Rebuilding Power Tool Batteries

[John Ziebron]

I have all Dewalt 18 tools. Up until about 3 years ago my batteries were all NiCad or NiMH. Although I still have some of those batteries as backups I really only use Li-Ion ones.

Just to set the record straight on these type of batteries, NiCads were the first rechargeables but they didn't offer much power for their size and they had the memory problem. NiMH batteries were an improvement in that they offered at least twice the power for the same size package, but still have a memory issue if not charged properly.

Li-Ion batteries have several advantages over the other two types. Their power to weight ratio is much greater. In the case of my Dewalt batteries the Li-Ion ones are physically smaller and weigh much less than a the NiMH ones but have the same power. Li-Ion batteries hold their voltage up until they are almost depleted. In using a tool, like a drill, it will gradually slow down and loose power with NiCad or NiMH batteries. But with a Li-Ion battery you basically have full power nad then the drill will just stop when the battery is depleted. This might scare first time users thinking there is a problem with their tool or the battery.

Li-Ion batteries are also much better in colder temperatures. And they have a much better storage charge. In other words, after a year of non use a NiMH battery will have lost at least half it's charge. A Li-Ion battery will still be at about 95% of full charge. The only downside to Li-Ion batteries is higher cost and you do need a special charger.

I don't rebuild any of my batteries. It can be dangerous with a battery exploding if it's heated too much when making connections. On the other hand, I don't buy Dewalt brand batteries because of their high cost and lower power rating. Dewalt's typical high power batteries (at least the 18 volt ones I use) are rated at 2000 Milliampere hours. I buy aftermarket batteries that are 3000 milliampere hours and cost much less. I've had good luck with batteryship.com. They even give you a free charger when you buy Li-Ion batteries.

[Allan Speers]

John, the main problem with Li-Ion, according to most articles, is that they start losing power after 1 year, and die completely after 2-3 years, whether you use them or not. (And that includes any time they spend on the shelf, before you buy them.)

Another problem is that (supposedly) they can be damaged if you run them to depletion.

For a tool that doesn't get used a lot, like my second drill, cordless recipricol saw, etc, that's an important factor. These are the reasons I haven't switched from Ni-MH.


Unless, of course, the newest breed have been improved in this respect, in which case that would be good to know.

[Wes Ramsey]

John, the main problem with Li-Ion, according to most articles, is that they start losing power after 1 year, and die completely after 2-3 years, whether you use them or not. (And that includes any time they spend on the shelf, before you buy them.)

Another problem is that (supposedly) they can be damaged if you run them to depletion.

For a tool that doesn't get used a lot, like my second drill, cordless recipricol saw, etc, that's an important factor. These are the reasons I haven't switched from Ni-MH.


Unless, of course, the newest breed have been improved in this respect, in which case that would be good to know.

I thought it was the other way around. I've never gotten more than 3 years or so out of my DeWalt NiMH (maybe NiCad) batteries. Had one go almost 4 years before it quit taking a charge. My Li-Ion Dremel battery still works after 16 years, though it doesn't last long enough to sharpen my chainsaw and just got replaced with a newer model. But it still works!

[Wes Ramsey]

A fair point, but do you really need 3600mAh? A Dewalt XRP, for instance, is only 2.4mAh.
I've seen 12-packs of 5000mAh NiMH SubC cells for $48. Expensive, but that will blow away the stock battery & still cost a little bit less. You can get 16 Tenergy 5000mAh for $64. That makes an awfully tasty 18v.

I guess it's a case-by-case decision.

Oh, and that soldering thing, if you use Li-Ion.

When I was researching this I just went with the 3600mAh as a baseline. Way better than any OEM rating and not that much more than the 3000-3200mAh batteries. Buying in bulk they went down as much as $1 each, but I just never got brave enough to buy enough to try it. And DeWalt is the only rechargeable I've ever had - maybe not the greatest for price-to-value comparison, but it's what I know.

I think if you have a quality iron then you might have good success just soldering the tabs. I don't and would have to rely on the a/c shop's CD welder, which is WAY cooler anyway and is safe for welding tabs on Li-Ion batteries. The weld happens in just a fraction of a second. How cool is that?!