@b264 is it standard that if the bms has a “B- or B0” Balance lead, it is intearnally connected to B-? How can you be sure they are connected. Genuine question.
Before charging through the balance leads, you should make sure the wires are rated for the charge current. For example, if you have 24 AWG balance leads, you shouldn’t use more than 3.5 amps for charging or you should connect the big black wire to the B-.
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You can use a multimeter and check reisstance between the two. Very low resistance means it’s connected.
There also shouldn’t be any kind of circuitry between them, as it likely connects to a common ground.
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Yes, what @TowerCrisis said and also why you should check to be sure. Sometimes you don’t even need a multimeter, you can see the copper traces connecting them if you look. But you should use a multimeter anyway and verify zero ohms between them.
Also some BMS don’t have B0 at all.
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thnaks for the info! im guessing a continuity test would also work?
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Still kind of new to all this, so I need to ask, what is this cable for? E switch install?
That’s the temperature sensor 
If you use this BMS for discharge, too (what I recommend) then you should connect B- in any case. Discharge (-) and charge (-) goes to C- on the BMS, no connection at P-.
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Why do you recommend using it for discharge to rather than charge only? Just wondering
Because of all the safety features like over-charge, over-discharge, over-temperature, short circuit protection for battery and charge port…
This BMS is for 60A cont. and can handle up to 110 or 120A for a short period of time. I use this BMS for discharge, too without any problems. And on my MTB I use a Bestech 50A BMS up to 100A. In the past I had a tiny BMS for charge only but I like the added safety.
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Where you found the max characteristics? I mean if a bms is rated for 60a, where I can find the peak current they can handle for which time? In the specs from bestech for example it’s nowhere mentioned. Always wanted to know that. As i was never sure I also never used a bms for discharge, only a fuse where I knew which current I can draw for which time.
Are you sure you don’t have those swapped?
This is a “discharge” style high-amperage BMS best suited for discharging through. There are pros and cons to both ways. Neither is “better”.
It’s the over current protection, the BMS in this thread has 120A (data sheet of manufacture). So 60A cont. is no problem, the BMS would cut off at 120A +/-10A. If the total battery max of both Vescs is set to 100A together the BMS will never cut off. But of course it would get hot when pulling e.g. 90A continious. So for your 4WD it’s maybe too small.
On a cheap/bad BMS the continious discharge rate is the same as over current protection (that’s why I don’t like Supower BMS). They claim 60A continious but in real life it’s more 30-40A because the BMS cut off at 60A which is a joke IMO.
My 50A Bestech BMS is 10 times bigger than my 40A BMS which I used for charge only. Because the 50A is real and the 40A fake.
When I ordered the Bestech BMS they only had the 50A in stock so they set 110A over current protection. I had a chat with a Bestech engineer where he confirmed that like 80A for 5-10 seconds and 100A for 1-2 seconds is no problem at all, just not continious. On every ride I reach between 60-100A but only a short period of time, never had problems with heat or anything.
As you can see on the diagram on the BMS, it’s charge and discharge on the same port (C-) so it’s 60A charge and discharge. I was confused in the beginning, too but had chats with manufacture who confirmed that only C- gets connected for both charge and discharge. And I have the same BMS in use connected to C- only so I’m sure.
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Really appreciate the helpful people that chimed in on this thread. I’m gonna have to get @Namasaki in here to help when I go to wire this BMS with lipos like the one in his famous 10s high power lipo thread.
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You first need to decide whether you will discharge through the BMS or bypass it and run it charge-only. You cannot know how to wire it until you decide that. There are pros and cons both ways.
The BMS in this photo is best suited to discharge through.
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I will probably run it for both charge and discharge then
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Do you plan to use 5x2s Lipos?
Most likely yes. Need to take some measurements. Either that or 2x 5s
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Modified the diagram above to your needs for 5x2s.
2x5s would be easier but more bulky.
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We need to add fuses on the charge port negative on these diagrams
I just haven’t fired up GIMP yet today