Battery suddenly drops to zero

[Wanana]

Hi guys,

I'm back with another strange problem. I was riding my bike when suddenly the battery went from 75% to 0%. The assist also stopped working. When restarting the bike it went back to normal for a few minutes and then the problem returns. Sometimes after a few seconds now.

When I check the battery in the menu I see that all 12 cells read about 3440mV.
Anybody got an idea? Getting a bit tired of this stuff. Motor with faulty controller has just been replaced out of warrenty.

Thanks in advance!

 

[docw009]

Do you mean you measured internally and got twelve readings at 3.44V for a total battery voltage of 41 volts, or do you mean the battery output is 3.44 volt? I see that the Brincker Brisbane M310 that you mentioned in the other thread is a Dutch bike, with a 12S 45V battery. That's unusual.

Let's say you measured 3.44V. The battery is probably unbalanced and it shut off, which means it's isolated the cells from the output terminal, so what you measure is just stray voltage, not the actual voltage.

An unbalanced battery means one or more of the twelve cell groups is undercharged, and shuts the battery off while the rest of the cells still have plenty of power. The 75% level on your display shows that, When you try to recharge, the healthy cells charge up first and shut off the charger, leaving the undercharged cells weak. Better batteries have balance circuits to fix this if you leave them on the charger for a long enough time. Give that a try, but keep an eye on the battery in case it gets hot or does something bad.

 

[Wanana]

Thanks for your reply. I'm a noob when it comes to batteries so I don't fully understand you.
This is what I see when I check the battery menu.
I also wanted to check for possible voltage sag but I can't acces the menu while riding the bike.

 

[E-HP]

Thanks for your reply. I'm a noob when it comes to batteries so I don't fully understand you.
This is what I see when I check the battery menu.
I also wanted to check for possible voltage sag but I can't acces the menu while riding the bike.

What are the pack voltage and individual cell voltages (page 3 and 4 of your pics) when charged (to 75%?)?

Might be obvious, but just in case, you need to charge your battery between uses.

 

[Wanana]

The battery is charged to 75%. It just jumps to 0 in the main display screen after a short while. In the last picture in the battery menu you can see it's still charged to 75% if I'm seeing it correctly.
Yes I know you have to charge the battery between uses

 

[E-HP]

What do page 3 and 4 look like when the pack voltage drops to zero?

 

[Wanana]

In the main screen the battery reads 0%. In the battery menu it still reads 75%.
So all the pictures are from the same moment.

 

[E-HP]

In the main screen the battery reads 0%. In the battery menu it still reads 75%.
So all the pictures are from the same moment.

Set your SOC view to voltage instead of percentage, and provide what voltage is present when the bar display goes to empty.

My guess is that your display/controller is auto sensing the battery to be 13S (48V) instead of 12S (43V). That may be causing the display/controller to think it's hitting the low voltage cutoff for a 48V battery, and cutting power. If doing the above shows a battery voltage that matches the detail screens, then it's like that's what is happening. You may need to fully charge and discharge the battery for the display/controller to re-recognize your battery as 12S.

 

[e-beach]

Have you checked all your connectors carefully?

 

[AGS]

It’s not something daft like your battery coming loose from the cradle when you hit a bump in the road?

 

[Wanana]

When turning on the bike.

And later after maybe 20 seconds of riding.

 

[amberwolf]

Sounds like a bug in the firmware of whatever kind of system it is. Either the firmware is not updating the battery page with actual information, or it's not updating the main page with actual information. One of them has to be wrong. Or the firmware is using an incorrect battery LVC or other SoC setting to create the main page data from.

If the system is actually talking to the battery BMS to get the cell readings, that's helpful, in that if the information it provides there is accurate and updated, it is telling you none of the individual cells are causing your problem, and the BMS isnt' shutting off, etc.

That should mean the main page is inaccurate, and that whatever part of the firmware that's shutting the systme off is only monitoring the main page itself--so because of whatever bug is in the firmware causing the main page to display the wrong battery info, the system reacts to the wrong info correctly by shutting down the motor to prevent battery damage.

One way to find out which one is right, if the settings for the battery are correct everywhere within all of the menus, is to monitor the battery with a separate voltmeter, preferably a wattmeter with it's own power supply or battery, so that if the battery cuts out or drops below the meter's operating limit it doesn't lose the data. This would let you see the minimum actual battery voltage at the moment of cutout, with the Vmin of the wattmeter holding that for you until you can stop and look at it. (even though the voltage goes back up on any of the other readouts).

If the wattmeter shows no significant voltage sag on the Vmin vs the no-load readout post-cutout, then it's pretty likely the battery page info is correct.

 

[E-HP]

Sounds like a bug in the firmware of whatever kind of system it is. Either the firmware is not updating the battery page with actual information, or it's not updating the main page with actual information. One of them has to be wrong. Or the firmware is using an incorrect battery LVC or other SoC setting to create the main page data from.

The interesting thing is that the voltage on the main display ties with the detail pages, but the battery bar doesn't (shows no charge), which seems to indicate whatever the battery bar is using is also what the LVC is using that's shutting down the assist. 41V would be kind of high for a 13S LVC, but the 12S with a little voltage sag might trigger it.

 

[Chalo]

So are we looking at a 12S LiFePO4 pack which is nominally 36V, or a 12S lithium ion pack which is nominally 44V?

What voltage does the display think it's working with? What is its low voltage cutoff value?

 

[E-HP]

So are we looking at a 12S LiFePO4 pack which is nominally 36V, or a 12S lithium ion pack which is nominally 44V?

What voltage does the display think it's working with? What is its low voltage cutoff value?

I assumed lithium ion. I saw the video below of a guy disassembling a pack from that company, and he was surprised to see Samsung cells, commenting that they hadn't marked that anywhere on the outside of the battery.

 

[Wanana]

This is what the sticker says

 

[E-HP]

If the system is actually talking to the battery BMS to get the cell readings, that's helpful, in that if the information it provides there is accurate and updated, it is telling you none of the individual cells are causing your problem, and the BMS isnt' shutting off, etc.

This is what the sticker says

Seems to be the case, or a poor connection/communications.

 

[Wanana]

What voltage does the display think it's working with? What is its low voltage cutoff value?

Where can I check this?

I was checking error memory when I saw this error 30. Seems like a communication error. Don't know if this is an active error or old since it's in error history. Could this be related?

 

[E-HP]

Where can I check this?

I was checking error memory when I saw this error 30. Seems like a communication error. Don't know if this is an active error or old since it's in error history. Could this be related?

Can you post pics of the battery interface/connection on the battery as well as on the battery cradle side? Since it's a proprietary/integrated system, the battery and controller have to maintain communications, so the theory about hitting a bump in the road or some sort of vibration interrupting that is viable

 

[Wanana]

Hey guys sorry for the late reply. Very busy with work and the family.
I checked the battery connection visually and everything looks good and clean. The power cutout also happens on flat surfaces without bumps.
I charged the battery completely full and now the problem is gone for this moment. But I don't trust it anymore for long rides. Will report back if the problem returns.