Need help on re-wiring BMS without shocking myself!

[cloudcover]

hi there -

long story short, i bought a battery system consisting of two separate battery packs and one capacitor bms. the bms failed so i need to swap out the old one with a new one (for now i'm going to use the existing wiring). does it matter what order i disconnect and/or reconnect the wires? there are a bunch of wires and i want to do it in a way that minimizes the risk of me getting any kind of electrical shock or of somehow harming the battery system.

i'm attaching a photo of the battery system as well as a close-up of the bms wiring, in case that's helpful.

thanks in advance!
cc

somewhat longer story for those who might be interested:
i wanted to obtain a customized battery pack for my bike and decided to order one from evassemble.com. i tried to be as detailed as possible with my requirements, including sending pictures of my bike, where i wanted to mount the packs, detailed diagrams of the packs, etc. but alas, what i received was not suitably configured and won't fit my bike properly. and unfortunately, they haven't been very helpful. when i pointed out the issues, the reply i got was something to the effect of: "this was a prototype (i.e., custom built) system and in such cases there is inevitably some changes required and so you can make those changes yourself." not what i'd hoped for. oh well...live and learn.

thanks in advance for helping!
cc

 

[dnmun]

what did you do to the first BMS to kill it?

not even sure what you are asking if they sent you directions. do you think their directions are wrong? there is a thread around here somewhere about how the BMS hookup directions were wrong.

 

[cloudcover]

not even sure what you are asking if they sent you directions. do you think their directions are wrong?

my mistake for not making my question more clear...apologies. my question is simple, really. for now, i'm planning to use the same wiring they supplied but just swap out the old (nonfunctional) bms with the new one. so the question is just this: does it matter what order i disconnect or reconnect the wires? i'd just like to do it in the order that's least likely to either shock me or ruin the system (e.g., by shorting something).

i'm going to edit my original post to make this more clear, so thanks for your comment.

 

[dnmun]

no need for sorrow. their BMSs provide enuff of that.

make sure you know where the sense wires have to connect so you don't reverse them by accident. i almost did that once.

but what did you do to the first one to damage it?

there is full battery voltage on that BMS too so make sure not to short something by accident. so connect the red from the pack last.

 

[Spacey]

I never got on with the capacitor based bms from that joke called Eveassemble.....seemed to dump really high voltage (over 4volts) into the last cell for some reason when balancing.

If you get stuck order a bms from Cellman, I have had no problem with over 10 of them so far....really easy to wire up.

Also check all your battery connections on the Headway pack they gave you.....best to order some 10awg RC wire from hobby king and get rid of the crappy crimped wires that came with it. Also buy some 20awg RC cable for the balance leads.

 

[cloudcover]

I never got on with the capacitor based bms from that joke called Eveassemble.....seemed to dump really high voltage (over 4volts) into the last cell for some reason when balancing.

If you get stuck order a bms from Cellman, I have had no problem with over 10 of them so far....really easy to wire up.

Also check all your battery connections on the Headway pack they gave you.....best to order some 10awg RC wire from hobby king and get rid of the crappy crimped wires that came with it. Also buy some 20awg RC cable for the balance leads.

yikes! didn't know i had so many things to worry about. my whole purpose of getting a pre-built system instead of putting one together myself was to avoid all of these things. i'd been trying to get a pack custom made by cellman, actually, but ended up switching to evassemble because cellman was busy with other business and didn't have the time to make a custom pack.

how can i tell if the bms from evassemble is dumping high voltage into the last cell? or more generally, whether it's working properly or not? and in terms of the battery connections on the headway packs, i assume that means i need to take off the shrink wrap, is that right? and if so, is it pretty straightforward for me to get more shrinkwrap to put back on when i'm done?

thanks,
cc

 

[cloudcover]

no need for sorrow. their BMSs provide enuff of that.

oh man...i'm getting a bad feeling about this based on all of the negative comments i'm hearing about their BMSs. :|

but what did you do to the first one to damage it?

the wiring was labeled in a confusing manner and so i inadvertently connected my motor controller to the charge cable on the bms instead of the discharge cable. at least i think that's what happened...i can't remember exactly, to be honest...it was a while ago.

there is full battery voltage on that BMS too so make sure not to short something by accident. so connect the red from the pack last.

in terms of the "connect the red from the pack last," just to be clear, can you tell me what alphabet letter that corresponds to on the photos that i attached to the post? also, just to confirm, that's the main thing i need to worry about...just making sure to connect that wire last? if i do that, i shouldn't have much other risk of some electrical problem? and finally, does it matter in what order i disconnect them when i'm detaching the old bms?

thanks again,
cc

 

[Spacey]

I never got on with the capacitor based bms from that joke called Eveassemble.....seemed to dump really high voltage (over 4volts) into the last cell for some reason when balancing.

If you get stuck order a bms from Cellman, I have had no problem with over 10 of them so far....really easy to wire up.

Also check all your battery connections on the Headway pack they gave you.....best to order some 10awg RC wire from hobby king and get rid of the crappy crimped wires that came with it. Also buy some 20awg RC cable for the balance leads.

yikes! didn't know i had so many things to worry about. my whole purpose of getting a pre-built system instead of putting one together myself was to avoid all of these things. i'd been trying to get a pack custom made by cellman, actually, but ended up switching to evassemble because cellman was busy with other business and didn't have the time to make a custom pack.

how can i tell if the bms from evassemble is dumping high voltage into the last cell? or more generally, whether it's working properly or not? and in terms of the battery connections on the headway packs, i assume that means i need to take off the shrink wrap, is that right? and if so, is it pretty straightforward for me to get more shrinkwrap to put back on when i'm done?

thanks,
cc

Just leave the pack on overnight and check each cell with a volt meter every few hours and note the voltages...see if they even out over
time.