Charger will not connect with Li-ion battery on tree trimmer

[Peter Brigg]

My son has asked me to look into this device pictured. Of course it is just out of warranty and now having the above problem. From my research the charger will not deliver it's output until it gets a signal from the battery (when connected) I have opened up both devices and taken photos. I can access some of the cells (10 in series) it looks like and they register 0.3v so perhaps they are finished?
I am careful with mains voltage (240v in Australia) and take my own safety seriously. One theory is that the battery became severely dischaged and cannot deliver a signal to the charger to start up.
Can someone suggest a repair? In the first photo the charger is on the R and the battery is in the L. In the second photo the image is of the BMS on top of the battery

 

[amberwolf]

If y ou mean that measuring from + to - on a single cell reads 0.3v, at the actual cell, then yeah, the ones reading that have failed.

If you're reading teh voltage at some other point than the actual cells, then there could be a connection or interconnect fault, or a protection opened, etc. (or failed cells)

 

[Peter Brigg]

Yes-unsure about exactly where the voltage is measured from-the cells are encased in a plastic holder and difficult to get back to the cell itself-perhaps just get the charger working and see if a charge corrects things. The design overcomplicates the situation. If you are designing a charger where there is lto be ittle chance of a spark or short occurring between the outputs then the standard push in plug keeps the terminals safely protected from shorting

 

[fechter]

Just measure voltage across B- to B1, B1 to B2, B2 to B3, ... etc. to get the voltages on the individual cells. Also check the fuse with an ohmmeter to make sure it's not blown.

If the cells are too low, it won't have enough power to enable the BMS circuit. It may be possible to use a bench power supply or individual cell charger to bring the cells up enough for the charger to enable.

 

[batteryGOLD]

low volts.. some slovenliness outhere.. Maybe all cells are finished or not.. if each one of 10 cells has at least 0,3V it could be revived.. depends on cells quality/brand (when cells go under 1V it could be unrecovered, or some go into internal shortcircuit, some cells break & go open.. or if recover possible it will loss some capacity, but still works..)

The best way is to connect the pack main minus and plus to a power supply and use limited current to recover it (use low current to recover until 3,0V per cell and stop. than use regular charger to chage the pack. if those cells heat, stop recovering process.. and start later for conclusions..)

do U belive in miracles? sometimes happens at battery recovery! but low chance to recover that! I bet maybe 30% chance recover

Try to recover with power supply @ limited current supply and post results plus cells brand, model.
We all want to learn from others experiments!

 

[MxusMick]

I rip those batteries apart and revive most cells individually with a good 18650 wiring positive to positive, negative to negative for a minute or so, they will charge when brought above 3v.

 

[E-HP]

Yes-unsure about exactly where the voltage is measured from-the cells are encased in a plastic holder and difficult to get back to the cell itself-perhaps just get the charger working and see if a charge corrects things.

As mentioned above, some of those tool batteries have strange BMSs and can be tricky to restart when tripped. Battery can still be good, but the BMS doesn’t reset like it should. I had one that I just jump started by applying voltage using a spare battery for a few seconds in my case. Looks like from your other posts that you may have a 36v charger (10s). You could probably use that to jump started the battery.