At a loss as to how to trouble shoot my BMS not discharging and wondering if you guys would be able to shed some light on if ive been an idiot and wired it up wrong.
The BMS is from LItech and looks very similar to a bestech one. Its 50amp charge 90Amp discharge as i wanted to discharge through the BMS ideally.
I wired it up using their pretty poor wiring diagram and other videos. the BMS will charge and balance when the charger is plugged in but when plugged into my vesc in via my anti spark switch i get no power on.
i have contacted them and they have not been very helpful and say they cant tell from my labelled photo how its wired and that i have probs wired it wrong. If i have then thats on me, but currently i think i have it wired as it should be.
so far i have:
Tried charging through the BMS which has worked and balanced the cells ( checked each cell)
The board will power up while on charge but not normally
Tried with the eswitch wires on the BMS connected and disconnected, no joy.
Any ideas what i could do next, at this rate i may bipass the discharge to get running again, but seems a shame as the BMS is so big if im just gunna bipass the main function i paid more money for.
The anti spark switch is there as it was part of my old setup and the image shown was me setting up the BMS for the first time before packaging it so left everything standard, even if plug direct into the VESC without the anti spark i get nothing.
The link is to the one i ordered and this is the one they sent me, i assumed it was a new model or something, since being in contact with them they havent said its the wrong one or anything.
Had the packs at storage charge and i charged up through the BMS and then checked cell voltage with my cell voltage checker and all cells were the same voltage at full pack voltage when the charger turned green.
My balance leads were what i was worried about but if i unplug the BMS side balance leads and check all cells, starting with the negative prob on the negative pin and work my way along from b1 to b12 i get the correct increase in voltage till i end on the last balance lead going to the primary positive giving full pack voltage.
You don’t have the red balance wire connected to anything on “P2 secondary” (we always count from negative to positive, but I’ll use what you have in the picture).
How would the BMS be able to sense the voltage on the last cell in that pack?
The red balance lead on P2 gives full pack voltage of the p2 so connecting the meter to that red and ground gives 22.5 volts.
After watching tutorials this res wire was always missed when using two lipo packs in series. If I did connect that wire I would have a spare balance lead at the end of the balance lead ?
Do you think that could be the source of the issue? I may draw it as a diagram and upload that to help.
First things first, use an Amass XT90S instead of an Amass XT90 connector, and test the setup without the antispark switch in the circuit. No reason to add another failure point when troubleshooting.
Second, I would triple check your balance leads as others have noted. You are also missing a “B0” in your text but there are 13 wires in the photo. So at the minimum, the text might be wrong.
The seller/distributor of the Bestech BMS units internationally (Litech power) does not charge enough to provide wiring troubleshooting, but we will gladly help you.
You also want a fuse on your charge port, rated from about 125% to about 250% whatever current you intend to charge at. So charging at 4A max, I would put a 7.5A fuse on there, for example.
Thanks again for the reply, I hadn’t seen xt90s connected and just had a look, good shout! I do intend on tidying up the wiring and hard wiring the packs and BMS into an enclosure so the xt90s will be gone after testing.
Ive uploaded a image and readings i just took as i feel i am being bad at explaining my set up so hopefully this helps me.
So i listed B1 -14 as total balance leads coming from the packs.
B1 - is connected to B- main negative on the BMS
B2- connected which gives me the 4 volts increasing by ~4v up to B6
B7 i missed as this voltage matches B8 and from online tutorials it said to miss this, because the cell voltage matched i thought this made sense. I could connect B7 then B8 but would have 2 matching voltages and be left with no where to connect b14 which is giving me full pack voltage at the end of the cells, or i could connect B7 and miss B8.
I will be charging at 5 amps so will add in a 8amp fuse to the charger.
Thank you for the help. I am glad for the help Litech has given but if it turns out i have wired it right and the board is faulty it would be nice to have some money back. if i am wrong and wired it up wrongly then i’m happy to buy another. Iim happy to add more pics and try bits but am still limited to one picture upload i think.
Bit of an update, been back and forth with litech, they have said they think that the e switch chip set is burnt out. I’m not sure if this is my doing or not?
Attached is the underside of the BMS and the pin layout. I know there is no used B14 on the BMS but when showing the layout of my wiring there is 14 balance leads coming from the battery packs. 1 of these goes to B-, (which on this board is one of the pins which saves running one to the big B- pad, i didnt know this was usually known as B0, thank you), and one is not used which is either B7 or B8. That leaves 12 used like you say.
Then it’s likely the standalone antispark switch is not the problem. To clarify, do they mean your standalone antispark switch, or an antispark chip set that’s on the BMS?
Sorry im struggling to follow in terms of B0+6 ,B1+6 and how that relates to pack 2. Does that mean how i have done it is not right with the skipping of one of the wires, what should i do with that wire? Sorry
They mean the antispark switch on the BMS, i just noticed that an area next to the BMS switch on the board was getting pretty warm.
If i remove the BMS and run my lipo packs, with antispark connected to my VESC it all works fine and thats how i’ve been riding so far.
I have just board a BMS bluetooth module after watching Lee Wrights youtube channel
i will run it bypassing the BMS on Discharge is the plan after reading the pros and cons on here.
Ah those diagrams make more sense and the way i read them shows me ive got my middle two balance wires connected slightly wrong. (although it did charge) i will change them but not sure it will make this BMS work, im not that lucky lol.
From what litech said i about the BMS switch wires, you can just connect them together and to have them connected when charging and discharging.
They want me to send the BMS back and if its their fault they will pay postage and the repair and if its my fault i pay. Think im going to cut my losses and not send it, if it turns out it is my fault it will cost me more than this new one ive ordered in the UK. Bit of a rubbish situation and a gamble.
Hopefully after your guy’s help and these diagrams will help with wiring up the new one when it comes
