Anyone upgrade an older drill to lithium? How's it working?

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Robin Dobbie
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Anyone upgrade an older drill to lithium? How's it working?

Looking for people who have actually done it and BMSs that cut off voltage at 4.20V when charging.

Edited by: Robin Dobbie on 05/18/2021 - 00:14
carmantl
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Why not do a 3S instead? 12.6 fully charged and good cells should stay above 4.0 for a while. My old Makita 12v ni-cad stuff ran pretty well on half-arsed worn OUT factory batteries, but they would deplete fairly quickly..

zoulas
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If you are retired and want to experiment, great idea.

Power tools are a form of technology. Changing the battery alone will leave you with the same old tool.

Nice to know it can be done but realistically, not a very good return on investment considering you can get a new cheap set that will have dozens of benefits over the old one. Of course this is my opinion.

Bort
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My concern is reverse charging the batteries accidentally. It would be more safe to take a drill that already uses lithium and swap out its worn out batteries becasue it will have a legitimate BMS already.

Why not use NiMH in series/parallel, you can beat the hell out of eneloops and they keep on ticking. And they don’t explode.

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chops728
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Bort wrote:
My concern is reverse charging the batteries accidentally. It would be more safe to take a drill that already uses lithium and swap out its worn out batteries becasue it will have a legitimate BMS already.

Why not use NiMH in series/parallel, you can beat the hell out of eneloops and they keep on ticking. And they don’t explode.

Reverse charging —I’ve never heard of that before — as far as a Li-ion BMS they’re out there no big deal — size/amp draw might be the issue —- I have some El Cheapo Ryobi drills (I have had Mitsubishi,Bosch ETC —these drills have been unbelievable for the money)— 2 were Nicad and 2 were Li-ion —I have all these because during the holidays it’s cheaper to buy another whole drill than a extra battery

I have taken the Nicad cells out of the cases and installed Li-ion with just a balance cable — they work great but you have to monitor your low voltage somehow

As far as going 4S for a 12v — more than likely you’ll fry something at the full 16.8 v — considering a Nicad at full charge is not much over 12v

Robin Dobbie
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Eneloops in a drill…

So we have 1 person out of 4 who actually upgraded an old drill. I guess that’s better odds than usual.

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chops728 wrote:
Bort wrote:
My concern is reverse charging the batteries accidentally. It would be more safe to take a drill that already uses lithium and swap out its worn out batteries becasue it will have a legitimate BMS already.

Why not use NiMH in series/parallel, you can beat the hell out of eneloops and they keep on ticking. And they don’t explode.

Reverse charging —I’ve never heard of that before — as far as a Li-ion BMS they’re out there no big deal — size/amp draw might be the issue —- I have some El Cheapo Ryobi drills (I have had Mitsubishi,Bosch ETC —these drills have been unbelievable for the money)— 2 were Nicad and 2 were Li-ion —I have all these because during the holidays it’s cheaper to buy another whole drill than a extra battery

I have taken the Nicad cells out of the cases and installed Li-ion with just a balance cable — they work great but you have to monitor your low voltage somehow

As far as going 4S for a 12v — more than likely you’ll fry something at the full 16.8 v — considering a Nicad at full charge is not much over 12v


You can google reverse charging to learn more.
Another thing that i thought of is that lithium batteries have a max safe draw rate, and power tools seem to need something like 10C.
I have a Ryobi tool with li ion, 18650s but only 1300mAh. Very high draw, 10C.

What is this balance cable you speak of?

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Robin Dobbie wrote:
Eneloops in a drill…

So we have 1 person out of 4 who actually upgraded an old drill. I guess that’s better odds than usual.


I’ve never seen it done but in theory it can be, aren’t those sub c cells are something like 1000mAh?

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Robin Dobbie
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Big thing I’m looking for now is BMSs or discrete balancers that actually cut off charging at 4.20V. Saw one that actually admitted to letting the cells get to 4.23 – 4.28V !!! But the nice thing was it only lets them get down to 2.72 – 2.88V, a nice departure from 2.5V, or less. Looked like a lower current than the 40A units, however.

Bort
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If you ever find a BMS that can take multiple cells of varying capacities i would be very interested in knowing about it, DIY Tesla Powerwall!

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chops728
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It’s just a basic balance cable I added like all RC car batteries have —it plugs into a balance hobby charger and balances out your pack—there’s also a cheapo volt meter with alarm you can custom set for discharging

https://www.amazon.com/Balance-Charger-Silicon-Connector-Adapter/dp/B073...

https://www.amazon.com/PACK-Battery-Voltage-Checker-Alarm/dp/B00XQ91ECA/...

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chops728 wrote:
It’s just a basic balance cable I added like all RC car batteries have —it plugs into a balance hobby charger and balances out your pack—there’s also a cheapo volt meter with alarm you can custom set for discharging

https://www.amazon.com/Balance-Charger-Silicon-Connector-Adapter/dp/B073...

https://www.amazon.com/PACK-Battery-Voltage-Checker-Alarm/dp/B00XQ91ECA/...


Understood, thanks

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Most of the drill packs I’ve taken apart have had 20Rs 25Rs or some type of Sony VTC cell inside —- the Li-ion drill packs that came with my cheapie Ryobi drills are only 1300mah also —I think they’re some kind of LG cell but they won’t die —even after 6yrs and at least 100 cycles —I used some Panasonic A cells in my make shift packs — they work as well as the factory packs —-also when the cells get down to 3.4 ish volts you can tell by how the drill is working —not that great

cyberpunk
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I have done a redesign for electric hedge clippers, it required:
- new BMS, with balance charging, up to 40A
- new batteries either two or four, in 2S configuation
- battery holders for the setup that fits inside the housing of the clippers
- connectors for external chargers that will be put in the housing
- a new external charger or power supply in the range the BMS allows (around 9V for me)
- this particular device was waterproof, so I needed a new gasket

You’d also need
soldering iron, heat shrink, multimeter, pliers, solder, flux

The costs for the conversion were FAR higher than buying a new device. I spent about 28$ plus additional shipping and then my time and effort, plus all the consumables. Regular, new hedge clippers are about 30$, with brand items around 65$.

Please note: this was for clippers only, not for a drill. A drill requires different batteries, different BMS and potentially more parts.

Robin Dobbie
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cyber, which BMS did you get and did you monitor cell voltages on your first charge to see if the BMS was allowing cells to go over 4.2V? Subsequently, did you then test what would happen if a cell was well below the other cells so that the charger would keep going above 4.2V per cell, if not for the BMS?

I bought this charger for $9 shipped:

I could have gotten a 3A for a dollar or two more, but nah. The cells are rated 4A continuous charge, but 2A is fine. Looks like it has the same barrel plug as the existing 12V wallwart dumb “charger”, so might not even have to mess with making a battery mount or install a barrel jack in each battery.

And I bought a bunch of these boards. 50 cents a piece.

If the cells get above 4.2V, like the BMSs, they’re supposed to bleed off excess onto the corresponding resistor. Which, if the BMS was going to do its job those boards would be unnecessary. That top balance current is only like 70mA so they can be parallel’d as much as you want if 70mA’s not enough. The BMSs without the balance were like a buck-eighty, so I grabbed one of those. There’s always the chance that these boards aren’t going to cut off at exactly 4.2, just like the BMS boards. But at 50 cents, I can try a few and maybe get a couple that are low enough to be acceptable.

cyberpunk
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This version is for a drill, 40A continuous
https://s.click.aliexpress.com/e/_A73We9

I believe that should be the correct one for a drill, please do check if the technical specs match your device or plans.

From what I can tell:
My BMS is not for a drill, it can not deliver continuous amperage that is required for drilling. It is only for hedge clippers or scissors, fewer amps.
I did monitor cell voltages and no cell goes beyond 4.2V, but please note that these BMS are not as accurate as the ones we see in flashlight chargers or battery chargers (but I haven’t seen anything weird so far). The cells I used were not matched, but the same chemistry and voltage. That should be enough for a BMS. So they are all 3.7V nominal lithium-ion cells and they are automatically balanced by the BMS, please note that they have slightly different capacities in my setup. that doesn’t seem to a problem so far.

Robin Dobbie
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You said the BMS you got was 40A. I thought 40A was 40A. Obviously if it’s 2S that’s different than 3S or 4S. I’m just wondering what would make a drill BMS special vs a non-drill version, all else being equal. I did notice some boards said they activated the over-current protection at 60A, some at 80A, so maybe that’s the thing. Maybe a difference in delay in under-voltage cut-off, too.

cyberpunk
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From what I have seen the batteries and BMS are different for a drill, because a drill requires continuous amperage (comparable to a very high output flashlight that needs different cells and driver). The simpler, cheaper BMS and batteries out there do not deliver continuous 40A. The 40A are also an example as I don’t know which drill you are working on or what requirements are at hand. The xS setup should match the voltage you are planning to use, I used 2S and 3S before and as long as the rest of the setup is aligned with the voltage, it should be fine. The drill motor should tell you the voltage it requires.

As an example, my hedge clippers don’t even have a real motor in there, just a strong mechanical servo that moves left and right, while the top scissor blade glides back and forth. That wouldn’t require much more than 10A in the worst case, a lot less in normal use. The general rule is to get a “higher rated’ BMS than what is required to have some headroom for the setup. The 40A BMS I have are not continuous, only maximum amperage.

Several BMS items I looked at tell the same story, if you need this for a drill, without the right BMS or batteries (high drain), it won’t start the drill and/or won’t deliver the continuous amperage a drill would need.
That is, unfortunately, all I know. Please feel free to play around with the various BMS out there and see if the drill starts?

edit:
There might also be an alternative setup for this scenario – if your device can handle direct-drive, you can put the entire “charging intelligence” into the charger and leave only batteries, resistors and the motor inside the drill. But in that case the BMS would be in the charger and not the device. I have seen this before on different car tools.

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I’ve upgraded a cordless drill from 3S 18650 to 6S sub-c NiMH RC pack with a 1m cable on XT60..
just because I have some, they’re easy to use, non-proprietary and I didn’t have a spot welder to make a new 18650 pack with (soldering is a no-no for li-ion batteries).
use it a couple of times a month, has been working great, torque, speed and runtime are great!
I put an XT60 socket and a 3-digit voltage meter on the bottom of the old battery housing so I can see what’s going on but you could get away without one, just use another battery when this one gets anemic (one can tell).
for yours, li-ion is probably not going to work out (cells won’t fit right, you’d need to figure out a proper charger and BMS)

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I also have upgraded two cordless drill with 4s rectangular Li-FePo4 batteries.
Earlier the BMS where too big to put inside the battery case.
So I mounted with glue a JST XH connector on the battery case for a balancer connection (hidden when ist plugged to the drill)
With a RC balance changer, I can safe charge it.
The backdraw of this old Ni-Cd converted drill is, that they are much lighter, so they topple/tip over Angry

Robin Dobbie
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Zelda, you might be the first person in the thread who’s actually upgraded a drill to lithium!

Thought about a balance charger, that’s the ultimate in intelligent charging and flexibility. But I didn’t want to have to mess with menus every time, and I want someone unfamiliar with it to be able to just plug and go.

Looks like everything would fit in the factory battery case if I just used 4 cells. But I’m considering a 2P setup because I have the cells and I hate dead batteries. It’ll be really easy to make a box of the correct size and use the existing top half of the battery case(which has the connector that goes onto the drill). Shouldn’t be a big deal to make it large enough that everything fits, and strong enough to be dropped without issues that didn’t already exist.