new built battery will not charge

[EBikeDC]

Hello Everyone,
I had an old battery inside a black container that slides into a holder on my ebike that needed to be rebuilt. The battery was a 36 v 10s5p configuration and there was room within the black case for a 36 V 10s6p so that is what I upgraded to. The batteries I purchased for the rebuild were all tested at 3.4 volts and all the series are at 3.4. The 3 - 3 - series voltage is 10.1 as expected and the total voltage of the battery pack is 34 volts. I have installed the battery onto my ebike and everything works well. I tested the bike up a few steep hills to test a load and it climbed with no issues. The battery level on the ebike states below 3/4 full and the gauge on battery states 1/2 full. cells are Samsung ICR18650 26J. Checked 30 amp fuse and it's good.

So here is the issue: the battery will not charge!

I've checked the 2 battery chargers that I have and they work on my other batteries, putting out 41 volts at 2 amps. The charging port is a two wire prong (5.5mm x 2.1mm coaxial) with the positive in the center and the negative is on the outside. I've confirmed that the new charging port is working in side the battery. Both chargers react the same, red light on, yellow charge light comes on for a second, and then the green charge light comes on. I think I can weed out a bad charger seeing it works on both of my other ebike batteries.

The other thing I've done is reset the BMS as well as removed the battery from the case, away from the BMS and tried to just charge the battery standalone and the same results as stated above. I'm confused why this battery will not charge and I don't know what my next move might be. Any help or suggestion would be appreciated. Is there some type of protection within the cells that is stopping the charge? The cell are unprotected. Would draining the battery down to a lower voltage help?

Vr-Dc ebike rider (EbikeDC)

 

[amberwolf]

Some questions and thoughts:

I had an old battery inside a black container that slides into a holder on my ebike that needed to be rebuilt. The battery was a 36 v 10s5p configuration and there was room within the black case for a 36 V 10s6p so that is what I upgraded to.

Was the original BMS reused, or was a new one used?

If original, what was the problem with the original pack requiring rebuild? (to ensure it's not related to your present issue)

The batteries I purchased for the rebuild were all tested at 3.4 volts and all the series are at 3.4.

Are they all at that 3.4v right now, when attempting to charge?

The 3 - 3 - series voltage is 10.1 as expected

What does this refer to? I don't know of any voltages in a 10s pack that should be 10.1 volts, so I can't think of what this might mean for your pack.

and the total voltage of the battery pack is 34 volts. I have installed the battery onto my ebike and everything works well. I tested the bike up a few steep hills to test a load and it climbed with no issues.

Is the 34v at the cells, the B+ and B- on BMS, or at the P- BMS discharge port, or the C- BMS charge port, or at some other point?

Is this under load during those rides, or an unloaded bench test?

The battery level on the ebike states below 3/4 full and the gauge on battery states 1/2 full.

Sounds like they were designed for different chemistries and/or pack voltages than each other, or simply just have different behavior designs (what voltage they equate with what SoC).

Checked 30 amp fuse and it's good.

Unless the fuse is on the charge port between charger and BMS, it wouldn't matter if it was blown or had a connection fault.

So here is the issue: the battery will not charge!

I've confirmed that the new charging port is working in side the battery.

Do you mean the BMS board's C- port? If so, what test was done, and what were it's results?

Both chargers react the same, red light on, yellow charge light comes on for a second, and then the green charge light comes on.

For the average charger, that normally indicates the charger can't feed current to the cells (the green light usually comes on once current has dropped below a few mA, and the charger shuts it's output off). This usually means the BMS has turned off the charge port because it sees some out of limit condition (cell too low, cell too high, cell voltage difference too great, pack current too high, temperature too low or high, etc)

The other thing I've done is reset the BMS as well as removed the battery from the case, away from the BMS and tried to just charge the battery standalone and the same results as stated above. I

If by this you mean that the cell block won't charge directly from the charger, bypassing the BMS and all interconnects outside of the cell block, and you are certain polarity is correct, then the usual fault for a "smart enough" charger is the current draw is too high so it sees a "short circuit" and goes into protection mode to prevent a fire in the charger, battery, or cabling.

 

[docw009]

If you hook the charger directly to the positive/negative of the cells, it will charge, right? There's nothing to shut off the charger when you do that. I don't understand why the cells won't charge if you put the charger directly to them. They have to, so I figure you did this wrong,

But if you hook the charger to the positive of the cells and to the C- terminal on the BMS, it does not charge? When you ran the bike, and climbed the hills, was the bike running thru the BMS? That would be positive output connectd to positive of battery, and negative connected to P- on BMS. The B- pin on the BMS connected to negative of cells.

You might want to unplug the balance cable, put a pin in the most negative wire, and check the next ten pins sequentially, making sure that the voltage goes up in 3.4V increments or whatever the cells are at. It's a good sanity test. Even the best of us sometimes wire a balance pin out of order.

Finally, I have had the same mysteries with BMS that were working, but after I did something like resolder a broken thermal sensor, they no longer worked. Could be static discharge or what. I don't know.

 

[EBikeDC]

I had an old battery inside a black container that slides into a holder on my ebike that needed to be rebuilt. The battery was a 36 v 10s5p configuration and there was room within the black case for a 36 V 10s6p so that is what I upgraded to.

Was the original BMS reused, or was a new one used? - I reused the original BMS. This is a good point!

If original, what was the problem with the original pack requiring rebuild? (to ensure it's not related to your present issue) - Battery no longer held a charge and failed at 50% of voltage indication. Battery would shut off on loaded climb. The battery was old and I didn't have the history of how it was treated before I purchased it used. It could of had some bad cells, but I didn't want to replace cells and then I'm chancing more bad cell down the road.

The batteries I purchased for the rebuild were all tested at 3.4 volts and all the series are at 3.4.

Are they all at that 3.4v right now, when attempting to charge? - Yes, they are all around 3.4v/3.3v right now and I checked the leads to the BMS too. They are also 3.4 when I try and charge it.

The 3 - 3 - series voltage is 10.1 as expected

What does this refer to? I don't know of any voltages in a 10s pack that should be 10.1 volts, so I can't think of what this might mean for your pack - Yea. I thought when I wrote this I should of removed it. It a reference point. If I check the voltage at the 3 - 3s6p they come out to 10,1 volts... Ie... 3.4+3.4+3.3 = 10.1. This is just noise and should be removed from the original post.

and the total voltage of the battery pack is 34 volts. I have installed the battery onto my ebike and everything works well. I tested the bike up a few steep hills to test a load and it climbed with no issues.

Is the 34v at the cells, the B+ and B- on BMS, or at the P- BMS discharge port, or the C- BMS charge port, or at some other point? - the 34 voltage is at the cells and at the P- (discharge port on BMS), C- BMS charge port. The 34v is also the lead to the BMS (is that the B+)

Is this under load during those rides, or an unloaded bench test? - I don't check the voltage under load, if that is what you are asking. I can say that the WATT on the ebike was max and the battery drop low as normal.

So here is the issue: the battery will not charge!

I've confirmed that the new charging port is working in side the battery.

Do you mean the BMS board's C- port? If so, what test was done, and what were it's results? - This was a continuity check and a voltage check to the BMS charge port C- at 41.1 v with the positive led on the positive incoming charger.

Both chargers react the same, red light on, yellow charge light comes on for a second, and then the green charge light comes on.

For the average charger, that normally indicates the charger can't feed current to the cells (the green light usually comes on once current has dropped below a few mA, and the charger shuts it's output off). This usually means the BMS has turned off the charge port because it sees some out of limit condition (cell too low, cell too high, cell voltage difference too great, pack current too high, temperature too low or high, etc) - This is great information as I learn. Thank you!

The other thing I've done is reset the BMS as well as removed the battery from the case, away from the BMS and tried to just charge the battery standalone and the same results as stated above. I

If by this you mean that the cell block won't charge directly from the charger, bypassing the BMS and all interconnects outside of the cell block, and you are certain polarity is correct, then the usual fault for a "smart enough" charger is the current draw is too high so it sees a "short circuit" and goes into protection mode to prevent a fire in the charger, battery, or cabling. - Polarity confirmed to be correct. I did this outside as I was concerned to the potential of fire. Glad to know..

I have 2 more batteries to build, but will hold off on them until this is solved.

Appreciate the Help! VR- EBikeDC

 

[EBikeDC]

If you hook the charger directly to the positive/negative of the cells, it will charge, right? There's nothing to shut off the charger when you do that. I don't understand why the cells won't charge if you put the charger directly to them. They have to, so I figure you did this wrong,

But if you hook the charger to the positive of the cells and to the C- terminal on the BMS, it does not charge? When you ran the bike, and climbed the hills, was the bike running thru the BMS? That would be positive output connectd to positive of battery, and negative connected to P- on BMS. The B- pin on the BMS connected to negative of cells.

You might want to unplug the balance cable, put a pin in the most negative wire, and check the next ten pins sequentially, making sure that the voltage goes up in 3.4V increments or whatever the cells are at. It's a good sanity test. Even the best of us sometimes wire a balance pin out of order.

Finally, I have had the same mysteries with BMS that were working, but after I did something like resolder a broken thermal sensor, they no longer worked. Could be static discharge or what. I don't know.

If you hook the charger directly to the positive/negative of the cells, it will charge, right? There's nothing to shut off the charger when you do that. I don't understand why the cells won't charge if you put the charger directly to them. They have to, so I figure you did this wrong,

When I connect the battery cell positive/neg leads to the charger.... No charging happens.

But if you hook the charger to the positive of the cells and to the C- terminal on the BMS, it does not charge? - Correct.. no charging.

When you ran the bike, and climbed the hills, was the bike running thru the BMS? That would be positive output connectd to positive of battery, and negative connected to P- on BMS. The B- pin on the BMS connected to negative of cells. - Yes, BMS was utilized on bike test ride.

You might want to unplug the balance cable, put a pin in the most negative wire, and check the next ten pins sequentially, making sure that the voltage goes up in 3.4V increments or whatever the cells are at. It's a good sanity test. Even the best of us sometimes wire a balance pin out of order. -- This is a good point. I double checked this right now and they increase at the 3.4 increments.

Finally, I have had the same mysteries with BMS that were working, but after I did something like resolder a broken thermal sensor, they no longer worked. Could be static discharge or what. I don't know. - changing out the BMS might be my next step. Good call. It is interesting that this BMS only has one thermal sensor, unless there is one built in the BMS that I don't see.

 

[amberwolf]

Are they all at that 3.4v right now, when attempting to charge? - Yes, they are all around 3.4v/3.3v right now and I checked the leads to the BMS too. They are also 3.4 when I try and charge it.

"around 3.4v/3.3v"? What exactly are the voltages of each group? BMS can be designed so that if there is a voltage difference between cells of greater than a certain amount (commonly 0.1v, which is what you see here) the BMS will shut everything off to prevent problems with the pack, because this amount of difference indicates a serious imbalance in the cells, meaning they are very different in capacity and characteristics, and have aged enough they might need replacement.

Is the 34v at the cells, the B+ and B- on BMS, or at the P- BMS discharge port, or the C- BMS charge port, or at some other point? - the 34 voltage is at the cells and at the P- (discharge port on BMS), C- BMS charge port. The 34v is also the lead to the BMS (is that the B+)

Just to be sure: are you measuring wiht the red + meter lead on the B+, and the black meter lead at each of these other points, and reading the same voltage from every one?

If so, it means that all of the ports are "working", assuming that none of the voltages drop when connected to the controller or some other load.

Is this under load during those rides, or an unloaded bench test? - I don't check the voltage under load, if that is what you are asking. I can say that the WATT on the ebike was max and the battery drop low as normal.

What specifically does "the battery drop low as normal." mean?

If by this you mean that the cell block won't charge directly from the charger, bypassing the BMS and all interconnects outside of the cell block, and you are certain polarity is correct, then the usual fault for a "smart enough" charger is the current draw is too high so it sees a "short circuit" and goes into protection mode to prevent a fire in the charger, battery, or cabling. - Polarity confirmed to be correct. I did this outside as I was concerned to the potential of fire. Glad to know..

If you measure 34v at the cell block main + and -, and no BMS was used, charger directly connected to the cell block's main + and -, correct polarity, and it still coudln't charge, there is nothing that could impede the charger's operation.

What voltage do you see at the main cell block + and - while the charger attempts to start charging?

If it only remains perfectly steady at 34v, and never even slightly changes (usually it should rise by at least a tiny amount as the charger ramps up current), it is likely the charger is not *actually* connected to the cell block.

you can verify this by measuring at the charger's internal board where it's leads connect. Before you turn the charger on, but after it is connected, you should measure 34v at that point. If you don't, please post what you do measure. If it's zero, then there's something wrong with the connection between charger and cell block.

 

[amberwolf]

- changing out the BMS might be my next step. Good call.

Assuming everything you've noted so far is true, then changing the BMS will do nothing for you about the posted problem, because it's not in the circuit when you connect the charger directly to the cell block main + and - and charging still does not occur.

The BMS could of course still have a problem somewhere, but it isn't causing this one.

 

[rafalg]

If charger doesn't work when connected directly to battery terminals then it's probably problem with the charger. But check also the DC plug/socket, they aren't usually high quality and can destroy themselves easily

 

[EBikeDC]

Hello everyone.. Thanks for all the support and conversation!

GOT IT...

The connection between the battery +/BMS C- and the charger was not making a connection. See photo. The ground (black) was ok, the positive (red) isn't good. When I did the continuity check it gave me a positive signal, however when it was connected all the way in nothing. It (most) always something simple... HELP TICKET --- closed..

This is my first battery build and I thought I did something wrong and I was ready to start disassembling it..

 

[amberwolf]

Thank you for coming back and posting the results...most people don't.

However...the fault you found that when fixed solves the problem means you couldn't have actually connected the charger to the cell block's main + and - after all....because that would have completely bypassed any of the BMS wiring including the problematic connection, and would have worked.

When asking for help, it is very very important to provide accurate information, so that you will get accurate and useful help.