Noob trying to check voltage on a battery

[Singularo]

I was riding my electric bike around the other day, when all of a sudden my motor started to make a grinding sound. I pull over to turn the bike off and on to see if it would fix the issue, and upon turning it off, it wouldn't turn back on!
I opened up the seat where the battery is stored and went to check the battery to ensure it was functioning (I figured it would be!), but when I went to check it, only some of the cables seem to be showing voltages. I attached a picture and circled the cables that have voltage in green, and the one that doesn't in red. What I want to know is, am I checking it wrong? If I'm not checking it wrong, does this mean the battery is completely dead now? This is the first time I've ever used a multimeter, so I'm pretty clueless. Thanks for any help!

 

[E-HP]

I attached a picture and circled the cables that have voltage in green, and the one that doesn't in red.

No picture

 

[Singularo]

I attached a picture and circled the cables that have voltage in green, and the one that doesn't in red.

No picture

Hey, sorry! I thought I attached it, but it was too large to attach so I had to resize it.

 

[E-HP]

Without knowing more about your scooter, I'd say the XT60 (yellow) connector is used for charging, so since you also have the male end in the pic, I'm assuming maybe you have a charging port/connector on the side of your scooter, so you don't have to open it up for charging.

I have no idea what the black circled connector is, especially if it's coming out of the battery, but is there a corresponding connector on the controller or bike? If so, maybe it's used for monitoring the battery, but that seems proprietary.
If the charging port has voltage, and the output (big wires) don't, then there may be a BMS inside the pack that tripped off. It should reset itself, so check the voltage again. I"d charge up the battery, in case the BMS tripped due to the battery being over-discharged, rather than voltage sag. That would be the BMS protecting the battery from destruction.

I wouldn't hook anything back up to the bike until you figure out what happened to the motor. If it shorted, then that could have fried the controller and tripped the battery too.

 

[Singularo]

Without knowing more about your scooter, I'd say the XT60 (yellow) connector is used for charging, so since you also have the male end in the pic, I'm assuming maybe you have a charging port/connector on the side of your scooter, so you don't have to open it up for charging.

I have no idea what the black circled connector is, especially if it's coming out of the battery, but is there a corresponding connector on the controller or bike? If so, maybe it's used for monitoring the battery, but that seems proprietary.
If the charging port has voltage, and the output (big wires) don't, then there may be a BMS inside the pack that tripped off. It should reset itself, so check the voltage again. I"d charge up the battery, in case the BMS tripped due to the battery being over-discharged, rather than voltage sag. That would be the BMS protecting the battery from destruction.

I wouldn't hook anything back up to the bike until you figure out what happened to the motor. If it shorted, then that could have fried the controller and tripped the battery too.

Thanks! I'll charge the battery up and try checking it again later.

 

[Singularo]

Interestingly enough it seems like the battery is full now. When the battery is charging, the charger I use turns on a red light. Now the light doesn't come on when I plug the charger into the battery (maybe it's possible that it's not charging anymore?). I'm still not getting any voltage from the red and black plug (still getting voltage from the XT60 cable though.

 

[Drunkskunk]

Your picture helps, but It's hard to tell where those extra wires go.

Very likely your batter has a BMS (Battery management system). it's a small simple computer that manages the cells's voltage during charging and when the battery is in use, ensuring things like the cells are balanced, the voltage doesn't go too high or drop too low, and limits the current in case the motor tries to draw more power than the cells can safely supply. It will shut the battery off if the voltage goes too low. Power will come back to the main wires once the battery is recharged

However, if the BMS detects that a cell has failed, it will shut down the output to prevent a fire, or worse. Basically, it gets bricked.

I think that is why you are reading no power on the main battery leads: The BMS has shut down the battery due to some perceived fault in the battery.

What was the rated voltage of the pack, and what voltage are you reading on the yellow connector now? Also, do you know the cell count?

 

[Singularo]

Your picture helps, but It's hard to tell where those extra wires go.

Very likely your batter has a BMS (Battery management system). it's a small simple computer that manages the cells's voltage during charging and when the battery is in use, ensuring things like the cells are balanced, the voltage doesn't go too high or drop too low, and limits the current in case the motor tries to draw more power than the cells can safely supply. It will shut the battery off if the voltage goes too low. Power will come back to the main wires once the battery is recharged

However, if the BMS detects that a cell has failed, it will shut down the output to prevent a fire, or worse. Basically, it gets bricked.

I think that is why you are reading no power on the main battery leads: The BMS has shut down the battery due to some perceived fault in the battery.

What was the rated voltage of the pack, and what voltage are you reading on the yellow connector now? Also, do you know the cell count?

It's a 36v battery. The yellow connector (earlier I referred to it as the xt60 connector, but it says xt30 on it) looks like it has 0.28 volts. The xt30 connector hooks up to an external power button to power on the battery. The black wire looks like it has around 14 volts, and this hooks up to a charging port that's also on the outside of the bike. I'll attach a few pictures.

It might be useful information that I cut a mysterious white wire inside the controller that others told me removed the speed limiter. It did seem to remove the speed limiter, but after riding it around for a few days at top speeds, this happened


xt30 voltage


charging port voltage


outside of bike

 

[HK12K]

Looks to my eye that the red encircled (Anderson Powerpole?) connectors are the battery's discharge leads. If that shows no voltage then the bms has disconnected the discharge leads to prevent catastrophic failure.

The black connector that is supposed to go to your charge port is showing 14v, which is likely your packs current voltage. Unless I'm mistaken that would be 1.4v per cell on average which is far below what any cell should ever be. Sounds like an internal failure to me.

I believe you're going to have to pull that pack from the bike, unwrap it, and start metering to figure out exactly what's happened. You might also want to meter your chargers output to see if it's actually functioning.

Happy to be proven wrong though, as I'm no authority.

 

[Singularo]

Looks to my eye that the red encircled (Anderson Powerpole?) connectors are the battery's discharge leads. If that shows no voltage then the bms has disconnected the discharge leads to prevent catastrophic failure.

The black connector that is supposed to go to your charge port is showing 14v, which is likely your packs current voltage. Unless I'm mistaken that would be 1.4v per cell on average which is far below what any cell should ever be. Sounds like an internal failure to me.

I believe you're going to have to pull that pack from the bike, unwrap it, and start metering to figure out exactly what's happened. You might also want to meter your chargers output to see if it's actually functioning.

Happy to be proven wrong though, as I'm no authority.

Thanks for the advice! Is there a good guide on how to take a sealed battery apart? As you can see from the first pic it's completely sealed in blue shrinkwrap. I've never done it before so I don't really know where to start with regards to safety.

I also went to meter the chargers output and it looked like it was working (I think it was like 41 volts).

 

[HK12K]

First find yourself someplace safe to work. Non conductive surface, no tools laying around to accidentally short circuit anything, preferably outside and under cover just in the event things go sideways.

Find an edge on the shrink wrap and carefully cut it just a little, then put the tool safely away and start peeling with your hands. It should unwrap pretty easily.

(Charger sounds good. 41v is pretty ideal.)

 

[E-HP]

The yellow connector (earlier I referred to it as the xt60 connector, but it says xt30 on it) looks like it has 0.28 volts. The xt30 connector hooks up to an external power button to power on the battery.

It sounds like you need to either connect this XT30 and flip the switch, or short the XT30 in order to turn on the battery and get voltage/power out of the main Anderson connectors.

 

[Singularo]

The yellow connector (earlier I referred to it as the xt60 connector, but it says xt30 on it) looks like it has 0.28 volts. The xt30 connector hooks up to an external power button to power on the battery.

It sounds like you need to either connect this XT30 and flip the switch, or short the XT30 in order to turn on the battery and get voltage/power out of the main Anderson connectors.

I plugged in the XT30 connector and pressed the power button on the bike (the power light comes on), but the anderson connector still doesn't get any voltage

 

[Singularo]

I opened up the battery and this is what I found. I checked the cells to see what voltage they were at (connecting B2 to B3 as an example) and they all had 4 volts. Is there anything I should be looking for?
I also tested B+ to B- and it was 40.4 volts.

 

[HK12K]

The cells themselves appear to be good based on those readings, at least on the surface, but the bms is failing to pass voltage for some reason. I can't tell but can I assume that blade fuse pictured is not blown?

I'm not at all familiar with your bike or how it's setup so it's hard to say for sure. My first impulse would be to think that the bms may have simply failed. Before we jump to that conclusion though, I'm curious, exactly what leads do you have going to the bms? All 3 different style connectors as pictured above?

If so it's conceivable that some proprietary design might use a switch on the bms to flip the discharge leads on and off as an ignition setup. Not something we're particularly used to seeing around here I don't think, but also not out of the realm of possibility. It could be as simple as an issue with the light up switch not passing voltage, so the bms doesn't even know it's being told to turn on. If we know more about the leads going to the battery it might paint a more clear picture, but might be as simple as jumpering the xt30 attached to the bms as mentioned earlier. The 14v on the charge port and no response when the charger is connected is pretty curious though, so it may be a boned bms after all.

 

[Singularo]

The cells themselves appear to be good based on those readings, at least on the surface, but the bms is failing to pass voltage for some reason. I can't tell but can I assume that blade fuse pictured is not blown?

I'm not at all familiar with your bike or how it's setup so it's hard to say for sure. My first impulse would be to think that the bms may have simply failed. Before we jump to that conclusion though, I'm curious, exactly what leads do you have going to the bms? All 3 different style connectors as pictured above?

If so it's conceivable that some proprietary design might use a switch on the bms to flip the discharge leads on and off as an ignition setup. Not something we're particularly used to seeing around here I don't think, but also not out of the realm of possibility. It could be as simple as an issue with the light up switch not passing voltage, so the bms doesn't even know it's being told to turn on. If we know more about the leads going to the battery it might paint a more clear picture, but might be as simple as jumpering the xt30 attached to the bms as mentioned earlier. The 14v on the charge port and no response when the charger is connected is pretty curious though, so it may be a boned bms after all.

Yeah, all three connectors (anderson, xt30, and the charging cable) are connected to the bms. Is there a way for me to check if the blade fuse is blown? I have a super73-z1 bike by the way.

 

[HK12K]

Should be able to see if the filament inside is broken or not. If you're not sure, post a close up looking down on it if you can.

 

[Singularo]

Should be able to see if the filament inside is broken or not. If you're not sure, post a close up looking down on it if you can.

 

[HK12K]

Hard for me to say with 100% certainty, but it looks like it might be blown. If that metal filament inside isn't continuous from one leg to the other, it popped for some reason. You may be able to see it better than I can in person. If it's blown it'll need to be replaced, but the question of why it blew to begin with would still remain.

 

[Singularo]

Can I just solder a new one on? Do I need to discharge the battery or anything before I do it?

 

[HK12K]

Yup, just solder a new one of the same rating in it's place. You could discharge the battery a bit if you're not going to get around to repairing it in the near future as cells don't particularly like being stored full, but aside from that I wouldn't worry too much about it. Just don't short anything.

 

[Singularo]

Thanks! I'll give it a go. I appreciate all the help!

 

[amberwolf]

The most likely reason for hte fuse to have blown now, vs before, is the limiter being disabled.

If the battery was designed only to supply the power for the limited bike, then it isn't really meant to provide enough power for the unlimited version, which uses up battery power faster, drawing more current, causing more heat, more voltage sag, wearing out the battery faster, etc.

So the fuse probably sized to protect the battery against this occasion, and your safest bet is to reconnect that limiter, until you can replace the battery with a better one that is capable of the power the bike uses in unlimited mode.

To be able to do that, you'll want to get a wattmeter to monitor power usage, and record the peaks of power (watts) and current (amps), and let you see the continous power and amps while riding, so that you can make sure the new battery pack is capable of handling that.

Alternatley instead of replacing the battery, you could get a second identical (or very similar) battery, and parallel it with the first one, so they share the load (more or less) and each one doesn't get hammered like it would when alone.


Some threads on wattmeters, if interested:
https://endless-sphere.com/forums/search.php?keywords=*wattmeter*&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search

 

[HK12K]

Sorting out why the motor suddenly decided to started grinding and why that grinding led to the battery being overdrawn is going to be the next priority I think.

 

[Singularo]

Sorting out why the motor suddenly decided to started grinding and why that grinding led to the battery being overdrawn is going to be the next priority I think.

What's the best way to go about this? If I'm able to get the battery working again (going to go buy a fuse today), should I just plug the battery back in and see if the motor works (not going to strain it very hard of course until I can solder the speed limiter back in)?