BMS Hook up for 14s 2P lipo - without smoke and fire!

Looking to hook up a BMS to a 14s 2P pack. I am fine with the BMS side as I have done this before...on a 13s pack.

The question someone might be able to help we with is around if it OK to hook up 2 X 14S Lipo pack in parallel and then hook up to a BMS.

The 14s packs are multistars that are configured as 6S+4S+4s in series. This work fine standalone.

So to hook up in parallel do I just put the 14s packs main leads in parallel making sure the pack are at the same voltage and also put the balance leads in parallel too and connect to BMS.
This sounds right but I think I remember reading here on the forum that this can cause issues. Anyone can confirm on way or another.

I have attached photos of the 2 X 14s packs I look to parallel and also the wiring diagram for the BMS for a single 14s pack. SEE PDF ATTACHED>

Any help appreciate. Also I assume if 14s 2p works then I could do the same model for a 14s 3 setup........

Any help appreciated.

I am curious about this as well. I have the same 14s2p setup. That works great but a BMS would be convenient. I would not think you would want to parallel the balance leads but I don’t know that for fact. Seems like you would want either a 28s BMS or two 14s ones.

If you want to use a BMS (good idea), then you need to parallel the balance leads. There used to be some parallel adapter boards that had connections for multiple packs. Not sure if those are still around. Before connecting the balance wires in parallel, you want to make sure the voltages are close to the same or you might have excessive current when you make the connection.

If you don't parallel the balance wires, the BMS won't be able to detect a problem in the packs that aren't directly connected.

An alternative is to use separate BMSs for each pack, then put the outputs in parallel.

gone_walkabouts said:

Looking to hook up a BMS to a 14s 2P pack. I am fine with the BMS side as I have done this before...on a 13s pack.

The question someone might be able to help we with is around if it OK to hook up 2 X 14S Lipo pack in parallel and then hook up to a BMS.

The 14s packs are multistars that are configured as 6S+4S+4s in series. This work fine standalone.

So to hook up in parallel do I just put the 14s packs main leads in parallel making sure the pack are at the same voltage and also put the balance leads in parallel too and connect to BMS.
This sounds right but I think I remember reading here on the forum that this can cause issues. Anyone can confirm on way or another.

I have attached photos of the 2 X 14s packs I look to parallel and also the wiring diagram for the BMS for a single 14s pack. SEE PDF ATTACHED>

Any help appreciate. Also I assume if 14s 2p works then I could do the same model for a 14s 3 setup........

Any help appreciated.

Click to expand...

I.M.O., it's all wrong.
One of the benefits of LiPoly is, if done right, you don't need a BMS.
LVC-there should be one in your controller, probably 42 Volts (for a 48V unit). 3.00 V/cell is kinda low, so you need to have an alarm, a PITA. I run either 12S or 13S, for LVC's of 3.65 V or 3.325 V, both very usable. I carry enough capacity that I almost never hit the LVC(maybe, once a year). And I also use a voltmeter for a "fuel gauge(another benefit of LiPoly, it discharges very linear). For 14S, a Cycle Analyst or perhaps one of the new sine wave controllers w/ an auto-ranging LVC would be better.

Charging-I got away from the unreliable "toy", RC balance chargers years ago and Bulk charge w/ the great Mean Well HLG-320H-54A;
https://www.mouser.com/ProductDetail/Mean-Well/HLG-320H-54A/?qs=DNaZHaGatO34iLHvVd%252bT2w%3D%3D&gclid=CjwKCAiA0IXQBRA2EiwAMODil6htC8us-T1BvA5hzWNv84RA0b5loF2VrWC-NC-yjuczGVBPx1-dahoCLbkQAvD_BwE
I adjusts up to 58 Volts, so it could be used w/ 14S.
I use it w/ Battery Medics to ck the cell Voltages and for the very rare event I need to balance. I go w/ the largest bricks that fit my space (to keep the brick count as low as possible) In my case 4) 6S/10,000 mAh bricks configured 2S/2P for a 12S/20,000 mAh pack;

View attachment 1

Here, 4) Battery Medics are hooked up. In your case 4) 7S bricks would have been ideal and you would only need 4) Battery Medics, but W/ your current configuration, you would need 6) B.M.'s



And here, charging my 12s/5,000 mAh aux. pack

If you press on w/ your BMS idea and decide to parallel the balance taps, be careful. The cell Voltages need to be exactly the same or you will get a "cross-rush" that will melt the wires. And remember, the Current actually "flows" backwards, neg. to pos. You can buy parallel adapters from Hobby Partz, Progressive RC, on Ebay and sometimes Hobby King and they are much easier than cutting and soldering ea. balance wire.

Cool - so seem that you can parallel the main leads and parallel the balance lead. Will do it outside just in case.Yes made the mistake of jointing two pack before in parallel with 20% voltage differences..i did not have a BMS in the lower one so it ran away.......
See video of local fire brigade........

https://www.youtube.com/watch?v=BSIss2MjxeA


[youtube]https://www.youtube.com/watch?v=BSIss2MjxeA[/youtube]




Currently do not have BMS and using battery medics etc - this is Ok but i am tried of been a BMS.......okay when packs are new but as they get older the seem to not say so in balance

As love the Smart BMS with bluetooth connection....make sense been able to see that this pack is balanced......

Currently do not have BMS and using battery medics etc - this is Ok but i am tried of been a BMS.......okay when packs are new but as they get older the seem to not say so in balance

Click to expand...

Sounds like you need new Multistar rather than a problematic BMS. It's cheap enough.

I've been running 2 10S 4P Tumich batteries with parallel BMS leads on my wife's trike for almost 1.5 years without a problem. Just charge, check occasionally and forget. Works for us.
otherDoc

It should work fine with a BMS and the packs paralelled, but I wouldn't use the BMS low voltage cut off to determine when to stop. You don't really want to go much below 3.5v per cell to keep the pack in balance. The BMS can balance a bit at the top of the charge, but it can't deal with the big discrepancies you get from deep discharged lipos, so you need a voltmeter, LCD or whatever to show your pack voltage, which you shouldn't let drop much below 48v. It'll be falling rapidly at that point so be careful.

Thanks Dave! We do carry wattmeters and alarms now but the best way I know to help batteries last is to know their capacity and use only about half of it. We have standard bike routes and distances of about 20 miles, and that use only half or so of our battery capacity. The meters and alarms are for making sure that the true capacity is not exceeded if there is a battery problem.
otherDoc