Problem with battery 72v 20ah

[makadam]

I have a problem with e-scooter battery 72v 20ah. Scooter has about 5000km, battery is 2 years old about 170 charging cycles. Battery voltage when is full charged is max 76.5V and only can be charged directly from battery connector( I need to remove battery from scooter and charge directly using battery C14 3pin charging port. When I try to charge from scooter plug (battery is connected with scooter with M25 plug 5pins), BMS stop working and I need to open battery to unplug 20pins connector (20s) and after some time to plug connector back. Using this method BMS is reset. Also charging indicator on scooter dashboard and battery itself is not accurate it show 50% when battery is empty (about 65V). Battery model is ZM11 LI-Ion with error diagnostic led. BMS model is BS01-B 181024 and motor is 3000W Bosch 72v. I measure all single series and all of them have 3.82V when fully charged!
Can some one give me some direction about resolving this problem.

 

[amberwolf]

I have a problem with e-bike battery 72v 20ah. Scooter has about 5000km, battery is 2 years old about 170 charging cycles.
<snip> Also charging indicator on scooter dashboard and battery itself is not accurate it show 50% when battery is empty (about 65V). Battery model is ZM11 LI-Ion with error diagnostic led. BMS model is BS01-B 181024 and motor is 3000W Bosch 72v.

Did the system ever work as you expect it to, or has it always worked the way it does now?

If full-charge voltage has dropped over time, or range has dropped, or performance, it's likely that cells in the pack have degraded or failed, and the BMS is trying to protect them from overcharge or overdischarge.

Do you ever see any of the error codes the label contains?

Battery voltage when is full charged is max 76.5V and only can be charged directly from battery connector( I need to remove battery from scooter and charge directly using battery C14 3pin charging port. When I try to charge from scooter plug (battery is connected with scooter with M25 plug 5pins), BMS stop working and I need to open battery to unplug 20pins connector (20s) and after some time to plug connector back. Using this method BMS is reset.

That usually indicates the BMS has detected a cell problem outside it's normal limitations, and has shut off the charge port to prevent cell damage that could lead to a fire. A well-designed BMS will do this, and will lock out charging (unless reset) so the battery won't catch fire from a damaged cell during charging, but cheap ones are hit-and-miss for this function.

Yours does do this, so it's probably just doing the job it's designed to do, and bypassing it this way may be dangerous.

Sometimes it just means the BMS has failed, but that's much rarer than cell failures.

Bypassing the charge port and charging thru the discharge port completely bypasses the BMS protection against cell damage and fires, and just exacerbates whatever problem the pack is having, potentially causing further damage to the cells.

I measure all single series and all of them have 3.82V when fully charged!

This is not very full for the typical Li-Ion cell. If the BMS is designed for long pack life it may be intentional, to not charge them fully, but the more common BMSs charge to 4.2v/cell.

Since we can't know for certain what the BMS is designed to do (no useful google hits on numbers from it), , we can make a guess based on charger voltage, and the 84v limit voltage on the case label, which matches the typical 72v battery of 20s, 84v fully charged, to 4.2v/cell.

What is the voltage the charger outputs when not connected to the pack?

If it doesn't output a voltage until it's connected to the pack, you'll need to put your leads on the charger output wires in a way that keeps them there even when not connected to the battery, but still allows you to connect it to the battery. Then do that, and then disconnect the charger from battery, watching the voltmeter display. It should rise to some voltage before shutting off, and that's the charger's actual output voltage, what it was intended to charge the battery to.

Knowing that, and guessing the 84v is what you *should* see, we can guess if it's a charger problem or a pack problem.

 

[makadam]

Did the system ever work as you expect it to, or has it always worked the way it does now?

Scooter was bought brand new and there was no problem with range (35-40km full charged) and now only 25-28km,

If full-charge voltage has dropped over time, or range has dropped, or performance, it's likely that cells in the pack have degraded or failed, and the BMS is trying to protect them from overcharge or overdischarge.

It has only 170 charge cycles I think that samsung 29e 18650 will do much more!

Do you ever see any of the error codes the label contains?

When this first time happened I charged scooter by regular port without moving battery out and there was no codes on battery indicator, battery was completely dead so I need to open it and simple remove 20s balancing wires and after couple of minutes putting back. This method reset battery and after that I only charge battery from battery charging port (3pin C13 plug.) not battery discharge which is M25 connector If I try to charge by scooter regular port is connected with battery with M25 5pin connector (maybe UART) which has 5 data wires that goes to BMS and instrument cluster and I think that something is wrong with data transmitted and received by BMS and simply cut the charging, Also when battery voltage is about 67V (empty 3,2v per cell) battery indicator shows about 40% power which is strange!

Bypassing the charge port and charging thru the discharge port completely bypasses the BMS protection against cell damage and fires, and just exacerbates whatever problem the pack is having, potentially causing further damage to the cells.

Battery has 2 different ports for charging and disharging only diference is data pins conencted to BMS when charging from regular scooter 3pin C13 port

What is the voltage the charger outputs when not connected to the pack?

I already tested it is ok 84V
My only logical explanations is that maybe BMS is programmed to lower cell voltage after some time but strange thing is that both battery indicators on dashboard andindicator on battery does not show correctly % od battery. When battery is charged with 76.5V it shows 100%. I put addition indicator on scooter to monitor battery voltage and when battery is almost empty 66v ON DASHBOARD i HAVE 40%. Before that dashboard worked correctly!
Charging port differences

 

[makadam]

To me and again, my opinion, this is very dangerous because it can cause a cell or more to overcharge which can incinerate the battery pack. Li-Ion fires are horrific. You don't want to take this chance OP.

Inside battery, BMS connection for charging and discharging is same only difference is that M25 (picture above) has additional 5 wires which I believe is for controlling discharge process and this wires are connected to BMS and maybe also for battery configuration (Uart,CAN, RS485). Also this port was designed to charge scooter battery without removing through this port and I was using this method of charging almost 170-180 times without any issue. Now I can't charge battery in this way because when battery is charged over 90% charging stops and bms is locking battery output and I need to reset it by removing balancing wires connector and after some time putting back. If I charge from battery charging port (this port has only 2 pins) charging is stoped on 76V and battery is working but not fully charged!

you could even experiment with a Smart, bluetooth BMS to monitor parallel voltages real time, swap out discrepant cells etc.

This BMS I believe it is top class and has a couple additional connectors which i believe is for programing and real time data with some additional hardware, because I found on company page that as option was monitoring battery cells and other information on your phone.
Also on BMS board is some reset button but I don't know the purpose of this button and I am affraid press it

 

[makadam]

After some testing, I recharge battery to regular scooter charging port up to 83.5V (charger is 84V 3A) and battery was shut down with led blinking error code (on battery description there is no such error code). Then I disconnected 20s balance wires and connect them again and battery start working without any problem with 83.5V. I measured every balance wire to check disbalance but all series have 4.17V-4.18V (20s7p).LCD display worked correctly (battery capacity and range on LCD was Ok) - i made 20km and voltage was 77v and battery 65%, until next day when battery capacity was again 100% (on battery display and scooter dashboard but voltage is same 77V. Battery is connected with dashboard using same M25 connector with 3 + 5 pin wires! (3pins is going to controller and 5 pin to dashboard). I think that BMS is broken or maybe some problem with software, but I cant find any documents on internet about management port but I know that is 5 pin maybe UART or CAN. Scooter is ZNEN E-F11 and I don't have any technical support from them!

 

[makadam]

After some testing i think bms has some software issues, I found that smd switch reset Bms so I installed external switch and connect with one on pcb. I dont have any bms documentation or find some info on internet about this Bms. I contacted China factory that produce this scooter but never get reply. I think that bms have some configuration bugs. I check batteries several times ( fully charged at 4.17v and empty with 3.2v there is no unbalance so only logical explanation is software bug when battery is fully charged bms simply blocking output.

 

[eMark]

That usually indicates the BMS has detected a cell problem outside it's normal limitations, and has shut off the charge port to prevent cell damage that could lead to a fire. A well-designed BMS will do this, and will lock out charging (unless reset) so the battery won't catch fire from a damaged cell during charging, but cheap ones are hit-and-miss for this function.

Yours does do this, so it's probably just doing the job it's designed to do, and bypassing it this way may be dangerous.

Sometimes it just means the BMS has failed, but that's much rarer than cell failures.

Knowing that, and guessing the 84v is what you *should* see, we can guess if it's a charger problem or a pack problem.

Could it possiby be a BMS programming problem and/or faulty BMS ??

I already tested it is ok 84V (referring to Charger output)

My only logical explanations is that maybe BMS is programmed to lower cell voltage after some time but strange thing is that both battery indicators on dashboard and indicator on battery does not show correctly % od battery. When battery is charged with 76.5V it shows 100%.

Is it possible that programming software issues have been altered resulting in a defective BMS?

I measure all single series and all of them have 3.82V when fully charged!3.82V?)

Are you sure all twenty p-groups were exactly identical at 3.82V with no variance between the twenty p-groups ?

I think that bms have some configuration bugs. I check batteries several times ( fully charged at 4.17v and empty with 3.2v there is no unbalance so only logical explanation is software bug when battery is fully charged bms simply blocking output.

Your Charger is able to charge to 83.4V (4.17V per p-group). Your Samsung 29E 20S battery doesn't seem to be the problem after 170-180 cycles. Do all twenty p-groups have identical voltages whether after discharge or charge ??

You have said all of the 20s p-groups were at 3.82V, and then again all twenty p-groups at 4.17V (fully charged). That doesn't suggest that one or more of the 20s p-groups is the cause of the problem. You seem to have done a pretty good dianostic and agree with you that the problem is just as likely or more likely the BMS than the battery. If it was a battery problem there would be some imbalance variance between the twenty p-groups after both discharge and charge.

When you say 4.17V fully charged are you sure that is the same/identical voltage of each of the twenty p-groups?

 

[makadam]

You have said all of the 20s p-groups were at 3.82V, and then again all twenty p-groups at 4.17V (fully charged).

When I charge scooter using scoter charging port battery is fully charged about 4.17 per parallels cell and bms is blocked. Before i found this reset switch i simply reconnect 20s balancing wires and bms start to work. If i charge battery from battery charging port after i remove from the scooter, it is only charged to 76-77v but bms is not blocked. Only differences between this two different charging methods is additional 5 pin data lines which is connected to battery when i charge scooter without removing battery. And yes Iam sure that there is no unbalancing between series more than 0.05v