Reviving a lithium ion battery

[gisselletdean]

Hey folks, I have a battery operated flymo lawn mower that is 4 years old. The batteries died last year and I got replacements. It's done it again and I am just outside of the battery warranty.

Given how expensive it is I though eff that for a game of soldiers buying more at nearly 100 a pop.

One battery is fine but the other won't charge. On a multimeter one is fine and the other is dead, multimeter is switching to ohms.

Can these be bought back in any way? I have read conflicting things but thought I'd ask here before going back to a corded mower.

[capabilitieso]

Not safely, they are prone to busting into flames, so it's a new battery yet again.

[OliverShultz]

Some batteries with a deep discharge issue can be jump-started with a power supply, but it’s hit or miss. If the battery’s BMS completely shut down, it can be tricky. Many of these packs manufacture in China have built-in protections that make revival difficult. External chargers with a boost function might work, but safety is something to keep in mind.