# Group Battery Purchase in Los Angeles



## dimitri (May 16, 2008)

Alliance is a US based distributor, so I don't get how group buy applies to them 

A123 is the most expensive cell there is, plus assembling the pack from puch cells is a much harder effort than using large prismatics. Usually these are used for racing EVs, not your typical Lead conversions.

With so many US distributors these days ( see ads on the right side of the page ) I have not seen anyone doing group buys lately, it just doesn't seem worth the effort.


----------



## Bottomfeeder (Jun 13, 2008)

Thanks for your insight, Dimitri.

While Alliance is a US distributor, we still have to pay shipping and customs on the order from China. By combining our purchases we can each save a few hundred on that. A hundred dollars is a hundred dollars, even if it is on top of $7000.

I'm also getting quotes from Thundersky directly, as well as other battery manufacturers. I just started with Alliance, because they were the cheapest so far. I'll look at some of the other sponsors.

I am familiar with A123 prismatic pouches. A coworker just put together a large pack with pouches, and I've been picking his brain on the process. I must say, the result is a sexy, sleek pack that might be worth the extra cost and effort. Pouches would come with an extra 180lbs of weight savings, as well as amazing charge/discharge rates. It's something to think about. Since I don't have to make any decisions just yet, I can follow the pipe dreams for a while.


----------



## ElectriCar (Jun 15, 2008)

Thundersky cells have a higher internal resistance which means voltage drop across the cells. You probably know this but in case you don't, that is power that is consumed internal to the battery and thus lowers voltage output under load, think sag like. Though the sag isn't as much as our lead, I still want all the voltage available to go to the motor and not be consumed internally. 

Though the internal resistance may not be much, when you are drawing hundreds of amps it can be rather large. I'm thinking the internal resistance of HP cells is like .001? don't recall exactly but seems like the TS cells were maybe .002. Not a large number but still was double the HP cells, whatever it was. 

To figure the voltage drop, multiply the amp draw times the resistance number to get your voltage drop (loss). Ie for 400A across .001 ohm resistance is .4V. Across the TS cells 400*.002=.8V, a HUGE difference! 

So for a 144V pack of 45 cells, that's only an 18V drop leaving 126V to your motor versus a 36V drop on the TS cells leaving only 108V for your motor, NOT GOOD!


----------



## PatricioIN (Jun 13, 2008)

I've gotten a quote (and a phone call!) from the US rep. for CALB. They have opened a warehouse in Pomona, CA and prices are $1.25/Ah from the warehouse. That includes straps and connectors. You would have to pay for shipping inside the US, but I assume they'd let you come pick them up if you're close enough. They have a physical address and a phone number in the US.

here is the guy's contact info:


Keegan Han
Sales Manager
[email protected]
Tel: 909-865-8809
Cell: 626-383-2957


----------



## ElectriCar (Jun 15, 2008)

Just talked to Keegan and he told me the warranty is 2 yrs. Also noted on the specs the internal resistance is <.0006 ohms. So a 400 amp draw would make the voltage drop per battery .24 or less & for a 45 piece pack at 144V you would have a drop of 10.8V max, leaving 133V minimum to move the vehicle!


----------



## MN Driver (Sep 29, 2009)

ElectriCar said:


> Just talked to Keegan and he told me the warranty is 2 yrs. Also noted on the specs the internal resistance is <.0006 ohms. So a 400 amp draw would make the voltage drop per battery .24 or less & for a 45 piece pack at 144V you would have a drop of 10.8V max, leaving 133V minimum to move the vehicle!


Don't forget that internal resistance is a moving target dependent on factors such as temperature and state of charge. 50% state of charge during the winter won't do as well as a battery fresh off its charge on a hot summer day. It's hard to work off of manufacturer provided internal resistance numbers because we don't know all the factors. ...but based on those who use them, I don't think you'd be disappointed. Especially comparing these to flooded lead-acid, there is no comparison, IMO.


----------



## azdeltawye (Dec 30, 2008)

ElectriCar said:


> Thundersky cells have a higher internal resistance......
> 
> So for a 144V pack of 45 cells, that's only an 18V drop leaving 126V to your motor versus a 36V drop on the TS cells leaving only 108V for your motor, NOT GOOD!


 
I’m not sure where you got the information on the Thundersky cells but it is incorrect. I have 45 TS 180 Ah cells (144V) and the voltage only sags to 133V when drawing 540 Amps. This includes the voltage drop introduced by all the connecting links and 35 feet of 2/0 welding cable.

This is the voltage and current seen at the controller according to the data logger files I took from the Soliton-1 controller during a typical acceleration event.


----------



## ElectriCar (Jun 15, 2008)

azdeltawye said:


> I’m not sure where you got the information on the Thundersky cells but it is incorrect. I have 45 TS 180 Ah cells (144V) and the voltage only sags to 133V when drawing 540 Amps. This includes the voltage drop introduced by all the connecting links and 35 feet of 2/0 welding cable.
> 
> This is the voltage and current seen at the controller according to the data logger files I took from the Soliton-1 controller during a typical acceleration event.


Dude that is awesome! Did you run that vehicle on lead before? Just curious the difference in the performance versus the same pack voltage using lead. Also what is the difference in the watts/mile in the TS vs lead pack?


----------



## ElectriCar (Jun 15, 2008)

MN Driver said:


> ...internal resistance is a moving target dependent on factors such as temperature and state of charge. 50% state of charge during the winter won't do as well as a battery fresh off its charge on a hot summer day...


Wow, I didn't know that. All I've found is the internal resistance numbers for various batteries on battery vendor websites.


----------



## azdeltawye (Dec 30, 2008)

ElectriCar said:


> Dude that is awesome! Did you run that vehicle on lead before? Just curious the difference in the performance versus the same pack voltage using lead. Also what is the difference in the watts/mile in the TS vs lead pack?


 
Sorry, the vehicle doesn't have any Pb battery history (other than the starting battery). The conversion started it's life on Lithium...


----------



## Bottomfeeder (Jun 13, 2008)

Thanks for the insight! I definitely feel better about getting Thunderskys if we went that route. I know they're very popular.

Does anyone have any experience with failure rates of Thundersky batteries? Is it normal to buy extra cells in case one or two are duds? What about other batteries?

I looked at a few companies on the side that are advertising, and they seem more expensive than Alliance and/or direct from China. CALB cells from Pomona could be an option...


----------



## EVfun (Mar 14, 2010)

No dud TS cells in my pack yet Bottomfeeder. I bought 42 and installed 40 cells. All the cells read within 0.01 volt of each other when received and the 2 not installed have only dropped 0.02 volts over the last 7 months (they are down to 3.28 volts.) I have hammered them briefly up to 5C (300 amps on a 60 amp hour pack) and not one cell has dropped down to 2.5 volts. The cells within the pack are staying very close though I don't have a lot of cycles on the pack and I have never removed more than 30 amp hours (about 50% DOD.) I'm impressed with the newer TS LiFeYPO4 cells!


----------



## Bottomfeeder (Jun 13, 2008)

At the moment ThunderSky is still in the lead as the battery we'll likely go with. I've got the money in my bank account right now, but I'm still going to wait until January, so a few others can join. And who knows, prices might just slide down a tiny bit in the meantime. Right now we've got about 6 interested purchasers. And oddly enough, we'll be buying batteries for 3 Spitfire conversions. 

There's still plenty of time to join in on the purchase and even have a say in which brand batteries we go with.


----------

