Playing with A123 20Ah lithium cells

[Daox]

In that case you would need definitely a BMS to detect when the battery is fully charged when plugged in, and also when it is depleated so you can switch over to the engine.

[bennelson]

I like that you needed a micrometer to show how thick they are.

Glad you got them home without short-circuiting!

In all seriousness, that many amps, with terminals that close - be extra careful with anything conductive.

One thing I like about group 31 batteries is that their terminals are farther apart than my socket wrench is long! To me, that's a great safety feature!

[Ryland]

Are the tabs foil or thicker?

[bennelson]

They are almost like soda can aluminum, but just a little softer.

[Daox]

I did measure the tabs. They are 1.775" wide x 1" tall. The positive terminal is aluminum and is .010" thick. The negative is plated copper and is .007" thick. So, as Ben said they are very thin. I'll add this info to the first post.

[Frank Lee]

Originally Posted by Ryland

I'm blown away by how cheap lithium batteries are now!

Hmmm, 60 volts' worth of those would look mighty fine on the Songi!

[Daox]

I made some quick end plates last night so I can hook the cells up to my powerlab charger. Nothing fancy, but they're quite similar to what I plan to use when the pack is assembled. I do have a slight concern about using the nylon threaded rod for a long length of cells (for a much larger pack), but for something small like this it should do just fine.


Just two plates of 6061 aluminum with holes drill on the ends for the nylon threaded rod to go through and clamp down on.



Plates installed. I'm not sure if I'm going to tap the plates for additional connections or what yet... We'll see.

[jjackstone]

I would suggest cleaning the aluminum with alcohol or ethanol to remove the ink, factory machining residue, and general oxidation. Additionally I was thinking that a conducting gel such as heat sink compound or similar might make for better conduction between the tabs and the aluminum stock(that's just a theory though).
JJ

[Ryland]

I forgot all about the dissimilar metals like copper and aluminum, they should not be in contact with each other! aluminum oxide is also not conductive, so I'd get something like a scouring pad, to clean up your contacts then grease them with dielectric grease or conductive aluminum never seize on the aluminum side and copper never seize on the copper side.

[oil pan 4]

Any ideas where we can get some of these if there is no drive green expo coming to town?

These cells seem like they could replace my 123A LiFePO4 cells for a little less money and in a unit half the size.

http://ecomodder.com/forum/showthrea...s-18547-4.html
The battery I built is posted on the dieselplace link, its crude but effective.