Ebike stops but power is on.

[dannello]

Using ebike to get to work the return journey is up hill. On return uphill 3 times, at the almost same spot, the motor stops working. Leave it for 30 secs and it starts ok but stops again after 100 Mtrs. Repeat and it stops again after 100 mtrs. At the time it stopped I replaced the battery with a spare to continue my journey but it still stopped after 100mtrs. On another day I used the spare battery for my daily journey but again it stopped at almost the same spot uphill. With both batteries the LED is still on when it is stopped indicating full charge. Lights still work when it is stopped. Multi meter tested both batteries, they were fully charged. One battery was a little bit hot but not extreme.. Seems to happen only on the uphill journey when using throttle and pedal power. Hill not that steep. Distance travelled only about 2 miles when it stops. Battery is 48v 15 amp. Can anyone advise what the problem might be. Is there an auto cutout somewhere? the motor or controller, Im pretty sure its not the battery. The brakes are not being used uphill.

 

[amberwolf]

Does the system itself actually power off (display go blank, etc), or does it just stop assisting?

If the latter, it means the controller is detecting a limit exceeded (too high a temperature (usually in the motor, but some monitor themselves, too), too low a voltage, etc) and turning off the motor to prevent damage to it or to the battery.

If the former, it usually means the battery's BMS is detecting a limit exceeded (temperature, voltage, current) and turning off it's output. The battery meter on it's casing would probably still show whatever charge it has, just the output would turn off until the limit resets.

What voltage does the battery read during the climb? Does it drop more and more until hte moment the system stops assisting? (and then rise back up?) What voltage does it read after the system stops assisting, and when it then allows the assist to start working again?

Is there only one LED on the battery meter, or several? If only one, how does it indicate the charge level? Etc.

Note that a battery getting hot means it is not really capable of the demand being placed on it; if it were correctly designed and built and rated for the job it's doing, it shouldn't heat up much for even the max current draw it is supplying. Unfortunately it's very common for batteries to be rated and used at their max possible capabilities, which is pretty hard on them, and can cause problems with them over time.

Is the battery 48v 15Amp (A), or 15Amp-Hour? (Ah) The distinction is very important, becuase the first is how much current it can supply, and the second is how much capacity it has, and mean completely different things.

What is the controller current limit? (often printed on the controller label)

What is the system wattage? (only really useful as a general guide)

 

[dannello]

Thanks for that. I have done a test run. Connected multimeter to battery terminals. Rode up and down a hill. Battery starts at 49v and slowly reduced down. After about 20 mins, up and down hill, power reduces, eventually went down to 40.2v under load and 44v not under load. Bike then stopped at 40.2v voltage and then mutimeter went up to 44v while stationary. Bikes display panel still working, did not go off. Waited only 20secs, bike started but stopped after only 15 secs at voltage 40.7v. Waited 20 secs again with 44v started pedaling uphill but it stopped again after 15 secs on 40.9v. Again it started after resting for 20 secs at 44v but stopped after 15secs on 41v. Bike panel display still on. On all occasions i didnt turn power off, I left it on. The motor hub was slight warm but not much, the controller was quite warm to hot, not uncomfortable to the hands but pleasant on a cold day. The controller is 48v 7A, low voltage protection 40v +/- 0.5v Max current 14+/-1A. Controller and battery came with bike. Bike 5 years old, not used much. Model KT48ZWSD-FSO6F. So how can I tell if it is controller low voltage cutout, controller overheating. On previous occasion I swapped batteries (at the time the bike stopped) for a fully charged one but still it stopped, does that eliminate battery problem as the 2nd battery was used when the bike had stopped and the controller was possibly cooling down during the battery transfer process but once started, with new battery) it didnt take long before the bike stopped again. Your help would be much appreciated. Sorry my multimeter does not do Amps. The battery is 48v 15Ah. Bike is 350w

 

[dannello]

the ebike is here: https://www.aliexpress.com/item/328...list_main.45.7e0f1802og6qfD#nav-specification

 

[dannello]

The controller is almost like this one however mine says rated 7A: https://www.aliexpress.com/item/100...!sea!NZ!123509113!&curPageLogUid=bXe2XjUZpiYt

 

[amberwolf]

TAfter about 20 mins, up and down hill, power reduces, eventually went down to 40.2v under load and 44v not under load. Bike then stopped at 40.2v voltage and then mutimeter went up to 44v while stationary.
<snip>
The controller is 48v 7A, low voltage protection 40v +/- 0.5v Max current 14+/-1A.

THis makes it very likely that it is just the battery running down far enough that under load it simply can't supply the current and voltage the controller needs at that point. So the controller cuts out at that voltage to protect the battery from damage.

The battery doesn't seem be starting at full charge, either. The battery should charge to around 54v full, for a 48v (13s Li-Ion) battery pack. If it doesn't charge that full, it either isn't a fully 48v pack (13s) or it is not working correctly, or the charger is not working correctly and unable to reach full voltage.

What voltage does your charger say on it's label?

If the charger is the correct voltage (on it's label, and measured at it's output pins) then it's probably the battery internally not working correctly. The most common reason is one or some of the cells (or groups of cells) are not the same capacity / etc as the rest, so they reach full charge voltage sooner than the others, and the battery stops charging. If it has balancers in the BMS, it will eventually rebalance the voltages of all the cells so that it will fully charge, but the problematic cell(s) will still have the same lower capacity, so they will simply reach empty sooner than the rest, and it will stop discharging sooner because of those.

But you can first try leaving the battery on the charger longer after it first says it's done, and see if it restarts charging after a while (could be minutes to hours to do this). If it does, then it should cycle on and off like this until all the cells are the same voltage (not the same capacity; that can't happen anymore once this problem begins, as it is the cause). Leaving the pack on the charger until this completes might give you a bit more range, but depending on how bad the imbalance is it can take hours, days, or even weeks if it's really bad.

Some batteries do not have a balance function in the BMS, so they cannot do anything at all about this problem, and either have to have the battery repaired or replaced, or be manually rebalanced by opening it up and individually discharging high cells to match low ones, or individually charging low cells to match high ones. (either one has risks, anytime you're working insiide the pack where things can be shorted out).

 

[richj8990]

Thanks for that. I have done a test run. Connected multimeter to battery terminals. Rode up and down a hill. Battery starts at 49v and slowly reduced down. After about 20 mins, up and down hill, power reduces, eventually went down to 40.2v under load and 44v not under load. Bike then stopped at 40.2v voltage and then mutimeter went up to 44v while stationary. Bikes display panel still working, did not go off. Waited only 20secs, bike started but stopped after only 15 secs at voltage 40.7v. Waited 20 secs again with 44v started pedaling uphill but it stopped again after 15 secs on 40.9v. Again it started after resting for 20 secs at 44v but stopped after 15secs on 41v. Bike panel display still on. On all occasions i didnt turn power off, I left it on. The motor hub was slight warm but not much, the controller was quite warm to hot, not uncomfortable to the hands but pleasant on a cold day. The controller is 48v 7A, low voltage protection 40v +/- 0.5v Max current 14+/-1A. Controller and battery came with bike. Bike 5 years old, not used much. Model KT48ZWSD-FSO6F. So how can I tell if it is controller low voltage cutout, controller overheating. On previous occasion I swapped batteries (at the time the bike stopped) for a fully charged one but still it stopped, does that eliminate battery problem as the 2nd battery was used when the bike had stopped and the controller was possibly cooling down during the battery transfer process but once started, with new battery) it didnt take long before the bike stopped again. Your help would be much appreciated. Sorry my multimeter does not do Amps. The battery is 48v 15Ah. Bike is 350w

48V 7A??? Seven Amp rated? OMG. And I thought my 11A rated controller was not up to the task. 7A is rated for 336 watts, that's pretty low for 48V. Sounds more like it's better for 24/36V. That is a really weak controller, it's no wonder that it's overheating.

And it's KT...another KT overheating issue, go figure.



Simplest two options:

1. Get another KT controller that's rated at least 15A with 30A max, if you are doing PAS. Make sure the controller connection to the battery is compatible; I've noticed that many have a different connection once they are rated over 750-1000W. Not sure if there is a battery adapter for that type like there is for the waterproof to/from SM ones.

2. If throttle only: get a new setup with a UART/SW900 display and 1500W / 30A controller that's compatible with SW900. That's what I just did, waiting for it in the mail. The throttle is noticeably smoother and they will not overheat with the rest of your setup. Again check for battery wire compatibility.

 

[marvin78]

I didn't realize you'd fix voltage drop from an old battery which seems to not fully charge, but by installing a beefier controller which would cause even more voltage sag from those same 5 year old batteries?

On previous occasion I swapped batteries (at the time the bike stopped) for a fully charged one but still it stopped, does that eliminate battery problem as the 2nd battery was used when the bike had stopped and the controller was possibly cooling down during the battery transfer process but once started, with new battery) it didnt take long before the bike stopped again.

Are you sure both your batteries are fully charging and not experiencing excessive voltage drop while under max load? If that controller has worked with those batteries in the past, it's more likely the batteries have aged to the point where they both have to much internal resistance to deliver the amps needed for any continuous load ( climb ) then that the controller suddenly starts overheating.

*unless you have a controller with something like leaking capacitors. but I think that almost never happens anymore .. at least not in comparison with the known degradation time of batteries.

This should be notable if you could monitor your voltage under load, and by monitoring the charging behavior as noted above.

I would ask local shops around you if you can try if a new battery would fix your issue ( not sure which model battery it is, looks semi universal ) with shutting down.

 

[dannello]

Thanks for all info. My multimeter voltage was on a used and uncharged battery. The battery started at 48v and went down to about 40v. I have now charged the battery and it says 54v so will repeat experiment. I am able to monitor the voltage whist riding and under load. Using either battery, one 5years old the other 1year old, the bike did the same thing ie: bike stopped after a hill climb, controller was warm to touch, Thanks for the info on my controllers rating of 7A not being sufficient ( is that what you are saying) as i do use the throttle a lot on hills. I would be surprised if it is the battery even tho one is 5 years old i do not use it much only for commute to work about 2 miles ( 1 mile being up hill). The other battery i bought as a back up and has not been used much apart from the recent test, and it was fully charged but the ebike stopped near the top of the hill and after waiting 15-20secs it started again but stopped 15 secs later and kept doing that until i was home.

 

[amberwolf]

My multimeter voltage was on a used and uncharged battery. The battery started at 48v and went down to about 40v. I have now charged the battery and it says 54v so will repeat experiment. I am able to monitor the voltage whist riding and under load. Using either battery, one 5years old the other 1year old, the bike did the same thing ie: bike stopped after a hill climb, controller was warm to touch, Thanks for the info on my controllers rating of 7A not being sufficient ( is that what you are saying) as i do use the throttle a lot on hills. I would be surprised if it is the battery even tho one is 5 years old i do not use it much only for commute to work about 2 miles ( 1 mile being up hill). The other battery i bought as a back up and has not been used much apart from the recent test, and it was fully charged but the ebike stopped near the top of the hill and after waiting 15-20secs it started again but stopped 15 secs later and kept doing that until i was home.

fwiw, a hgiher current controller would make the problem worse, since you're seeing a fair bit of voltage sag.

if the controller has a temperature sensor in the motor or in itself it might also be shutting off for that, but you are seeeing voltage drop down to and below the controller lvc, and that cuases the controller to stop powering th e motor.

voltage drop like what you see when it rises back up after a time is caused inside the battery by cells that can't handle the load at that voltage.

if the rise back to normal voltage was instant after the load goes away, it could be a connection problem between battery and controller, but if there is a delay in voltage rise it's inside the cells.

*unless you have a controller with something like leaking capacitors. but I think that almost never happens anymore .. at least not in comparison with the known degradation time of batteries.

oh, it's still common enough in all sorts of devices, evven on very short time scales. more in stuff that gets hot near the caps, but even in stuff that stays room temp. i get a lot of stuff other people don't want to fix, even when tis' new or nearly new, and of the stuff i have time to open up to peek at, a siggnificant amount of things with electrolytic caps have swollen or blown caps in them.