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Greenworks 80V Battery Repair


ryan.bunce

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Hello all - first post!

 

I've been learning all about how these tool batteries are constructed and I've been learning how to repair them using multiple techniques.

 

I've fixed a few of these 80V Greenworks batteries by either bringing the voltage back up by jumping to another battery or by opening the pack and charging each individual cell with a hobby charger.

 

The packs I have are the 2Ah packs which are 20 18650 cells in series yielding ~80V (72v nominal).

 

I have one pack that I can charge up with the hobby charger and it works fine in the tool but when I go to charge it on the Greenworks charger it thinks the pack is bad (blinking red LED on charger).

 

If you're familiar at all with the internals of this pack it has BMS that's looks like it's split between two PCB boards - the main part of the BMS is where the charge indicator lights are.  Like most BMSes its covered in resistors that are used to discharge overcharged cells to bring the groups into balance.  The main BMS is then connected to the other end of the battery where the main discharge and charge terminals are.  On that PCB there are two MOSFETs, a couple of resistors, and some voltage regulators.

 

I have swapped the main BMS from another battery known to be good and the behavior remained the same.  I therefore suspect that something on the terminal PCB, likely one of the MOSFETs is bad.  I've tested it as best I know how with my current limited knowledge set.

 

Anyone out there have an electronics degree and can help me troubleshoot?

WIN_20200617_17_53_26_Pro.jpg

WIN_20200617_17_53_35_Pro.jpg

WIN_20200617_17_53_40_Pro.jpg

WIN_20200617_17_53_44_Pro.jpg

WIN_20200617_17_53_50_Pro.jpg

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  • 8 months later...

Hey, I have a 2Ah battery that is 4 years old and doesn't old back that much energy.

 

I was wondering if I could change those 20 18650 cells (of 1000mAh?? making 2Ah?) to something else, probably something from this website (around 5$ a cell)

https://www.18650batterystore.com/collections/18650-batteries

 

I was thinink to use 3000 mAhm which will make the battery a 6Ah I think? instead of 2Ah?

 

It would be much cheaper then buying a real 5Ah (at more then 500$)

 

But does the electronic can handle these increase in mAhm?

 

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  • 4 months later...

 

I have a separate issue with two 5.0Ah 60v.  Twice I've had these batteries quit on me when the mower is pushing through taller grass.  Both times I've cracked open the case to find the metal piece on the board snapped.  I assume this is there for protection (not an engineer, but enjoy taking things apart).  Could a fuse not have been used?

 

Is this repairable with a weld or replacement part?  Would love to get these batteries back in the mix.

 

Pictures here, good battery on the left.  Appreciate the guidance!

 

https://photos.app.goo.gl/oLdxUTsK3V3Jod419

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  • 5 months later...
On 6/17/2020 at 2:56 PM, ryan.bunce said:

Hello all - first post!

 

I've been learning all about how these tool batteries are constructed and I've been learning how to repair them using multiple techniques.

 

I've fixed a few of these 80V Greenworks batteries by either bringing the voltage back up by jumping to another battery or by opening the pack and charging each individual cell with a hobby charger.

 

The packs I have are the 2Ah packs which are 20 18650 cells in series yielding ~80V (72v nominal).

 

I have one pack that I can charge up with the hobby charger and it works fine in the tool but when I go to charge it on the Greenworks charger it thinks the pack is bad (blinking red LED on charger).

 

If you're familiar at all with the internals of this pack it has BMS that's looks like it's split between two PCB boards - the main part of the BMS is where the charge indicator lights are.  Like most BMSes its covered in resistors that are used to discharge overcharged cells to bring the groups into balance.  The main BMS is then connected to the other end of the battery where the main discharge and charge terminals are.  On that PCB there are two MOSFETs, a couple of resistors, and some voltage regulators.

 

I have swapped the main BMS from another battery known to be good and the behavior remained the same.  I therefore suspect that something on the terminal PCB, likely one of the MOSFETs is bad.  I've tested it as best I know how with my current limited knowledge set.

 

Anyone out there have an electronics degree and can help me troubleshoot?

WIN_20200617_17_53_26_Pro.jpg

WIN_20200617_17_53_35_Pro.jpg

WIN_20200617_17_53_40_Pro.jpg

WIN_20200617_17_53_44_Pro.jpg

WIN_20200617_17_53_50_Pro.jpg

Did anyone reply with the remedy?  I have similar issue with kobalt 80v batteries all same they all look good charged up to 80volts put into tool and starts 1 second then dies.  I think its in the main chip not letting it discharge.  Let me know please

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  • 3 months later...

I had a fault where one of the connections on the opposite end to the led arrangement had failed.  It happened while I was using it and I think it was likely a poor connection to begin with and under a high load condition it has let go completely.  In my case the fuse link that Collins showed was still good and I accidently put pressure on the failed connection when the battery was upside down and resting on the test button.  It started to light up as I was poking around and led to me to the dodgy connection.  Soldered back on and good as new.  

 

The symptoms in my case was that it would not operate the trimmer or show any charge with the test button.  It also tried briefly to charge and then would cut out suddenly.  

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