Why does the battery show a minus voltage when checked with the voltmeter?

[ingolf915]

Hi from Sweden

My charger stopped working so i bought a new one and that one did not work either..

Then I started to measure the battery with my multimeter and found out that minus are now plus?

Any tips what i can be or what i can do? Please see pictures.

EVERYTHING else works and it´s "driveable" but wont charge only...

+red on battery to +red cabel on the multimeter and the same with the black one as it should be when you measure it correctly. And when i do that i get -58 volt... And when i measure it the "wrong way" black to red it´s shows normal +58v ... It´s like plus has become minus on my battery.

Kind regards !

 

[Gionnirocket]

Hi from Sweden

My charger stopped working so i bought a new one and that one did not work either..

Then I started to measure the battery with my multimeter and found out that minus are now plus?

Any tips what i can be or what i can do? Please see pictures.

EVERYTHING else works and it´s "driveable" but wont charge only...

+red on battery to +red cabel on the multimeter and the same with the black one as it should be when you measure it correctly. And when i do that i get -58 volt... And when i measure it the "wrong way" black to red it´s shows normal +58v ... It´s like plus has become minus on my battery.

Kind regards !

In photo 2, it looks correct but it is hard to see clearly. Red is showing +58v
I can't tell what you are testing in photo 3 and 4... Where does it trace back to?

 

[ingolf915]

pic 1 and 2 are from the battery to the controllbox and that shows the correct value. Pic 2 and 3 are cabel directly from the battery that are used for charging and that one shows minus when measured correctly.

Super thanks for the respons !

 

[Gionnirocket]

pic 1 and 2 are from the battery to the controllbox and that shows the correct value. Pic 2 and 3 are cabel directly from the battery that are used for charging and that one shows minus when measured correctly.

Super thanks for the respons !

Well that's kinda impossible if both are going to the battery
I suggest that you trace the wires as something is either mis_wired of there is some hardware on the charge wires before reaching the battery that has failed.

 

[ingolf915]

See picture. That are the cabels are not to kind to open the case.. I no it kind om impossible so my mind are saying that there are som kind of circuit board or something inside that makes this problem..

I dont know if it´s a good ide to try connect the charger to the other cabel that are showing correct value. Have very little knowledge about this kind of battery....

FYI my friend that are a electrician and measured it all and he was super confused.

But like i said before must be some kind of circuit board in the battery that are failing or some other electrical component.....

 

[Bitmugger]

You've for sure got two wires swapped somewhere, looks like on the battery. I'm surprised your controller isn't upset about the voltage being reversed but it's certainly straight forward to build one that wouldn't care about polarity of the power being supplied so perhaps its how your controller is built.

 

[ingolf915]

Thanks for the answer Bitmugger! The funny thing that i haven't changed ANYTHING at all... It just stopped charing but are still runing so I can drive it but not charge it...

So after i tried my latest charger that wont work and notice the the +- was -+ I tried to swapp the cables on the charge without success...

 

[Bitmugger]

Sounds baffling but the battery chemistry doesn't allow for a polarity reversal so it's got to be something simple and overlooked, figuring out where is the challenge and don't trust what you believed in the past, perhaps there's a scenario where the wiring has been wrong all along but worked because of some anomaly. Perhaps some wires have shorted somewhere. If you can post more pics of the wiring and maybe just isolate the battery entirely from the system and charge it that way to establish it can be charged off the bike? (or perhaps you've done that). I'm guessing you only have the 1 battery?

* EDIT * Did some reading and lithium ion polarity reversal is possible but doesn't seem like it would be likely unless you have no BMS and completely drained the battery to empty.

Battery Myth | Can a Battery ‘Reverse’ its Polarity?

Guilty As Charged Blog Post touching on the battery myth of reverse polarity. Can a battery, after installation, reverse its own polarity? Not by itself, but with external stimulus, it is possible.

www.batterystuff.com

 

[Gionnirocket]

See picture. That are the cabels are not to kind to open the case.. I no it kind om impossible so my mind are saying that there are som kind of circuit board or something inside that makes this problem..

I dont know if it´s a good ide to try connect the charger to the other cabel that are showing correct value. Have very little knowledge about this kind of battery....

FYI my friend that are a electrician and measured it all and he was super confused.

But like i said before must be some kind of circuit board in the battery that are failing or some other electrical component.....

Inside the battery case is most likely a BMS. Basically a battery manager circuit board that controls charging and discharging. It is a safety device so if you bypass it, it is very easy to over charge and/or create a dangerous situation/fire.
If you want to fix it correctly, you need to open the battery case.

 

[Gionnirocket]

Sounds baffling but the battery chemistry doesn't allow for a polarity reversal so it's got to be something simple and overlooked, figuring out where is the challenge and don't trust what you believed in the past, perhaps there's a scenario where the wiring has been wrong all along but worked because of some anomaly. Perhaps some wires have shorted somewhere. If you can post more pics of the wiring and maybe just isolate the battery entirely from the system and charge it that way to establish it can be charged off the bike? (or perhaps you've done that). I'm guessing you only have the 1 battery?

* EDIT * Did some reading and lithium ion polarity reversal is possible but doesn't seem like it would be likely unless you have no BMS and completely drained the battery to empty.

Battery Myth | Can a Battery ‘Reverse’ its Polarity?

Guilty As Charged Blog Post touching on the battery myth of reverse polarity. Can a battery, after installation, reverse its own polarity? Not by itself, but with external stimulus, it is possible.

www.batterystuff.com

If you back up and look at the photos, the battery polarity is correct... it's the charging leads off the battery that are reversed.
It has to be a BMS malfunction.

 

[ingolf915]

True true can be wrong from start! I guess you want me to "open" the battery and send you pictures?

The battery has never been drained to empty ...

If you back up and look at the photos, the battery polarity is correct... it's the charging leads off the battery that are reversed.
It has to be a BMS malfunction.

Thansk for the respond! Iam just confused when it worked for 2 years and now this fault and there is NO changes made..

 

[Bitmugger]

True true can be wrong from start! I guess you want me to "open" the battery and send you pictures?

The battery has never been drained to empty ...

Thansk for the respond! Iam just confused when it worked for 2 years and now this fault and there is NO changes made..

I really don't want you to open a Lithium Ion battery pack unless you are totally comfortable with it. Drop a tool across the wrong set of contacts and you'll have a dead battery pack or dead cells or a fire or a ruined BMS or more, you'll certainly need to change your pants if you set off a spark show with a dropped tool.

I also don't feel there's anything to "see" inside the battery pack, it'll be a battery and some charge leads and some discharge leads and some balance wires connected to a BMS. A broken wire wouldn't cause your symptoms. If you are equipped to check into the voltage levels of cells and probe around the BMS then great but I get the feeling you aren't a big electronics guy and you are relying on a friend to assist. I'd at least have them present if possible. One thing you might see I guess is NO BMS, if that's the case then you might have a legit polarity reversal situation and a ruined battery pack.

I am now thinking what if you have no BMS and through some mishaps the battery got fully drained then your charger (probably the new one) had the wrong polarity and charged it in reverse? I really didn't think that was possible until reading the article I linked to.

 

[Gionnirocket]

True true can be wrong from start! I guess you want me to "open" the battery and send you pictures?

The battery has never been drained to empty ...

Thansk for the respond! Iam just confused when it worked for 2 years and now this fault and there is NO changes made..

I think it best left to a professional as it requires some experience to replace a bms.... You might not be able to find an exact replacement and this will require further experience as well.

 

[harryS]

I see nothing wrong - from picture 2

You haven't changed any wiring, so nothing is wrong, Don't be chasing ghosts.

Now think about why a "charger doesn't work".

First answer is bad charger, but you have a second charger, presumably good. I assume it has a new mains (AC) cable and that is firmly inserted into he charger.

Second answer is the battery is at fault if it's not taking a charge. We know the bike still works, so the battery is putting out a useable voltage. What causes a battery to not charge? Is there a charger fuse on the battery? Check it.

If the fuse is good or you can't find a fuse, is your charger connector on the battery easily probed? Carefully look for 58V on its pins. That shows it's connected to the internal cells, and there is no fuse issue.

Finally and this just occurred to me, if this is a 14S lithium battery, i.e, 58.6V, it's already fully charged (your picture shows 58.46) and the charger won't charge anyway.

 

[Gionnirocket]

I see nothing wrong - from picture 2
View attachment 93436

You haven't changed any wiring, so nothing is wrong, Don't be chasing ghosts.

Now think about why a "charger doesn't work".

First answer is bad charger, but you have a second charger, presumably good. I assume it has a new mains (AC) cable and that is firmly inserted into he charger.

Second answer is the battery is at fault if it's not taking a charge. We know the bike still works, so the battery is putting out a useable voltage. What causes a battery to not charge? Is there a charger fuse on the battery? Check it.

If the fuse is good or you can't find a fuse, is your charger connector on the battery easily probed? Carefully look for 58V on its pins. That shows it's connected to the internal cells, and there is no fuse issue.

Finally and this just occurred to me, if this is a 14S lithium battery, i.e, 58.6V, it's already fully charged (your picture shows 58.46) and the charger won't charge anyway.

Good call on checking for a fuse. I can't visualize it but if a fuse is blown can he be picking up a voltage on the negative and seeing the bms as a load.... I think not on a dc circuit, but I'd have to draw it out or be in front of it to see clearly.
If you look at photos 3,4 that's where he says he's connected to the charging port.. And that is showing reversed polarity which should not be.
I'm still leaning towards something funky with the bms... On a printed board with many components things can easily cross with failure

 

[Bitmugger]

Wait in the first set of pics that showed -58v your leads were reversed? They aren't in the pic HarryS highlighted. I am confused now. Did you actually check the battery voltage before in the past and see with certainty it wasn't reversed compared to your readings now?

 

[Gionnirocket]

Wait in the first set of pics that showed -58v your leads were reversed? They aren't in the pic HarryS highlighted. I am confused now. Did you actually check the battery voltage before in the past and see with certainty it wasn't reversed compared to your readings now?

Yes, you're confused.

 

[harryS]

Who knows what he's showing the other pictures. Let's see a picture of the charge connector on the battery or bike..

I've taken apart enough batteries and the positive end of the battery always goes directly to the positive side of the out[ut connector, and also the charge connector. It's the same wire. They cannot be different.

 

[Gionnirocket]

Who knows what he's showing the other pictures. Let's see a picture of the charge connector on the battery or bike..

I've taken apart enough batteries and the positive end of the battery always goes directly to the positive side of the out[ut connector, and also the charge connector. It's the same wire. They cannot be different.

Read post #3... Though I do think he has a typo and meant to say photo 3-4 (not 2-3) as that's what I asked about in post #2
So I understand the OP as...
Photos 1 - 2 show main battery terminal to controller... First red probe on Black wire, then on Red wire from the battery
Photos 3-4 are showing charging leads from the battery... First red probe on red wire then red probe on black wire used for charging

 

[ingolf915]

Read post #3... Though I do think he has a typo and meant to say photo 3-4 (not 2-3) as that's what I asked about in post #2
So I understand the OP as...
Photos 1 - 2 show main battery terminal to controller... First red probe on Black wire, then on Red wire from the battery
Photos 3-4 are showing charging leads from the battery... First red probe on red wire then red probe on black wire used for chargingYou

You got I right! on the pictures Sorry my messy post!
As you understod it´s just showing minus on the cables used for charing. And the cables from battery to controller shows normal values.
So must be some kind of faulty logic board or something inside the battery case..

Really sucks when everything works except for the charing...