DeWalt 18V...worth rebuilding?

[Westex93]

I've got literally a stack of 18V DeWalt batteries that are shot (faulted, won't take a charge at all). Are these really worth sending for a rebuild, or should I just get new ones? You can get the 2-pack pretty often for less than $100 and the rebuild service (at least from MTO Battery) runs from $37 to $82.50 for the 18V, ranging from the 2100mAh standard rebuild to the 3600mAh heavy-duty build. I would love to swap to the new Lithium Ion DeWalt batteries as a retrofit, but, DANG, they're high! And, although they will fit, they don't exactly fit the body profile well.

On another note, though, the last battery that just died is one of the 2-pack sets I bought a year or so ago. Maybe the quality is that much better on the rebuilds to make it worthwhile? Any experiences?

I'd love to upgrade to the 36V Lithium Ion set, but with three 18V drills, two recip.saws, three chargers and a circular trim saw that see regular use, I just can't see it. They do the job just fine. Anyway, if I never try the 36V, I'll live happily in ignorance, never knowing what I'm missing....

[Uncle Cracker]

I have found the new 2-packs on sale (usually on the sidewalk) at Lowes for as low as $75. At this price, it made no sense to rebuild. Longevity has not been a problem since the yellow-top batteries came out like 4 years back. I have not had to replace any of them yet, although I know that I will, soon enough.

[wan2fly]

What I've done

Hello,
I have about seven cordless drills that I keep regularly used bits in. Over the years their batteries have failed also.
I thought I'd see what was in them. Sure enough, they were just a bunch of "AA" size NiCD's. I soldered up a bunch of new packs and put them in. I got highest capacity cells available and am quite pleased.

If you're willing to sacrifice a pack for experimentation it just might be a solution. DeWalt nor any other manufacturer of tool makes their own proprietary NiCDs. They are just generic ones made by any number of manufacturers.

It is a very reasonable do-it-yourself job. Maybe.

[lum]

wat2fly ... you wrote: "they were just a bunch of "AA" size NiCD's. I soldered up a bunch"

I've soldered wire to flashlight batteries using resin core solder. I wondered each time whether the heat might have been cooking the battery. The finish on the contacts did not accept solder readily. What was your technique?

The 18V pack here has 4 small screws and the batteries almost fell out. There was a strip of double sided adhesive on the bottom of the 1.2V batteries, but the protective strip had not been removed. So, they slipped out easily.

However, the inter-connections have been spot welded. The individual cells could be "C". I don't have one around to compare. The positive connection has a large surface area. ie. Not a regular flashlight cell. But, someone could make a reloadable system.

And now that the 18V tools are around there's the approach of using 9VDC units and the matching snap on connectors and avoid soldering to a battery post, plus making the next battery install painless.

9VDC units are space efficient. The electrical current available might surpass the AA battery setup.

I've got a Makita that's perfect mechanically complete with two dead batteries and a really cheap 18V unit that is also in good shape.

I replaced them with a small Skil lithium ion tool that holds charge and has plenty of power for my purposes. Plus, if it is put back on the charger between uses it will run all day. However, it is a quick-change, rather than a tool that takes round shank drills.

Watcha all think?

[LCHIEN]

well, for many years I have bought the argument that you should change batteries as a set. I am becoming a heretic.

That was always expenisve because if one battery failed (out of the 12 in a 18V pack) then you have to replace all 12 even tho only one was bad.

The argument is that batteries are usually from the same lot and exhibit similar capacity when originally assembled, some manufacturers even go so far as to match them. The reason being that when one goes empty, it gets reverse charged by the others.

Now my thinking has been, why not put a new cell in with the old? THis will cost you maybe $2 for the battery vs 24. Usually the new cell will have the greater capacity and so when you run the pack down its 11 cells going very flat rather than one and you won't be able use it more and risk reverse charging the one. And, those cells that you saved were destined for recycling anyway, what's the risk of damaging them?

So I haven't tried this theory yet, it involves opening the pack and figuring out which cell(s) are bad. You can in this case cannabalize other packs for their still good cells or buy some from battery rebuilders.

As for soldering directly to cells, that is usually futile (the steel of the battery case is not solderable) as well as bad for the cells. Most packs use metal tabs welded to the cells. You should cut the table where you need to break the pack and solder tab to tab if you can. replacement cells should be obtained with tabs. Use short pieces of #16 solid wire to connect tabs where the tabs don't line up.

Like I said, I haven't tried this but the battery packs are hsitory anyway, the only value they would have in the old approach is to salvage the case which you can still do.

BTW Lum, tools usually use what are called Sub-C batteries, the same diameter as C but a bit shorter.