Qstns about a homemade 3p li-ion pack.

[powerup93]

Im am trying to make a 3p li-ion pack for my p7 mag. I have three li-ions in parallel utilizing simple ~20ga copper wire connections across the batteries and if I measure the current at the end of the whole pack it says only about ~1.6A to ~2A. But if I measure at the intersections of the 3p li-ions, they pull ~2.7A (pretty much exactly what I want). Is this a normal behavior with strictly parallel packs? On the other hand, my 4S C-size Nimh makes 2.8A+ though.

 

[VidPro]

I measure at the intersections of the 3p li-ions, they pull ~2.7A .

I dont understand what your saying here. it doesnt make sence the way i am interpreting your connections vrses the current your seeing.

|--{=====]--|
|--{=====]--|
|--{=====]--|

 

[powerup93]

I was measuring the leads off of the parallel pack and it was low. But when I measured at the inter-connecitons between batteries, it was high and what i expected.

 

[VidPro]

I was measuring the leads off of the parallel pack and it was low. But when I measured at the inter-connecitons between batteries, it was high and what i expected.

well (assuming i understand) it should not be.

the current from each parellel item should be about the same.

|--{=====]-----------1A----|
|--{=====]-----------1A----|-----3A total----|
|--{=====]-----------1A----|


if your getting differences in amps from each cell item
|--{=====]-----------0.5A--|
|--{=====]-----------2A----|-----I leave out the load here, because there is cross charging or imbalances----|
|--{=====]-----------1A----|
or something like this picture
Then
your cells are either not balanced, or at different voltages (or charge levels or ammounts or capacity).
the cells should all be at the same voltage (about) before tying them together. and it is better if they are also the same capacity.

Notes: putting an ampmeter in line with anything adds in some resistance via the leads and the shunt, so not everything you read is as it would be exactally. using much better copper speaker wire (for example) when doing the low voltage stuff, for the leads, and keeping the leads short helps reduce the resistance. your average DMM leads have a lot of resistance.