Hi
I have parallel chevy Volt module on my Smart last year with great success (first pic). Amps are shared between module whatever the internal resistance of the cells since they are mecanically connect (8 AWG wire).
More details here: http://www.diyelectriccar.com/forums/showthread.php/smart-fortwo-ev-high-power-version-51472p31.html
Nom I'm planning to build few 45v 135Ah or 180Ah battery with few 12S modules (45v 45Ah). I hope to be able to reuse the orange original BMS connector to plug defferent module in parallel via a custom ''PCB board''.
The small wires on this connector have a external diameter just under 0,0625'', so my bet is they are 24 AWG. Of course this kind of small wires will fused instantly if large Amps pass inside. The trick is to reduce current flow with a resistor to save the small wire.
A small search show me a fusing current of 29A for 24AWG wire and I bet they can handle 4-5A for few minutes without problem. So, let me know if I'm wrong:
0,1v of imbalance between two parallel cells under load will give a current of 2A in the link between both cells with a 0.05 Ohm resistor.
0,5v of imbalance (huge and improbable imbalance) will give a current of 10A with 0.05 Ohm resistor... right?
*If you ask why parallel the cells, the answers are:
-12S BMS only
-Without BMS, manually balance 12 cells is easy. 36 or 48 cells, harder, longer, complex.
-Without BMS a lower capacity cell will cause problem at full charge or full discharge
-Without BMS a cell with a slightly different internal resistance will end with an imbalance who can cause problem at full charge or full discharge.
I have parallel chevy Volt module on my Smart last year with great success (first pic). Amps are shared between module whatever the internal resistance of the cells since they are mecanically connect (8 AWG wire).
More details here: http://www.diyelectriccar.com/forums/showthread.php/smart-fortwo-ev-high-power-version-51472p31.html
Nom I'm planning to build few 45v 135Ah or 180Ah battery with few 12S modules (45v 45Ah). I hope to be able to reuse the orange original BMS connector to plug defferent module in parallel via a custom ''PCB board''.
The small wires on this connector have a external diameter just under 0,0625'', so my bet is they are 24 AWG. Of course this kind of small wires will fused instantly if large Amps pass inside. The trick is to reduce current flow with a resistor to save the small wire.
A small search show me a fusing current of 29A for 24AWG wire and I bet they can handle 4-5A for few minutes without problem. So, let me know if I'm wrong:
0,1v of imbalance between two parallel cells under load will give a current of 2A in the link between both cells with a 0.05 Ohm resistor.
0,5v of imbalance (huge and improbable imbalance) will give a current of 10A with 0.05 Ohm resistor... right?
*If you ask why parallel the cells, the answers are:
-12S BMS only
-Without BMS, manually balance 12 cells is easy. 36 or 48 cells, harder, longer, complex.
-Without BMS a lower capacity cell will cause problem at full charge or full discharge
-Without BMS a cell with a slightly different internal resistance will end with an imbalance who can cause problem at full charge or full discharge.
