Electrical short in the system.

[mvalent000]

Hello all I am new to the Forum.
Looking for some knowledge.
I have a issue with an Ancheer electric bicycle, it's the Sport folding model.
I can ride the bike on full electric mode for a whopping 2 minutes (if that), then the whole system shuts down, no power whatsoever. But within a half an hour or so the battery will go back to its original charge and I can power up the system again.
-Battery holds a charge forever.
-the controller does not get hot nor does any of the wires.
-The display is the only component the gets warm.
-i took the .motor apart and everything looks to be in order...no broken wires.

Bad controller? If it is the controller where would i pick up a comparable one from with the same or similar plugs?

Any ideas would GREATLY BE APPRECIATED!
Thank you!

 

[AHicks]

Tell us more about the battery. Expand on "holds a charge forever". Do you know exactly what the voltage is when the bike shuts down? When you hear about one that shuts down like this, my first instinct is wondering if the low voltage cut off voltage has been exceeded.

If this is the case, it could be your charger shutting off early for some reason, could be a dead cell in the battery, or even the battery's BMS. The ONLY way you're going to troubleshoot is with a good voltmeter that can read exact voltages.

 

[mvalent000]

Thanks for your reply.
Battery when charged sits at 40.1 volts and stays there for over a week. When the system shuts down the battery will read very low double digits...11-15 volts if I recall....and will start to creep back up.
I will get back to you on exact voltages it drops to if you need it.
I just put it on the charger and it did seem to recharge the battery very fast...say within 30 minutes. Don't know if that is normal or not.

 

[harryS]

How old is the battery? If your meter is accurate, 40.1 volts says you have a bad battery. It should be 42.0V. Could be unbalanced, or could be defective cells. An unbalanced battery can be rebalanced by leaving it on the charger after the light goes green. A battery with defective cells will never balance and might go up in flames if left on the charger. Keep that in mine if you try rebalancing. Do it in a safe place/manner. You might try giving it two hours and then checking the voltage with your meter to see if it's still going up. Be careful. A guy on another forum says he charges his batteries in a place where he doesn't mind a fire,

Your 36V battery consist of ten groups of cells. Each group should charge to 4.2V, so a fully charged pack is always 42.0 volts. When charging, the battery shuts off charge when any group reaches 4.2 volts. Then the charger light goes green. With a balanced battery. when this occurs, the other nine are not too far behind. Then if the charger is left on, the battery goes into balance mode, bleeding some charge off the first fully charged group and letting the next one catch up. This goes on until all ten groups are at 4.2 volts. For a balanced battery, this happens quickly, A badly unbalanced pack can take a long time. If the low groups are defective, it will never balance,

The other indicator of an unbalanced pack is a high output (40.1V) and short run time (5 minutes). You could have one group sitting around 3.3 volts, and 5 minutes is enough to take it below the batteries internal limit, and it shuts off. By the way, when it shuts off, you're looking at residual charge. The actual voltage on the internal cell array never goes much below 30 volts. Sometimes, if a pack is left to sit a long time, the cells that power its internal circuits get run down and go into imbalance.

 

[mvalent000]

That is some serious knowledge! Thank you for that. I will put the battery and bike outside tomorrow while i am working and see if it will balance out after 2 hours on the charger.
Thank you again for the info! much appreciated!

 

[AHicks]

I'd give it 4 to maybe 6 hours.....
IF that does improve things noticeably, it may take several charge and discharge cycles for the battery to "fix" itself.

Keep in mind there's still a pretty good chance you have something else going on.

 

[mvalent000]

Thank you again, at least it's step in the right direction.
On a side note, can I run the motor controller without the sensors hooked up? (brake sensors and crank sensors)

 

[AHicks]

Yes, assuming you have a throttle.

 

[mvalent000]

Cool, thanks. Yes I have a twist throttle. Battery is on the charger right now. I will let you know how it goes tomorrow.

 

[mvalent000]

Well I gave it two days on the charger and I can only get it up to 41.0 Volts if I unplug and re-plug in the charger. So going off your information I would guess the battery is bad.

I went as far as to have my meter on the battery and tried to get it to short itself and when it did, the volts dropped to 11V and started to climb back up.....when I plugged the charger in the volts jumped right back up to what they were before the volts dropped! This is what is leading me to believe the battery to be bad.....am I wrong?

 

[harryS]

So you gained a little voltage, but it still dies after 5 minutes. Then it's probably a bad cell. It's sagging under the battery's minimum limit (probably 3V) under load, which shuts off the pack. The battery turns back on, because removing the load allows the bad cell to recover.

Is it an old pack, or should it still be under warranty? Only mad scientists try to replace a bad cells.

 

[mvalent000]

Makes sense to me. Thank you again for your help.
Do you think it is worth it to take the battery to a battery repair place? Or should I just dump the bike off as non working for parts or repair?

 

[AHicks]

Do you like the bike? Would you ride it if it were repaired?

If so, you can likely replace that battery for less than what another bike would cost.....

 

[mvalent000]

I think the electric aspect of it is kind of cool but the bike is steel, it's heavy, I'm used to aluminum-framed mountain bikes and pedaling..haha. thanks again.

And your previous question....the bike is way out of warranty. I have already contacted Ancheer about tech help and they are worthless.

 

[harryS]

What kind of battery is it? Is one that slides inside the frame, or an external pack? Ancheer packs are around $250.

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I haven't ever tried to ship one, but I suspect shipping one legally for repair will cost as much as just buying a replacement when looking at batteries for off-brand ebikes, It seems to me they charge 2-3x more for the big bike name batteries, so those are more cost effective to repair. A $250 pack, you just replace it.

 

[mvalent000]

It's an external battery. Goes on the handlebar in a soft case.
I flip it local....the bike ways a ton so shipping would be pricey.