I have an Acedeck NYX Z1 with the 14s5p Molicel P42A pack. I love basically everything about this board, but am always left wanting in the range dept.
I am not super versed in the DIY side of theings (yet), but would like to extend my range.
From talking to people that are more comfortable with batteries, they say I should be able to add another acedeck pack in parallel “no problem.” I plan on buying Acedecks slightly smaller NYX Street battery pack and adding it in a pelican case in parallel to my pack hopefully making it effectively either a 14s8p or 14s9p.
i had a similar idea with a different board and was advised against doing it that way as issues could arise mainly because both packs could discharge at different rates amongst other issues. i’d say it’s a better idea to deplete one battery and then plug the other battery into the esc if you go that route, or just get a new battery built which will probably be better for both weight balance and form factor
it could be made safer by having that external battery use a DCDC but then you might as well use whatever battery not 14S specifically… although that makes charging easier lol
This thread is begging for a @Battery_Mooch speech to get pasted in.
Search for all the threads already on this topic, and then let us know what specifically differs about your setup compared to those, and we can tell you how that affects the advice given out in other threads. Generally, using batteries in parallel can have some serious risks. But it’s all about the details. Do the work and we can help you. We’re not doing the work for you.
I can tell you this is not correct and possibly a large fire risk:
That’s preposterous…of course there can be problems. It’s pretty easy to damage a pack and possibly even set it on fire. But it can also go very smoothly and be as safe as using a single larger pack. Like just about everything we can’t just simplify things down to good/bad, safe/unsafe. Not without going into all the details that no one wants to deal with.
If you have things set up perfectly and do everything right, every time you use paralleled packs, then there’s no reason why you would ever have more trouble than you would just using a single larger pack.
The problem is that you need to set things up properly and use them properly and that takes a lot more knowledge than what we can toss you here. It’s why we default to recommending not to parallel packs.
Not because it can never be done safely, but because there’s just a lot to learn and do to make that happen. A forum is just not set up to get you all that info and make sure you use it properly.
My recommendation is not to parallel packs until you have learned what all the risks are and have taken the proper precautions to prevent them from becoming actual hazards.
You can ask specific questions here but things like “what do I have to worry about when paralleling packs” just won’t get answered. It would take half a day to type all that out.
If those two batteries have their BMSs and all safety equipment still intact, aren’t wired “bypass”, in other words the negative goes through – and not around – the BMS on both batteries, and they are at the same voltage when they are connected together and they are not disconnected once connected, there is a chance it may be okay. This also depends on the specific BMSs used and whether they are “double-blocking” or not. (how the BMS PCB is built) That’s a ton of ifs and also it’s not straightforward to find out how the BMS PCB is wired: this won’t be something that’s labeled on it.
They aren’t smart or bt BMS… but from what I thought I understood, so long as they were close in charge / voltage when hooked together they should charge / discharge at the same rate.
Putting new and old batteries in parallel is often a bad idea.
I’ve seen huge currents flow between 2 3s1p batteries than were only 0.3v resting difference, and the cells are same age/make, as they once were i series in a 7s 1p pack.
I’d have a way to use one battery until it was~ 3.3vpc, un plug it from esc, and plug in the other battery to Esc, and charge them separately.
I have some ‘ideal diodes’ which only drop 0.04v across them, but are only good for 50 amps, and I am not sure of their max allowable voltage, and they’d likely pose issues with regen.
EMTBs are using small water bottle range extenders. I dont know what goes into that, but they seem to not get anyone scared. I bought a thingie from ebay, that is supposed to make connecting two batteries together regardless of state of charge safer. I will snap a pic of it and hope some here can identify. I have some ga cells that I could parallel with my molis, but am hesitant. I was thinking of a box that had receptacles, like heavy duty speaker grill ball and sockets.
The cells for a 3S pack will probably have a total of at least 45mOhm of series DC internal resistance, if not a lot more. Add on the spot-weld, cell interconnect, wiring, and pack connector resistance and each pack is probably at least 50mOhm.
Connecting them in parallel means you have 0.1ohms of total system resistance for the current to flow through from one pack to the other. With a 0.3V difference pack voltage difference that results in 3A flowing between the packs.
What made you realize much more current than that was flowing?
The switch max voltage is probably limited by the MOSFETs they are using. You could check their Vds rating.
It would be very tough for that 0.04V drop to be at that 50A you mentioned. It would mean 0.8mOhm Rds-on (total) for the MOSFETs….verrrrry low. Unless it’s a huge switch with lots of FETs in parallel?
Good point about the regen. Unless designed for two-way current flow they would block regen and charge current.
this honestly sounds like a terrible idea and i would highly recommend either getting a new battery made or switching the connector from one battery to the other
Maybe a safer option is having xt90 outputs for both batteries easily accessible, maybe panel mounted. And then run an extension from your esc. Connect to one battery, ride, run out of juice, disconnect, connect to second battery, ride.
Won’t be the most aesthetically pleasing, but at least you don’t have to worry about separate pack voltages and cell health.
