# Battery Comparison



## IamIan (Mar 29, 2009)

tony3811 said:


> I'm trying to decide between these three batteries for my EV and I don't know enough about Amp Hours, KWH, or C's to know what I'm getting or even talking about.
> 
> 38 LiFe04 (100AH) = $5064
> 10 Deka AGM (100AH) = $2732
> ...


You need to know more than the type of chemistry and the Ah rating.
Do you have specific batteries in mind? ... a link?
From specific manufactures , Specific model numbers?

120V @ 40 MPH for 40 Miles .... in what vehicle??? There is a big difference between me wanting to do that on my bicycle vs doing that on a 50 ton battle tank... So what type of vehicle are you intending to use?
Make , Model , Year.


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## pflipsen (Jul 19, 2010)

tony3811 said:


> I'm trying to decide between these three batteries for my EV and I don't know enough about Amp Hours, KWH, or C's to know what I'm getting or even talking about.
> 
> 38 LiFe04 (100AH) = $5064
> 10 Deka AGM (100AH) = $2732
> ...


 
You do get essentially the same KwH from each pack you list here (120V X 100 AH = 12 KwH). How far you can go will certainly depend on the vehicle final characteristics which will determine how many KwH / mile you will be using.

That said the Lithiums (at least according to the manufacturers, no one has used them long enough to know for sure) should last you 2000-3000 cycles. And you can discharge them to 80% DOD (20% SOC) without problem which means you would have 9.6 KwH of usable capacity. With a typical EV using 350 wh / mile you'd have about 27 miles range. With a very light, very aerodynamic EV using 200 wh / mile, you might have as much as 48 miles of range.

The AGMs will last you anywhere from 200 to 500 cycles depending on how far you are going to discharge them. AGMs don't ever do well going below 50% (200 cycles) but can last 500 cycles at 20% DOD. If we assume 50% DOD that means you will only have 6 KwH useable capacity - if you take a typical EV using 350 wh/mile, that might give you about 17 miles of range for typical EV (30 for a light one). But accounting for Peukert effects (not that much of an issue with Lithiums apparently) you would realistically have 11-12 miles of range for a typical EV (as much as 16-17 for a very light EV). But the up front cost is much lower than lithiums as you note and they can handle higher current draws than Gels.

The Gels will last you up to 1000 cycles and you can take them down to 80% DOD. But they can't handle high current draws (i.e., no more than 200 amps or so) so they would not be suitable for a bigger EV or for hilly terrain and probably not for highway speeds. That said your range values could be the same as the Lithiums but less about 40% to account for Peukerts. So you range is more likely limited to about 28-30 miles with a very light EV (16-17 with a typical EV).

Given the "potential" life of the lithiums they should be a better value in the long run. But few have used them for more than a few hundred cycles so far so we really don't know if they will in fact last that long. Confidence is growing in them recently.

There is also the question of adding a battery management system (BMS) for the lithiums which could add up to $1500 to the system (much cheaper ones are certainly also available). Conventional wisdom is that one is necessary for a lithium pack to prevent the cells from going out of balance. A few (e.g., Jack Rickard) have suggested they cause more problems than they solve and you may be better off without them.


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## dtbaker (Jan 5, 2008)

here are some thoughts copied from my site page
http://www.envirokarma.org/ev/01.Design.shtml

I took a while to decide between 12volt or 8 volt... I liked the idea of less weight and cost for the 12v battery system at the same pack energy. But, the smaller class 31 12v batteries had pretty low aHr ratings, and the total energy wasn't looking better than the (12)8v batteries. US battery offers a larger 12v sweeper battery that would give higher total pack energy with 12 batteries, but just would not fit in the space available in the Swift as they are about 3" longer than the 8v batteries. So, for FLA batteries, the most I could get into the Swift and retain the back seat was (12) 8v batteries having a footprint of 10.25x7.125x11.25 and 183 Ah at 20hr rate, or 95 minutes at 75 amps, which translates to about 100ah at a one-hour use rate which is more typical with EVs. 
I did look very closely at the LiFePO4 batteries like Thundersky, Nilar, and some others. I was even ready to pay a lot more because of the reduced size, weight, and longer life. The problems were that nobody could really tell me exactly how much longer the life would be, and the BMS required to manage the batteries is not available 'off the shelf' in 2007. Things have changed fast, and now (in 2010) prices on the Li cells have come down, more people have been using them so they are getting to be more of a standard if you can ante up the initial cost. The advantages of Li are great... 1/3 the weight, 3x or 4x the life, very low internal resistance and almost no voltage sag during normal use. 
(8/2010) - I have revised my cost analysis to fit actual use parameters better now that I have some experience with using a pack of FLA through their life cycle. To compare apples to apples I think the best way is to come up with the cost/mile over the life of the battery. Both FLA and Li have longest life if 'normal use' doesn't exceed 50% Depth of Discharge (DOD) per cycle and average amp draw is no more than 2C or 3C for brief accelerations. Comparable capacities in my case would be the 8v FLA, and the 100ah LiFePO4 cells. If you start with the basic parameter of a 96 volt system using 8v batteries like the usbattery  8vgchcxc , which has a 1-hour a rating of a little over 100ah. This would give a total pack capacity of about 12 x 8v x 100 ah = 9.6kWhr and the cost (delivered) would be around $1600. They can be expected to last about 700 cycles at 50% depth of discharge with good maintenance before they start losing capacity. FLA don't die completely all of a sudden, but the capacity (range) does start dropping noticibly after 18-24 months around 20%-30% less than when new. At 50% DOD I was getting about 20 mile range. This gives the raw lifetime cost/mile = $1600/(700*20) = $0.1143/mile . Keep in mind this is a rough number, and highly variable with how hard you push batteries, if you can continue driving as range drops, etc. Its very possible these batteries would perform acceptably for 1000 cycles, which would bring the cost down to $0.08/mile. 
Working through the numbers for Li has gotten very interesting... life cycles are still somewhat unknown as people have not really been using them in EVs long enough to prove they are going to last 3000 or 5000 cycles; but for my purposes I feel pretty safe using the more conservative number of 3000 cycles at 50%DOD, which would get the same car a little further because of the lower weight and internal resistance, probably closer to 25 miles at 50% DOD which gives (conservative) lifetime miles of 75000 at a current cost around $5500 for 38 x 100ah cells delivered. So the bottom line is lifetime cost/mile = $5500/75000 = $0.0733/mile, or if you believe spec sheets these batteries may last 5000 cycles giving a cost of $0.044/mile 
How does this compare to gasoline? Well, this car used to get 40mp. Current gas prices are about $2.75/gal which gives $0.0688/mile ....and the price of gas will likely return to the $3 level before too long. To compare to electric you have to add in the cost of electricity. My little car uses about 200 Whr/mile; at current retial price of $0.09/kWhr, thats only an extra $0.018 per mile added to the cost of the batteries. To be really fair, you'd have to add in the considerable 'other' costs for a gasoline engine such as the oil changes and average maintenance that electric motors simply do not require. 



The rough numbers are that Electric car w/ Lead costs about $.10/mi to operate, LiFePO4 is down around $.056/mi, and gasoline would be closer to $.07/mi (at $2.75/gal), or $.08/mile as prices rise back toward $3/gallon.


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## tony3811 (Jul 30, 2010)

pflipsen said:


> The Gels will last you up to 1000 cycles and you can take them down to 80% DOD. But they can't handle high current draws (i.e., no more than 200 amps or so) so they would not be suitable for a bigger EV or for hilly terrain and probably not for highway speeds.



My commute is on hilly terrain, nothing major for a prolonged period, but 1/4 mi of hill about 3 times each way. I also live up a hill, it's about 1/2 mile total up the road to my driveway. It's steep but not like San Francisco steep, more like "normal" freeway uphill grade steep, I don't actually know the slope. 

I just don't know what this climb will want to draw from the batteries. Is there typically a built in limiter on controllers to prevent too much draw from batteries at once? 

Thanks!


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## EVfun (Mar 14, 2010)

I wanted to point out that the available capacity of these battery choices are quite different. Most users are reporting the ability to use around 80% of the available capacity of a ThunderSky or Sky Energy LiFePO4 cell while the lead acid choices will have a lower available percentage of capacity available at EV discharge rates (roughly the one hour discharge rate.) Peukert rears his ugly head with Lead.

I would estimate that the Lithium pack would provide 80 amp hours, the AGM pack about 60 amp hours, and finally the gel-cell pack about 50 amp hours. The Lithium pack will have a greater range than the lead options even though the stated capacity is about the same. The lead acid batteries only deliver the full rated capacity over slow 20 hour discharge.

I do not recommend gel-cell batteries for EV applications and this article explains why nicely.


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## dtbaker (Jan 5, 2008)

tony3811 said:


> I just don't know what this climb will want to draw from the batteries.


depends on the gear and the speed. 



tony3811 said:


> Is there typically a built in limiter on controllers to prevent too much draw from batteries at once?
> Thanks!


yes.

controllers have max output they can pump thru, and thats all ya get. Chances are at slow speeds you don't even get full amps. For steep hills you still might have to use 1st gear to get enough torque at the wheels to get up to speed....

If you go with Li batteries, you want to be sure to size your controller, or clamp down the max, so that it CANNOT pull more than 3x the rated capacity... or you risk shortening the life of the batteries significantly. i.e. getting 100ah batteries, and running a Zilla 2k controller full out would be a waste of money and batteries unless you are drag racing and don't care how long the batteries last.

Floodies can handle at least 200-300 amps for fairly long periods of time. If you expect extended heavy draw, you need to go with a higher voltage system to keep the amps down....


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## dtbaker (Jan 5, 2008)

EVfun said:


> The lead acid batteries only deliver the full rated capacity over slow 20 hour discharge.


absolutely....

if you want to compare similar capacities a 100ah Li battery pack would be pretty close to FLA system with 20 hr rating of 180ah or so, and maybe 160ah or so of AGMs since they have less sag under load (but have other issues like less range and slower charge to prevent gassing, which introduces balancing issues)

A good 'value' lead pack balancing range with cost is to use 8v FLA (either trojan or USBattery 'floodies').... compared to 100ah Li for aprox equal capacity.


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## mszhao (Oct 17, 2009)

tony3811 said:


> I'm trying to decide between these three batteries for my EV and I don't know enough about Amp Hours, KWH, or C's to know what I'm getting or even talking about.
> 
> 38 LiFe04 (100AH) = $5064
> 10 Deka AGM (100AH) = $2732
> ...


Hi Tony,i see you live up a hill.like other people's opinion,i advice you to use Lifepo4 batteries.Lifepo4 performs much better than AGM OR GEL batteries when discharge current is relative high.


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## mszhao (Oct 17, 2009)

Hi Tony $5064 is the total price of 38pcs of 100ah lifepo4+BMS+charger or just batteries?
are you from USA or other coutries?
do you prefer to contact with Chinese manufacturer directly or buy from local US distributor?
pls send email to me [email protected]
i can help you everything and save cost for you.


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## dtbaker (Jan 5, 2008)

mszhao said:


> do you prefer to contact with Chinese manufacturer directly or buy from local US distributor?


the typical issues with buying LiFePO4 at this point is being aware of how the price can change depending on delivery options, getting all the duty and import fees taken care of and the final ground freight forwarding.

You will find vastly different prices for FOB China, and delivery from stock that might be in LA or San Francisco. Little things like the bus bars or strapping might not be 'included' in a quoted price, etc. Quoted prices might include all duty and fees, or maybe not....

It is not generally possible to deal with Thundersky or CALB directly for small individual orders. Dealing with a Chinese wholesaler presents some communication issues... which can be overcome, but generally require multiple emails to figure things out and nail down a price for what you are getting and how to get it all the way to your garage.

There are a couple reputable US wholesalers, a couple with little or no track record, and one or two absolutely bad ones that have a record for not delivering goods even when they have been pre-paid in full. It is worth paying a little more for delivery from stock that is already in your county, perhaps paying by credit card so you can chargeback if there are delivery problems, and worth seeking out a seller that has a good reputation for delivery.


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## tony3811 (Jul 30, 2010)

dtbaker said:


> ... and worth seeking out a seller that has a good reputation for delivery.


Dan, 

I live about 1hr from SF (and have access to a truck) and about 5 hrs from LA (possibly worth the drive). 

Do you know any reputable dealers, or have any suggestions? 

Someone recommended this one but I don't know if they are any good: http://www.powerscaner.com/product_1.php?id=123

Thanks!


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## mszhao (Oct 17, 2009)

tony3811 said:


> Dan,
> 
> I live about 1hr from SF (and have access to a truck) and about 5 hrs from LA (possibly worth the drive).
> 
> ...


Tony,batteries is one of the most important part.
but desides battery,you also need to pay attention to BMS and charger.
for the batteries,i think the wise choices for you is to contact manufaturer directly or local US dealer.it is up to you.
if possible,i will be very glad to work with you.and we accept 30% deposit.
for the 38pcs of 100ah,our price is no more than USD4200


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## dtbaker (Jan 5, 2008)

well.... powerscaner is one with zero history, and no reported sales in the US... so I don't think I would want to be the first.

EvolveElectrics.com has a good rep so far, and ships out of SF thru a wholesaler alliancerenewableenergy.com that has been around for a long time and seems to be good. They are getting a shipment in the next couple days and would have stock available at a higher price than FOB China, but ready to ship....

Dave Kois at http://currentevtech.com seems to have his heart in the right place, but may not have stock in hand, and is a little mired in legal issues and extraction from previous employment w/ EVComponents.com (James Morrison); so I dunno if he is able to deliver from stock, or still putting together a container order.


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## dtbaker (Jan 5, 2008)

mszhao said:


> i will be very glad to work with you.and we accept 30% deposit.
> for the 38pcs of 100ah,our price is no more than USD4200


delivered where? 

Is this price FOB China, or from LAX with all duty and import paid? Shipped by boat and requiring freight forwarding? or air freight all customs and duty paid, to final destination?

Do you have any recent US customer testimonials?

and what kind of batteries are these? Thundersky? CALB? something else?


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## JRoque (Mar 9, 2010)

Hi mszhao. If you kindly answer the posted questions, I have one of my own.

I like that you're willing to take a 30% deposit instead of requiring the full amount. Still, 30% is some money thrown over to an unknown vendor. Our only protection as consumers is to have it charged to a credit card so we can make a claim in case.... something goes wrong.

So, do you take credit card payments?

Regards,
JR


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## mszhao (Oct 17, 2009)

dtbaker said:


> delivered where?
> 
> Is this price FOB China, or from LAX with all duty and import paid? Shipped by boat and requiring freight forwarding? or air freight all customs and duty paid, to final destination?
> 
> ...


FOBChina of course.
www.heter.biz
yes we have US customers in US,Europe,Australia,New zealand,.we have been in lithium batteries business for many years.
our delivery time is very fast.for most batteries,no more than 20days.


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## mszhao (Oct 17, 2009)

JRoque said:


> Hi mszhao. If you kindly answer the posted questions, I have one of my own.
> 
> I like that you're willing to take a 30% deposit instead of requiring the full amount. Still, 30% is some money thrown over to an unknown vendor. Our only protection as consumers is to have it charged to a credit card so we can make a claim in case.... something goes wrong.
> 
> ...


we have paypal account.
is it acceptable for you?


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## mszhao (Oct 17, 2009)

JRoque said:


> I like that you're willing to take a 30% deposit instead of requiring the full amount. Still, 30% is some money thrown over to an unknown vendor. Our only protection as consumers is to have it charged to a credit card so we can make a claim in case.... something goes wrong.
> 
> So, do you take credit card payments?
> 
> ...


hi JR,i understanding your concerning.we are not a new comer and have existed many years.it is extremly not worthwhile to damage our reputation because of any deposite.you can feel free to keep me in touch and make some evaluation by yourself.


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## mszhao (Oct 17, 2009)

our warranty is three years
for the payment term,many lithium supplier require 100%T/T in advance.
but we agree to accept 30% to make you more released and secure.
here show you some pictures about our products and our company.


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## dtbaker (Jan 5, 2008)

mszhao said:


> for the 38pcs of 100ah,our price is no more than USD4200


ok, recent exchanges clarify that this price ($1.105/ah) is FOB China for a brand of battery that I don't think anyone in this group has tried or used. 

I did find some information on your website at
http://heter.biz/en/product/index.aspx?MenuID=052803
But, none of the 'detail' buttons work, so I could not see if you document specific test results, output C ratings, or any Third-party laboratory comparisions to the batteries we are more familiar with (Thundersky and CALB)

After more poking around the website, I found that clicking on the IMAGE took me to a detail page. I saw that the 115ah unit for instance is rated for only .25 continuous use, and 1C Max... which won't work very well for full size EV application.
http://heter.biz/en/product/detail.aspx?ID=163


I would like to see alternative batteries for sale... but would want to see performance comparisons at 1C, 2C, 3C, and price FOB US port after all duties and customs are paid. I would also like to see several of your actual customers join this group so we can discuss with them actual experience with purchase and performance.

I don't see how you can promise such rapid delivery... except by air freight, which obviously adds high cost to deliver. Can you disclose the typical cost to ship by ocean versus air (including duties and all fees)?

The last issue is method of payment... PayPal does not *really* protect the buyer; at least not like a major credit card where the charge can be reversed without question. Hence the hesitation working directly with a China-based purchase. It would be better to have stock available FOB US that could be paid by credit card (perhaps with a 3% service fee) as a payment option.


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## mszhao (Oct 17, 2009)

dtbaker said:


> ok, recent exchanges clarify that this price ($1.105/ah) is FOB China for a brand of battery that I don't think anyone in this group has tried or used.
> .


the FOBChina price could be lower than USD1.105.
pls notice the price is no more than USD4200 intead of equal to USD4200.
from China port to main port of US,the shipping cost by sea cost around $150~300 within 1CBM.
duties and importing fees are generally depending on local area.
most of the time,the customer do customers clearance and pick the goods by themselves.our shipping agent can help you do this and send the goods to the door which is DDP.we can quote you when we know the exact address and exact weight/size/cartons of the goods.

the shipping date is exluding shipping time.
if you hope to receive the goods faster,airfeight is available.
for the 120v100ah pack,it may cost $900~$1200.let's quote exactly via email.

we will use 2pcs of 3.2v50ah in parallel to get a 3.2v100ah.
so there will be 76pcs of 3.2v50ah in the pack.
or the customer could consider our 115ah and 110ah cells.

what kind of credit card do you mean pls? have you found any other Chinese supplier can accept payment via credit card?
if we have this payment method,we will accept and do everything to support you.so far we receive payment most are T/T,a small part is paypal.
Paypal is a good way of protecting buyer's profit.


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## JRoque (Mar 9, 2010)

Hello mszhao, I'm not sure how many here share my impression but so far you have answered more questions and with more specifics than most other China battery vendors posting ads on this website. Thank you for that!

The credit cards are Visa, Master Card and others as issued by a US-based bank, for us living in USA. These cards have standard purchasing protection which ensure us a safe transaction. If you read some of the forum threads you will see at least one company that took people's money and blatantly stole it by not delivering the prepaid batteries. That's part of the reason we are very sensitive to payment methods. Paypal, as I understand it, has limited protection to customers and claims expire 45 days after purchase which is typically sooner than it takes to receive the orders from China.

Regards,
JR


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## dtbaker (Jan 5, 2008)

JRoque said:


> Paypal, as I understand it, has limited protection to customers and claims expire 45 days after purchase which is typically sooner than it takes to receive the orders from China.


exactly.... paypal complaints are also an interative process, and judgement is completely up to PayPal rather than the fairly iron-clad guaranty from Visa or Mastercard.

on a technical note, the battery cells I looked at on the website did not have adequate rated output for EV use.... .2C continuous and 1C max probably would not work in most cases. I amy have missed the more suitable cells though. can you supply a link to the detailed info for cells recommended for EVs? ones with 100ah or more capacity and hopefully at least 1C continuous output?


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## mszhao (Oct 17, 2009)

i know that much business is done by credit card but it is perhaps limited within US not internationally.
how many charge and discharge do you require pls?
our batteries can meet most customer's demand.
Paper is only paper and doesn't stand for everything.
some supplier claim 5C,or cycle life reach over 3000times,paper= reality? it is a question.
1C continuou is no problem.and this is the most conservative saying.
pls chec the following charge and discharge curve.


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## mszhao (Oct 17, 2009)

JRoque said:


> Hello mszhao, I'm not sure how many here share my impression but so far you have answered more questions and with more specifics than most other China battery vendors posting ads on this website. Thank you for that!
> 
> The credit cards are Visa, Master Card and others as issued by a US-based bank, for us living in USA. These cards have standard purchasing protection which ensure us a safe transaction. If you read some of the forum threads you will see at least one company that took people's money and blatantly stole it by not delivering the prepaid batteries. That's part of the reason we are very sensitive to payment methods. Paypal, as I understand it, has limited protection to customers and claims expire 45 days after purchase which is typically sooner than it takes to receive the orders from China.
> 
> ...


hello JR thanks very much for your understanding.i believe 45days is enough to protect you.if delivered by express,you are likely to have received the goods already.if delivered by sea,the goods are on the ship.even though you have not received the goods,we may have sent you B/L.then what are you worried about?
i understand it takes time for you and other people to trust me,trust my company,trust our technology...i have the patience and confidence that this day will come.it is my pleasure to offer service here.i expect to do some business with you and other people who is interested in lifepo4 batteries.expecting your emails.


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## mszhao (Oct 17, 2009)

http://heter.en.alibaba.com/product/286725480-201188144/LiFePO4_battery_3_3V_115Ah.html
here is another website.you can find our products here clearly.


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## Jimdear2 (Oct 12, 2008)

mszhao,

I have a question which may have been asked and answered but I missed it.

Do your batteries require strapping and do they come with battery connector straps and hardware?

Since this hardware is not shown with the batteries are these extra charge items? 

If your batteries do not require strapping, why not? Is it because of the low charge and discharge rate, or some other reason?


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## JRP3 (Mar 7, 2008)

tony3811 said:


> I'm trying to decide between these three batteries for my EV and I don't know enough about Amp Hours, KWH, or C's to know what I'm getting or even talking about.
> 
> 38 LiFe04 (100AH) = $5064
> 10 Deka AGM (100AH) = $2732
> ...


I'm running 36 SE/CALB 100AH cells in my 2500 lb Fiero and have gotten as much as 50 miles max range. All my 100AH cells tested at 110AH or more, I've pulled 5.5C for a few seconds from them, though most driving is between 1-2.5C. If you will regularly be doing 40 miles, especially in colder weather, I'd recommend 120AH or larger cells, though if you heat and insulate the pack you'll probably be ok with 38 of the 100AH cells.


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## JRP3 (Mar 7, 2008)

mszhao said:


> here show you some pictures about our products and our company.


Interesting, I've heard of a gray cell but thought it was something new coming from CALB. One possible problem I see with the Heter cells, with TS and SE/CALB we are used to the cells coming in over spec, a 100AH cell is actually a 110 or better. It looks as if your 115AH cells are barely 115Ah's and might be a little less if I read your literature correctly. I think you are better off promising less and delivering more which gives you some protection from over discharge problems.


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## mszhao (Oct 17, 2009)

Jimdear2 said:


> mszhao,
> 
> I have a question which may have been asked and answered but I missed it.
> 
> ...


hello Jim,we have connectors without any extra charge.
pls see the picture of our connector.
and our batteries do not neccesarily require strapping.if you want to strap them,it is ok.this is not a problem of low charge or discharge rate.
batteries made by different manufacutures are of different technical features.i know TS batteries require strapping,isn't it?


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## mszhao (Oct 17, 2009)

JRP3 said:


> Interesting, I've heard of a gray cell but thought it was something new coming from CALB. One possible problem I see with the Heter cells, with TS and SE/CALB we are used to the cells coming in over spec, a 100AH cell is actually a 110 or better. It looks as if your 115AH cells are barely 115Ah's and might be a little less if I read your literature correctly. I think you are better off promising less and delivering more which gives you some protection from over discharge problems.


it is a good question.what is the actual capacity of Heter 115ah?
the actual capacity is always higher and never less.
Heter has been in lithium batteries many years.Heter has nothing to do with them.but it is know to us the relation between TS and SK.


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## JRP3 (Mar 7, 2008)

mszhao said:


> it is a good question.what is the actual capacity of Heter 115ah?
> the actual capacity is always higher and never less.


On this product page it says typical capacity 115ah and minimum capacity 113ah, which lead me to believe the cells could come in at less than 115ah. 
http://www.heter.biz/en/product/detail.aspx?ID=163
Do you test each cell for actual capacity and internal resistance, and do you provide that data?


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## mszhao (Oct 17, 2009)

JRP3 said:


> On this product page it says typical capacity 115ah and minimum capacity 113ah, which lead me to believe the cells could come in at less than 115ah.
> http://www.heter.biz/en/product/detail.aspx?ID=163
> Do you test each cell for actual capacity and internal resistance, and do you provide that data?


among hundreds of 115AHcells,there are indeed a very small amount of cells which is below 115Ah.It is estimated only1%~2%cells are 113~115ah,the remaining cells are above 115AH,a certain part of them are over 120ah.this space is limited,i can only show part of the data list.
but you can consider our 3.3v110ah or 2 cps of 3.3v50ah in parrallel .we have stock of these batteries(delivery time within 15days exlude shipping time).for the 115ah,no stock there are these days.sorry i get notification until today.


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## mszhao (Oct 17, 2009)

you can see most of the actual capacity is above 115AH,some of them are over 120ah.it's a pity the pictures here is not so clear.
this is only an example of 115ah.the other cells are with the same situation.so please never worried about this.we will definitely offer more and never less.nothing is more important than customer's satisfaction.
we aim at doing business in long and pleasant term.


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## JRP3 (Mar 7, 2008)

mszhao said:


> you can see most of the actual capacity is above 115AH,some of them are over 120ah.it's a pity the pictures here is not so clear.
> this is only an example of 115ah.the other cells are with the same situation.so please never worried about this.we will definitely offer more and never less.


It looks like of the 49 cells shown 5 of them are less than 115AH. That's about 10%. I'd be a bit disappointed if my order included those cells.


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## mszhao (Oct 17, 2009)

JRP3 said:


> It looks like of the 49 cells shown 5 of them are less than 115AH. That's about 10%. I'd be a bit disappointed if my order included those cells.


hi JR you are very careful person.
this data list is not the one that we sent to our customer.it is a record of our batteries in stock and were selected at ease by me.the average capacity is higher than 115ah.this is for sure.have you ever noticed that how many pertentage of cells that is over 115ah and how many cells over 120ah?
and the 5 cells'capacity are 114100(-0.9ah) 114143(-0.9ah) 113225 (-1.8ah )113672 (-1.3ah )114747(-0.2ah)mah,totally-5.1ah.
then we take some cells over 120ah to make up these cells with less capacity.only one cell over 120ah can do it!
on the whole,you still get much more capacity.
if you can not accept any cells with a bit less capacity,no problem.
we will treat this very seriously and delecte all the less cells.
moreover,we will choose the cells with closest technical parameter.so their capacity will be very close to each other.
generally the actual capacity of cells will be over 115ah when we make a battery pack.
for the cells less than 115ah,we will treat them in other way.
in a word,the actual capacity is always a bit higher than how many AH we charge.


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## zwmaster (Nov 23, 2009)

mszhao said:


> hi JR i admit you are very careful person.
> this data list is not the one that we sent to our customer.it is only the datas of 49cells that was selected at ease by me.the average capacity is higher than 115ah.this is for sure.have you ever noticed that how many pertentage of cells that is over 115ah and how many cells over 120ah?
> and the 5 cells'capacity are 114100(-0.9ah) 114143(-0.9ah) 113225 (-1.8ah )113672 (-1.3ah )114747(-0.2ah)mah,totally-5.1ah.
> then we take some cells over 120ah to make up these cells with less capacity.only one cell over 120ah can do it!
> ...


 
I'm following this thread with interest. 
When cell are used in string (normally in EV) the whole string is limited to the cell with minimum capacity (if we don't want the risk of destroying the week cell or to overcharge all others). Balancing can help to some degree, but only in "overcharge area" not in discharge phase. 
Am I wrong with these assumptions?


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## mszhao (Oct 17, 2009)

zwmaster said:


> I'm following this thread with interest.
> When cell are used in string (normally in EV) the whole string is limited to the cell with minimum capacity (if we don't want the risk of destroying the week cell or to overcharge all others). Balancing can help to some degree, but only in "overcharge area" not in discharge phase.
> Am I wrong with these assumptions?


your question makes sense but not completely correct.
we have the following measures to protect the batteries:
1,consistency is important for any battery packs.without good consistency,some cells may be over charged/discharged.we make sure good consistence of each battery pack before sending out.
2,protection from charger.
 Intelligent temperature compensation function in the charging process, preventing the damage to battery caused by charge-off or charge due, greatly extending the lifespan of the battery.
3,protection from BMS
BMS not only monitor but also manage and balance the cells.
in the above ways,batteries are protected both in charging and discharging process.
thus battery pack can be lasted as long as possible


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## JRP3 (Mar 7, 2008)

zwmaster said:


> I'm following this thread with interest.
> When cell are used in string (normally in EV) the whole string is limited to the cell with minimum capacity (if we don't want the risk of destroying the week cell or to overcharge all others). Balancing can help to some degree, but only in "overcharge area" not in discharge phase.
> Am I wrong with these assumptions?


You are correct in that your usable range is limited by your smallest capacity cell, and balancing cannot change that. I feel it's very important for packs to be as closely matched for capacity as possible, and indeed if they are close enough they really don't need active balancing. I run my pack with no BMS at all and just use my smallest capacity cell as the limit.

mszhao, are you saying that you ship cells matched by their capacity? Could the customer specify that all cells be within 1 AH of each other? I would suggest selling any cells less than 115 AH as 110 AH cells so as not to disappoint customers. I think human nature causes us to calculate the best case scenario when building a pack, so the 10% cushion that TS and SE cells provide by under rating their cells can help prevent people from being unhappy with their cells and give them better range than they were expecting. It also allows cells to retain their rated capacity longer as they age.


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## mszhao (Oct 17, 2009)

JRP3 said:


> mszhao, are you saying that you ship cells matched by their capacity? Could the customer specify that all cells be within 1 AH of each other? I would suggest selling any cells less than 115 AH as 110 AH cells so as not to disappoint customers. I think human nature causes us to calculate the best case scenario when building a pack, so the 10% cushion that TS and SE cells provide by under rating their cells can help prevent people from being unhappy with their cells and give them better range than they were expecting. It also allows cells to retain their rated capacity longer as they age.


yes of course we will match their capacity to make a good battery pack.
we must and have managed to minimize the distance of capacity of each cell.
if most of the cells are less than 115ah,we will sell them as 110ah without doubt.anyhow thanks for your kind advice.


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## JRP3 (Mar 7, 2008)

Thank you for your willingness to discuss in detail. Ideally a member here or a trusted dealer could get one of your cells for testing and post independent results.


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## tony3811 (Jul 30, 2010)

Dan, Flipson, Everyone... thank you. Based on what I've read and the links you've pointed me to I have decided to go with LiFePO40 batteries from Thundersky. I'm doing a 100AH battery, on a 120volt system, and if the calculations are correct then it will work out great... thank you. 

As far as purchasing, I'm going with a local distributor in the SF area so that I can drive up to the warehouse and pick them up myself.

Thanks again! 

Tony


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## JRP3 (Mar 7, 2008)

Which distributor and what price are you getting?


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