Building a boost-battery using A123 Cells

[jumpjack]

I bought 20x A123 cells (70A/120A, 2,4 Ah) to make some experiments with battery building, BMS, and so on: I have two old electric scooters, a Zem Star 45 (1500W/60V, 2x60V/24Ah Li-Ion batteries) and an Oxygen Lepton (1800W/48V Lead-Acid battery). Both of them have old batteries no more capable of powering the vehicles for much kilometers; I'd like to see if by adding a "boost battery" I can keep using them.

So I bought two BMS, a 48V/60A/150A and a 60V/60A/150A.

I preferred cells equipped with tabs because I read it's very difficult to solder tabs, but I think there's an issuye here: the tabs are 1 cm wide and less than 0,5 mm thick, which means the section area is less than 5 mm^2: is this enough to carry 70A/120A?!?
Another issue is that tabs are no split in two over the batteries like these ones:

They look more like these:

Are they fake or what?!?
I bought them here, just to avoid chinese products!
http://www.linergy-shop.de/product_info.php?info=p494_a123-anr26650-m1a-2300mah-lifepo4-zelle-a-version.html

Here you find my blog (in Italian) about pack building:
https://jumpjack.wordpress.com/tag/a123/

 

[dogman dan]

You should be able to test the internal resistance of the cells, and find out quick if they are fake.

If voltage sags like crazy at one or two c discharge rates, they are fake. The tabs should be up to 5c or so, they don't look that thin to me.

If you think about it, you aren't going to be pulling 160 amps from a single cell through a single tab. You will have a parallel group of cells. When you connect a group of cells to a wire, that wire needs to be big enough to carry the current from all the cells added together though.

 

[jumpjack]

You should be able to test the internal resistance of the cells, and find out quick if they are fake.

If voltage sags like crazy at one or two c discharge rates, they are fake. The tabs should be up to 5c or so, they don't look that thin to me.

0,3 mm.

If you think about it, you aren't going to be pulling 160 amps from a single cell through a single tab.

Perhaps not 160, but possibly 60: this is a boost battery carrying just 150 Wh, it's use is to sustain high current demand during accelerations!

 

[dogman dan]

So 60 amps from just 1p of those cells? Uh huh. 4p would then be 15 amps per tab, that's what I'm trying to say.

Do some tests, and see how hot the tabs get. Cool is good. Warm is acceptable. Hot means it's too much.

 

[999zip999]

Be careful as the case is neg. and the pos. tab can hit the neg.side of the case and short. Only the center post is pos.

 

[jumpjack]

the case is in plastic.

 

[dogman dan]

Yes, and it's easy to melt holes in it as you solder, especially torch solder. Then the tab can contact at the edge of the top of the case. Many just don't realize that the entire metal can is the - till somebody points it out.