New here and have some capacitor ?s

[dialadrone]

Hey y’all I’m working on my first emoped built mostly out of parts I had around. It has a 48v controller with 63v caps and motor with a 60v battery. Not the ideal combo but it’s what I have. The battery has never been charged over 60v and it ran great until today.

I went to ride it for the first time in about a week today and now the bike seems to loose power If I go over 15 mph. At about 17 mph the bike powers off and won’t turn back on. If I check the voltage of the battery after it dies with a multimeter it is way down to 25v. After it sits for about 15 minutes the voltage goes back up to 59v.

I’m a little unsure what the capacitors in a cheap controller do? Would a blown cap cause to much current to go through and trip the bms on my battery? Can a bike even run with a blown cap?

Last does this look like a blown cap or just some Bay Area corrosion?

Thanks for the help and sorry for the néw guy questions.

 

[amberwolf]

I went to ride it for the first time in about a week today and now the bike seems to loose power If I go over 15 mph. At about 17 mph the bike powers off and won’t turn back on. If I check the voltage of the battery after it dies with a multimeter it is way down to 25v. After it sits for about 15 minutes the voltage goes back up to 59v.

That means the battery has a problem inside where it's BMS is shutting off output to protect it from damage.

This could be voltage sag, overheating, imbalance of cells, or simply not being charged up full enough to work properly.

If it is a "60v" lithium battery, then that probably means 60v is it's *average* voltage, not it's full one. If true, then it's probably a 16s battery (60v / 3.7v = 16.something, round down), which means it should be charged to at least 67.2v to fully charge and balance it.

If 60v is really it's full-charge voltage, then it's overcharged for a 14s battery, and undercharged for 15 or 16s 3.7v-average / 4.2v full type of lithium cell. It also doesnt' work out for LiFePO4/s 3.6/3.65v full cells.

Without more complete info on the battery itself, I am just speculating. If you provide more detailed info about it, I can give you better answers.

But in any case, it isn't likely anything to do with controller capacitors.


Test ride the bike with the voltmeter on the handlebars where you can see it when it cuts out, and watch what voltages you get under various riding conditions--the heavier the load, the lower the voltage will go. When you see the voltage at the lowest point just before it shuts off...that's where the battery is panicking and shutting down. Make a note of all of what you see, especially that last, because it will help you determine the problem.

 

[dialadrone]

Without more complete info on the battery itself, I am just speculating. If you provide more detailed info about it, I can give you better answers.

But in any case, it isn't likely anything to do with controller capacitors.

I appreciate the reply! The battery is a 60v 29ah niu scooter battery. I’ll have to brainstorm around how to get my multimeter on there while riding. I’m totally confused since nothing has changed since I last rode it earlier in the week, the bat is at 59v and now I can’t even get to the end of the street?

 

[electric_nz]

That corrosion looks very bad- rip out those caps and replace

 

[amberwolf]

I appreciate the reply! The battery is a 60v 29ah niu scooter battery.

Are you using hte original charger that came with it? If not, does this charger output the exact same final voltage the original did?

If you don't know, that's ok, just say so--it's very important that we figure out what the actual fully charged voltage is *supposed* to be, so we can make sure it is actually being fully charged, and thus is able to do it's balancing, etc. Otherwise we don't know if the problem you're seeing is a sudden failure, or just the end result of not being able to balance or fully charge for however long it's been used that way.

If it is this exact kind (not necessarily from this place)
https://www.ebay.com/itm/Niu-N1S-battery-accu-lithium-60v-29ah-electric-scooter-/174525126129
then based on what it says "Niu N1S Battery Remanufactured original Panasonic 60v 20ah lithium ion " (if this is accurate)
it would probably a 16s and 60v would have to be it's average voltage, not it's full voltage. So it would have to be charged to at least 67.2v to work as designed, and charging to only 60v will never fully charge it or balance it. If it is 16s, then about 48-51v would be empty or very near it, and would shutoff somehwere around that voltage.

This site
https://www.niu.com/en/n-series/battery/
says
"We have taken 170 battery cells and connected them in parallel to create a robust 29Ah "
(leaving aside that they couldn't connect them all in parallel or it would only be 3.7v )
but 170 doesn't divide up into anything that makes a tyipcal "60v" battery. The closest it comes is a 17s 10p battery, which with the typical 18650 would be a 63v battery, average voltage, and 71.4v full voltage, and 51-56v would be near or at the shutoff.

Based on the behavior you've reported seeing, I think this last is actually the most likely thing. If it is true, then we need to know what voltage your charger actually charges it to, because 60v isn't even nearly half full (which would be 63v).

Another possibility is suggested by this on that page:

Furthermore, we have adopted PTC technology which compartmentalizes each cell, so if one cell goes awry it doesn’t compromise the performance of the entire battery pack.

THis means that each cell has a device in it to cause a high resistance if too much current flows thru it, so if you have cells that aren't contributing current then other cells in the same group will try to make up for that, and then their PTCs will shut them down, and other cells in the same group will then have evne more load and *their* PTCs will shut *them* down, so almost instantly the entire group is disconnected, and the BMS would then shutoff the pack because it isn't working anymore. When the PTCs cool down and recover, the BMS will detect the cells again and turn itself back on.

This also fits the behavior you've seen, where it takes significant time for it to turn itself back on.

I’ll have to brainstorm around how to get my multimeter on there while riding. I’m totally confused since nothing has changed since I last rode it earlier in the week, the bat is at 59v and now I can’t even get to the end of the street?

Just to be certain:

Just rode it normally with no problems, turned it off, parked it, left it for a few days, then rode again now but now it has a problem?

No charging, didn't leave it turned on, no rain, no puddles, no bumps, didnt' get knocked over, hand-wheeled from one spot to antoher, no weather changes, etc.?

Nothing happened on the last ride, or before, like a crash, a fallover, someone knocking it over while parked, no rain, etc? Completely plain and ideal conditions, etc?

(important in troubleshooting to know *everything* that happened, in sequence...any step could be the cause and thus help find the problem).


If so, and assuming it's actually being charged to it's full charge voltage (which it doesn't sound like it is), then something in the battery has probably just suddenly failed, a cell has gone bad and drained other cells in the same group, or a balancer in the bms has stuck on and done the same thing, and that cell group is now lower in capacity / voltage than all the others.

 

[amberwolf]

That corrosion looks very bad- rip out those caps and replace

There is corrosion there, but it's not from the caps--it's almost certainly from water that's gotten in and created an electrolysis path from the main power lead to the shunt (positive to negative), and allowed copper leaching from the traces/pads there (or the power lead wires).


FWIW, if the caps had failed, they would almost certainly have bulging tops or sides, or be lifted off the board by the bulging rubber cap underneath, and there would probably be dark liquid stains at the leak point, as well as white corrosion on the caps and around them (from corroding aluminum on the cans). I don't see that.

It is, of course, possible that the water intrusion that corroded the copper to make the green stuff you see also got in other places and damaged other parts...but the controller proobably wouldn't work at all if that were the case, or would work in an unusual way (odd noises or behavior from the motor, etc), and not just cause the battery to shutdown after a very short ride. (this too, could happen, but it isn't that likely).

Using a new controller of the same type (with the same shunt mod) would test this theory...but I really think there's something with the battery, most likely not being fully charged, rather than the controller or anything else.