Thanks for the input guys!
hotrod: haha exactly what I would have done
Dave S: Thanks for the sight, I've actually done a few of those connectors for charging multiple packs myself. Nice to have graphics
EDIT: BTW, are you the same Dave_S as at URC? just noticed from the parallel balancing board thread
Originally Posted by
howardcano
If the cells are significantly different in capacity or internal resistance, you may need to increase the gauge of wire and connector current rating over that used for the balance connector.
You are probably aware of this, but make sure that the cells to be connected in parallel are within a few mV of each other when you make the connection, to avoid large currents.
Right, I know if one power source (lipo cell in this case) gets say .3 volts lower than the other in series, then the higher voltage source will pull almost all the current. It's ridiculous how a very small voltage difference means a huge load difference in parallel. I would only be connecting them at storage or a full charge though so the surge current shouldn't be an issue.
Originally Posted by
Dave H
Yep, conceptually the idea makes sense, good question, but the balance wires may not be large enough to handle a significant imbalance with large loads. Full scale lithium E cars are typically connected this way, but the relative load is much smaller (Range is an issue, but they do go longer than 10 minutes or so)
In any event it’s best to somewhat regularly check pack balance when starting charging. Lipos are relatively cheap and expendable, shouldn't be using packs with balance issues anyway. Especially in a high draw use.
The Tesla, leaf, ect probably huge huge wire/tabs together to wire in parallel too lol Impressive that almost all the technology used in those cars is less than 10 years into development too. The packs I would be doing this to though are 4s 5amp packs though, so they were $50 lol
To both Howard, Dave H, and everyone else: I just thought of this.
While in use, say two cells get .05v apart in parallel, then by that point, the lower cell is constantly being charged by the one it's wired to. Say the internal resistence of both cells is 5 Milli-ohms (.005ohms) so with V/R=I (derived from V=IR) in the circuit around just those two cells, the voltage difference is .05 and total resistance is .01ohms. .05/.01=5amps charge for the lower cell, 5amps discharge from the higher cell. At this rate the cells would equal off almost immediately. Then the only concern is the voltage drop being different between the two.
I'll probably try it on my mini-revo first since those packs were $8 and already have seen some use...lol If I start running into warm balance wires, I can always order some .1 or .01ohm resistors to put in between them to limit the current lol