Battery cutting off.

[Westfall]

Hello all, I have a problem here that's just iching my brain for days now.
I have installed a new brainpower motor and throttle to my e mountain bike. Everything is working as it should with one problem. The battery is cutting out. No matter if I use full throttle or in bursts or even slightly pressed the battery will cut off and been running for around 5 seconds. I have messed around with the settings based of other forms but still no joy.
The bike is a year old and only been used 4-5 times.
Any help would be appreciated.
Thanks you.

 

[harryS]

Does the S866 display have a voltage setting? I think it it does., and is it set for 36 volts? It may be powering up expecting a 48V battery, and your fully charged 36V battery is around 41-42 volts, which would cause a shut-off.

 

[Westfall]

Yes it does have this setting, I have set it to 36v. After running more tests I believe the problem is the battery itself, it could be the battery just isn't strong enough and the controller is pulling to much power from the battery, triggering the bms. I though changing the voltage, gear and speed settings in the parameters would have solved this. However it was just doing the same thing, it would run for around 15 secs then cut off.

 

[harryS]

The controller is on the modest size. I have a Brainpower unit, but set it aside because it was pretty mild mannered, Probably 13A like yours. The battery is 8.7AH, so it's also small. Should still be capable of 10A though. Maybe you can borrow another battery to do a comparison test.

I assume you can lift the wheel, hit throttle, and it spins on w/o cutting out? Did you do the self learning thing on the Brainpower? If it didn't learn the motor connections exactly right, it might be spinning on a false positive phase setting. That's when the motor spins with no load and at low speed, but will run really rough and draw excessive current,

 

[Westfall]

I did a self learn test last week when building it reset the computer to factory this was when I was trying to get the right combination of the phase wires. I will give it another go today once I get in from work. On the note of lift test it does the same thing, runs for a bit then Cutts off however I did notice it would jerk a couple of times before starting up. I figure the self learn will fix that issue?

 

[Westfall]

I have just ran a self learn test and it's just the same result, the wheel spins up runs for 3-5 sec then just shuts off. Based on these results I believe the battery is just to weak to handle it. Which is a shame because it's nearly used and still in good health.

 

[Slaphappygamer]

I think a good way to test if the bms is being triggered would be to change the current limit in the display. I’d set it to 8 amps. Then ride the bike. If the bike rides fine, then it could very well be the bms tripping.

I had the same setup on a scooter. The motor can be a bit rough when at low speeds from a squarewave controller.

 

[Westfall]

I think a good way to test if the bms is being triggered would be to change the current limit in the display. I’d set it to 8 amps. Then ride the bike. If the bike rides fine, then it could very well be the bms tripping.

I have tried lowering all the settings trying to find the sweet spot but for some reason the opposite effect happens. Where I give it the power and then it's as if the bike just can't be bothered so it shuts down again. Would the to torque sensor cause this to happen?

 

[Westfall]

I have run a test with the power supply plugged in and it runs fine. No problems what so ever.

 

[Slaphappygamer]

You shouldn’t be lowering all settings. You probably may have lowered the voltage setting. Only p14 should be adjusted. Please restore your other settings and try changing the current limit to 8 amps. Then check the function again.

Your torque sensor should have no effect. Test the bike with throttle only, once that is functioning well, then try the torque sensor again.

Here is the manual explaining all settings……if you didn’t already have this.

https://manuals.plus/lcd/s866-lcd-instruments-v1-0-operating-manual

 

[Slaphappygamer]

I have run a test with the power supply plugged in and it runs fine. No problems what so ever.

If your display is set to 36v then it seems you have a bad battery. The power supply will emit about 42 volts and would be on the edge of LVC for a 48v setting, as Harry has mentioned above.

 

[Westfall]

If your display is set to 36v then it seems you have a bad battery. The power supply will emit about 42 volts and would be on the edge of LVC for a 48v setting, as Harry has mentioned above.

Thank you for the help it's very much appreciated. I have ran countless tests for over a week now and the direct power supply giving it the 42v makes me more sertin that it is a battery issue. Do you think a batter with 36v but higher ah would give it the power it needs or would I need a 46v battery?

 

[Slaphappygamer]

That is hard to recommend at this point. The battery either has a bad cell group that makes the voltage sag worse OR the bms is tripping. When the bike powers off, are you able to see the voltage level? I’d also be curious to know what the voltage level is when the bike shuts off. I know you say that when the power supply is plugged in everything is fine. This scenario leads me to believe the bike is not under load and should still run fine because there is not high enough current to trip the bms. This is why Im asking you to change the p14 setting to 8 (well below the assumed bms value) to see if the bms is the limiting factor. If you can ride the bike with a limit of 8amps, then the limit is with the bms. Of course you should restore the other settings that you have lowered previously.

When the bike is running without a load (ex, wheel only lifted from the ground) the current would be roughly 2-3 amps tops.

 

[Westfall]

That is hard to recommend at this point. The battery either has a bad cell group that makes the voltage sag worse OR the bms is tripping. When the bike powers off, are you able to see the voltage level? I’d also be curious to know what the voltage level is when the bike shuts off. I know you say that when the power supply is plugged in everything is fine. This scenario leads me to believe the bike is not under load and should still run fine because there is not high enough current to trip the bms. This is why Im asking you to change the p14 setting to 8 (well below the assumed bms value) to see if the bms is the limiting factor. If you can ride the bike with a limit of 8amps, then the limit is with the bms. Of course you should restore the other settings that you have lowered previously.

When the bike is running without a load (ex, wheel only lifted from the ground) the current would be roughly 2-3 amps tops.

I shall get working on it just now and try to get as much information as I can gather.

 

[Westfall]

That is hard to recommend at this point. The battery either has a bad cell group that makes the voltage sag worse OR the bms is tripping. When the bike powers off, are you able to see the voltage level? I’d also be curious to know what the voltage level is when the bike shuts off. I know you say that when the power supply is plugged in everything is fine. This scenario leads me to believe the bike is not under load and should still run fine because there is not high enough current to trip the bms. This is why Im asking you to change the p14 setting to 8 (well below the assumed bms value) to see if the bms is the limiting factor. If you can ride the bike with a limit of 8amps, then the limit is with the bms. Of course you should restore the other settings that you have lowered previously.

When the bike is running without a load (ex, wheel only lifted from the ground) the current would be roughly 2-3 amps tops.

So as it stands bike is powered on. P14 is set to 8. I have 38v once I hit the throttle it's jumps to 41v with 1a then it Cutts out.

 

[indianajo]

I bought a couple of batteries that measured fine until I drew more than 100 watts, when they would drop to 7 volts on 1, 11 volts on the other. Got my money back on the Amazon one. Having a continuous reading on the battery with a separate fast meter was key to spotting the problem. The voltage on the display is usually not good enough. I skinned the insulation on the fat wires to put alligator clips on to take the reading, and rubber banded the DVM to my front rack. I have since learned the alarm power connector of the controller (if one) has the battery voltage plus and minus on a convenient receptacle. Just buy a pack of matching connectors and solder up a pin for the DVM to read.

 

[Westfall]

I have now done a multimeter reading on the battery to the controller. It sits default on 38v drops to 29v when throttling then as soon as the wheel moves it jumps to 41v and stays there. The only way I can keep the bike on and running is by running it for 2 sec then let it rest back to 38v and rinse and repeat. If a continuous hold on the throttle it will stay at 41v and the battery bms will kick in. Changing p14 seems to be doing nothing I have tried all the values and just the same readings.

 

[Slaphappygamer]

I think this is enough to identify the battery as the fault. Though, I’d like to see @harryS or @indianajo put their 2 cents in, in case I’m missing something.

The battery will sag when initial load is applied, but that’s too much sag. As I’ve read, 4 volts sag is acceptable and it the case with my 48v battery. As the battery ages, sag will worsen.

 

[harryS]

I would agree with slaphappy abut this being a bad battery. Some cells lose ability to pass high currents, and when they try, the cell voltages sag and trip the low voltage alarm circuits.

It might only be one cell group out of the ten cell groups in a 36V battery, but it still shuts off the battery.

 

[Westfall]

I would agree with slaphappy abut this being a bad battery. Some cells lose ability to pass high currents, and when they try, the cell voltages sag and trip the low voltage alarm circuits.

It might only be one cell group out of the ten cell groups in a 36V battery, but it still shuts off the battery.

I believe this is the case. I bought another controller with a lower voltage rating to see if this was the problem. How ever the results were the same. I then did a multimeter reading direct into the battery it's self. One pin was reading 35v and the other 41v so my only option left is change the battery.
I have learned loads from doing this build and want to thank you all for you help.