BMSB battery will not charge from 38.5V

[A..dam]

I got 11.6 Ah Panasonic bottle style battery.
This is the FIRST time I am charging this battery.

When arrived voltage was 41.5V and 4 segments on the capacity indicator were green. After setting some parameters and testing the system voltage dropped to 38.5V and I have 3 green capacity indicators.
Connected charger model #120 from BMSB and there is no charging current going to the battery.
The voltage of the charger is 41.8V and the status light on the charger is green = battery charged.

Also a quirk. Battery has 0/I switch but power to the motor is available in both positions.
Website says switch to I position for charging...

Is this battery behaviour normal???

Thanks, A..dam

 

[amberwolf]

The switch may be fused into the "O" position internally, if switching it to "I" does not allow charging.

You'd have to measure voltage at the charging port or continuity on the switch.

 

[d8veh]

The switch goes directly to the BMS. It interrupts the charge and discharge mosfets; however, there are different versions of the BMS, so I can't guarantee that. You need to take the top off and have a look at the BMS to see if there's anything obvious wrong. Unplug the switch to see if you can switch the battery manually by bridging the pins.

While you're there, check the voltages on the multi-pin connector's from the cells. If your BMS is the same as mine, there' s two connectors. The sequence is strange and swaps from side to side - something like B1 swap; B2, B3 swap; B4, B5 swap; and so on.

 

[A..dam]

Can topping up be performed on this battery at any time OR the voltage must drop down below a certain threshold?

Other info:
1. Yesterday, I used bike for few kms, current voltage without load 36.7, still no charging
2. Tested charger under the resistive load (lightbulb). It provides the current
3. Connected voltmeter (>20 kOhms/V) to a charging port of the battery. For the first few minutes voltage is 25V and then jumps to 36.7V
4. I am including photo of the battery. The (black plastic) bottom with the charging port is secured with 3 screws, top (black plastic) also has 3 screws. Do I need to remove just the bottom plastic to see connections of BMS/switch? Any tips how to handle removal?

P.S.
I have contacted BMSB, and waiting for an answer to my problem

 

[A..dam]

Got response BMSB.
Battery should charge at any time. A sliver of hope is gone.
Bad battery management system must be the cause.
(if the battery external switch is "fused" in the closed/on position, it should not interfere with charging of the battery as the switch is supposed to be in a such position for charging)
N.B. Battery still has the ORIGINAL and INITIAL charge.
Battery was received in April, but my do-it-yourself project of building my own electric bike was delayed by lack of parts.
I never tried to charge the battery until recently, in July.

Right now, I am trying to negotiate replacement with BMSB, I have paid 400$ USD incl. shipment for it...

 

[d8veh]

When the voltage of the battery on the output terminals measures 25v, it means that the BMS has switched off the discharge for whatever reason.

 

[A..dam]

I connected a voltmeter 20 kohm/V to a charging port, (NOT discharge terminal) it shows voltage of 23.4V for a few minutes and than it jumps to the current voltage of the battery which is now 36.0V. It needs some very minor current to flow to show the full voltage. When I connected a digital meter with very high internal resistance , the voltage stayed at ~ 24V until I connected 40 kohm resistor across.
I did this testing ONLY to see if the charging port of the battery is connected to the circuit inside.
I also tested charger under resistive load (light bulb). It provides ~0.5A to a 35W halogen 120V lamp at 41.5V.
So, charger looks OK to me.
Tomorrow, I might test the charging of the battery with a power supply where I can set independently both the voltage and the current.
But, I am 99% sure that this is BMS issue not the charger...
Plus, wtf with the on/off switch which does not work from the day one.
I disregarded that switch issue unfortunately. I should have contacted BMSB right away...

 

[d8veh]

I connected a voltmeter 20 kohm/V to a charging port, (NOT discharge terminal) it shows voltage of 23.4V for a few minutes and than it jumps to the current voltage of the battery which is now 36.0V. It needs some very minor current to flow to show the full voltage. When I connected a digital meter with very high internal resistance , the voltage stayed at ~ 24V until I connected 40 kohm resistor across.
I did this testing ONLY to see if the charging port of the battery is connected to the circuit inside.
I also tested charger under resistive load (light bulb). It provides ~0.5A to a 35W halogen 120V lamp at 41.5V.
So, charger looks OK to me.
Tomorrow, I might test the charging of the battery with a power supply where I can set independently both the voltage and the current.
But, I am 99% sure that this is BMS issue not the charger...
Plus, wtf with the on/off switch which does not work from the day one.
I disregarded that switch issue unfortunately. I should have contacted BMSB right away...

If it was the charge port at 25v, then the charge mosfet has been switched off by the BMS for whatever reason. The normal reason would be that one of the cells has reached 4.2v. The balancing system will then bleed the charge from that cell until it goes down to about 4.15v, so after some time, the BMS will re-open the mosfet, if that's the reason.

You need to measure the cell voltages, like I said above.

 

[A..dam]

It is impossible for any cell(s) to be fully charged at this point.
The BMS MUST BE the culprit.
I have offered to BMSB trying to charge with a different charger, and waiting now for their response as I do not want to be "blamed" for any damage.
The other charger I have in mind has fully adjustable voltage 0-50 V and current up to 1 A.

 

[d8veh]

It is impossible for any cell(s) to be fully charged at this point.

No it isn't. We're trying to help you, but you never listen. if you know best, carry on.

 

[A..dam]

I told BMSB representative that there is a problem with the battery NOT the charger more than 3 weeks ago.
After convincing them about that, they now want me to troubleshoot battery by opening the case.
Every e-mail exchange takes 4-5 days so it might take till Christmas ;-( to resolve the issue, if I am lucky.
I paid with shipping 375 US$ and have expectation of a GOOD product.
The battery is BAD and I told them to send a new battery.
Will keep you posted...

d8veh:
I strive to put forward logical explanations of the results of testing and observations.
"If it was the charge port at 25v, then the charge mosfet has been switched off by the BMS for whatever reason."
As I explained, the voltage would rise to full batery voltage if there is a minimal current flowing.

"The normal reason would be that one of the cells has reached 4.2v. The balancing system will then bleed the charge from that cell until it goes down to about 4.15v, so after some time, the BMS will re-open the mosfet, if that's the reason."

Battery would stay in its state for weeks without signs of "balancing system will then bleed the charge from that cell" or BMS opening the mosfet. This would point to the issue with battery management system not working properly.

It appears (did not measured actual A) that battery provides good power to the motor and its capacity seems reasonable for the distance covered and taking into account drop from 41.5 V to 36 V.
So my question would be: could charging be completely inhibited if one of the 10S series is somehow bad? Or, I should loose only 1/4 of the capacity?
Thanks, A..dam

 

[A..dam]

I got 11.6 Ah Panasonic bottle style battery
https://bmsbattery.com/ebike-battery/734-36v116ah-bottle-ebike-battery-pack-with-charger-battery.html
1. When arrived, battery voltage was 41.5V and 4 segments on the capacity indicator were green.
2. After using it for a dozen kms or so voltage dropped to 36V and I have 3 green capacity indicators.
Looks like battery provides good power to the motor.
3. Connected to charger, no current flowing into battery. This was the FIRST time I was charging this battery.
4. Tested charger, is OK, tested battery charging with other charger, battery will not charge.
5. Strange quirk. Battery has 0/I switch but power to the motor is available in both positions.
6. Opened the case. Unplugged the rocker switch, it works, it is open or closed as measured with ohmmeter.
N.B. this switch connects to BMS only, as seen on picture.
7. Measured voltages between B “minus” and B1, B2, through B10, see v label on the picture. B1 was 3.6V, B2 7.2V and all next voltages increased by the same amount of 3.6V to voltage between B “minus” and B10 being 36V.
Questions:
Q1. Are cells OK? OR it is BMS issue?
Q2. What is arrangement of cells? 4 in parallel x 10? OR 10 in series each which are then connected in parallel?
Q3. Does anyone has diagram of the circuit AND wiring going into the battery holders?
N.B. It is very difficult to see connection within battery holders
Q4. Why the rocker switch has no input on working of the battery?
What else can I troubleshoot?
Thanks, A..dam

 

[d8veh]

Right, your cells are all OK. The battery is working, but it won't charge with two different chargers. The on/off switch appears to be working

Two reasons I can think of why it's not charging.

1. The charge isn't reaching either the BMS or the cells even though the mosfet is open. That's easy to test. You need to connect the charger to the main output positive and the negative to the point on the BMS where the wire from the charge socket is soldered. That will eliminate/confirm whether the charge socket is faulty. If still no charge, then you need to connect the negative to the cell side of the BMS (Bypass BMS). That will confirm whether the mosfet is closed or whether there's a downstream connection fault. Those two tests will logically point to where the problem is, so do them and report back.

2. The charge mosfet is closed because the BMS rightly or wrongly thinks that there's a problem. The output mosfets are open, so it can't be a sense wire connection or low cell. Another reason to switch off the charge mosfet is when a cell reaches 4.2v, but your measurements show that that's not the problem. The third reason is that the temperature sensor is telling the BMS that the temperature is too high. Lastly, the BMS could just be faulty. These last two possibilities are not so easy to test, but, on the good side, they're not so likely, so let's leave them until after the easy tests above.