@goldenHusky great, thanks! What about the fuse? What do I need there?
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The switch could handle more, there is just no ATO sized fuse with more than 40 amp. 40A is like the standard value for a fuse in an electric board, I don’t think you will pull more, especially at 12s.
My LED switch is powered directly by a 12V BEC. Using resistors to drop the voltage is an option, but it burns more power than you’d expect…
The LED in those switches are usually 15 mA
R = V/I = (50.4-12)V / 0.015A = 2.56 kΩ
However, this burns over half a watt of power:
P = I^2R = (.015A)^2(2560) = .576W
Those little resistors you see everywhere are only 1/4W resistors. So you would need to use two 5.2kΩ 1/4W resistors wired in parallel, or two 1.3kΩ 1/4W in series. Or use a 1W resistor like the image above
If you want to use only a single 1/4W resistor, you’d have to limit your LED to current to 6mA by using a resistance value around 6.4kΩ. The power dissipation in this case would be .23W
You don’t need a fuse if you are discharging through a 60A BMS. The BMS is essentially a self-resetting fuse. If you happen to go over 60A for some reason, it just cuts the load and automatically recovers a few seconds later. Much better than blowing a fuse and completely shutting down your board
The switch only cuts the negative line, so you don’t need to bridge the pads. You can use the anti-spark without a fuse by just connecting one of the two positive output solder pads (upper right in image above) to your positive line. You don’t even need to use heavy gauge wire. A small 22AWG wire is more than sufficient
Do you mean these 2 up here? (Blue Circle)
Yeah those ones. They are connected to each other via large traces on the PCB. So they are effectively the same
So ive tried wirong up my bms but it will only output 2 volts - input voltage is 46 volts. Am I doing something wrong? I plugged it in in the order: B- Balance cable P-
Whoa don’t give it 46V input! You might have fried that thing already
The SuPower BMS only acts on the negative main line. The positive main is completely untouched.
B- goes to Battery negative P- goes to anti-spark switch negative (or VESC negative)
@jmasta Im sorry, that was a but unclearly worded - the voltage across B- and Battery + is 46v. The voltage right before the anti spark switch (and at P-) abd the plus line is 2v.
That’s weird…
Use your voltmeter to check the following voltages, and maybe I can help you troubleshoot
- B+ to B- = 46V
- B+ to P- = ?
- B- to P- = ?
@jmasta Without “load” (no vescs plugged in) B+ to P- = 43.58v B- to P- = 1.926v With load: B+ to P-: 0.0v B- to P-:46v Thinking about it, this is very wierd.
check your balance lead order. its easy to get them crossed. weird shit happens when the streams cross. hellfire and damnation, dogs and cats living together, total protonic reversal.
@longhairedboy Ok, so from B- as - i tested the voltages for all Balance wires. From Left to right, they have the following voltages: 3.7 7.5 11.3 15.17 19.1 23.4 26.9 30.8 34.6 38.4 42.2 46.1 As I understand it, the voltages without load from my last post would be somewhat correct? Edit: i tested without the bms - the vescs lit up. Looks like the problem really is there.
hmmmm… the distance between those numbers should be more similar than they are. The pgroup cell voltages should be more even, but yours appear to be as follows:
3.7, 3.8, 3.8, 3.87, 3.93, 4.3 (not so good!), 3.5, 3.9, 3.8, 3.8, 3.9
They should all be within a tenth of a volt of each other. I think you may have overcharged one of your p groups some how. If you have a single cell charger, try charging each p group individually and see if it will go all the way up to 4.2 without issue, then assemble the pack and se if the BMS complains, then fully discharge the whole pack and re-charge and see if the BMS is able to balance it again properly.
@longhairedboy Ok - I have a single cell charger! Ill hook the batteries up now to test. Also just tested - when I plug the vesc in, it lights up for a second before turning off. Maybe the BMS limiting the output? Checking the batteries - some cells are at 3.9, while some are at 3.8. Is this a problem?
@longhairedboy @jmasta I’ve also noticed that the BMS makes a sound when it gets olugged in (circuit is closed). Its high pitched and goes even higher until it is bearly audible to me. Sounds like something charging up?
They should be as close to each other as possible. If you can get them all to 3.9 (if that’s the highest besides the overcharged 4.3v outlier) it would be ideal. And ideally if you could discharge that overcharged pgroup down to 3.9 slowly using a small drain like from a flashlight or tiny motor or something then that would be good too. Otherwise you may have to rely on the BMS to trim it down which may not happen if the issue is with your BMS.
The point of all of this is to see if the cells stay balanced, that way you can see if your BMS is doing its job or fucking off instead.
I’m in the middle of a pgroup transplant on an evolve mod pack that got sent back. The cells they ordered weren’t from a reputable source, so some of them just weren’t up to snuff and made the whole pgroup suffer. So now i’m digging through the spare cells they sent trying to line up a few good ones and charging them individually on my Sunkko. The charger on the Sunkko 788H is legit. IT takes a while but you get a full and properly trickled in charge. But at 3-4 hours per cell its taking me a couple days.
TL;DR i feel your pain.