Rebuilding power tool battery packs

[Mick Bailey]

All of my rechargeable power tools are now at the end of their battery life, at best only lasting 10 minutes of light work and replacement batteries are no longer available. Despite this, the tools are all in excellent condition and I'm considering replacing the cells. It looks like I'd need to get equipped with a spot welder for the contacts. When I go to my local recycling centre I see a depressing number of rechargeable drills, sanders, strimmers, hedge cutters and other tools in the small appliance skip. I'm thinking this is yet another problem waste stream, populated with use-then-throw-away rechargeable tools that are otherwise perfectly serviceable.

Is anyone here doing any DIY battery reconstruction?

[nevetslab]

Hmmmm.......I KNEW there was a reason for me NOT to purchase battery powered tools. Though I failed to contemplate your plight with fine tools....if there was only a simple way to use them. I haven't been aware of any reconstruction efforts to combat this sad state of affairs. I gather you've done extensive search on the internet to see what you can find on the subject.

[tedmich]

Mick, can I assume these are (now ancient) NiCd batteries?
My Dad has a ton of the "brand yellow" tools he's loath to replace when these NiCds die.
The Lithium are readily available at almost every price point and adapters abound on Etsy and other places.

Spot welding is the best practice but not required in all but the highest current applications I believe.

The best lithiums do eventually die, sad but true, dispose of properly

[big_teee]

I love 20v lithium battery tools.
I've got a bunch of them.
No electric cords, or no gas engines to keep running, no pull ropes to break.
I have Dewalt tools that all use the same batteries.
I get the generic dewalt compatible batteries.
https://www.amazon.com/s?k=dewalt+co...f=nb_sb_noss_1
I like the 6 amp size.

PS I tried getting a 18V battery rebuilt, one time, and it never worked right, there after.
T

[Tom Phillips]

...Is anyone here doing any DIY battery reconstruction?

I have considered doing this. The issue I have experienced is the cost of sourcing the correct and good quality replacement cells in small quantities. I have one project in process but gave up on another when I found that the Gen I circuitry built into my original battery had been upgraded in the new battery offering to solve a severe self discharge problem. I never took the old battery pack apart but I did see one person advertising rebuilds on the Web for about 65% the cost of a new battery pack. I ended up just buying a new Gen II battery pack. It was a Milwaukee product and they were still offering batteries for my 15 year old tool.

[Mick Bailey]

These are all lithium battery types. Mainly items I had to evaluate for a German supermarket chain and are pre-production models that weren't sold in the end or got changed - hence no replacement battery packs being available. Decent quality, though. By comparison, my old NiCd drill I bought in the 90s lasted 20 years before it finally gave up altogether. I think I got a disappointing 5 years from my lithium Bosch drill. I really liked that, but a single replacement battery cost more than the drill + 2 batteries + charger did. I've done some research into rebuilding the packs, but whether its worthwhile is uncertain because the only cells that make it feasible are cheap AliExpress types and may not be durable. Or my house and workshop burn down when they set fire.

My other option is to install a cord in the tools and power them off a DC supply. It's handy having cordless stuff, but for bench use having a cord isn't too bad. The small size is more important - my mains powered equipment is cumbersome when working inside a chassis or cabinet.

[Chuck H]

I've thought about rebuilding battery packs before. There is a ton of good info on line from others that have done it. There were A LOT of reports cautioning against using anything but the best replacement cells. It's easy to find reviews on line so a trusted product isn't hard to find. But the expense of the better cells was such that rebuilding a battery pack was about half the cost of a new one (this as it applied to my DeWalt drill at the time). In your case, with no replacements available, there's no other option if you want to stay cordless. But since you're handy and industrious I think half price is a good deal. Having to acquire a spot welder not withstanding.

EDIT: Regarding the cost of new tools... This is what kept me from rebuilding my batteries. My old unit was a NiCad. Li Ion was available when I bought it new but I stayed with the old tech because at that time manufacturers were still working out the kinks with Li Ion batteries and I heard a lot of complaints in the field. So I stayed with the old, heavy but trustworthy technology. What a mistake. The new batteries lasted about two years wth light use and correct treatment. So two years after I bought this drill I was faced with buying two new batteries at $128 (they're actually still available and cheaper now) or get the new Li Ion drill model with two batteries and a charger for $199. As per your observation above I was really dissapointed in the two year battery life because the drill I had before lasted over fifteen years doing the same work. So I wasn't about to spend my money on two more crappy batteries and instead took my chances with the new drill model. So far so good. But if I'm faced with replacing THESE batteries I probably will rebuild them if it's cheaper. I don't have a spot welder either but I know a guy that does.

[mozz]

Before Sears went into hiding, i had bought the cordless drill along with the 90degree standup drill and got 2 batteries. When we just bought this house it saw a lot of use, until............batteries died and had very short life. I took one apart, 15 cells, 18 cells? I forget, but sub C sized. I bought the batteries with the tabs already on, current was supposedly (way) higher than stock. Nimh or Nicd i don't even remember. Rebuilt 1 pack, was cheap but i didn't want to rebuild both as i had no idea how good this was going to be. Sears wanted $69 for 2 new batteries, complete new drill wasn't much more. That was at least 10 years ago, still works fine. I can not find the website, they use to spam me constantly with battery deals/specials. Wife did get me a Dewalt for xmas one year so i have that also, batteries seem small but i don't work it hard, no major projects.

[tedmich]

these guys do a great job testing drivers and recently reviewed a reasonably priced "all brand" battery from PD Nation

[tedmich]

Here is the channel making their own battery pack

they're car guys so they started with impact drivers, and then flashlights but now test air tools and many other types!
They're fun and scientific!

[pdf64]

I've rebuilt the nimh battery pack for my Aldi hedgetrimmers, bought in the early 2000s. It was fiddly, I took plenty of photos and sketches. I just soldered them, the replacement batteries had solderable tabs, the battery size was C, got them off Amazon.

[Chuck H]

Well it's good to hear about some longevity enjoyed with the rebuilt packs. After my experience with the two year life of brand new DeWalt batteries I was of the mind that the major tool manufacturers were counting beans and specking cheap cells. So why buy their new batteries for a premium? Rebuilding packs with known quality cells that will last at half the price of a new battery would seem to make sense in this light.

In other words and in my humble, limited observation the only way to get a good battery is to rebuild the factory battery when it fails. As a nod to tedmich I still have to watch the videos and see what those guys are doing. It's probable that someone actually is offering good rebuilds at a competitive price. I only know I don't trust in the quality of the tool manufacturers batteries anymore.

EDIT: Hi. Chagrin here checking back in
I guess I can't account for why my factory DeWalt NiCad batteries suffered a short life because after viewing tedmich's videos it does appear that the tool manufacturers tend to use quality cells. At least that seems to be the current trend with Li Ion packs. So I shouldn't suppose it was any different with the older NiCad's. But I can't know because I never took them apart.

Great videos tedmich. Thanks for posting them

[Pixel]

About 20 years ago I bought a stack of a dozen or so RC car battery packs on closeout for a buck apiece. After a few years a few of the packs weren't performing well so I cut them open and tested them under load to see what voltage each cell was putting out. I recycled the really bad cells and made new packs with the cells that were close to each other in voltage.

I still have four packs that will run the car about as well as they did when they were new. I would probably have a few more working packs but some of the cells found their way into other projects along the way.

[Chuck H]

FWIW my old 12V NiCad DeWalt batteries were capable of very large currents for brief periods without meltdown. I'm remembering an episode where I found myself stuck in a remote location with a low battery in my van. Not stright up dead but nothing but CLICK CLICK CLICK CLICK CLICK when turning the ignition. It only took me a few minutes to concoct a plan...

I took one of my drill batteries and jammed a couple of nails against the electrodes in their plastic pockets and then clipped my jumper cables to them. BOOM! Fired right up and I was on my way to the auto store to get a new battery for my van.

[The Dude]

FWIW: This is not an endorsement and results may vary. I've rebuilt some battery packs with good success. I will always check eBay first. Many times, I've been able to find aftermarket battery packs cheaper than buying separates to rebuild. I've not had any bad luck with them. They seem to last as well as the factory originals.