9s charger - capacity and charge

Hi Guys,

I have 3000 or so cells soon to be all tested.

I have been into ebikes for the last few years so i have a heap of lipo chargers laying about, one of those is the UNA9+ that charges and capacity tests 9 cells , i have two of these units :

Basically i should be able to charge and capacity test 18 cells at once : all individually

Great thing is i can set the charge and discharge voltages too so i can fine tune it. It gives the time it took to charge each cell and the capacity, very handy for us DIY powerwall nerds..

So next up i simply have to make up some brackets , any good ideas ?

I was thinking some copper pipe brackets, i could screw one end in and then shape the other side to be a contact ? only need something simple. Thinking ill put tiles underneath for fire protection.

Cheers

Jesse

Can that charger actually test all 9 cells individually? Ie does it report back the capacity per cell?

Brackets for what? Holding cells? If so get your self some good holders.

Are you sure this device does discharging and capacity testing? Doesn't look like it!

yep each cell independently full details on discharge capacity per cell ! these are about 120USD each. so cost wise if your starting from new, then the opus probably are the go. these also so get shitty about low volt bats, so for those you need to use the opus i guess.

holders for charging the cells for testing. Not mounting in the packs

I did a quick test tonight,

The unit shows both charge and discharge capacity for each cell. Is there any benefit to knowing the charge capacity ? Maybe if I know how much it took to charge vs discharge I can get a better idea of cell health?

The discharge is whats important. But in generall for good cells the charge should be just slightly above dishcarge. Lets say max 1%. But this is also shown in terms of heat and internal resistance and self discharge.

Charge capacity can be interesting if it is above the specified capacity or above a reasonable capacity for a used cell. Since charging efficiency of a lithium cell is usually very high this means something is wrong and energy was used to do something other than charging the cell. Most likely that energy is turned into heat and the cell got hot during charging.
On normal cells the ratio between discharge and charge is always almost 1. Maybe 0.99 or 0.98, don't know the exact figures, but definitely in this range.

jestronix said:

yep each cell independently full details on discharge capacity per cell ! these are about 120USD each. so cost wise if your starting from new, then the opus probably are the go. these also so get shitty about low volt bats, so for those you need to use the opus i guess.

holders for charging the cells for testing. Not mounting in the packs

Click to expand...

The method I use for low voltage batteries is boost them up with an RC charger (imax b6 clone) and use the NiMh program and very low charge current - 50ma (keep a good eye on them - low capacity cells can reach high voltages very quickly) Once they reach 2.8v I change to the LiPo program - and charge them at 100ma.

The opus take care of low voltage cells so there is generally no need to do it anywhere else. The cells it wont take ie below 1v or something then bump charge with just a resistor for a couple of secodns and into the Opus and it takes over

The 9s charger really is only good for charging. The discharge capacity readings are way off. 1000mah test is really 1600 mah. However their charge capacity readings are very close.