Bms soldering help

2-alex-2 · November 3, 2016, 8:50pm

Ok so my bms has arrived and wanted to know a few things. Is anyone running the same bms as me and help with wiring it up. If not hopefully shed some light.

This is the bms 6s 5a I won’t be running the esc through this it’s only for charging but would like an led to activate and deactivate with this along with my esc low voltage cut off.

So far I think I have this right. B+/ B- is where I solder the battery wires to ? P+/P- is where I solder my charging wires? And lastly where would I solder a led indicator so if the bms picks up a low cell and the bms shuts down the led. Would I wire Led+ to P+ and them led- to D- would this work ?

chinzw · November 3, 2016, 9:25pm

There’s a separate circuit for LVC and HVC, you would need to identify is and plug to that. If i were you, i wouldn’t mess with the bms. Any change in resistance, etc, will probably change the way it works.

chinzw · November 3, 2016, 9:43pm

Actually, now that i think about it, this should be pretty simple. 12v led and a 10k/20k voltage divider between d- and battery positive.

2-alex-2 · November 3, 2016, 9:46pm

That’s if D- is the hvc output from looking at the boards routing I think it is.

Stef · November 3, 2016, 9:47pm

What you suggest probably works fine, though if the ESC low voltage cutoff is earlier than the BMS’s, then the LED wont really be of much use as your ESC will cut the power to the motor when your BMS is still lighting up your LED.

2-alex-2 · November 3, 2016, 9:50pm

That’s correct but if in say a years time when cells are getting old and say once set of cells drop voltage faster than the others the bms will pick that up I hope. As esc only picks up the total combined voltage.

chinzw · November 3, 2016, 10:18pm

Yep, for the ESC LVC he will need to wire to the esc, not the bms.

2-alex-2 · November 3, 2016, 10:20pm

But it’s only a 5a bms so I won’t do that will let the esc handle the low voltage cutoff and the bms handle the low cell voltage but led indicator but hopefully bms will actually not be needed as esc will do its job.

chinzw · November 3, 2016, 10:23pm

So… lets see, if you want an LED to turn off when the BMS LVC kicks in, just wire as i said. If you want an LED to turn on when the ESC LVC kicks in then you will need to wire it to the ESC.

2-alex-2 · November 3, 2016, 10:33pm

No just for the bms lvc as I have a battery % guage on top on the deck as well so should all be fine anyway but just making sure it’s safe and not ran to low and seeing as I’m rebuilding the board may as well do it now.

chinzw · November 3, 2016, 10:40pm

then just do a voltage divider with 10k/20k resistors between the d- and battery +, easy stuff. If you want the led to turn on when the LVC kicks in you can use a PNP transistor.

2-alex-2 · November 3, 2016, 10:44pm

Was just gonna ng to get it to turn off when it kick in easier to wire up.

chinzw · November 3, 2016, 10:46pm

It will be ON all the time tough, as long as the battery is plugged to the BMS

2-alex-2 · November 3, 2016, 10:51pm

Well my switch has a separate led on it when switch the vedder soft switch on the led will come on but powered by the bms I hope lol

chinzw · November 3, 2016, 10:55pm

Oh, then you can just use the + from the antispark switch and the D- from the bms, that way you wont need resistors or anything else.

2-alex-2 · November 3, 2016, 10:59pm

Yea it’s also a 24v switch so the led should already have one in it I would emagine.

2-alex-2 · November 4, 2016, 3:08pm

Does anyone recon that I could upgrade this to handle more amps. As if you compare my pictur about and this 12a version.

There just seems to be more fets at the one end. Would it be possible to get it to run say 60/80a if I got some better suitable fets

chinzw · November 4, 2016, 6:32pm

Im not sure how the over current protection works on this BMS, so it might not be possible, but looking at the first picture: You dont even need to change the FETS, just buy 4 more of the exact same FETS that are already on the board. Those FETS are in parallel, so by adding 4 more you would theoretically increase the A rating from 5A to 15A. Or if you need more amps you can replace the FETS with ones that are rated even higher.

But, as i said before, depending on how the over current protection is designed this might not work.

2-alex-2 · November 4, 2016, 8:24pm

Yea I’m guessing they are 5a fets but if I got higher amp ones not sure if would work or not all depends on weather the board can handle 80a

chinzw · November 4, 2016, 8:35pm

The traces are fine for higher amps, they tend to use the same pcbs for low and high amps, sometimes even same board between 6s and 7/8/9/10s or higher. But whatever is shutting down the fets in case of an over current, might still shut down at 5A even if you change the fets.