Hi Everyone,

I'd like to know how you check the charged voltage of each cell in a 3s1p pack.

My LHS sells them all soldered and shrinked wrapped nicely and i'd like to know how i can use my multimeter to check?
do i have to desolder the pack to check each cell individually? and what is the leeway allowed for the difference? (how many volts? 0.1, 0.2v?)


Also how do you start charging a new pack assuming that the cells are balanced. take a 3s1p kokam 2000mah super high discharge cell as an example.



lastly how do you charge the individual cells if you find that they are unbalanced? unsolder them again?

Sorry if they are stoopid questions but i wanna learn more about these lipos before i start using them wholesale.

Thanks in advance to any one who answers my questions!

My Irate 3s pack has two extra small gauge wires brought out for checking the balance voltage of the cells. That is one reason I bought the Irate pack.
At least a couple of brands have the extra wires on their packs, the wires are there if you ever need to use them.
Vette

You don't need to unsolder the pack. You just need to get to each terminal. You can use a pin or something like that to go through the heat shrink and touch the terminal.

Good packs made with good cells will stay balanced. I have had my very small cells from Kokam get out so I started making those packs with center taps. It only happened to 2 145mAh 2S packs. since then I have made several 130mAh and 210mAh E-Tec packs without it happening so I have stopped putting in the center taps.

I am concerned about a large pack that needs center taps. Why do those cells get out of balance. Are they poorly manufactured so that they are not equal. I just don't know.

I fly almost exclusively E-Tecs now and haven't had a problem with balance. (Disclaimer - I sell E-Tecs so I might be called prejudiced.)

Marty

No need to unsolder cells, if you make your 3 measurements between the arrows as shown. You probably will have to remove some wrapping, so you might want to add some wires now, to the connected tabs, so you can check/charge individual cells next time.

If you use your cells hard, I can almost guarantee an unbalanced pack in the near future, so now might be a good time to prepare to rebalance them by adding taps.

I admit I am new to using Lipos but I think the center taps are a good idea.
I like having the manufacturer spend the extra nickel's worth of wire and time
to save me the trouble of cutting into a pack to check the balance. Probably as
the batteries continue to improve checking the balance will become a non issue
but for my piece of mind right now, I will be easily checking my $90. Irate pack with the factory installed center tap wires.

Vette

Rats, didn't show up

Originally Posted by uglystick

Rats, didn't show up

Nice! thanks for the pics.

I have checked my 3s cells, and the 2 outside which are bloated are 4.23
and the inner is 3.81 thats a massive 0.42 diff

nice...in future will have to check voltage before buying....zzzzzzz