Cordless tool battery fix.

[toglhot]

I have a number of Milwaukee tools: Drills, rotary tool, angle grinder, hackzall, no problems with the batteries on these, then again, considering the price you shouldn't. I also have a number of cheaper cordless tools branded Ozito, or Einhell in other parts of the world. Unfortunately the batteries don't seem to last too long, they show two LEDs out of three but won't run the tool and when placed on the charger both red and green LEDs flash and the battery won't take a charge. In the past I've binned them, but, over the last few months I've checked the individual cells and found a couple of them not showing any voltage, so, I put them aside, intending on removing the duds and replacing with good cells from another battery.

Another battery went today so I stripped it and discovered two cells reading zero volts the remainder four. Before I fired up the soldering station to replace the cells, I did a little test: Hooked the two dead cells in the battery up to a 5 volt charger. When they reached 4 volts I reassembled the battery, stuck it in the drill and what do you think happened - it worked. To check, I ran the tool until the battery died then stuck it on the charger and you beaut, it charged up. Apparently the tool only flattens a couple of cells in the battery, rather than all of them, the tool won't work with a couple of dead batteries and the charger won't charge the battery when there is a discrepancy in voltage across the different cells, very odd!

I don't know if this would work with other brands, but it certainly works with Ozito batteries. Give it a try, these batteries aren't cheap.

 

[toglhot]

This is the second cordless battery on the 5 volt charger, I haven't been able to get it passed 3 volts. Don't know if that's enough. I'll assemble it later and give it a try.

 

[bosco659]

I have a number of Milwaukee tools: Drills, rotary tool, angle grinder, hackzall, no problems with the batteries on these, then again, considering the price you shouldn't. I also have a number of cheaper cordless tools branded Ozito, or Einhell in other parts of the world. Unfortunately the batteries don't seem to last too long, they show two LEDs out of three but won't run the tool and when placed on the charger both red and green LEDs flash and the battery won't take a charge. In the past I've binned them, but, over the last few months I've checked the individual cells and found a couple of them not showing any voltage, so, I put them aside, intending on removing the duds and replacing with good cells from another battery.

Another battery went today so I stripped it and discovered two cells reading zero volts the remainder four. Before I fired up the soldering station to replace the cells, I did a little test: Hooked the two dead cells in the battery up to a 5 volt charger. When they reached 4 volts I reassembled the battery, stuck it in the drill and what do you think happened - it worked. To check, I ran the tool until the battery died then stuck it on the charger and you beaut, it charged up. Apparently the tool only flattens a couple of cells in the battery, rather than all of them, the tool won't work with a couple of dead batteries and the charger won't charge the battery when there is a discrepancy in voltage across the different cells, very odd!

I don't know if this would work with other brands, but it certainly works with Ozito batteries. Give it a try, these batteries aren't cheap.

I’ve done this before but not to individual cells. I’ve applied 20V to an 18V battery pack to get it to charge again. Sometimes it worked but I found when it worked, the battery pack didn’t last very long.

 

[ReycleBill]

I ad cords and convert all of mine to run on 120vac or 12 vdc . I'm tired of screwing with batteries.

 

[bosco659]

I ad cords and convert all of mine to run on 120vac or 12 vdc . I'm tired of screwing with batteries.

New lithium ion batteries are pretty good nowadays but you still need to “care” for them. I make sure my batteries are rotated in use; never charged until fully discharged; long term storage at a little less than 50%. NiCad batteries were horrible and gave cordless tools a bad name.

 

[toglhot]

Well, it's worked well so far, two batteries fixed with no more problems.

 

[MaxPete]

I used to fly electric RC aircraft and the performance you could get out of those was quite remarkable (every bit as fast as any IC engine would give). Lots of us in the club had 2-5 lb models that would climb vertically right out of sight and do more than 100 mph with flight durations (at slower speeds) of as much as 20-30 minutes. Even electric ducted fan models work well with even higher speeds - and the sound makes the hair on the back of your neck stand right up.

The difficulty is that those high performance batteries could be temperamental and so model AC folks always use what are called "balance-chargers" that ensure the voltage level across all the cells in a pack are equal within a very very small margin. We also use battery conditioners which ensure that the packs are charged to the optimal level for storage or use as the case may be.

As @toglhot says, given the cost pack replacements for cordless tools, messing around a bit to maximize durability is well worth the effort.

Pete