Range extender packs freak me out.
However, they can be made a bit safer by fusing the extender pack’s discharge.
The rider safety downsides of discharge fusing don’t really apply to an extender pack. The main remaining downside is added resistance.
FTFY
it’s not bad to aim for identical pack voltages, but the it’s also not bad to have the packs .1V per cell off of eachother, so long as you plan to either not fully discharge the packs/are going to charge them together before going out
To add to that, they also need to be closer if they are in the mid-charge range. On the top and bottom of the ranges, they can be slightly further apart, I think.
So then it would seem to be better to only use dual packs if they each had a common-wire-BMS and they were both wired for discharge.
No bypass, no separate wire BMS.
Notice how I made a nice helpful reply concerning technical details and machines, without any direct insults to a human.
Though the capacity change per voltage change ratio changes at different charge levels I don’t think that affects the level of current flowing between the packs when connected. That would be determined only by the combined resistances and voltage difference (Ohm’s Law).
Doing it at a lower voltage (for both) would, I think, result in the current running for a longer time though. I guess that can be viewed as a negative.
Contrary to what this thread sems to suggest, I want to run two different battery packs (Same cells) to the same charge port using XT60 connectors to an existing 20S 8P and a new 20S 4P (35 cycles difference between both) is this approach feasible ?
Depends entirely on the small details.
Are you planning to leave them connected or to reconnect them periodically?
No it’s a permanent design I know voltage surge when connected and disconnected may cause damage or worse I was just making sure I was acknowledging all the variables. Thanks for the info
What BMSs are you using?
Are they double-blocking (common wire) or single-blocking (separate wire) ?
I don’t really know what you
Mean by that, my board is a Kaly XLR, I’l probably use the same BMS twice. It’s an LLT 20S smart BMS 50Ah discharged bypassed.
That’s not going to safely work. That’s a double-blocking BMS. Bypassing it causes other issues as well.
Also found this BMS, don’t know how you tell difference between normal and double blocking, I usually prefer bypassing for safety reason in case of malfunction lemme know if it would work with that one.
Using two BMS doesn’t work very well unless the ESCs are powered independently with no wire interconnections, and this isn’t good because then they don’t share a ground and can’t communicate with CANBUS, UART, PWM, et cetera.
At a minimum you’d need high side switching BMSs that had double-blocking charge ports, and BMS that switch the high side seem extremely rare. The chances of you finding that [for a reasonable price] are extremely low.
What you should do is make one battery from the two packs.
Indeed might have a problem using two BMS since the 2nd won’t be able to cut charge if overcharged how about connecting in parallel all balance lead with good quality wires and soldering, I have all the equipment for this. Soo at the end i’l only have one BMS to the 20S 12P
Yes, connecting the balance wires together and using one BMS seems the only workable option.
Thanks for the help. Simple yet effective solution i’l only have to change the Ah with the Metr app.