in series with the current. It will cut it off if any of the 13 cells (or groups) exceeds 4.2V. Also will cut off if any cell drops below 2.8V. Also it detects over currents both while discharging and charging and will hence cutoff. Also it will cut off if it detects a short circuit external to the module. Finally it has one or several thermistors that can detect if the area is getting too hot. There is no need to have protection per cell when there is already a microfuse per cell, and the voltage and current of each groups of cells is continuously being monitored.

The cells are guaranteed to have minimum 3250 mAh capacity. A fake cell will not be 3000 mAh. It will be at very most 2000 mAh. This can easily be detected by a capacity test. Also the markings on the cell steel case are often a giveaway.

Are bulk purchasers of Pana (Sanyo), LG or Samsung cells reporting fakes? The only report of fakes I have seen are from purchasers of retail eBay cells. If you know of any bulk purchases of fakes, I would like to hear about it. But speculation of the unknown should not stop a project.


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## jff (Oct 19, 2012)

Maybe I'm missing something here.
I can see the advantage in energy density of using 18650 or similar cells, but the cycle life seems to be less than 25% of lipo prismatics, making them an expensive option for long term use.


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## Flatstone (Sep 14, 2017)

This is true, but if you are looking for range and you have limited space, you need as much density as you can safely have. BMS can greatly I ncrease the number of cycles you can get out of 18650?s and if you don?t fully deplete or fully charge each time then cycles increase also.


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## Solarsail (Jul 22, 2017)

jff said:


> Maybe I'm missing something here.
> I can see the advantage in energy density of using 18650 or similar cells, but the cycle life seems to be less than 25% of lipo prismatics, making them an expensive option for long term use.


Lifepo has 3 times the cycle life of lico (3,000 vs. 1,000). (Lipoly has same cycle life as lico).

On the other hand consider that lifepo is 3 times heavier, and is over 3 times larger. And new lifepo is 50% more expensive than new lico.


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## john61ct (Feb 25, 2017)

Really? So LFP these days roughly $500 per 100AH, no assembly required.

Are there LCO prismatics, or is there a reliable source of quality made assembled packs for under $170 per 100AH?


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## Solarsail (Jul 22, 2017)

john61ct said:


> Really? So LFP these days roughly $500 per 100AH, no assembly required.
> 
> Are there LCO prismatics, or is there a reliable source of quality made assembled packs for under $170 per 100AH?


On Alibaba,
LFP prismatic at $120/100Ah = $375/kWh
Panasonic NMC 18650 3.4Ah (assembly required) = $272/kWh - reliable source, quantity 100
LG NMC 18650 3.4Ah (assembly required) = $257/kWh - quantity 100
Tesla claims $200/kWh dropping to $140.
Packs made in China with BMS add about 20% to cost.

$170/100Ah LCO = $472/kWh. 
You can get LG assembled packs w/BMS for 1.2*257 = $308/kWh

See http://www.diyelectriccar.com/forums/showthread.php/18650-13s10p-project-48v-x-34ah-188618.html

There are LCO prismatics. Leaf, Volt, FIAT on used market are LCO prismatic.
FIAT used LCO prismatic = $151/kWh


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## john61ct (Feb 25, 2017)

Solarsail said:


> On Alibaba,
> LFP prismatic at $120/100Ah = $375/kWh


Is that per 3.2V cell?

I was quoting per 12V or four cells.

Delivery usually adds few hundred.

No effective guarantee unless buying from an in-country seller.


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## Solarsail (Jul 22, 2017)

Heh - yes, it was per cell, and LFP is 3.2V. In the li-ion world nobody speaks about 12V. That is the lead acid world.  Over here, mAh is either cell or pack, depending on context. And it is preferred to speak about kWh rather than mAh.

Yes delivery by air is about $1.10 per 18650 cell, Q100. But it is possible to arrange by sea, I am told.

Alibaba can manage the transaction and if one has an issue, they will intervene. For a small order, that may be sufficient protection.


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## john61ct (Feb 25, 2017)

I was talking prismatics, minimum 180AH per cell. What's this mAh?

And no way would I buy Alibaba when better in-country guarantee options abound for around the same or cheaper.

Hazmat shipping cost usually make all the fifference.


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## Solarsail (Jul 22, 2017)

john61ct said:


> I was talking prismatics, minimum 180AH per cell. What's this mAh?
> 
> And no way would I buy Alibaba when better in-country guarantee options abound for around the same or cheaper.


mAh is Ah * 1000.

If you can get NEW 4x 100Ah LFP prismatic 3.2V for $500 locally, or $125 per cell, that is a very good price. Equivalent to $400/kWh local. Can you provide a link to that? I suspect they are used cells.

This will be cheaper than new LCO cells delivered by air assembled and with BMS. These are $477/kWh (edit) and local. Are you sure?

Problem is that LFP will be 2x heavier and 3x larger (in volume) than LCO, and will need BMS (unless it is a 12V lead acid replacement, which it will already have a BMS).


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## john61ct (Feb 25, 2017)

Not counting delivery, that's always the killer.

And not regular suppliers, just ballpark on occasional deals, otherwise more like $700.

And I'm only talking LFP, = LiFePO4


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## Solarsail (Jul 22, 2017)

LFP (LiFePO4) is safer, but 2x heavier and 3x larger.

Without delivery cost, then new LCO assembled with BMS is $393 /kWh. So is a bit cheaper than LFP. And you can order at any time. Don't need to wait for special deals.

(see previous post for edit)


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## Karter2 (Nov 17, 2011)

jff said:


> Maybe I'm missing something here.
> I can see the advantage in energy density of using 18650 or similar cells, but the cycle life seems to be less than 25% of lipo prismatics, making them an expensive option for long term use.


 Quality 18650s can be expected to give 4-5000 cycles if not abused (overcharge/discharge, temperature, etc)..to 80% capacity
Tesla offer a 8 year warranty on their EV packs.(18650 cells)


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## john61ct (Feb 25, 2017)

Yah price that Tesla pack for us when you find a source. 

To get anywhere close to quality like that from 18650s via DIY, good luck not cheap, and price your labor including research time.


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## Solarsail (Jul 22, 2017)

john61ct said:


> Yah price that Tesla pack for us when you find a source.
> 
> To get anywhere close to quality like that from 18650s via DIY, good luck not cheap, and price your labor including research time.


A DIYer doesn't do it because he or she is saving a few bucks or because their time has no value. They do it to seek knowledge and for the love and fun of creation/production.

Top quality Panasonic 18650 3.4Ah cells are $3.28 each at Alibaba, Q100. LG is even less. Hard to beat such quality and prices.


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## Karter2 (Nov 17, 2011)

john61ct said:


> Yah price that Tesla pack for us when you find a source. .....


 I guess you have trouble with search engines too. !
$1375 for each 5kWh module
$366 /kWh fully assembled.
http://www.evwest.com/catalog/produ...ucts_id=463&osCsid=807hjq4afmj1nlh428hlod7bv0
Several other sources available


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## Solarsail (Jul 22, 2017)

Karter2 said:


> $366 /kWh fully assembled.


I would think that you would agree that the "raw deal 18650" is a better deal?

Tesla advantage:
Comes with a nice enclosure and interconnected
Automotive version of the Pana 3.4Ah (continuous 2C)
Disadvantage:
USED cells
Needs rack to mount the module and BMS.
21.6V too low, 500A too high
Only 2 thermistors
74p is way too high and can result in problems

18650 Pana 3.4 Ah advantage:
Cheaper at $272/kWh
NEW cells
Make any configuration you want.
Add any switches, dials or displays or devices to the enclosure
Can have more thermistors
Standard connector
Disadvantages:
Must be interconnected
Needs enclosure
Continuous 1.5C.

Conclusion: Tesla too expensive at $366/kWh.


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## john61ct (Feb 25, 2017)

Karter2 said:


> I guess you have trouble with search engines too.


I was never imagining considering used batteries.

If Tesla doesn't make its packs , powerwall etc available to consumers new with support and warranty, then AFAIC they don't yet exist for this market.

I am not a hobbyist, interested in fooling around with this stuff for fun, I want to know what I buy will reliably work for many years.

With prismatic LFP, ten years daily usage is at the low end of my expectation.


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## Karter2 (Nov 17, 2011)

Lets review that when you have accurately assessed your costs for testing, assembly components, labour time, etc etc. ..and completed a 500 cell pack build.
Sure they may not suit your specific application, but that was not the question.
However there are methods of reconfiguring the interconnects to give 12s 37p.
The Tesla cell is different to the 18650B ( closer to the BD or BE) and custom designed for EV applications.( discharge rating, cycle life, etc)
Tesla module construction has also been extensively tested and proven to meet various regulatory requirements


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## Duncan (Dec 8, 2008)

Hi John
I would bet good money that "prismatic LFP" will have a much much higher failure rate than buying a second hand EV pack from a Leaf/Volt or Tesla

The only reason that I can see for not going that route is if you need such a funny shape that you have to build your own pack from small cells


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## john61ct (Feb 25, 2017)

No idea what you mean, and why would you use scare quotes for a standard term?

Among the top say dozen mfg, QA processes are excellent, warranty taken very seriously, output bought mostly by military buyers, what the heck are you talking about?

And the cells at high AH are about 2" by 8" by 12-18" high. Three strings of four gets 500AH at 12V in a big ammo case.


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## Duncan (Dec 8, 2008)

Hi John
Take a poll on this site
How many people have had "prismatic LFP" that have failed?
Just about every conversion has had at least one cell fail
I had about 15% failures on the ones I bought

_Among the top say dozen mfg, QA processes are excellent, warranty taken very seriously, output bought mostly by military buyers_

That is ALL dubious - certainly it does not tally with the experience of the people using the things 
And as an experienced Quality Manager I would want to visit any company I dealt with to see if it actually had decent procedures - or (as many do) just said that it had them

Automotive manufacturers on the other hand like to deal in failures per million AND all have excellent quality procedures

The comment about size is because the Automotive modules are quite large - my Volt battery could easily be used as "modules" - going below that to the cell level is a LOT more difficult - but the modules are quite large


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## john61ct (Feb 25, 2017)

Maybe some people here are buying based on price from dubious sources, perhaps from individuals, or shipped from overseas or even secondhand?


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## Duncan (Dec 8, 2008)

john61ct said:


> Maybe some people here are buying based on price from dubious sources, perhaps from individuals, or shipped from overseas or even secondhand?


Good luck on getting "prismatic LFP" that is NOT from "overseas" - unless you are based in China

Most people have bought new from legitimate sources - and they still have failures

You could ask if there is anybody who has built an EV with "prismatic LFP" that has had zero failures


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## john61ct (Feb 25, 2017)

Yes of course they're made there.

What *is* with all the weird quoting?

Have you got better synonyms for these words?


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## Solarsail (Jul 22, 2017)

john61ct said:


> Three strings of four gets 500AH at 12V in a big ammo case.


John, in the EV world, you start at 48V for bicycles and bikes. Now these are going up to 96V. For automobiles, you start at 144V and then goes up to 346V.

To string the prismatics to get to 346V, you need 108 cells stringed. Do you think it is possible to string 108x 2"x8"x15" prismatics? You will need a pickup truck.

And this only gives you 150 miles range in a small car. If you want 300 miles range, you need 216 prismatics. You will have to fill the trunk and back seats with prismatics.

4 prismatics gives you 12 volts? So you will fit 16 prismatics on a bicycle?

Prismatics are only good for golf carts.


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## Karter2 (Nov 17, 2011)

john61ct said:


> I was never imagining considering used batteries.
> 
> If Tesla doesn't make its packs , powerwall etc available to consumers new with support and warranty, then AFAIC they don't yet exist for this market.
> 
> ...


 Are you planning a project that will use all new, proven , warranted, commercially available , components ? If so it would be interesting to hear some details.
But if not, why the big hang up about using salvaged batteries ?
The only way to know if anything is going to be reliable is to thoroughly test it before assembly...even new warranted cells have been known to fail or be outside useable specification.
If you really want to, you can buy a new Tesla power wall (14kWh) or Power Pack (110kWh) if you can afford it.
If you are planning anything mobile, bike, car, truck, etc, then you will be wasting your money on LFP..


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## john61ct (Feb 25, 2017)

House storage, not propulsion.

Yes it seems the DIY EV world is very different.

And no, as I said I have no interest in secondhand cells.


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## aquabiologist (Sep 8, 2017)

Safety would be an argument pro Lifepo.

Gesendet von meinem E5823 mit Tapatalk


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## Karter2 (Nov 17, 2011)

john61ct said:


> And no, as I said I have no interest in secondhand cells.


 Ok, but that means you seriously limit your options and oportunities for cost savings.
The simplest, most economical, and reliable, storage for domestic solar/wind storage, is the grid.


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## john61ct (Feb 25, 2017)

I am also only off-grid, homes, boat, van & caravan


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## Karter2 (Nov 17, 2011)

Off grid due to location , or by choice ?
Flow batteries are starting to become popular..
https://www.zcell.com
Vans and boats are normally space critical, so generally the most energy dense battery is preferred.


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## john61ct (Feb 25, 2017)

LFP banks are the only non-lead chemistry allowed on boats AFAIK, that is if you want insurance. And certainly the only one I've ever seen in use as a House bank. And of course that's prismatic cells bought new, 99% as a Systems install from Victron, MasterVolt maybe Redarc down under, usually on racing boats for the weight advantages. 

The ABYC committees are working on detailed standards for surveyors to follow. I know they are not considering any other LI variant due to thermal runaway concerns, and pretty sure the idea of secondhand or DIY packs would elicit shock and laughter in that context. 

I don't install DC electrics in a grid-tied situation, but that's not based on principle, just that I don't choose to own such property.


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## Karter2 (Nov 17, 2011)

NMC/NCA LiCO is the current defacto standard for domestic battery banks EG ..Tesla, LG, Panasonic etc


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## john61ct (Feb 25, 2017)

I think you'd find non-lead chemistries to be well under a single percentage point of the installed base.

May climb over 10% over the next five years as demand accelerates.


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## Solarsail (Jul 22, 2017)

Lead-Acid is still about half the price of Li-ion power storage. They will be around for a while.


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## john61ct (Feb 25, 2017)

More like 20% counting specialized infrastructure required, apples to apples on New and top quality.


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## Solarsail (Jul 22, 2017)

john61ct said:


> More like 20% counting specialized infrastructure required, apples to apples on New and top quality.


Yes, I was comparing new to new, and top quality to top quality.

New Panasonic li-ion assembled in a pack is $325/kWh and 4.0 kg/kWh. Tesla claims their batteries cost them $140/kg, which is cheaper than lead acid.

Trojan battery, deep cycle T-105 6V 225Ah $278 makes it $205/kWh and 21 kg/kWh

The li-ion require no maintenance, while LA batteries have maintenance.

Therefore, lead acid is 63% the cost of li-ion, and 5 times heavier, and a lot larger.


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## Duncan (Dec 8, 2008)

Solarsail said:


> Yes, I was comparing new to new, and top quality to top quality.
> 
> New Panasonic li-ion assembled in a pack is $325/kWh and 4.0 kg/kWh. Tesla claims their batteries cost them $140/kg, which is cheaper than lead acid.
> 
> ...


Nope -
The horrible person Puekert has his evil way with the Lead Acid - so that 225Ah becomes about 112Ah
And you can't discharge Lead Acid to 20% like Lithium - you need to keep it above 50%
So your 225Ah in a vehicle becomes less than 70Ah usable- which puts the cost up to $660/Kwh and about 50 Kg/Kwh

In other words 50% MORE than Lithium Ion AND with a much shorter life

If you are using for stationary storage at less than the 20 hour rate then you can ignore Puekert
But you still have to take into account the discharge requirements

Lithium - 80% usable discharge - which puts the cost up to $406/kWh
Lead - 50% usable discharge - which puts the cost up to $410/kWh

Same cost but much shorter life and much more attention required


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## john61ct (Feb 25, 2017)

Note not advocating for lead in OP use case, just discussing relative costs. 



Solarsail said:


> Trojan battery, deep cycle T-105 6V 225Ah $278 makes it $205/kWh and 21 kg/kWh


Deka/Duracell GC FLA ~$180 for the pair, 230AH @ 12V. I see more trouble reports for Trojan these days. 

And no delivery cost for most. 

No replacement charger, no added protective OVD / LVD, balancing, no new learning required. 



Solarsail said:


> Panasonic li-ion assembled in a pack is $325/kWh and 4.0 kg/kWh.


No labor required? New charger, BMS, what else? Links to a source and cookbook howto would be appreciated. 

NMC thermal runaway risk makes me nervous. 



Solarsail said:


> Tesla claims their batteries cost them $140/kg, which is cheaper than lead acid.


What's that got to do with the price of cheese?


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## Solarsail (Jul 22, 2017)

Duncan -

Actually Li-ion is even better than 80% - I would deep cycle it at 90% depth. Leaf I believe runs theirs at 95% depth - (note however, most people don't arrive home at 0% SoC anyways).

So price of Li-ion pack (including BMS) = $325/.9 = $361 /kWh.

John -

No labour required - that is pack price. BMS already included in the pack. A power supply with li-ion CCCV charging is not more than $15 to $20 extra.

NMC thermal runaway - BMS includes thermal monitoring. I understand cell connections are fused and isolates an internal short cell. Check with Alibaba packager. How many Panasonic, LG, Samsung 18650's have had thermal runaways lately, or ever?

Source: Alibaba price for new Panasonic 3.4Ah $3.28 a cell. Add 20% for enclosure, BMS, and packaging labour. Packager will do any configuration. For example 13s10p = 48V x 34Ah.

Sorry the $140 price for Tesla is per kWh (not kg). They claim they have reached this level. This is very significant. The price for 18650 at $250/kWh today is going to drop for 2170 cells to $140/kWh. I understand Panasonic will be marketing these new cells. That will bring down li-ion packs to about $200/kWh (new cells, including BMS and enclosure) - lower than lead acid I believe.

For lead acid, usable DoD is only 50% SoC, and as per Duncan, the cost of lead acid Deka/Duracell is $180 / (230 * 12 * 0.5) = $130/kWh. Although cheaper, is not 20% of li-ion price.

And also note that Deka whatever at $180 for a 12V x 230 Ah, the thing is Chinese made and has nowhere the quality of brand name Japanese made or US made, and the 230 Ah is most likely just 190 Ah.


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## john61ct (Feb 25, 2017)

Solarsail said:


> And also note that Deka whatever at $180 for a 12V x 230 Ah, the thing is Chinese made and has nowhere the quality of brand name Japanese made or US made, and the 230 Ah is most likely just 190 Ah.


I'm very confused, East Penn is a highly respected US manufacturer, maybe not Rolls Surette, but as good as Trojan, Crown, Superior and US Battery. 

Do a proper 20-hour load test once broken in, and you'll likely find capacity is 105+% of rated. 

Unless you were referring to your NMC stuff?


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## john61ct (Feb 25, 2017)

Solarsail said:


> the cost of lead acid Deka/Duracell is $180 / (230 * 12 * 0.5) = $130/kWh.


Sorry please lay out that calc with units. 

Yes 50% usable, 230AH, what is the *12 for? get to kWh?


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## john61ct (Feb 25, 2017)

So with that pack, how much would 200AH @ 12V be? 

I would want to charge at least 100A rate, with LFP I use 13.8V, what is correct for NMC? End charge at whoat tailing C rate? 

How do you know genuine Panasonic, not counterfeit or factory rejects, reputable vendor on Ali? What is the return policy, do they pay the return shipping?


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## Solarsail (Jul 22, 2017)

Clearly they are importing it from China and rebranding it. They have seen the dead end (for LA) in the road, and decided to cash in their reputation. They probably claim they manufacture it in China. Which means buying OEM from any dozens of mom and pop sweatshops.

Panasonic cells are manufactured by Panasonic in Japan and have a $50 billion historic name behind it.

20 hr discharge? Panasonic tests are at 5 hr discharge.

NMC has been surpassed by NMA. Less a safety problem and more capacity. Lots more technologies down the road.

All these heavy metal US battery makers have been caught napping. Instead of flooding the market with li-ion battery packs at very low margins to grab market share, they want to milk their existing products as long as possible. Well, then some newcomer is going to come in, win the li-ion market share, and eventually drive all of them out of business. A Tesla will be done on them. Fact is that li-ion is not a mom and pop operation. The amount of technology needed for quality and economical manufacturing is astronomical. They should stop putting their resources into LA, and start working with the big guys to secure their li-ion cells, and go for market share. In 10 years, there will be no LA market, except to old-timers.


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## Solarsail (Jul 22, 2017)

john61ct said:


> Sorry please lay out that calc with units.
> 
> Yes 50% usable, 230AH, what is the *12 for? get to kWh?


Pack price per kWh = $180(pack price) / (230(Ah) * 12(V) * 0.5(DoD)) = $130/kWh


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## john61ct (Feb 25, 2017)

Solarsail said:


> Clearly they are importing it from China and rebranding it.


Who are you talking about? 

Any lead batts imported from China, most of the cost would be shipping, would have to be cr^p quality to be price competitive. 

Which may well be true from big box retail and automotive sources, there aren't real deep cycling there, just fraudulently labeled. 

But the 5-6 mfg I'm talking about are all top-notch some family-run, all 100% US made with great tech support, call them talk to an engineer, tour the plant whatever. Great warranty service, local dealers, help you install on your boat whatever you need. 

And if taken care of, the banks routinely last 7-12 years. 

Seeing that no insurance surveyor will pass a boat with NMC on board, I think it will take a while to even start to touch that market. 

Maybe RVs, but most of those are still buying batts from Wally's.


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## Solarsail (Jul 22, 2017)

john61ct said:


> So with that pack, how much would 200AH @ 12V be?
> 
> I would want to charge at least 100A rate, with LFP I use 13.8V, what is correct for NMC? End charge at whoat tailing C rate?
> 
> How do you know genuine Panasonic, not counterfeit or factory rejects, reputable vendor on Ali? What is the return policy, do they pay the return shipping?


Pack unit price = 180*1000/(200*12*0.5) = $150/kWh.

For NMC depends on the number in series. 12V is a bad place for NMC. 3 in series too low, 4 too high. 3 ends in 9V, which is useless. 4 starts at 16.8V which can break things. 24V is 7s (7 in series). 48V is 13s. Charge rate is usually 0.5C. So a 200Ah NMC would need 100A charge rate.

Charge voltage is such that the pack receives 0.5C (i.e. half its Ah rating) constantly. As the voltage rises, when it gets to S(number in series) * 4.0V, the voltage is increased slower so that charge decreases to 0.1C and eventually 0.05C. The charge voltage does not go above S*4.2V. Then it is cut after a while. The li-ion charger does all of this automatically, and the user just needs to connect it and turn it on.

I just bought a batch of Panasonic 3.4Ah from Alibaba. Those are good questions which I have answered in 
http://www.diyelectriccar.com/forums/showthread.php/18650-13s10p-project-48v-x-34ah-188618.html


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## john61ct (Feb 25, 2017)

Solarsail said:


> 12V is a bad place for NMC. 3 in series too low, 4 too high. 3 ends in 9V, which is useless. 4 starts at 16.8V which can break things.[/url]


Well then not wasting time , not worth messing around when all the loads, charge sources and infrastructure are already standardized at 11.5-15V, doing DCDC conversion just adds cost and points of failure.

I'm sure fine for other use cases though.


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## Solarsail (Jul 22, 2017)

The return policy is "we guarantee you the Panasonic specs" - no cell below 3.25Ah with 5 hr discharge.

Return shipping must be negotiated. For 130 cells, then no. For 5,000 cells, maybe ...

Please see my thread on the project.


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## Solarsail (Jul 22, 2017)

john61ct said:


> Well then not wasting time , not worth messing around when all the loads, charge sources and infrastructure are already standardized at 11.5-15V, doing DCDC conversion just adds cost and points of failure.
> 
> I'm sure fine for other use cases though.


Yes, no DC to DC conversion will make sense, unless for low power accessories.

But for 12V then use LFP 4s.

For 24 volts and up, use NMC 7s, 10s, 13s, 20s, 26s, etc.

Nowadays anything motorized has moved to 24V and going to 48V and high power will move to 96V. The only people using 12V are the automakers! The model-T standard.

Remember what happened to the NiCad power tools market? Is anyone missing them? Is anyone complaining about li-ion power tools? My Dewalt (A123 LFP) is as good as brand new.


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## john61ct (Feb 25, 2017)

Solarsail said:


> for 12V then use LFP 4s.


Yes, I do for power packs a human can carry, but usually too expensive once past 3-400AH. 

And boat insurance requires robust BMS, brings pricing to 7x lead. 

Windlasses, winches, bow thrusters are still 99% 12V. 

Propulsion motors yes, usually 48V, but so far just hobbyists in the small vessel sizes, stick close to coastlines.


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## Solarsail (Jul 22, 2017)

john61ct said:


> Yes, I do for power packs a human can carry, but usually too expensive once past 3-400AH.
> 
> And boat insurance requires robust BMS, brings pricing to 7x lead.
> 
> ...


Bow thrusters still at 12V? OMG - that was invented during the French Revolution! Boats should move to 48V and let DC-DC converters power the electronics. Anything mechanical should move up.

I plan to get a sailing catamaran and replace the diesels with two Torqueedo 10 kW 48V, and 100 kWh of Panasonic cells. What do you think? The Torqueedo also hydrocharge.

But the main source of charge will be solar - lots of floating solar panels. 50 square meters.


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## john61ct (Feb 25, 2017)

I think a backup diesel charger would be a good idea. 

Sometimes not having full power available is life-threateningly dangerous. 
And if you keep the mast you'll get shading issues.


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## brian_ (Feb 7, 2017)

*Lithium and RVs*

The lithium batteries that I have heard of used in RVs are lithium iron phosphate. They normally use four cells in series, use chargers set for a higher voltage than usual for lead-acid, and depend on the BMS packaged in the battery.


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## john61ct (Feb 25, 2017)

*Re: Lithium and RVs*



brian_ said:


> The lithium batteries that I have heard of used in RVs are lithium iron phosphate. They normally use four cells in series, use chargers set for a higher voltage than usual for lead-acid, and depend on the BMS packaged in the battery.


Yes, boats too. Systems from Lithionics (OceanPlanet), Victron, MasterVolt, Redarc in Australia come packaged with a propietary BMS as systems and cost thousands for just a few hundred AH.

These AFAIK are the only non-lead batts allowed by insurance surveyors, LFP only specifically.

I know several RV/van dwellers that use bare cells (CALB, GBS etc) with off the shelf LVD /OVD components, maybe add their own temperature protection, because

they don't want active cell balancing

amp rates on OTS BMS are puny

the charging voltages on canned systems are set way too high, for longevity best to keep at maximum 3.45Vpc or 13.8V

Some use "drop-in 12V" with internal BMS like BattleBorn, but with a small sacrificial lead batt in parallel to prevent "load dump" damage to electronics if the batt's taken offline unexpectedly while charging.


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## Solarsail (Jul 22, 2017)

john61ct said:


> I think a backup diesel charger would be a good idea.
> 
> Sometimes not having full power available is life-threateningly dangerous.
> And if you keep the mast you'll get shading issues.


Yes, the mast and sail are kept. And yes, there will be shading, probably 30% under shade, depending on how you spread the panels. For example there is no shade aft of stern.

A light portable genset is necessary for emergencies. No need for diesel genset when the solar panels are delivering 10 kW (850 amps at 12V). But generally the 100 kWh pack has a good SoC to take care of emergencies.

LFP is possible, but NMC would be preferred. There will be individual cell fuses to prevent runaway events. Also fire detectors and fast pump and seawater supply to inside of battery packs. 100% safe I believe.


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## john61ct (Feb 25, 2017)

Challenge will be getting an insurance company to share that belief. 

Seen the big German one? $15 mill I believe


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## brian_ (Feb 7, 2017)

*Re: Lithium and RVs*



john61ct said:


> ... the charging voltages on canned systems are set way too high, for longevity best to keep at maximum 3.45Vpc or 13.8V


This is interesting, because 13.8 V would be below the absorption charge voltage of a typical RV converter/charger intended for lead-acid batteries, yet the model of Progressive Dynamics converter/charger intended for lithium batteries runs at a _higher_ voltage than the lead-acid version of the same product... 14.6 volts. It also runs at constant voltage, rather than the multi-stage profile of the lead-acid version.

Inteli-Power® PD9100L Series


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## john61ct (Feb 25, 2017)

Yes not a single "LFP ready" charge source out there, or cells or BMS-packaged "system" vendor is set up to help LFP banks last past the 2000 or whatever cycles quoted. 

Just sacrifice a few percent of AH capacity (will still be above rated) from the top end, avoid that shoulder of the curve, and they last a **lot** longer.


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## brian_ (Feb 7, 2017)

john61ct said:


> Yes not a single "LFP ready" charge source out there, or cells or BMS-packaged "system" vendor is set up to help LFP banks last past the 2000 or whatever cycles quoted.


To be fair to Progressive Dynamics, their description in the catalog includes:


> Output Voltage can be FACTORY ADJUSTED to meet OEM requirements for various Lithium Ion Battery Chemistries and Voltages. Standard “L” Series Voltages are set for 14.6/28.55 Volts to meet requirements for Lithium Iron Phosphate batteries. Other chemistries may require different voltages.


So you can just tell them what voltage you want. 

There are lots of charger suppliers, but if anyone wants another option for 120 V AC input, Progressive Dynamics offers these in nominal 12-volt and 24-volt versions in sizes up to 1.3 kW, and they can be parallel and series connected to suit the required voltage and current. I have a couple of their normal units in RVs, and have no problems with them, but I don't know enough about their performance or about other brands to have any comparative comments.


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## john61ct (Feb 25, 2017)

Better if the user can adjust as needed. 

PD is good otherwise.


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## john61ct (Feb 25, 2017)

john61ct said:


> Seen the big German one? $15 mill I believe


http://www.cruisersforum.com/forums/showthread.php?p=2492443


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