It depends on the numbering scheme of your BMS.
Assuming the numbers start with 0 being the B- pad, then 1 would be 3.7v more positive than that, and on and on.
In that case, the numbering would look like this:
So only the negatives of the packs that feed 1~5 would go to B-. The negatives from the ones that feed 6~10 can either go to 5, or be not connected at all.
Okay that all makes sense now, so thank you for that. Although I thought that the cell that supplied the main+ lead also supplied the first balance wire, with the the next cell providing the second, and so on
Also, when you say that the negatives from 6-10 can be either connected or not, is that optional? Or is it one or the other haha
One of the balance wires must be connected to pin 5 of the balance connector, as labeled in my last post. It doesnât matter if itâs the most-positive wire from the negative half, OR the most-negative wire from the positive half, OR both. You can see in the diagram that those two wires are basically shorted by the series link anyway.
The only thing you absolutely should NOT do is not have anything connected.
Again, it depends on the BMS. Most start from B- and count up towards the positive rail. Some start from B+ and count towards the negative rail.
Some start with B- being labeled 1, and go up to 11 for a 10s BMS, some start with B- being 0, and count to 10. Yours apparently does away with that first negative wire on the balance connector entirely, and just uses the main B- pad.
You will have to refer to the specific BMS you plan to use.
Iâve been using Kafuter adhesive for a while, specifically the white thermal glue. Itâs quite good.
For what itâs worth, Iâve had very good luck doing JST strain relief with the black got glue. If your gun is hot enough, you can leverage the tip leakage to finesse just enough to create an even concave application around the entire connector with essentially no mess and good results.
Itâs what I ended up doing for the drone batteries.
Maybe itâs worth trying.
Sorry for all the questions Iâm just a bit confused here. So a lipo has a balance connector that has one more pin then the number of cells. So my 5s battery has 5 positives and then the last wire of the connector is striaght from the negative lead. So is your quote saying I can just wire the bms 1-10 with the positive balance leads, wiring the negative balance from the pack supplyng the positive lead to B- (pins 1-5), and ignoring the negative balance lead from the pack supplying the negative lead (pins 6-10)?
No, you have that backwards. The negative balance wire from the negative pack goes to B-, because it is the most negative. Then the other five wires go to the balance connector, then the negative wire from the positive pack gets skipped, then the other five wires go to the balance connector.
Look at my diagram again, itâs all there.
Send me a picture of the balance connector labels on the BMS youâre using please, I want to check something.
Alright, not only did you have this bit backwards,
but also your drawing
is numbered in reverse order.
The most negative balance wire is B-, and goes to the first pin on the BMS. Thatâs for the wire from the negative terminal of cell 1. The second pin on the BMS is the wire that goes to the positive of cell 1, and also the negative of cell 2.
So in order, the eleven pins on the BMS connector are:
Pin 1: B-, cell 1 negative.
Pin 2: Cell 1 positive, cell 2 negative.
Pin 3: Cell 2 positive, cell 3 negative.
Pin 4: Cell 3 positive, cell 4 negative.
Pin 5: Cell 4 positive, cell 5 negative.
Pin 6: Cell 5 positive, cell 6 negative. (This is the one you can have either wire connected, or both)
Pin 7: Cell 6 positive, cell 7 negative.
Pin 8: Cell 7 positive, cell 8 negative.
Pin 9: Cell 8 positive, cell 9 negative.
Pin 10: Cell 9 positive, cell 10 negative.
Pin 11: Cell 10 positive.
Measuring with a voltmeter, with one probe connected to the negative wire going to the vesc, you should see the following voltages:
Pin 1: 0v
Pin 2: 3.7v
Pin 3: 7.4v
pin 4:11.1v
pin 5: 14.8v
pin 6: 18.5v
pin 7: 22.2v
pin 8: 25.9v
pin 9: 29.6v
pin 10: 33.3v
pin 11: 37.0v
what gauge wire is everyone using to make their balance cable ?
if my charger output is 4A, would AWG22 (or perhaps even AWG24) be most appropriate ?
I only have AWG18 and AWG26 at home, so I suppose AWG18 is overkill and AWG26 is a no-go ?
I just hate those cheap plastic wires that come with the BMS and want to replace them with silicone wiring.
Iâve used 26awg silicone for balance wires without issue. Balance current is tiny with most bms. If you were using something like a 2a active balancer, that would be a different story.
Yep, looks good.
Sorry to be so nitpicky, but if you get that wiring wrong, the best-case scenario is that the BMS doesnât do its job. Less-good outcomes are also possible, ranging from insta-dead BMS, to possible battery fire.
The charge current wonât flow through the balance wires, so it doesnât matter. The only current that flows through the balance wires is the balance current, and thatâs usually less than 100mA. Generally not recommended to go much smaller than 28AWG or so, just because wire that small is mechanically weak and more fragile.
26 should be fine.
thank you guys
Use 22/24. The balance wires only carry a few hundred mA. The PVC is annoying to work with. But itâs functional enough for most use cases
If I understand your question correctlyâŚ
The smaller connector is probably 2.0mm pitch JST PH.
The larger connector is probably 2.5mm (not 2.54mm) pitch JST XH.
Easily confirmed by measuring the pin-to-pin distance though.
I love standards sooooo much⌠screwed me over with the JSTs i bought for my bms
Sorry to hear that!
