# Decisions, (battery) decisions



## notailpipe (May 25, 2010)

My other thread got a little hijacked, so starting a new thought here to keep things clearer.

Guys I have been active on this thread for a a little while now and if I could request your thoughts on just one topic, this would be it. I keep going back and forth with my battery decision and part of that is the route I want to go, I am not sure I could do it. Maybe I need someone to say, "you're right, that's too hard" and maybe I just need some encouragement to try it... 

So here is the background to my problem. I have a 90 Honda CRX, 2-seater, with a WarP9 motor and Zilla1K. I really wanted this to be a screamin red flyer. It's turning out with my budget to be a lamo golf cart to go the prismatic route... I've got a bunch of aero mods and it's a light, small car, so I am using 250Wh/mi as worst case, but I expect it'll be more like 200Wh/mi. I only have a 12-mile total commute, but was shooting for 40-50 miles to make the car a little more useful.

Okay, so the problem is, after all the money I've spent so far. I only have about $5500 to $6000 reserved for the batteries. I might be able to push this a bit, but it's gonna cause stress with the wife. We've already sunk a considerable amount of cash into it. I *am* going to use BMS, but I've already got money set aside for that.

Okay, so I'd really like everyone's thoughts on my options or which one you guys think I should do. I'll outline them below, but keep in mind my goal is to have a 0-60mph car in 6s or less. That seems feasible. The VTEC CRX had about 150HP and 0-60 in 7.5s. So I'm not sure yet if I scaled that to 200HP and then calculated equivalent peak battery watts if that's all I need to do. The problem is, it doesn't matter anyway, since I have a fixed budget. 

So therefore, the goal is *how can I get peak power at a fixed budget, and relatively low range goal*? The obvious answer to me seemed to be Headways. So I did a bunch of research on Headways and the 38120S cell seemed to be perfect energy/power density tradeoff. But...

1. I'm not sure I can assemble a custom pack like that by the end of the year. I need to get the project done by the end of this year for a wicked 85% (!!!) tax credit from my state. I can probably put off some work, like gauges and things, and technically still be "done" enough to get the credit. So, I started leaning towards prismatics because it's a known solution, 99% of all people here do that so there's a lot of resources, and it would be quicker than building a custom cell. Can anyone encourage me that it's doable or point me to some good resources for off-the-shelf solutions for building the boxes?

2. The only way these can compete on cost is if I get them direct from the supplier. I've got a price quote for $12.50/piece direct from China (Gerson/yeZero at hotmail). IF I could get these and not have all my money stolen, kinda scary with that amount of dough, then I could buy 10 cells per bundle, and 45 bundles in series. This would give me a 144V system, with nominally 100Ah/bundle. They're rated 5C *continuous*, so that should be plenty for a CRX, and I can dump 1500A per cell peak (limited by my Zilla to 1K anyway), which would be a 10C burst, which should get me my acceleration goals. Total pack would be 14400Wh which would give me 46 miles at 80% DOD, which meets that goal too. Best part is, that 450 cells would be $5625 + shipping from China, which would fit into my budget. Gerson said only $100 for slow shipping, but that may just be to the coast (I'm in Colorado).
2a. I'm not sure if this price includes those connectors/cell holders or if that blows my budget. Is this a BS "introductory price"?
2b. I'm not sure if trading this much money is safe. Does anyone have any experience with Gerson? I got his name from another person on here, and he seems pretty friendly and helpful, but who knows.

3. Assuming I went this route and the batteries took 2 months to arrive (Gerson quoted me 1mo on the slow boat). That leaves just November and December to assemble the packs and complete my project (minus loose ends that aren't required by the tax credit). Is that doable? I'm afraid things'll get busy at my work (shooting for a promotion this year) and I'll either not finish the car or not work enough weekends to get the promotion. Anyone know how many hours it took them to assemble these packs? Or is it roughly the same time as the prismatic builds?

Thanks for reading this far.  I really appreciate this community and the great resource that all of you are. Please help me to make this decision because I keep going back and forth and the calendar pages are flipping...

--Notailpipe


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## dimitri (May 16, 2008)

Every time I look at Headway vs. CALB in detail, I end up seeing CALB as better choice. Here is why:

- they are cheaper per AH
- they have excellent reliability record ( so many horror stories of bad Headway cells, rusting terminals, self discharge , etc etc )
- less connections to manage
- easier to build a pack of bricks than cylinders
- C rates are not that much different
- they are in US warehouse ready to ground ship with excellent service

I would strongly suggest you to take 100AH CALB cell and see how many you can afford and fit in the car. This will tell you voltage and wattage you can afford. Don't get stuck on 1000 battery Amps, your Zilla will only do that for few seconds anyway. Can your transmission/clutch handle such burst of power anyway? I bet you will end up breaking mechanical stuff before your battery will give in.


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## notailpipe (May 25, 2010)

dimitri said:


> Every time I look at Headway vs. CALB in detail, I end up seeing CALB as better choice. Here is why:
> 
> - they are cheaper per AH
> - they have excellent reliability record ( so many horror stories of bad Headway cells, rusting terminals, self discharge , etc etc )
> ...


Hi Dimitri, I'll go over your points one by one. They aren't what I've found, but I could be wrong.

"- they are cheaper per AH"
I am quoted $12.50/cell for Headways, at 10Ah, so that's $125 for a 100Ah cell. Best price I see on 100Ah CALB is about $137 at CurrentEVtech.com

"- they have excellent reliability record ( so many horror stories of bad Headway cells, rusting terminals, self discharge , etc etc )"
You might be right about this one, but I don't know. I haven't heard those stories either way. I am hoping Rwaudio or CroDriver can comment here.

"- less connections to manage"
You're right on, this is my main concern as it will lead to more time to finish it. That shouldn't affect BMS connections though.

"- easier to build a pack of bricks than cylinders"
True, rectangles waste less area but I can also build these packs in any shape/size to use space more effectively. I've also heard that having the cells like that individual it's easier to cool them by blowing air over them than over the plastic casing to a prismatic. You can't really cool a prismatic where the chemical heat is happening.

"- C rates are not that much different"
CALB is 4C continuous, Headway is 5C. So you're right on continuous. Headway have higher peak, but this is hard to go by. I've heard some of these "peak" quotes are for like 5 milliseconds, which is useless.

"- they are in US warehouse ready to ground ship with excellent service"
True, that was one of my concerns.

For the same budget I can only buy 41 CALB 100Ah cells, which is only 131.2V (instead of 144) and 42 mile range, which is slightly less.

Even if I'm not running 1000A through my Zilla, let's say I set it to 800A for argument's sake. It will be the same C-rate for either case, but for the Headway's closer to continuous output, so less straining on them.


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## dimitri (May 16, 2008)

I would not use CurrentEVTech as price source. Check out dealers section on this forum. Call Calibpower and Lithiumstorage, they have phone numbers listed on their sites and AFAIK have best prices and service in USA. Get a real quote with shipping and connectors, so you can compare apples to apples. You might be surprised.


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## dimitri (May 16, 2008)

Last year I bought some cells from China, thinking it would be cheaper. By the time I paid all import and duty fees it came out more expensive than locally. Plus you'd pay ground shipping from the port anyway. Apples to apples....


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## frodus (Apr 12, 2008)

dimitri said:


> so many horror stories of bad Headway cells, rusting terminals, self discharge , etc etc


[citations needed]

a bit of an exaggeration Dimitri. Only heard of one guy with rusting terminals and from what we gathered, it was likely because they used steel as the bussbar and it migrated as well as the fact that he was coastal with a ton of salt in the humid air. I've got 200+ and I've seen no rust and they've been in a garage for over a year in Portland, OR where it rains a ton in the spring, winter and fall. Same thing with a friend that has had 250 for almost 2 years. Mine have been just sitting uncovered in a box. I've not seen any rust issues with all the people I've worked with. As far as self discharge? I haven't noticed any significant discharge with any mine, nor any of my customers who use them correctly with a BMS. I think I've only had 1 bad cell, and that was my fault for overdischarging during a test.

Apart from your exaggerations above, I do agree that CALB are a better choice for a car for reliability, low cost, no enclosure is required, less complexity and the fact that there's a US warehouse for them. If it were a motorcycle, it'd be a different story.


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## frodus (Apr 12, 2008)

dimitri said:


> Last year I bought some cells from China, thinking it would be cheaper. By the time I paid all import and duty fees it came out more expensive than locally. Plus you'd pay ground shipping from the port anyway. Apples to apples....


+1

Totally agree....By the time you pay customs and freight, you're way more per/Ah.... 

A little over 2 years ago, I set up a group buy with Headway for 34 customers. We bought just over 1500 cells. By the time I paid customs, brokering fees, warehouse fees, freight ... the cost of the cells were about $16 my cost and I had to wire the money and wait a month and a half. I only saved by living in Portland where there's a port. I just picked it up from the warehouse.


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## EVfun (Mar 14, 2010)

I would be inclined to choose the CALB or Winston 100 amp hour cells for the assembly and schedule reasons you gave. I've been nailing my 60 amp hour Thunder Sky (Winston) cells at the 6C peak rate and they don't seem to care. Jack Rickard over at EVTV has been hitting 180 amp hour CALB cells at up to 5.5 C and they seem fine with that. If you could get a deal on 45 100 amp hour cells, perhaps even $1.25 per amp hour, you would have about 124 volts at 600 amps, or about 85 horsepower at the motor shaft. You won't break the 6 second 0-60 time with that amount of power but you will have no problem keeping up with traffic. With the broad flat torque band from the electric motor it will feel quite peppy.


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## dimitri (May 16, 2008)

notailpipe said:


> but keep in mind my goal is to have a 0-60mph car in 6s or less. That seems feasible. The VTEC CRX had about 150HP and 0-60 in 7.5s. So I'm not sure yet if I scaled that to 200HP and then calculated equivalent peak battery watts if that's all I need to do. The problem is, it doesn't matter anyway, since I have a fixed budget.


Unfortunately you are very unlikely to reach these goals together. You don't have enough budget to get so much power from the pack and I doubt that Warp9 can even produce such acceleration. Remember that your car will be heavier than ICE version due to battery weight and adding more battery to get more power also adds more weight, which drags you down more. You have a chance to get a very peppy ride that you will enjoy driving, but you won't be breaking records. I strongly recommend to go at least 50 cells if you want more than average performance at 100AH size. I have 41 cells in my EV and I am known for reckless driving  , but my biggest regret with my EV is not having more voltage.


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## Duncan (Dec 8, 2008)

My two cents worth

I am building a lightweight 2 seater - and I don't need much range

So I decided to go Headway - I have bought 12 16Ah cells as a sample to work out how to mount them

I have a front battery box - built for lots of prismatics,
I intend mounting the Headways vertically, this will give me space for four rows of three cells in parallel 17 series
I intend to start with four rows of two cells 11 series 
88 cells - 44Kg
Headway 16Ah are 10C continuous, 15CBurst (5sec) 
So that gives 44 x 3.2 = 140v
16 x 2 x 10 = 320Amps continuous, 16 x 2 x 15 = 480 Amps burst 
Which is close to the voltage and current limits of my OpenRevolt controller

To get that power with CALB I would need 100Ah+ at three times the cost and weight

I am hoping to be under 500Kg with the Headways - CALB would add 100Kg! to the vehicle

If I upgrade the controller I can go to 
17 x 4 x 3.2v = 202v
16 x 3 x 10 = 480 amps (continous) 16 x 3 x 15 = 720 Amps burst
202 cells - 101 Kg -

Mounting the cells vertically makes the connections easy and I end up with four rows that I can split for safety and for monitoring


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## dimitri (May 16, 2008)

Duncan said:


> 16 x 2 x 10 = 320Amps continuous, 16 x 2 x 15 = 480 Amps burst


So, your car will run for whole 6 minutes on one charge and your pack will be constantly at maximum stress, likely not live more than a couple of years. What kind of strategy is that? When someone takes years to save money and invest in a daily driver I would assume they want the investment to last and the way to do it is to keep C rates low.

Under such C rates your cells will generate substantial amounts of heat too, are you planning to manage that somehow?


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## drgrieve (Apr 14, 2011)

Use the money you have put aside for the BMS, and buy more battery. When you're on a budget there's always sacrifices. You can add a BMS later.

Many people successfully run calb or winstons cells with no BMS. Just make sure they are balanced (bottom or top) and don't over and under discharge. Which means a good ah counter and a reliable CC CV charger.


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## Duncan (Dec 8, 2008)

Hi Dimitri,

_So, your car will run for whole 6 minutes on one charge and your pack will be constantly at maximum stress,_

That is when I am playing at silly buggers, on the track or strip

My daily drive of 4 Km at 50Kph will probably require 10Kw - about 70 Amps or 2C

_under such C rates your cells will generate substantial amounts of heat too, are you planning to manage that somehow? _

I am going to mount the cells so that will have the ability to blow air past them, the standard Headway mounts will block the airflow so I am separating them

I won't install the blowers until I have checked the temperatures - may not need them

The intention is to have a car that I can use to drive to work AND play on the tracks - sprints, short hill-climbs and 1/8th mile drags

I don't need the range.
Prismatics will cost a lot more (I'm a Scotsman) and reduce my performance


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## Duncan (Dec 8, 2008)

Hi NoTailPipe

_I only have a 12-mile total commute, but was shooting for 40-50 miles to make the car a little more useful_.

Have you looked at your actual use-age?

I found that last year I was either under 25Km (90%+) or over 180Km so any range over 25Km and under 180Km was wasted
(Most days it was under 16Km I only went to 25Km once last year)

A pack to do over 180Km was very expensive a little pack to do 25Km seems a better option

A bit more mileage may seem a good idea but how much is it actually worth?


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## GizmoEV (Nov 28, 2009)

drgrieve said:


> Use the money you have put aside for the BMS, and buy more battery. When you're on a budget there's always sacrifices. You can add a BMS later.
> 
> Many people successfully run calb or winstons cells with no BMS. Just make sure they are balanced (bottom or top) and don't over and under discharge. Which means a good ah counter and a reliable CC CV charger.


+1 on this one.

I ran 11 months without top balancing my pack, charged to 3.485vpc and the difference between the extreme cells at that point was 0.1V. I then took my BMS boards off (I stayed below the balancing voltage) and measured the individual current draw at 3.400V. The high current one was 1.016mA and the low current one was 1.010mA. The voltage difference between the high and low cell after 11 months could be partly due to this slight imbalance on the pack.

My point is this. If you have a good Ah counter like the CycleAnalyst (ebikes.ca), a good CC,CV charger which shuts off very reliably at the saturation voltage (my Zivan NG1 and NG3 are both very consistent in this regard), and you stay away from the top and bottom of the voltage curve of your cells you can go quite a while without getting a BMS. (FWIW, I'm now running a new test with only a half-pack voltage monitor. See http://2003gizmo.blogspot.com/2011/07/battery-pack-balance-monitor.html for more info.)

Also, your controller will work from 72V up to its limit so you can increase your pack voltage later as long as your DC-DC works in the same voltage range. Also, if you bundle 100Ah cells so each set is an even number it will be easy to purchase another set of 100Ah cells and buddy pair them for double the capacity at the same voltage.

For 40 miles of range to 80%DOD you need a 12.5kWh pack if your efficiency is 250Wh/mi. This is 40 100Ah cells for a nominal 128V pack. If spending the money you have for a BMS can be put toward a 50 cell pack and then get the BMS later you will be much happier. I'm sure Dimitri will still be around when you are ready for his BMS. Besides, are you going to save/get some money with the tax credit/rebate? If so, build the car sans BMS, get the credit/rebate and spend it on a BMS.


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## notailpipe (May 25, 2010)

frodus said:


> Totally agree....By the time you pay customs and freight, you're way more per/Ah....


How much are these customs and freight fees and taxes? I was quoted $100 for the shipping on the slowboat, but I think that was only to get it to port. So what are we talking for customs/import duties/whatever other names they can think to take my money...?


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## galeson (Oct 25, 2009)

I bought 540 headways from Lorraine last year. I wired the money and later that day I got a confirmation and a projected schedule for delivery, which was a 1 week wait for my order to be filled by the factory and another week to be delivered by air. Everything was taken care of ahead of time execpt the customs which was about $150 as I remember. UPS picked up my batteries at the airport and delivered them to my house and stacked them neatly in my garage.

My invoice is as follows:

540 cells @ $13.00 $7020
430 nickled 4 hole connectors @.50 $215
550 plastic blocks @.15 $82.50
express freight $1657

Total $8974.50

So I paid $16.90 per battery with air shipping and customs. Take out the express shipping and substitute $100 and it would have been $13.83 each. I live near San Francisco so maybe the freight would have been more if I were in Colorado. If you email Lorraine she will give you firm numbers.
As far as assembly goes I timed how long it took to assemble my last sub pack. It was 13S6P and took almost exactly one and a half hours. But I already had my busbars for the end cells already fabricated so you need to add that in.


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## notailpipe (May 25, 2010)

Thanks for the thoughts, all.

A couple people have mentioned saving the BMS til later so I can afford more battery now. The problem is I am about up to what we (my wife and I) decided we wanted to spend on the project. For example, the car needs a paint job which will add a significant cost on top. So it's not really a case for paying for the BMS later. And we will max out the CO credit, but anything else we get now will be essentially 10% back from the federal tax credit later.

You are right about the apples-to-apples price comparison. I have emailed both Calibpower and Lithiumstorage to see what they quote me on price..

It sounds like a lot of you still say go for the prismatics. Also sounds like maybe my car just isn't going to be as fast as I originally was going for. If it's as fast as a CRX Si, then I'll be happy (it's a DX). Maybe if I can save on some of the other components, and can get a good deal on batteries, then I can up the voltage or the Ah and have a pretty quick car.

Galeson, thanks for chiming in on how long it took you to build one of your packs. If anyone else out there can give me an estimate on how much extra time this took them, maybe relative to prismatics, I'd still consider the Headways.

Better mull this over a bit...


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## dimitri (May 16, 2008)

notailpipe said:


> It sounds like a lot of you still say go for the prismatics. Also sounds like maybe my car just isn't going to be as fast as I originally was going for.


I have to admit your case is not simple because you have conflicting requirements of cost/power not the usual conflict of cost/range. Cost/range conflict is easy, you go as far as you can afford. Cost/power is more difficult because you are facing C rate limits, but cells with higher C rate cost more, so the cost/benefit balance is a moving target.
I'd say you should not discard Headways until you can do apples to apples cost comparison. Try to price them against CALBs using US based prices for Headways, for a more fair comparison.



> Take out the express shipping and substitute $100 and it would have been $13.83 each.


I don't think it works like that. Express shipping by UPS also covers variety of import fees, which you would pay out of pocket if you go FOB route. If you go FOB route you have to deal with import broker and you have to pay for their service and port fees and customs, etc etc. Salesperson in China will never tell you these things.

I would say, whatever you decide with battery, make sure you plan for future upgrades, either adding cells in parallel if you go with small Headway cells or adding cells in series if you go with larger prismatics. And keep in mind that running at max C rates for long time stresses your cells and reduces their life.


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## Yabert (Feb 7, 2010)

notailpipe said:


> I am hoping Rwaudio or CroDriver can comment here


Unfortunately for you, both guys now use A123 20Ah instead headway...

I personnaly order 400 Headway from china at 13$/cell and the final price is closer to 17.5$/cell.

Headway seem the right choise for your situation, but the price is effectively higher then Calb... and if you don't feel good with the assembly of hundred of cells why don't put your hand on Calb 70Ah???

If you limit the battery amps to 700A and motor to 1000A you will have impressive low end torque and around 130-140 hp peak for few sec.
60s(192v nominal) of 70Ah = 5650$

It's can maybe the compromise between easely of integration, price and your wife...


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## EVfun (Mar 14, 2010)

You need to consider the actual voltage under the proposed peak load (current.) My hunch is that the cells will be at about 2.5 volts each when subject to the manufacturers peak load. That means you will have to set the controller battery voltage limit a little lower and it starts getting harder to use that to help protect your pack. 

I don't know of anyone regularly hitting either Thunder Sky or CALB cells with 10C peak loads. If someone here is doing that it would be great to hear how long the peak load is held and what the actual voltage under that load is. The same data from users of Headway cells (also which model cell) would also help Notailpipe make up his mind. Amps are only half the equation, power is measured in watts.


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## frodus (Apr 12, 2008)

notailpipe said:


> How much are these customs and freight fees and taxes? I was quoted $100 for the shipping on the slowboat, but I think that was only to get it to port. So what are we talking for customs/import duties/whatever other names they can think to take my money...?


Not sure how many $100 shipping was for.....

They also don't tell you because they don't charge you the customs fees.... customs charges that in order for them to release it. There's also warehouse fees and broker fees.

Shipping and fees for my 1500 cells was pretty close to what galeson paid. They quoted me something like $800 for shipping, but it was another 2.4%, plus fees, plus broker for sea freight. Ended up being something like $1600ish, maybe a little more.

Don't expect air to be cheap either.... I think you have to pay customs on that too.


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## lockduke (Dec 25, 2009)

Hello gentleman here is one other suggestion, for shipping here in Indianapolis we have a duty free zone for commerce. It might save some by shipping to a duty free area and not having to deal with all the port fees and only deal with customs and pick up at terminal. We have done this on several occasions to pick up extremely heavy safe's for delivery for some of our customer's that purchase off shore due to high costs of some of the US based manufactured units. When we pick up the only thing we have to do is make sure that the customer has taken care of the duty tax based on declared value and the customs inspectors very rarely question the value that is stated on the bill of laiding so we rarely have any time spent with paper work.







Duke.


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## drgrieve (Apr 14, 2011)

I've previously started on making a spreadsheet so one can compare different batteries parameters. An average IR is what is missing on the manufacturers spec sheets.

I've found a post (don;t remember where) that the headway 10ah cells have an average IR ranging from .03 to .035. If you take the .035 figure, from 3.3v you'd end up at 2.95v at 10C. This is a 12% voltage sag at 10C. [Note I'd rather see a pack voltage sag at a certain C rate to confirm this data]

From Jack Rickards dyno test of calb 180 cells at 1000 amps he got a 28% sag at 5.55C (not 22% sag as he mentions). This works out to be an IR of .126. This is 3.3v dropping to 2.7v at 5.55C


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## EVfun (Mar 14, 2010)

drgrieve said:


> From Jack Rickards dyno test of calb 180 cells at 1000 amps he got a 28% sag at 5.55C (not 22% sag as he mentions). This works out to be an IR of .126. This is 3.3v dropping to 2.7v at 5.55C


It seems that you have some way of measuring the effect of sag that I don't understand, but would like too understand. Where does the 0.126 come from?

Here is what I get from JR's data. The cells sags from 3.3 to 2.7 volts at 5.55 C (1000 amps.) The internal resistance is given by the formula V = A * R. So... 0.6 (volts) = 1000 (amps) * R (ohms.) The result I'm getting is 0.006 ohms (0.6 milliohms.) When I do the same tests on my Thunder Sky 60 amp hour cells at 6C (360 amps) I get 1.4 milliohms.


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## DavidDymaxion (Dec 1, 2008)

It seems clear to me you want the 8 Ahr "P" cells, not the 10 Ahr "S" cells.

The "P" cells are spec'd for 25C (200 A) continuous. The "S" cells are spec'd for only 10C (100 A) continuous. The "S" cells also have much higher internal resistance.

If range is truly not an issue, but power to weight and cost are, you could get the same current with 1/2 the number of cells. For power, the "S" cells are 0.85 kW/kg, but the "P" cells are 1.2 kW/kg.

http://www.manzanitamicro.com/produ...page=flypage.tpl&product_id=61&category_id=29

http://www.manzanitamicro.com/produ...page=flypage.tpl&product_id=83&category_id=29


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## galeson (Oct 25, 2009)

There are some nice color graphs of the difference between the S and P cells at:
www.diyelectriccar.com/forums/showthread.php/high-power-cells-a123-saft-headway-43400.html
I tested about 300 of my P cells and my results varied more than I expected. In my set-up I tested at 6 1/2 C and immediately bumped that up to 12C to find the IR. It was winter and the temperature in the room was about 55 degrees F. At 6 1/2 C the voltage was in the range of 2.8V and at 12C it was about 2.6V This probably corresponds to the low points on the graph of the P cells and then the voltage starts to rise as the cells warm up. 
What really surprised me was that the IR varied from a low of around .0045 to a high of .0070. I retested some of the cells at the ends of the spectrum and pretty much confirmed these values. I then tested these same cells at the ends of the spectrum and the IR seemed to have no effect on the amp hours at all. They all came out well over 8Ah.


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## drgrieve (Apr 14, 2011)

EVfun said:


> It seems that you have some way of measuring the effect of sag that I don't understand, but would like too understand. Where does the 0.126 come from?


Thanks for the correction.

I made two mistakes (I was in a rush) It is .6 volt drop not .7 oops. And I was copied over the wrong column the 0.108 was for the C rate so you can compare with ah taken into account. As you can put smaller cells in parallel to drop the IR.


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## rwaudio (May 22, 2008)

Although I didn't go with Headways in my build I would say they are very good cells. The only prismatic comparison I personally have is 100ah TS, and the prismatic’s are MUCH EASIER to work with! They just don't have the current output that headways do. Headways don't have the current output that A123's do. So it's all relative, you must pick the point where price/simplicity/performance work for you. I would say that either battery (Calb/Headway) could give you a reliable and fun EV. Headway might get you a bit better numbers in the 0-60, but if you don't intend to keep your peak currents high for very long the Calb just might work. (I've never tested a CALB though so I really have no idea how they perform, how they heat up etc.) 

As for buying from China it's not too difficult, but you have to be aware of all the costs and know up front what you are getting into. For us Canadians for example the cost to import from China is usually lower than importing from the USA, so for the most part unless you live close enough to the US seller to have low shipping costs it can be very expensive to buy from the USA. One of the biggest things to consider is Duty, some items have duty applied and some don't. Legally a LiFePO4 cell can fit in a few categories, it can be a battery, an electric car part, etc. Pick a category up front and tell the supplier what to put on customs forms, this is usually in the form of an H.S. code 0000.00.0000 is the typical format, but only the first 6 digits are universal worldwide. Buying from China isn't a free ride, but if you do your homework and come prepared with everything you need to know it can be much less expensive. If you are not comfortable doing all of this yourself, then buy from a dealer, they've taken care of all the hard work and will sell to you for a slightly higher price. To some people this price is well worth it, especially if the dealer has cells in stock and you have get them in your hands within a few days.

On a separate note, I'm not aware of a single person being screwed by buying cells from China. There are the cases of Americans screwing Americans but not Chinese screwing Americans. The other consideration is Warranty, by buying cells from China you often have to initiate the terms of what Warranty is included. By default there might be NO WARRANTY! Shipping TO China can be expensive, so make sure it's worth it to ship cells back for replacement/refund. Otherwise buy some extra cells and eat the cost of the defective ones. OR buy from a dealer with a good Warranty in place!

Inform yourself and make the decision you are comfortable with.

As a final note, I'm definitely not an expert but for performance based on my research and personal testing my only two choices were Headway or A123 PERIOD.


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## notailpipe (May 25, 2010)

Thanks everyone. I got a price bid from Calibpower that I might be able to work with. Basically my whole EV is coming down to compromise (good learning lesson for me from the project):

-Based on my tax-credit end of year deadline, I'm probably going to have to compromise on the high-performance and go prismatics, in the interest of less time to assemble the packs
-I think I might be able to afford 45 of the 130Ah cells, instead of the 100Ah ones. So even though prismatics are lower C than the Headways, if I can bump up the Ah then a 4C continuous is 520A, which should be plenty for my car. Bumping from 100 to 130Ah makes me feel a little better about the battery lifetime at higher currents.
-Found another CRX online that had a similar setup to mine, and a (heavier) 19kWh pack. He was getting 211Wh/mi. With this slightly lighter pack and the aero mods I'm doing, I might be able to get that lower. But even if not, that's a nice far range of 70miles at 80%DOD. I know that I mentioned I don't need that range, but that's also part of the compromise is my wife is more excited about the car with more practical range, so we can take it on shorter side trips to other nearby towns. That will help me bargain on the price for going up to 130Ah. 
-Going 144V instead of higher is probably okay for me. It will help keep the cost of my DC/DC and charger down and save a little bit (every little bit helps) on my BMS.

I think I see a path to done. Thanks for everyone's input, I value all of it. 
--Notailpipe


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