Ebike Wrong Voltage showing On APM Please help.

[johnjapan]

The APM is showing the wrong voltage and as a result the motor will not move at all
I am stumped as to what the problem is, here is what the APM is showing around 46volts



Here is what my 72 volt pack is showing around 75 volts



I then connected the controller to the battery and probed the controller side to check the voltage, here is what i got.



Strange..... its showing a lower voltage

I assumed a faulty connector on the controller side so I crimped on some fresh Anderson connectors and I'm still getting the same issue can anyone figure out what's happening any help would be appreciated thankyou !!

 

[Drunkskunk]

is this an SLA battery pack? if it's near dead, it can hold full voltage, but then drop voltage on the smallest load.

 

[johnjapan]

is this an SLA battery pack? if it's near dead, it can hold full voltage, but then drop voltage on the smallest load.

These are 24 headway cells 40152
I don't think they are sla no.

 

[docw009]

Your battery with no load reads 75.8 volts. WHen connected to the controller, you see 58 volts at the connector, so you're losing 16 volts. You changed the connector, so the Andersons are probably good. Anyway, shouldn't your motor run at 46 volts anyway, unless 48 volts is unbder the low voltage cutoff of the controller.

This looks like a battery problem to me, when you lose that many volts under load. DId it used to work?

If these are 40152 headway, the Headway spec says their full charge voltage is 3.65 volts. And you said you had 24, so 24 x 3.65 is 87.6 volts. Doesn't seem like your pack is fully charged.

 

[johnjapan]

Your battery with no load reads 75.8 volts. WHen connected to the controller, you see 58 volts at the connector, so you're losing 16 volts. You changed the connector, so the Andersons are probably good. Anyway, shouldn't your motor run at 46 volts anyway, unless 48 volts is unbder the low voltage cutoff of the controller.

This looks like a battery problem to me, when you lose that many volts under load. DId it used to work?

If these are 40152 headway, the Headway spec says their full charge voltage is 3.65 volts. And you said you had 24, so 24 x 3.65 is 87.6 volts. Doesn't seem like your pack is fully charged.

You bring up an excellent point!
Everything was working fine before Until i removed 4 batteries from the pack and reconnected them,
Maybe they aren't connected properly or I connected them in reverse but wouldn't there be shock / sparks if I did reconnect them properly? I will reconfirm the pack more pictures on the way!

Thankyou!

 

[dustNbone]

The first pic shows the meter reading negative voltage, and it appears the probes are red to red and black to black. Is the polarity right?

Second pic shows probes reversed in the Anderson, and positive voltage.

 

[johnjapan]

The first pic shows the meter reading negative voltage, and it appears the probes are red to red and black to black. Is the polarity right?

Second pic shows probes reversed in the Anderson, and positive voltage.

Oh oh,

You're right so if the polarities are wrong would that damage the cells?
Because I took apart my whole battery pack and found 1 dead cell with voltage of 0.2v
I've tried leaving it in the charger for 4 hours but it won't hold the charge at all.

I'll just have to figure out this polarity issue your speak of

 

[johnjapan]

New update
Just took apart the pack to check all voltages and noticed that all the cells poles have been reversed
Somehow I backwards charged my whole pack where positive became negative and negative become positive are all my cells ruined?

How do I get it back to normal ?

 

[Gregory]

Just took apart the pack to check all voltages and noticed that all the cells poles have been reversed

If you are saying you have checked a single lithium cell (parallel string of cells) with red probe on cell positive, black on negative and you see negative x.xx Volts on a DMM, then those cells are utterly ruined.

Likely user error, but cheap chargers have also been known to ship with reversed polarity on the leads.

 

[johnjapan]

Just took apart the pack to check all voltages and noticed that all the cells poles have been reversed

If you are saying you have checked a single lithium cell (parallel string of cells) with red probe on cell positive, black on negative and you see negative x.xx Volts on a DMM, then those cells are utterly ruined.

Likely user error, but cheap chargers have also been known to ship with reversed polarity on the leads.

**** ALERT UPDATE*****
Yes red on + black on - gives a negative voltage reading
Just found out that 1 out the 24 cells in the pack is dead!
I've been charging my pack with 1 dead cell for god knows how long could that of caused the reverse polarity?

Are you saying there is no way to fix this?
Cant i just use these as is and change the connectors ?
Convert to a smaller pack and change the charger settings and connectors accordingly?


All the cells are reversed :/

 

[johnjapan]

Just checked the leads on my charger turns out they are reversed as well so all this time my charger has been reverse charging !

It's been working fine for a year but can I continue safely with this reverse issue?

 

[Gregory]

I suspect you are confused and don't know the +ve from the -ve end of the cell.

Otherwise none of this makes sense.
The battery has definitely not been usable for a year if the cells were reverse charged the whole time.

Start your testing/diagnosing again from the beginning.

 

[amberwolf]

And check to make sure you have the black meter lead in it's "common" or "ground" connection, and the red meter lead in the V connection.

It would be best if you post photos of exactly how you are connecting everything, so we can help you find which connection is wrong.

 

[Gregory]

Ha Yes, COM is the black probe!

There's (part of) your problem.


edit:

Now that confusion is passed, measure individual cells, note down the voltages, add them up.
How does that compare to overall battery voltage (i.e before the BMS)?
And Voltage after BMS.

If one cell is 0V a BMS should shut off to protect the battery. And can give suspiciously low voltage readings like 45V.
Charging the one dud cell slowly up to 3.6V may revive it, but it will never be the same.

 

[johnjapan]

Ha Yes, COM is the black probe!

There's (part of) your problem.


edit:

Now that confusion is passed, measure individual cells, note down the voltages, add them up.
How does that compare to overall battery voltage (i.e before the BMS)?
And Voltage after BMS.

If one cell is 0V a BMS should shut off to protect the battery. And can give suspiciously low voltage readings like 45V.
Charging the one dud cell slowly up to 3.6V may revive it, but it will never be the same.

Omg Thankyou so much the black probe is as not in COM thank gir the cells are ok felt for one
There is no Bms with this pack by the way
The defective cell measures at 0.17 volts
Trying to wake it up now hopeless?

 

[danielrlee]

Oh dear..... part of me thinks that you shouldn't be messing about with lithium batteries.

May I suggest a more suitable battery chemistry:

 

[docw009]

Well, at least you learned a little bit on how to use a voltmeter. There's no way a battery and charger could both flip polarities spontaneously.

Those headways screw in, don't they? Maybe you shouldn't be messing with this battery, but a knowledgeable person would replace the bad cell, and check the other 23 cells too. That person would also install a 72V balancing BMS board too. WIth 24 cells at $35 each, it makes sense economically to put in the $60 BMS, even if you don't care about safety.

 

[johnjapan]

Well, at least you learned a little bit on how to use a voltmeter. There's no way a battery and charger could both flip polarities spontaneously.

Those headways screw in, don't they? Maybe you shouldn't be messing with this battery, but a knowledgeable person would replace the bad cell, and check the other 23 cells too. That person would also install a 72V balancing BMS board too. WIth 24 cells at $35 each, it makes sense economically to put in the $60 BMS, even if you don't care about safety.

Appreciate the responses guys!
I took apart the battery pack because I was packing it for transport and then changed my mind.
When I reassembled it I accidentally dropped a screw between the pack and sparks flew
It sparked for about 3-4 seconds then the screw fell to the ground and it stopped. I put the pack outside for safety.
At the time I hadn't repackaged the pack with shrink I guess my fingers were a little unsteady.

I have now tested all the cells with multimeter on the right setting as instructed by the previous poster and all the cells are at 3.3v accept for the dead cell

I was told that these cells can be managed without a bms if you know what your doing and these cells are more forgiving if terms of minute over charging on these cells.

I have now turned my 72v pack into a 60v pack 20 cells and I am changing the charger settings to charge for 73 volts instead of the 87.6 volts the setting for 24 cells x by 3.65 max voltage per cell.

I'm no genius but I'm not stupid either I'm learning just like everyone else did before you knew it all.
So far the cells appear fine and I'll hook up the new 60v pack to my controller today and try it out if I thi to the same problem ill msg again guys!

Thankyou!!!