PowerTank Battery goes from 100 to 0 as soon as placed in mower

[OtagoHarbour]

I have a 24 volt PowerTank battery for a Worx WG782 electric lawn mower. I fully charge the battery (8 hours until the light is fully green) then check the battery power. It says fully charged. I place it in the lawn mower and the mower just putters faintly. I check the battery power and it is practically dead.

 

[Rivets]

Time to replace the battery, sounds like it has one or more bad cells.

 

[MowerMike]

Out of curiosity, how old is the battery ? Those batteries rarely last more than 3 years. The bad news is that WORX no longer sells this battery, and they are almost impossible to find anywhere. The good news is that you can rebuild it for about $25. It uses two 12 volt 5 Ah SLA batteries that you can buy as a 2-pack on Amazon. I recommend the MIGHTYMAX brand. It's all soldered together inside the case, so you you will want cut the old batteries out, and replace everything with flat terminal crimp connectors. To make it easier to reassemble, extend the wires by about 3" per connection with at least 14ga insulated stranded copper wire.