one possible explanation is the wire from Point14 to the cellpack is broken where it is soldered to the cells.
Can this battery be revived?
- Thread starter Richtea70
- Start date
Likely #14 is low approx. 2.7 - 2.8 volts and the reason why the BMS doesn't switch.
With the other cells at 4.1v it makes sense that #14 is low, one needs to try and get a correct reading for #14.
Can you not probe directly on the cell group ends rather then the wiring ?
One can also get a cell reading via the JST connector , place a needle or pin in Red wire #14 position and also one in Red wire #13 position (don't allow pins to touch/short out). Probe both pins with a meter (again don't allow probes to short each other) one should get a correct voltage reading.
To get the BMS to work one will have to raise #14 manually to 4.1v or very close , then the BMS will switch on. No use charging to a much lower figure on #14 as the BMS won't balance a huge difference in voltage.
The reason the BMS doesn't switch is because it detects a fault , that fault being one cell group is low and below the minimum cell group voltage it expects to see.
Sometimes one can get away with 3v but it is all dependant on how the BMS is programmed.
During the non use period the BMS has bled down #14, most common fault is an open bleed resistor or the battery sw left on .
To manually charge one will need an old 5v mobile phone charger, cut the charge connector off and split the two wires. Pair back the wire ends and solder on a arduino board pin to each wire, check polarity and heat shrink a bit of Red and Black to each pin.
Then one can charge the cell group directly or via the JST sensor connector.
If the JST has 14 thin Red wires , simply put the 5v charger Red pin in the very last Red wire position and the 5v charger Black pin in the 13th Red wire position.
Switch the charger on and then carefully monitor that cell group voltage , once the group reads 4.1v or very near try charging as normal.
With the other cells at 4.1v it makes sense that #14 is low, one needs to try and get a correct reading for #14.
Can you not probe directly on the cell group ends rather then the wiring ?
One can also get a cell reading via the JST connector , place a needle or pin in Red wire #14 position and also one in Red wire #13 position (don't allow pins to touch/short out). Probe both pins with a meter (again don't allow probes to short each other) one should get a correct voltage reading.
To get the BMS to work one will have to raise #14 manually to 4.1v or very close , then the BMS will switch on. No use charging to a much lower figure on #14 as the BMS won't balance a huge difference in voltage.
The reason the BMS doesn't switch is because it detects a fault , that fault being one cell group is low and below the minimum cell group voltage it expects to see.
Sometimes one can get away with 3v but it is all dependant on how the BMS is programmed.
During the non use period the BMS has bled down #14, most common fault is an open bleed resistor or the battery sw left on .
To manually charge one will need an old 5v mobile phone charger, cut the charge connector off and split the two wires. Pair back the wire ends and solder on a arduino board pin to each wire, check polarity and heat shrink a bit of Red and Black to each pin.
Then one can charge the cell group directly or via the JST sensor connector.
If the JST has 14 thin Red wires , simply put the 5v charger Red pin in the very last Red wire position and the 5v charger Black pin in the 13th Red wire position.
Switch the charger on and then carefully monitor that cell group voltage , once the group reads 4.1v or very near try charging as normal.
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I would rather have something specifically for charging single cells. I use the charger module out of Poundland USB packs for reviving cells.
Mocked up a charger and put a charge through the pack, still nothing registering after having the charger on for nearly 2 hours. I would expect to see at least some voltage in the cells after this amount of time surely?
Beginning to think it might be duff cells after all. I charged via the jst pins so my only other option is to put the phone charger directly on the cells to rule out duff connection/wiring but I’m not holding out much hope
Beginning to think it might be duff cells after all. I charged via the jst pins so my only other option is to put the phone charger directly on the cells to rule out duff connection/wiring but I’m not holding out much hope
I wouldn't lose heart just yet. Can you show a picture of how you are measuring voltage on the last bank which seems to be showing 0V?Mocked up a charger and put a charge through the pack, still nothing registering after having the charger on for nearly 2 hours. I would expect to see at least some voltage in the cells after this amount of time surely?
Beginning to think it might be duff cells after all. I charged via the jst pins so my only other option is to put the phone charger directly on the cells to rule out duff connection/wiring but I’m not holding out much hope
As Neal advised above, 5v phone charger, put through the 14th (positive) and 13th (negative) pins of the jst connector which normally plugs into the BMS
I suspect what you refer to as a 'charger' is in reality just a 5V power supply.
How can that power supply, on its own, 'charge' a Lithium battery properly ?
It can't do the whole job, and needs to be manually monitored to prevent overcharging. It works because the charger is dumb, so doesn't worry about being dragged down below 5V, and at 500mA, it is slow enough for a careful user to disconnect it before exceeding 4.2V on the target cells.
But not to be left unattended.
Thanks Matthew,
Yes, I have been monitoring and as you say it’s just to get a charge into the first bank of cells.
At the end of the day any generic charger is just that, a power supply whether 24, 36 or 48v etc,etc.
One needs to understand that which the 5v charger is being purposed for.
It isn't to charge a complete battery pack, at only 5v it is for single cell or cell group charging, it's a simle technique to manipulate single /group cell voltage upwards whilst being monitored.
If the voltage of the #14 cell group is not showing a reading then it may well be dead.
Not wishing to teach one to suck eggs , did one check the out put of the charger to ensure it does show 5v ?
The use of a small 5v input dumb charger /power supply is a common feature used on ebike forums for trying to restore a single cell voltage, once volatge is suitabe the normal dumb charger used can finish off the job.
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Yes, pins are outputting 5v. Had it on charge for a couple of hours this morning with the 5v charger but this time directly on the cell group rather than the Jst connection.
Still not showing anything, so I think I'm going to give up!
If there's anyone in the Reading/West Berkshire area who wants it they can have it, it's a 52v 20ah and all of the other cell groups are taking/holding a charge,
Thanks
How easy?
I guess I'd need to cut away the dead cells, and then solder up to a new BMS? My soldering skills aren't great!
And if I removed the duff cell (which consists of 4 batteries), what would I be left with a 48v/10ah battery?
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Hi RichB . I have been following your thread with interest. I appreciate it will be very frustrating and annoying to you but wonder if I may ask a question out of curiosity?
Whoosh suggested a broken wire. I know very little about ebike batteries but the thought had also occurred to me so I’m interested to know if B14+ back ro the BMS has good continuity. Did you check the wire from its connection to the cells back to the BMS? No loose connections, dry solder joints or hidden breaks under the insulation sleeve?