USB charging device that works off the batteries for your rechargeable hand tools: I built one

This was  fun maker-style project.  I believe that if I was doing PEP (which I am not because it's for a very different bioregion than the one I am in) this would have qualified me for some Oddball points.  

Backstory: We are pretty rural.  We have a tone of devices that charge via USB.  Phones, e-readers, tablets, little lights, personal fans, all kinds of stuff.  And the electrical grid is at least a little bit fragile; we get ice storms in in winter and pretty regular power outages during thunderstorm/tornado season.  

One of our adaptations is that we've got a lot of those small "cell phone charger" auxiliary batteries.  The kind that are the size of two packs of gum and hold enough juice to charge your phone a few times.  They don't cost much, but they don't hold much juice, either.  And the fun adventure (after you find one in the dark) is wondering whether it's got a charge in it.  When was the last time I charged this thing?  Was it in this calendar year?

One day, I got a notion.  I've been standardized for close to a decade on the Black & Decker homeowner grade 18v rechargeable tools.  They are almost completely obsolete now, but there was a huge line of yard tools and power tools that all used the same 18v lithium batteries, the ones about the size of 2/3 of a brick.  Most of those lithium batteries have failed from age, and new ones used to cost $40 or so, so the tools go for cheap at garage sales with no-good batteries.  Up until about a year ago, I was getting pretty short on working batteries, but I have a huge collection of the tools that I bought for $1, $2, and $3 over the years.  Then some cheap Chinese nickle-metal hydride replacement batteries hit the market: about $20 with perhaps 30% more amp-hours of charge storage than the old lithiums had when new.  So now I have plenty of the batteries again.  

So what was my notion?  I thought "Wouldn't it be nifty if I had a USB charger that plugged into those tool batteries?  We'd be set for weeks on device charging, given how many of those batteries I have sitting around on smart chargers all the time."  

First I went out and looked for a commercial product.  No joy.  Dewalt (I think) sells such a charger, but it's for a totally different (22v?) battery system.  One or two outfits sell boom boxes (radio/cd players) styled like their tools that take the batteries and have USB outlets on them, but not Black & Decker that I could find.

Then I did a little research.  I discovered that aftermarket USB charging sockets for cars (12v) are frequently designed to sell into the marine market (24v) also, so with a little looking, you can find a $5 charging socket that takes any voltage from 12 to 24.  My tool/battery system is 18v -- perfect!  The one I bought a few months ago has doubled in price since I ordered mine; I suspect a derangement in the supply chain.  (Lots of things on Amazon cost twice as much now as they did in January.)  But I'll bet you can find a cheap one if you look.

So that was easy, but the other end is the clip that snaps onto the battery terminals.  I could do it with alligator clips, but that's rinky-dink.  I wanted a more elegant solution.  

My "bright idea" was to salvage a battery clip from an existing Black & Decker tool.  I've often bought them in lots -- a drill and a saw and a weed eater, say.  When the whole pile comes with batteries (probably dead but one likes to check) and costs $5, I don't think too hard about how badly I need each tool in the collection.  So I surveyed my inventory and found a leaf blower.  WTF, a leaf blower?  When am I gonna blow a leaf?  I don't have any hard surfaces at my house that need cleaning, and leaves get to lie where they fall as mulch.

Seven screws later, the leaf blower fell apart in my hands.  I had a battery clip to play with!  And guess what?  It used the same spade connectors as came on the USB charging socket.  My wires are coded red and black for pos/neg, and the spades on the charging socket are marked pos/neg. Could it really be this easy?

No, not quite.  The spades on the blower motor were soldered in place.  One of my leads (red/positive) from the battery clip thus had to be cut off short so I could crimp on a new spade connection.  (Two came with the USB charging socket.)  But on the black/positive line, there was a tiny switch between the clip and the motor.  That spade connector was not soldered, so I just unplugged it.  Just like that, boom!  I had a charger to charge USB devices from 18v Black & Decker tool batteries:



The spade connectors on the battery clip looked a little bit fragile, so I protected them with a bit of black electrical tape before plugging the battery clip onto a battery.  Hey, look the LEDs on the USB charger socket are glowing!



Look at the pretty glowy lights on the front:



Then it was time to wrap the whole thing in black tape and test it with a "load".  Happened to have an LED gooseneck light on my workbench so that became my USB test item.  Hark, what light through yonder LED breaks?



It's a silly little project but I'm very pleased with it.

Dan,

What a cool little project!  I love the ingenuity.  I considered something like this but using Ridgid batteries instead.  Like you I planned to make use a charger for my interface.  My plan was to buy an old charger off eBay, strip out the power cord and electronic guts and simply use the charger as a physical base to interface with the battery.  My father is a ham radio operator and he does field days where they set up outside and practice emergency communications.  He was interested in this idea for charging tablets.

In the end I built my little battery box HERE:

https://permies.com/t/40/135729/permaculture-projects/Building-pair-battery-generators#1120689

This accomplishes much the same effect but is just a little more flexible and is set up to be charged via a solar panel.

But great workings you have!  Personally I think it is worth a BB bit, but you would of course have to run that by sometime other than me.

Very good!

Eric

Eric, thank you!  I'm pretty pleased with how it went.  

I was serious though about not doing PEP.  I'll admit to the temptation just because badges are cool and I'm a sucker for gamification of things due to too many years of online gaming (or vice versa, hard to parse cause and effect there).  But when I actually get to looking at the bits, they fall into at least four categories for me:

1) fun, slightly challenging to do and document, could happily earn that bit
2) boring life skills I have been doing all my life, just tedium/drudgery to run through it taking pictures
3) task that I wouldn't normally choose to do or would accomplish in some other way, due to some sort of philosophical quibble with the viewpoint of whomever specced out the bit
4) task that's impossible or ludicrously impractical (or just silly) in my bioregion.

There's not intended to be a word of criticism in any of this.  PEP is cool and seductively fun-looking but it's for a purpose that's irrelevant to my current life trajectory.  There's no reason for me to mess with it, cool badges or not.

Very cool Dan! I might make one of these... I like the idea of tool batteries as a backup USB bank.
I could see a couple of variations.
1.) add a cigar lighter plug and a set of alligator clips to the kit (could use in any car, on ATV or tractor without sockets, on a boat...)
2.) and make a de-mountable connection (insulated spade/bullet/or Anderson power poles/etc...) so these could be swapped easily

I'm currently using Milwaukee M12 and M18 tools, and there's an M12 to USB adapter available (it's maybe $10-$20?)

Hey, Dan, I forgot to mention something in my earlier post.

I am a huge fan of repacking batteries.  I have an old Craftsman drill that I got as a Christmas present in 1996.  Over the years the battery packs failed, Craftsman stopped making replacement batteries and I still loved the drill.  I built two decks, several homecoming parade floats and countless smaller projects with that old 13.2 volt  3/8 inch drill.  The drill itself is still a very useful tool a quarter century later.  

But without batteries it would all be for nothing.  Right now I can’t remember if I am on the 3rd or 4th repack, but each time I repacked I got back a better battery for a fraction the price of a new one (even if a new one was available).

I eventually (Christmas 2006?) supplemented that single drill with a 5 tool kit by Ridgid, based on a 1/2 inch hammer drill.  It too was a nicad battery system and eventually all 3 of those batteries failed but I repacked with Nickel Metal Hydride cells and they still get occasional use.  

I can believe that many people would simply by new battery packs or even new tools altogether but I find it far more efficient to do a simple repack for at least a 50% discount over the new battery.  This is one of those cases where old can be perfectly new again.

Glad to know there is someone else out there that can appreciate a repack.

Eric

Kenneth,

Ridgid also has one of those little slide on USB power adapters.  I imagine that your batteries would provide awesome power for charging.

When I first thought about doing this project myself, as I mentioned in my first post, I was planning on getting an old charger, stripping out the electronic guts and using as a mounting base for a USB adapter.  But I might adapt this further to include not only USB, but also 12v power and a power pole attached to a buck converter to allow me to dial up a range of voltages.

This is kinda a cool little thread!

Eric

Well done! I've been planning the same trick to convert two old Ryobi work lights with NiCd batteries into LEDs.

The guts of the adapter will drop the voltage from 18VDC to 5VDC and then a resistor in series will drop it to the voltage specified for the LED module. Should have an amazing run time.

That said, it's been an amusing flashback to use these work lights with their original incandescent bulbs. Instead of sticking out the way LEDs do, the colour temperature nicely matches fire, candles, and kerosene lanterns. Aesthetically pleasing but less practical.

Eric Hanson wrote:Hey, Dan, I forgot to mention something in my earlier post.

I am a huge fan of repacking batteries...

I have watched some videos on that with great interest, and I might try it some day.  I have at least a dozen old Black & Decker 18v "dead" batteries to refurb if I ever dive into that project.

My problems are (1) I have never actually picked up the skill of soldering, so I'd have to pick that up as part of the project; and (2) by all accounts, lithium batteries are a little bit unforgiving to play with.  It's not that hard to make a mistake that turns them into small toxic incendiary grenades.  It's not enough to make me not want to do it, but it has kept the project from rising to the top of the priority list so far.

On the upside, I have a semi-local friend who in an engineer and a battery repacking enthusiast.  When the pandemic is over, he would happily spend an afternoon teaching me what I need to know.

Douglas Alpenstock wrote:That said, it's been an amusing flashback to use these work lights with their original incandescent bulbs. Instead of sticking out the way LEDs do, the colour temperature nicely matches fire, candles, and kerosene lanterns. Aesthetically pleasing but less practical.

I have a hand-held spotlight in the Black & Decker 18v tool line that has the old halogen bulbs.  Bright as hell but also a unique light spectrum.

Dan, you are certainly not wrong about lithium batteries.

So far, all but one of my battery repacks were based on a NiCad battery.  Conveniently, even old NiCads are making improvements and Nickel Metal Hydride are even better and are completely backwards compatible with NiCads.  So by now all my old NiCads are actually Nickel Metal Hydride batteries.  That improvement is a fairly easy upgrade.

Being in the Ridgid tool line, I eventually acquired 5 4-amp hour Lithium Ion batteries.  They are great.  However, Ridgid has recently converted to an Octane line of batteries and I can no longer get a 4 amp hour battery.  I can get a 3 amp hour or step up to a whopping 6 amp hour battery.  Also, my daughter left my Ridgid 18 volt fan on—for over a month!  The battery was well and truly dead.

I took the battery pack off to a local battery repair shop where I have serviced other batteries and long story short, the circuit board inside the battery case was bad (I am sure because it was left on for a month!) and the repack price was close to the original purchase price.  I would have just gotten another battery but they are not available so I told them to do it.

Funny thing was when I got the battery back, something seemed off.  It worked and all but there was something definitely different.  Turns out they gave me back a 5 amp battery instead of the 4 amp battery.  I was satisfied but I hope someone else had not sent off a 5 amp battery and got my 4 amp battery back.

Long story short, I still find it economical to repack batteries.  The new Ridgid line of batteries is more expensive than the old line (surprise surprise) so even an expensive repack is cheaper than buying new.

Eric

Thanks, Eric. I didn't realize NiMHs were available for repacking. Are they all sub-C sizes? What sources have you found? Gets me thinking about all the old batt packs around here. "Bring out your dead!"

Douglas,

So I have not actually done my repacking with my own hands so it is a little bit difficult to discuss the exact battery sizes.  But I had a long chat with the battery guy that the local repack store.  I was bringing in one of my old Ridgid 2ah 18 volt Nicad batteries.  I was told that the basic chemistry was sufficiently similar to NiMH that they could be swapped for one another, the charger would work fine and the new chemistry gave me about a 25% (or so, depends on the exact Nicad) bump in power output.

I then asked if it were possible to put in Lithium Ions and was told no.  The Lithium batteries cannot be discharged below about 30% or they will never charge again.  They actually have a little circuit board inside the pack to prevent this excess discharge.  Apparently the battery pack circuit board also interacts with the charger (I think this is correct, honestly I was swimming in details) which is why an old Nicad charger won’t charge the lithium battery.  Or rather the old charger will ruin the lithium battery if left on too long (which is not very long at all).  

But swapping Nickel Metal Hydride for a Nicad is a very simple process that gives a nice boost in performance.

Eric

Nice job.
Makita make a straight usb charger for their batteries it's also cheap, it's not something I own as nothing in this house charges on usb but I can see it being useful for people with smartphones.

I'm actually going to try a repair on a Li-ion pack soon (rainy day project) that appears to have one dead cell. It's the tiny 1.5 Ah pack so not a big loss if it goes poorly, since it is already broken now...
If that goes well, I may look into repacking some old NiCad packs as NiMh to regain the use of a set of tools just collecting dust! Thanks for the info Eric!
My other option was to create an adapter from old tool base to new battery top (Milwaukee reversed the male/female-tool/battery relationship between older V18 and newer M18)

Another thing I wonder about is running a laptop directly from a tool battery (I've seen output voltages on mains adapters that were 18v?) seems like a good fit? Remove AC cord and transformer and add battery clip instead? thoughts?

Kenneth,

Awesome that you are considering repacking a lithium battery to get rid of just one dead cell and not the whole thing.

Also cool that you see the potential of repacking NiCads with Nickel Metal Hydride.  I still have a couple old 18 v NiCads that I intend to repack as a NiMH battery.  These type of batteries are perfectly good for more stationary applications.

Regarding a laptop, the voltage varies from one laptop to another, but a very common voltage is 20 volts.  Computers are very sensitive to voltage and if you want to go this route I recommend something called a buck converter.  A buck converter allows you to dial up an exact voltage like, say 20.1 volts.  These are not expensive and I am wanting to have one on my next battery box.

Good Luck!

Eric

Eric Hanson wrote:Kenneth,

Awesome that you are considering repacking a lithium battery to get rid of just one dead cell and not the whole thing.

Also cool that you see the potential of repacking NiCads with Nickel Metal Hydride.  I still have a couple old 18 v NiCads that I intend to repack as a NiMH battery.  These type of batteries are perfectly good for more stationary applications

My philosophy for broken things is to open them up and look inside. What am I going to do? break it?
I get a chance at a repair, and learn what makes it work, and what made it fail (informing an improved repair? rather than a direct replacement).
Also possibly salvage parts if total repair isn't possible (for other projects or a future repair, I'm a fan of brand/model loyalty just for opportunity of a complimentary repair).

Yes, the repacking is of particular value since I have 6 or 7 tools that would bring back to life. A few of which I don't have a duplicate at the moment. Perfectly good for shop use, to avoid the cord or hose, and charger at hand. Having a kit in the shop saves me lugging the kit in the truck back and forth.

Kenneth, everyone,

There is something I probably should have mentioned earlier.  

Lithium are awesome batteries.  They have a very high energy density and are very, very light compared to lead acid batteries (lithium vs lead is a no brainer here).  NiMH are even better than lead acid but don’t have the energy density of lithium.  Lithium batteries are highly desirable on power tools, but especially so in portable electronics, but there are two significant drawbacks.

Drawback #1 is the price which is pretty obvious.  In an application where portability is not a major concern, the price of lithium batteries kinda offsets the benefits.

Drawback #2 is even more serious.  Lithium batteries have a limited number of recharges compared to Lead acid or NiMH batteries.  Lithium batteries typically have approximately 500 charges-discharge cycles, whereas Lead and Nickel batteries have something closer to 2000 charge-discharge cycles.  This means that those awesome but expensive lithium batteries get even more batteries expensive over time as replacements add up.

My current interest in battery applications is a battery inverter generator that would produce about 3 kilowatts output.  This is a significant amount of electricity, exceeding some small gas generators.  But as this will be based on a rolling tool case, weight is not much of an issue and I can find a 100-125 amp hour battery that will do the job admirably and affordable and will likely outlast a lithium battery.

For your power tools though, if they are set up for a lithium battery then by all means stick to that.  It would actually be dangerous to mix battery cells of different chemistries.  But if you have a stationary application like a little charger (like my battery box), older chemistry batteries might be the way to go.

Also, I agree with the philosophy of learning from a broken tool.  It’s great to know how these things work, especially if fixing them becomes a real possibility.

Food for thought,

Eric  

Bump -- great thread!

I'm surveying my collection of "superseded" lithium battery packs from laptops and power tools and thinking it's time for a great big purge.

Except: I know that the individual cells (or paired/ganged cells, even better) match up with my ancient old 15W solar panels. I can direct-charge them to run LED lights, monitoring their charging with a multimeter (4vdc cutoff or they'll pop).

But I have to be practical about how many I will *actually* use.

Douglas Alpenstock wrote:Bump -- great thread!

I'm surveying my collection of "superseded" lithium battery packs from laptops and power tools and thinking it's time for a great big purge.

Except: I know that the individual cells (or paired/ganged cells, even better) match up with my ancient old 15W solar panels. I can direct-charge them to run LED lights, monitoring their charging with a multimeter (4vdc cutoff or they'll pop).

But I have to be practical about how many I will *actually* use.

I have a large collection of 18650 lithium batteries from a Tesla model S,  over 100 batteries.

I am working to re use these in my Dewalt drill.

So, I'm going to admit to not having done those repair or repacking projects... yet.

However, I did learn something about Li-Ion packs in the meantime. I got a "free" M12 6.0 Ah pack out of the recycling shed at my town's transfer station, it had no charge, and when placed on a charger it gave the "damaged" flash code. Oh well, it would be another rebuild to add to the pile. Or, so I thought.

When I mentioned this rebuilding project to a friend, inquiring if he had a spot-welder for batteries, he told me that often if a battery had been too deeply discharged, the charger wouldn't see the voltage it was expecting and refuse to charge the "damaged" battery pack. The solution to try was to make "jumper cables" for the battery packs! This allows a "good/charged" battery to be connected directly to the "damaged/discharged" battery, to raise the voltage on the dead battery enough for the charger to charge it up like normal. The jumping doesn't take long, I tried just 10-15 seconds at a time, (not wanting to actually damage my good battery) followed by placing on the charger, and repeating a few times if necessary until the charger accepts it. The cable is simple, just two short lengths of hookup wire (one red, one black) with 4 blade type crimp connectors. The simplicity makes it "universal", the colors help keep the polarity obvious (rather than using lamp cord), but still requires thinking and caution to not be dangerous.

It worked!! I got one 18v battery and that 12v battery to charge again, and have used and recharged them both since.
By reviving these batteries without resorting to the rebuilding, I still DID achieve the desired result.

Kenneth Elwell wrote:However, I did learn something about Li-Ion packs in the meantime. I got a "free" M12 6.0 Ah pack out of the recycling shed at my town's transfer station, it had no charge, and when placed on a charger it gave the "damaged" flash code. Oh well, it would be another rebuild to add to the pile. Or, so I thought.

When I mentioned this rebuilding project to a friend, inquiring if he had a spot-welder for batteries, he told me that often if a battery had been too deeply discharged, the charger wouldn't see the voltage it was expecting and refuse to charge the "damaged" battery pack. The solution to try was to make "jumper cables" for the battery packs!

That's good information. I scrounged three "dead" Lion Ryobi battery packs from the recycling centre. The charger won't accept them. I was thinking of using my old school "dumb" car battery charger (15VDC, 2A) to give them a little boost, just to see if I can revive them -- if not for tool use, at least to power a flashlight. I think I will do this outdoors for safety.

I've recovered a few hundred cells for my ebikes with good success. A lot of times the BMS shuts off for various reasons. It depends on what happened. If one of the safety features turn it off like a short circuit, or the whole pack starts to fall just below the voltage threshold, then it can usually be jump started like mentioned. It can be the same when you install a new BMS, if it doesn't work, a quick tap of the correct voltage range to the input will turn it on.  

Another thing that happens if a pack is left for many months or more, the battery management circuit very slowly draws power from only one of the parallel cell(s), because it would be too inefficient/costly/heavier to draw from the whole pack and use a larger buck converter to power itself. So you end up with one of the parallel cell(s) much more drained to the point the BMS shuts off. These are the packs that would be dangerous to just throw at the charger. If one cell is too low, the difference will be added to the other cells which over volts them! That's the dangerous part.

Some tool BMS's don't balance the cells with the BMS. Some only do it on the charger like RC cars. Some only balance near the end of charging called 'top balancing', and often this ends up with it trying to burn off a few mA per cell on the higher ones so the low one can catch up. If a battery sat really long or has a dead cell then it may never correct itself and needs those cells charged separately or replaced.

I noticed some of the USB-PD and other car chargers take 12V and 24V input, often having higher output at the higher voltage. I hooked one up to a couple different batteries advertised as 18V-20V and it was able to charge my Chromebook in use for hours which takes 15V.

Daniel Schmidt wrote:I've recovered a few hundred cells for my ebikes with good success. A lot of times the BMS shuts off for various reasons. It depends on what happened. If one of the safety features turn it off like a short circuit, or the whole pack starts to fall just below the voltage threshold, then it can usually be jump started like mentioned. It can be the same when you install a new BMS, if it doesn't work, a quick tap of the correct voltage range to the input will turn it on.  

Another thing that happens if a pack is left for many months or more, the battery management circuit very slowly draws power from only one of the parallel cell(s), because it would be too inefficient/costly/heavier to draw from the whole pack and use a larger buck converter to power itself. So you end up with one of the parallel cell(s) much more drained to the point the BMS shuts off. These are the packs that would be dangerous to just throw at the charger. If one cell is too low, the difference will be added to the other cells which over volts them! That's the dangerous part.

Some tool BMS's don't balance the cells with the BMS. Some only do it on the charger like RC cars. Some only balance near the end of charging called 'top balancing', and often this ends up with it trying to burn off a few mA per cell on the higher ones so the low one can catch up. If a battery sat really long or has a dead cell then it may never correct itself and needs those cells charged separately or replaced.

I noticed some of the USB-PD and other car chargers take 12V and 24V input, often having higher output at the higher voltage. I hooked one up to a couple different batteries advertised as 18V-20V and it was able to charge my Chromebook in use for hours which takes 15V.

At least one of my packs to be repaired has just one low cell. Is it possible to charge that one drained cell while it is welded in place in the pack, or does it need to be removed to charge it? Is the cell powering the BMS easy to identify by extra wiring or by it's location in the circuit?

I use cheap knockoffs of the SkyRC iMAX B6 charger from Amazon. After seeing the way many of the big name brand chargers actually operate, they seem more dangerous than what I'm using. I put alligator clips on the charge cables so I can get in to any part of the battery and just charge that parallel set. I trickle charge it and see how it behaves. If it gets over 3V in a rather short time at low current (highly dependent on cells and capacity) then it's usually going to recover decently. Doing multiples of the same packs like I did made it easy to see the few sets of cells that weren't going to take a charge. Obviously I had to babysit this whole thing in a noncombustible place, so I would find things to work on and glace over every so often.

I try to be very judicious with my expectations. If you have a particularly well worn battery and instead of a battery that is more aged than worn then this won't fix that problem. If they were stored poorly for too long then a charger can't fix that either. Trying to push in or draw out the maximum the cell spec sheet says on a used cell has the potential to fail catastrophically.

I've seen too many videos about what and how things go on with the cells, with various debates. Depending on who made the BMS (which can change even on the same model battery) it can work a bit different and have different protections and cut-off points and tons of other factors. There's a great explanation towards the end of the video here:


I just tried out a newly assembled pack while riding from St Augustine to Jacksonville and back by lunch, and I forgot to put sunscreen on my legs!

I love that this thread got bumped!

As a sort of parallel, I have been building my own USB charger, but one that does much more than charge electronic devices.  It looks like this:

The front panel has six USB type A charge ports, and two type C ports.  Below the USB row on the bottom left is an XT60 port that will serve as both a 30 amp power out and a charge port.  On the bottom right I have four Anderson Power Pole connectors that can have a max capacity of 30 amps output.

The total capacity is 105 Amp Hours @ 12 Volts.  It is circuit broken to a maximum capacity of 30 amps.

It is all controlled by a BMS system that can connect to my phone via BlueTooth.

I still have a few kinks to work out, but now that I am back from the Outer Banks of NC and my summer is really starting, I have a project!!


Eric