Introduction: Converting Cordless to Lithium Li-Po

Picture of Converting Cordless to Lithium Li-Po

As time moves we find that our drill don't cut it any more as now there are all of these new powerful cordless drills with lithium but the price of one of them cost about an arm or leg so what do you do?

Convert them to lithium,

Motor technology has been the same since 20 years ago and it's still the same in all new drills "DC Brushed Motors"

Up on opening my "Old" drill and having a look at my motor my motor looked very new and the brushes ware far from worn if not still would go strong for many years to come.

On the other end the battery's ware totally on the end of its life.

Step 1: Opening Your Battery Pack

Picture of Opening Your Battery Pack

When you open your battery pack your going to find sets of sub c battery's which are most Likely cheap cells depending on your make of your drill since we only care about the enclosure you can throw away the cells or keep them for a different project doesn't matter what we need to know is the inside dimensions as that will tell us how big the battery can be.

Order a smaller battery then the dimension as it will allow you to move the battery around.

Step 2: Soldering the Power Connector

Picture of Soldering the Power Connector

Once you have found the best location for your battery you have to solder the power connector to your original battery connector

Always do one lead at a time solder the positive wire then heat stink the connector and then the negative wire and then heat shrink it.

Also helps to add a deans connector to make charging very simple.

Step 3: Closing the Battery Pack

Picture of Closing the Battery Pack

At this stage you can close every thing up and drill a hole for your balancing connector and call it a day.

And if your like me then you want a battery pack with no loose wires hanging out then the next step is for you.

Step 4: Soldering DIN Connector

Picture of Soldering DIN Connector

The connector used was a 5 pin DIN connector,
male for the charger and the female end for the battery as their are glued to the battery cover for a nice flush finish

I'm always throwing my tools around and this is the best method as it doesn't interfere with any thing or get pulled.

Step 5: Enjoy the Power of Lithium

Picture of Enjoy the Power of Lithium

What old drill ? Lithium power baby

The power gains I received was very amazing and even tested it with a power meter my battery's are well within the power the motors requires

As along as you don't let your voltage drop low then your all fine

Step 6: Charging Your New Lithium Battery

Picture of Charging Your New Lithium Battery

Due to many comments talking about its a bad idea to charge your battery with your original Ni-CD / NI-MH Duhh you don't say!

I dint think in this day and age that I will still think people will charge lithium battery's on a NI-CD/ NI-MH

Lithium battery's are no longer new and I'm guessing if your on this site then I'm sure every one knows about the charging procedure.

But you still get a few saying its a bad idea because in your low IQ head you think I'm using the original charger think why would I go through the trouble of fitting a DIN connector as a balancing connector. any ways.;

You must use a lithium charger to charge your battery packs!

The set up I'm using is a very simple LI-PO charger made by Hobby King HKE4.

Which iv set the charge rate to about 1.8 amps and removed the dial.

ATM I'm running the charger off a 12v battery in my shed but an ac adaptor is the best option for taking it to site.

Step 7: Low Voltage Cut Off

This is one topic that I will be adding as ATM I'm using a cheap LIPO buzzer and I would like some sort of low voltage light or cut off.

The problem I'm facing ATM is that I want it to draw 0 current.

When I sort this issue out I will update it.


themisv (author)2017-09-19

very helpful instruct able. I would like to replace the battery of a nicd bosh drill that runs on 18v . I was thinking of buying one 22 volt lipo battery , do you think this would work? If you think I should stick to 18 volt , do you know of a way of arranging 1 3.7v and 1 14,8 to work with the drill? Can I connect them in series and have 18volt output? And if so do I have to charge them separately afterwards? Thank you

ronald.johnson.7399786 (author)2017-09-15

For the simplest radio shack, or maybe car parts store LVC circuit, i'm wondering.... Using a potentiometer and a relay. If you wired the pot in series with the coil, and perhaps a shunt. I think you might create a magnetic switch that will fail if there is an insufficient sustenance voltage. Wiring it up series on either the negative or positive side may also provide a useful feedback voltage drop. The nice thing about this would be it would draw 0 current until the trigger is pulled.

Adeldor (author)2013-09-27

Hi henal,

Great project! Just one small correction: judging by the images, I believe you'll find that you're not using a BNC connector, but a DIN connector.


vex_zg (author)Adeldor2017-01-06


For safety reasons lithium based batteries must be used with a BMS circuit which monitors per-cell voltage and preferably temperature and ensures cells are balanced. This is even more important where battery pack is consisted of several cells connected in series. Disbalance between cells can result in cell inversion, especially in the high load situation such as cordless drill

Lack of a BMS can result in failure, expolsion, toxic fumes.

Lipo are even more sensitive than LiIon and more prone to thermal runaway.

Cordless drill takes tens of amperes of load from the cells and this increases the risk.

Do not mess with lithium batteries if you are not qualified for it. Yes you will probably get lucky and get away with it but you should not take such big risks.

Behind every power tool battery pack are thousands of engineer hours spent on designing and testing the BMS and battery pack. The BMS is there for a reason.

DakLak (author)vex_zg2017-02-02

I 100% AGREE! My company uses Lithium and LiPo batteries by the carton - the dirty brown carton - and you should NEVER charge these battery types without a BMS (Battery Monitor System) aka Battery Balancer.

There are about ten circuits on Google if you want to make one.

Remag1234 (author)2013-10-01

Nice Mod BUT, you can buy an 18v. 1/2" Hammer Drill for $54.99 add an extra battery for $14.99 without any hassle @ Harbor Freight. For $70 it will do the job for most DIY's, if it breaks just throw it away and get another. It doesn't get much better than that.

ac-dc (author)Remag12342017-01-16

It gets much better than that, to buy something from a major brand that lasts 4X as long for only 1.5X as much money. Plus, no don't just throw it away, the batteries are toxic to the environment and the rest, senseless landfill waste.

dpavliv (author)2016-09-20

Just all to know, for RIDGID & AEG tools you may use original new & cheap li-ion PowerStroke battery with some adaptation, here is video manual -

tstevens-1 (author)2013-09-28

Also, lipos have a threshold. If you discharge the batteries beyond this point, they won't recharge. So if you run the drill down to where it quits, you've likely ruined your lipos.

valveman (author)tstevens-12016-08-09

True but if you open the case and disconnect the balancer, you can use a power supply to get the voltage up past the threshold and connect everything back together it will start charging again.

I have done that several times with laptop batteries that would not charge because they were discharged below the threshold voltage.

For what it is worth, I have the Craftsman C-3 Series tools and switched from NICADS to LITHIUM - Sears provides the battery packs so re-building is not the issue. But, your comment does not comport with my experience (over 18 months now) witht the lithium batteries and chargers that Sears provides. I am using the tools that came with NICADS and the Sears lithium batteries. I regularly use the tools unitl it 'quits.' Then, pop it in the charger, then use it again. BTW They have a charge guide built into the Sears litium battery unit - you prss a button and it glows, Green, Yellow or Red to indicate the state of charge.

makya (author)charlessenf-gm2013-10-02

you are using Lithium Ion batteries, which are the defacto standard for power tools. they put out 3.3volts per cell, versus the 3.7 volts of LiPo. Li-Ions are also composed of a more stable cell structure and do not heat up and have a danger of fire when run below 3.2-3.4 volts.
the reason LiPo batteries are more popular in radio control is that they have a higher amp draw than Li-Ion.

BigAndRed (author)makya2013-10-02

Im using Li-ion 18650 3.7V cells, have never found any at 3.3V

makya (author)BigAndRed2013-10-02

D'oh! you're right! I was confusing the voltage rating between Li-Ion and Li-Fe.. The rest of what I said still stands, but I apologize for the voltage mix-up

BigAndRed (author)makya2013-10-03

I didnt know about Li-Fe batteries, will have to have a look at them.
I build small solar power systems and use Li-ion to store power as smaller, lighter and more efficient than Lead-acid.

That is probably true for the Sears pack. I would bet most people who are rebuilding these packs do not have any kind of charge protection on the lipos they put in their pack. So, we both are right!

rjnerd (author)charlessenf-gm2013-10-01

The batteries you are using have a charge controller. They track the cells state of charge, and if you are about to dip below the safe point, they shut the pack down. Typical, older RC batteries won't include the controller. If you abuse them beyond the safe point, you kill them.

TomF8 (author)2015-07-01

What about li-ion? I have a Ryobi 14.4v drill, and I'm tired of buying Ni-Cads for it (Home Depot has quit selling them). I have thought of using the old battery case and installing four overcurrent protected 18650 Li-ions in series. They may not produce the torque of the originals, but I know they are good for at least 3A - they produce that in my flashlights - is that enough? Would it be safe to use the original Ryobi "Smart" Charger? It's no-load voltage is quite high, but it doesn't blow up the NI-Cads...

jchavis2 (author)TomF82016-02-05

That won't be enough. Milwaukee made a retrofit Li-ion battery for the Power-Plus 18V tools after they started to discontinue Ni-Cd. The cells they used were rated for 40A discharge. At only 3A, your tools will work, but very slowly and with low torque. Your best option is to convert them to 3000mAh Ni-MH for $50. They have a longer lifespan, no cell memory, and 50% higher capacity than most Ni-Cd. I still have 2 full 4-tool Power-Plus kits, otherwise I would just go buy the Ridgid kit for $400. If you register the product within 90 days, you will get a lifetime warranty...even on batteries! The disclaimer is that they only cover the batteries that came with the tool, not the extended capacity batteries.

aah8822 (author)2016-01-08

only thing I would have added is a cheap lipo alarm ($2 on hobby king) so I wouldn't have to worry about running them below 3.0V/cell

1Teamstar (author)2015-05-15

Guess the "be nice" comment policy doesn't extend to the one who posts the instructable using bad spelling and grammar while calling others low IQ heads.

russ_hensel (author)2015-02-05

Just a note to let you know I have added this to the collection: Cordless-Drill-Battery-Maintenance !


Take a look at a bunch of different/similar approaches to this project.

baratacus (author)2014-12-30

I have a ryobi one+ with high capacity packs. 5s2p. that's 10 li-ion 18650's. Cost of replacing the batteries is about $100 plus time, parts and labor. expensive because, The original li-ion's in my packs are a 5-10C rating. meaning they can safely discharge at 13-26 amps without damaging the cell. cheap Li-ions are only about 2C rating, meaning they would be dead in a week if used over 5 amp discharge. A brand new pack is $50-$60. The stock high capacity packs are a must for a circular saw or reciprocating saw, but even then the high discharge kills the pack after about a year of use. I've been wanting to go Lipo with them and this instructable inspires me to do it. For all of the readers, I emphasize that you NEED a low voltage cut off circuit. (you can buy one at places like hobby king), You NEED an external charge connector and balance connector that go to a LiPo charger. The LiPo's are 15-20C rating. They will work better on high drain equipment and if you follow the directions and use the right charging equipment they will be perfectly safe. Improper use and improper charging is what causes fires. You have LiPo's in your bluetooth head set, in your tablet, in your phone, in your micro rc toy.

Costarus (author)2014-02-04

These batteries provide a small current. And small capacity. I used 12 PCs 18650 scheme 4 x 3. Could 14-15 Volts and capacity of about 4-5 Amp*hours. Homemade box.

henal (author)2013-10-05

Nice mod mastelios

mastelios (author)2013-10-05

Nice!Well done!done mine a long time ago,with some 3s lipos I had from my rc flying days, I have learned to be careful around lipos so I did not add any low voltage circuit.I just check it with a checker now and then.I have found that with the lipo it goes strong for way more than it used to because of the different discharge curve of the batteries.Also mine was supposed to be 14.4v nicd but I used a 3s setup.In practice there was no power loss.Here as a couple of photos,not as good as yours but I needed something fast at the time plus the drill itself was not worth it(a cheap Chinese one)

henal (author)2013-10-04

Thank you for all your comments iv added a step for charging the battery pack, hope it clears a lot of negative comments.

BigAndRed (author)2013-10-02

if the Li-ion pack is same voltage as old Ni-Cad then use the same old charger dock.
it will have all the correct circuits to charge with over voltage protection built in.
this has worked on a 14.4V Ryobi drill with 4x 3.7 V Li-ion 18650 cells, works better than before with lots more working time.
5x 3.7V = 18.5v for bigger battery pack.

Spokehedz (author)BigAndRed2013-10-03

This is a bad idea. A very, VERY bad idea. The charging profiles are not the same, and just because it works does not mean it will work for very long. You cannot drive a Ford Tarus like a NASCAR and expect it to last.

I heartily recommend against this, and that you read up on how a NiCad battery charge profile is nothing like a LiPo/Li-Ion charge profile.

BigAndRed (author)Spokehedz2013-10-04

OK, well i think the dock can still be used if the circuit inside is replaced with
Li charging circuit. easier than putting extra plugs in?

Spokehedz (author)BigAndRed2013-10-04

Seems like a lot more work to do all that, than to put a DIN connector on the side of it and use that to charge. You are already taking the battery pack apart, so how much more effort would it be to put that DIN connector on there? You could even go with a MiniDIN/PS2 as the charging voltages are low enough for those pins. Might be a bit tricky to solder, but hey. What is life without a challenge?

manicmonday (author)2013-10-02

Can you tell more about the lithium batteries? Where did you get them? How much did they cost? Thanks

BigAndRed (author)manicmonday2013-10-02

look on ebay, there is many different types of Li-ion cells to pick from.

nthomas12 (author)2013-10-02

this is great, ive wanted to try this for ever, glad to see it done so i know it works, and i dont have to worry about the risk!! Thanks

henal (author)2013-09-28

Yes I'm using a balanced charger ATM which I'll take full blame for not providing a step for the charging section will update it by tomorrow.

Currently I'm trying to work on a circuit which uses a light to turn on when the battery is low or some thing which MUST not take any power.

This is my first guide on this website and I'm doing it through my phone's app which is not as easy as doing it on the computer.

makya (author)henal2013-10-02

here you go. My apologies for being harsh earlier. After seeing what happened to Mike's Hobby Shop in Dallas last year,I'd hate to see that happen to someones home. here is a link to a low voltage alarm for a couple of bucks:

mtoddh (author)2013-10-01

Very nice. Unfortunately, I just threw out 2 old drills that I had been hanging onto in my shop for several years.

On the other hand, these chargers and packs are really expensive. I lot more than I paid for any my cordless drills.

makya (author)mtoddh2013-10-02

they don't have to be.
you can buy a charger for less than $15 if you don't mind charging in 2 hours. $20 if you want to charge in an hour.
batteries are about $8-10 a piece.

ardnaz (author)2013-10-02

Very good idea!
question: Where can I buy the lithium cells, and, more importantly, how do I get a charger. (or build one) since I assume that you need a special charger for lithium batteries.

makya (author)ardnaz2013-10-02

many of the Radio control car/plane suppliers carry them. You will also need a low voltage alarm for each battery pack to prevent the dangers of LiPo batteries catching on fire. the alarm starts beeping to let you know when the cell voltage drops and needs to be recharged.

you can try valuehobby, they are in illinois, and shipping is pretty cheap. look at their batteries and chargers. I got my charger from them for $20

rjnerd (author)2013-10-01

So how do I find a comparable sized Li cell to my existing NiCd pack? I know they are sub C, but they aren't marked for capacity. How many MaH is a typical sub C?. I assume that I will try to fill the pack, to get max capacity, matching voltage...

throbscottle (author)rjnerd2013-10-02

Cheap sub C nicads are often 1300mAH

Wingloader (author)2013-10-02

I knew I was keeping my dead drill for something.this is one of the most useful Instructables I have seen yet. Now I just need to find out where to get the din connector without spending $12 for shipping :-)

ricoj (author)2013-10-01

for the people that are not into RC; always use a dedicated lipo charger!

I'd consider adding a simple lipo saver, there's plenty around, with a light or a buzzer that'll warn you if the voltage drops too much.

makya (author)2013-10-01


you need to warn people about LiPo fires from running the batteries below 3.4 volts per cell, and the danger of fires from doing so. You also did not mention that you have to use a LiPo specific charger. We almost had a track burn down in Dallas last year from a Lipo fire, and it is actually a requirement at r/c car racetracks to use a fireproof container to store and charge your battery packs in to prevent a Lipo pack fire from spreading.

I'm sorry this is not more constructive, but this is dangerous advice

Gilo (author)2013-10-01

I never charge my lipo batteries indoors or I put them inside some fireproof vessels like a pyrex bowl or a metal container. Lipos can heat up and burn if charged wrongly or if they get knocked hard (as in dropping your drill from a high spot) . I keep an eye on my lipos when charging.

charlessenf-gm (author)2013-10-01

On my Sears C-3 se, there are three connectors in the battery pack/tool. Does anyone know why?

rjnerd (author)charlessenf-gm2013-10-01

the third terminal is often a temperature sensor.

rickharris (author)2013-09-28

To get the best life from the battery you should get a balanced charger.

The voltage of the old battery pack and the new need to be close as well or you drill will run slower/faster (may burn out)

Yes, voltage needs to be correct - and (I would assume) correct amperage is as important.

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