Questions on cells in a 18V Makita Li-ion pack

[dchomak]

I have another couple of dead Ridgid 18V packs that I would like to repair. I have already replaced the 3 cells in a bad 12V Ridgid pack that had Chinese cells.

Here's why Ridgid Li-ion Tools have such a poor rep

I and many others have had a lot of trouble with the Li-ion Battery packs of Ridgid power power tools. In fact recently, because of the bad rep that they have had, Ridgid has implemented a “Lifetime Service Agreement” When you buy a new Li-ion power tool, the batteries are guaranteed for life so long as you register them. (they have serial numbers) Tonight I opened up a bad pack that was not guaranteed. Here is what I found. [image] [image] [image] Now what is probably the underlining probl…

This time the Ridgid packs have quality cells, They are 18V, 10 cells packs that have 5 pairs of 2 18650’s in parallel for twice the capacity. Somewhere I read recently, I can’t find where, that it is common for the first cell in the serial chain to discharge during standby. Once they are run down, they are damaged. It must be true because both of the 18V packs have dead cells, first ones in the chain. All other cells are sitting at 4+ volts.

Now on to my questions.

The other day, at Home Depot, I did what I often do. I checked in the Li-ion recycle bin that they have next to returns. I am constantly looking for Li-ion packs to salvage cells for these 2 that I have. Of all the packs I see, I would have to say that 95% are the 18V Ryobi NiCad packs. Those are the worst ever. I have maybe 10 and they are all shot. Anyway I found an 18V Makita that physically looked pretty good on the outside, so I grabbed it.

It was easy to open and inside were 5 of these.

Trouble was that when I measured the voltage across each one, they all came in at between 0.35 and 0.40 volts. My heart sank, but what the heck, I threw one on the charger and after about 5 minutes it was up to 2.5v. I took it off and let it rest and about an hour it was still holding the charge. So I tried each of the other 4 and got them all up to 2.5. All seems well and good, so I charged them all up to 4.15v. I measured them again, warm off the charger and put them aside for 18 hours. The next day I re-checked the voltages fully expecting to see a big loss in voltage, but no, they only lost 0.02v each!

So by now I’m thinking maybe these cells are going to be ok? I ran them thru the only real world benchmark I have, my FandyFire Warrior. It has a built in charge gauge that I can use to give me a good “feel” for the cells. For instance, 3 brand new UltraFire “3000” mAh cells only run for about 40 seconds before the charge indicator drops 1 peg. Total crap cells. The Panasonic true 3400 mAh cells will run for longer than I care to wait (more than 30 minutes) These cells, from this pull, even though they went thru such abuse and were discharged down to 0.35V, run for about 15 minutes before the indicator lights drop a peg. This in spite of these cells being only 1300 mAh high discharge cells in the first place.

The question is, could it be possible that these cells are going to be OK?
Do the cells in Li-ion packs more forgiving to severe discharging?

I am planning on using 4 of the 5 to repair the 2 18V Ridid packs I have.

BTW, each of the 2 Rigid packs have different cells in them. One came with Samsung cells and the other had Sanyos.

[StyXSIS]

As long as the mah rating is the same as the other cells, those rebuilds should be fine. I’ve done lots of rebuilds with different brands, but i’ve only ever replaced with the same mah rating, never higher, and never lower than what’s already in the pack and it’s worked for years, for me. Make sure the cells you use to replace the bad ones have a voltage that is around the same voltage as the others when you rebuild, e.g, 3.85, 3.79, 3.82, 3.82, replacing the e.g. 0v cell should be charged to around 3.8v, that will make the pack almost even and when put on charge it will charge like the rest and not get overchared or under charged.

[Rufusbduck]

The cells in Makita packs are high drain cells. They have to be to run grinders, reciprocating saws, and circular saws along with the lower drain tools like drills and impact drivers. The packs have a cell monitoring pcb that’s supposed to monitor the voltage and condition of each cell(1.5Ahr) or pair(3Ahr) of cells as well as temp, charge, and discharge rates. Some of the knock -off batteries have the pcb but font bother to make the extra internal connections. On the batteries I’ve retired the most common failure is the spot weld on a cell. If this happens the cell is immediately rejected by the charger and cannot be recharged. I haven’t attempts to repair any of them yet because I don’t like the idea of mixing different aged cells in the same pack even if the have the same capacity rating. At different ages they won’t have the same capacity anymore.

[GottaZoom]

Love those cells, also found in Dyson packs. Makita service center can check the pack for recharge cycles. If it is low they may warranty it due to the drain problem - they swapped me a 10 cell for a 5 cell that way.

Suggest rebuild using cells with similar discharge capacity and then re-charged voltage. After that, they need to be kept charged so the PCB doesn’t drain the PCB power cell again.