Playing with A123 20Ah lithium cells

[Daox]

That doesn't look like a horrible deal. However, like I said, the A123s have far superior power density. The GBS cells can only put out 10C pulse where as the A123s can put out 18C pulse. Their life is also supposidly much longer than Chinese prysmatic type cells. The only ones that seem to have a rival cell IMO is CALB's new CA type cells (the grey ones).

[sendler]

Originally Posted by Daox

That doesn't look like a horrible deal. However, like I said, the A123s have far superior power density.

At this grey market price, the A123 cells are a great deal. The normal price through a certified vendor is usually almost 5 times higher. Then, not so much even considering the higher discharge rating.

[Daox]

I would definitely agree. Though I have heard typical prices are around $60/cell (not verified).

[oil pan 4]

I have seen authentic A123 AMP20 cells for as high as $99 each.
But could not get a reply from the company selling them.

[sendler]

I like the innovative case and terminal set up of the GBS and the dialed in BMS/ balancing modules/ charger that will help optimize the cycle life. The GBS cells are the same price per Wh as the raw A123 cells which still need to be packed up into a protective case and fitted with terminals and balancing boards for EV use. It would take me a lot of extra work to put together a 48v/ 100ah pack out of 80 of those AMP20 cells though it would turn out to be a bit smaller.

[oil pan 4]

I finely got around to putting together my super diesel cranking battery.
I built my 8 AMP20 cells into a high power diesel cranking battery. Its most of the way wired up, just need to put the finishing touches on it.

Just hooking up 8 cells (worth somewhere around 0.6KWH) took several hours. Is there really anyone wanting to wire up a few dozen of these for use in an electric vehicle. Because it would be a huge PITA.

There has got to be a better way.
Are there any premade clips or connectors we can buy???

Check back soon for pics!

[sendler]

Tons of info about the Amp20 cells from the Ebike builders at Endless-sphere.
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Endless-sphere.com • View topic - A123 20AHr Pouch Cell Battery Build & Info Thread
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Li batteries are fussy about cell balance. You will want to check the voltage of each parallel group of cells carefully at first to make sure they all stay in balance. If one cell group goes too low it will lose capacity compared to the others and next time the battery is charged, it will go much higher, sooner, and puff gas. At least these LiFe cells don't usually catch fire like the earlier LiCo chemistry when overcharged. 3.6v per cell is very full for LiFe. Also, if low state of charge Li cells are hit with any sizeable charge current when they are below -5C temp they will undergo permanent plating and lose 20% of their capacity in one charge cycle.

[oil pan 4]

Originally Posted by sendler

Also, if low state of charge Li cells are hit with any sizeable charge current when they are below -5C temp they will undergo permanent plating and lose 20% of their capacity in one charge cycle.

I did not know this. Is this a LiFePO4 thing or something that applies to all lithium batteries?
I dont run my CR26250 cell based starting battery down very far in between chargings. They have hardely seen any use below -5'C (temp) but I know when they get much below freezing they really start to hate life.

[Daox]

I've always heard charging is an issue in the cold, but not discharging. Do you have any specific info to point me towards that shows this?

[oil pan 4]

Me?
Well my problem is my batteries cant put out enough power to run the glow plugs and crank the engine when the batteries are below freezing.
Thats why I installed them with forklift battery quick dissconnects, so that they may be quickly and safely removed and installed even in total darkness. That will allow me to protect them from the cold at night.

To crank the diesel engine I need those little CR26250 batteries to run at about an 18C rate for a few seconds.
When the temperature gets below freezing you cant get 18C out of them anymore.

My solution; build a bigger battery, adding AMP20 cells to my existing CR26350 packs so that the batteries only have to run at 6C rate to crank the engine.
They should, or at least I hope they will put out more than 6C to well below 0'F.