I got a couple of Logitech cordless, optical mice for cheap from an eBay auction. They work great, but they are battery hogs. A pair of AA alkalines only lasted a week or two, and when I used rechargeables, they only lasted a couple of days before needing a recharge.

At one point I mused that it would be nice to be able to power the mice with the BL-5C Lithium Ion batteries that power my cell phone. They recharge quickly and hold a lot of current. Only problem is they are 3.7 volt batteries and the mice are designed to run on a couple of AA's in series... 3 volts. I wondered if the extra .7 volt would be a problem. One way to find out. A couple of jumpers later, I had my answer... the mouse seemed quite happy with 3.7 volts.

The hard part was finding a way to stuff the battery inside the mouse. You have to chop a lot of the battery compartment plastic out, remove the springs, and install a connector assembly that will match up with the BL-5C terminals (if you want it to be removable, more on that later).

Step 1: Not a Step, Just a Pic

Picture of Not a Step, Just a Pic

These two mice are the same model, just different color. The one on the left has been modified to run on a Nokia BL-5C 3.7 volt lithium ion cell phone battery.

I also installed a small slide switch with which I can turn the mouse off to conserve battery power.

Step 2: Clearing the Way

Picture of Clearing the Way

I used a Dremel tool to carefully destroy the battery compartment.

You must take great care not to remove plastic which supports the right and left mouse buttons... nor any that affects operation of the mouse wheel.

Look it over real good before you start chopping!

It might even turn out that the mouse you want to modify cannot accomodate this size and shape of battery and remain functional.

Step 3: The Connector

Picture of The Connector

I butchered a flash card connector out of some other piece of equipment to get this improvised connector which I hot-glued in.

Only two of the finger spring contacts are actually used, the others I bent slightly so they are flatter and don't protrude.

Step 4: Making Contact

Picture of Making Contact

The terminals of the battery are somewhat recessed and my spring contacts had a hard time making contact so I built the terminals up with a little solder. My phone didn't care.

This requires hit-and-run soldering. You have to have the iron just the right temperature so you can get the solder on quickly and remove the iron before you melt the battery case.

SAFETY NOTE:  Lithium ion batteries are dangerous critters.  They don't take kindly to abuse. These batteries have a safety device built into them to prevent overcharging or over-current (short circuited) which ends up disabling the battery, but that's better than the alternative which the industry euphamistically calls "venting with flame".  When even the euphamism sounds scarey, you're dealing with some serious doo-doo.  Don't do anything to one of these batteries that can pierce it, overheat it, or otherwise tick it off.

Step 5:

Picture of

I put some foam rubber in the front end of the battery compartment to keep the battery in snug contact with the connector.

In retrospect, perhaps I could have left that spring in there.

Step 6:

I made this modification about a year ago, before I had a simple way to recharge a Lithium Ion battery ... if it were not removable from the mouse. I have just been using my cell phone to recharge the battery when it needed it, which is about every two weeks or so. (I never remember to turn the mouse off at night with the switch.) I have several of the phone batteries, so I can just slip a charged battery in and put the depleted battery in the phone for charging in just a few seconds.

Step 7:

Picture of

I just received this gizmo from Hong Kong. It is a nifty intelligent Lithium Ion battery charger designed to charge cell phone batteries by slipping them under the spring-loaded clear plastic part, bringing the battery contacts against the two adjustable arms.

It is a simple matter to clip on a couple of jumper cables to charge a battery, even if it were still in a mouse.

Making and mounting the battery contact assembly in the mouse was probably the hardest part of the project and required a lot of fiddling and adjustment. The whole mess could be avoided by hard wiring the battery and just using one of these chargers, but you couldn't use the mouse while you wait for it to charge.

This charger cost me $1.50 US with free shipping! from an eBay auction and it works like a champ.

I've been powering this mouse with BL-5C's for over a year now and the over-voltage has produced no adverse effects, so I decided to share it with the world.



JCar90 (author)2016-04-20

I would like to do this to my Turtle Beach x41 headset. Would the process be basically the same? This headset eats batteries like crazy.

nataku (author)2013-08-27

Hi Dave,
your posting inspired me to do exactly what you did on a wireless keyboard.
Except I left the battery on the cellphone. May be in the long term I will try to move the battery into the keyboard and make DIY battery compartment. Sounds very challenging though. May I'll just hot glue the whole cell phone on the keyboard. :)

krisley (author)2013-03-25

So, on a battery such as that, only two of the contacts are actually used to power something? I have a few HTC G2 batteries laying around that I wanted to repurpose. I see where they note negative and positive. I just have to make contact with these for it to work?

ironsmiter (author)krisley2013-08-19

Usually, the extra pins are for battery temperature monitoring.

As long as you are using a charger that plays nice with only the + and - pins then
YES, you only really need the two pins.

tfarris (author)2013-07-31

I will do this with conductive wire glue

moccor (author)2011-07-26

That mouse must be huge... I'm currently doing this with a logitech mx600 laser mouse, and I'm having a hard time figuring out where I can mouth the USB piece I have to take the power from the battery. I completely removed the battery compartment haha.

trogabird (author)2011-06-02

Hs anyone tried using a cellphone battery on a digital camera? This is my battery hog. 2 new double a battries will last for onlt about 10-12 pics and then they are to weak. I definetly have to use rechargables fot this dood. They last just as long and saves lots of money. 2005 model HP. It will also run them down lust being in the camera.

trogabird (author)2011-06-02

I hyave a 2005 Logiech cordless mouse that uses 2 AAAbatteries. I use rechargables and they last at least a month on a charge with my wife playing pc games 4-5 hours a day. Model #M/N:m. RN67 Just have to clean lent out of it monthley or it gets crankey. You have a good instructable.

Nilson13 (author)2011-05-28

Great Mod!!! I want to put a lithium polymer battery in a controller I have, but I do not know if it can handle the voltage difference. It uses two AA batteries and I want to put a 3.7 lipo battery. Is there any way to test if my device will be ok with it or will I just need to wire it and hope for the best? Thanks.

moccor (author)2011-05-26

Do you think maybe this would also work with this keyboard?
The keyboard can take up to 4x AA batteries. I don't think its completely necessary to have 4 batteries to power it tho, provided the batteries in it have enough juice. But if you think just one 3.7v wouldn't be enough, how about 2? 7.4v seems like a much greater amount then 6v though,

rollandb (author)2011-03-13 has a universal charger that can be used on any flat phone battery with end connectors, it is under $10

digitalstruggle (author)rollandb2011-04-20

Would you be able to find a link to this device, please? I'm having trouble finding it.

Davetech (author)digitalstruggle2011-04-22

Here is the eBay auction where I purchased mine:

It is still active as of today.

Davetech (author)Davetech2011-05-10

He has revised the auction and raised the price to $2.50. I don't blame him. LOL

zippydaspinhead (author)2011-05-09

Crazy idea... but so that you don't have to worry about charging it when its dead and not being able to use the mouse... Why not use one of those charging mats as a mouse pad when it dies? I mean only use it while its dead otherwise your effectively making it a corded mouse.

Then again having no personal experience with those charging mats I don't know if this is a benifical idea.

Oorspronklikheid (author)2011-04-19

I have the exact same mouse at home a pair of rechargeable batteries last up to six months on mine, so i find weird if your batteries only last a couple of days , maybe they are deffective , i don't know.

That is amazing. What brand of batteries are they?

regular 2500mah AA's nothng special or super expensive

plesperance (author)2011-04-21

My mouse only uses one AA I use rechargeable Duracell's for it and a few other things I am actually charging my battery before it goes right dead.
I use the control panels mouse battery meter as a guide and only once have found my self swearing at it because it ran out of power. lol I won't be trying it on this mouse but I was given an idea about remote maybe I will try to customize a remote to use a dead cell phone battery since the battery are excellent just the phone is dead.Great Idea anyhow later

ansil (author)2011-04-19

great mod. i keep this idea as mandatory at my house. nothing uses disposable batteries anymore. we take batteries from cellphones that won't hold a full charge anymore and mount them in universal remotes. i have gotten 3 years off one charge from a "dead" battery.

take it a step further and try upping your current capabilities in your ups. i managed to double mine. led flashlights using laptop cells. glad someone is writing this stuff up

fofs (author)2011-03-22

Changing battery has always been a hassle for me. This is a great idea!

67spyder (author)2011-03-15

You are right these batteries need special care. Very important is to not let them fall below about 0.9V to be safe most devices won't let them drop below 2.5V. There is very little power between 2.5 and .9 V so there is no point going below 2.5. There is great info about these cells at if you are going to undertake a project with LiIO batteries you should do some reading and possibly save burning your house down.

Having said that they are amazing cells and with a little care can really shine in a project like this.

sodiumcanine (author)2011-03-10

Great project, but what stuck out was:

"Carefully Destroy" was priceless.

Mastros (author)sodiumcanine2011-03-14

There is, um, a point in pointing this out.
But careful destruction is what archaeologists do all the time. In fact, they sometimes stop short from excavate the whole ancient site, saying that they want to preserve something for future generations with better methods. When it comes to archaeological excavations, you only have one chance.


I totally agree, being careful in destroying is the most fun-da-mental thing..

felipenavas (author)2011-03-14

You recharge the battery when it still conected to de mouse ?

Nice work!

juanoporras (author)2011-03-14

Nice mod, I have the same mouse and was thinking on doing something like this, they are battery guzzlers, I used to get around a week on Energizers 2400 mAh but those batteries are garbash, then I got a couple of sanyo 2100 mAh, best batteries ever, I also added a switch so I could turn it off when not in use. Now they last for 3 - 4 weeks. I wonder if the eneloops are better.

the good thing about this mod is that you can use it in other gadgets :).
thanks for sharing the info.

valibb (author)2011-03-13

If you want to loose 0.6V use a diode

profpat (author)2011-03-13


i did this cellphone battery swap with my 3 AAA battery powered LED desk lamp too...using the same china made universal battery charger..

cybergod (author)2011-03-13

Nice . . . :) I like this idea.

ARJOON (author)2011-03-13

i used the rechargable battery from my small broken mp4. lithium ion 1600mah 3.7v. just made a hole behind the mouse to connect the mini-usb cable and all set. my problem with my mouse is that the overvoltage burned the red led. so i replaced it and is going fine. also my range of use has decreased to about 50cm due to overvoltage. but i can still use it.

kelseymh (author)2011-03-09

That's an excellent project, and very nicely documented. Thank you!

Davetech (author)kelseymh2011-03-09

Well, that makes it all well worth it! Thanks for the props! :-)

buteman (author)Davetech2011-03-13

Just one other thought, you could put a silicon diode in series with the battery ( maybe a 1N4001 ) and it would drop around 0.6 volts so you would be nearer the original 3.0 volts.

technosasquatch (author)2011-03-09

are those maybe early generation cordless? I have one from logitech and my batteries last at least 2-3 months. its an M-RAT95a. also I'm curious how many a milli-amps of power yours consume. mine is 100ma

Davetech (author)technosasquatch2011-03-10

Good question, technosquatch. Why haven't I ever measured the current draw? I don't know. But I hauled out the meter to answer you and was disturbed by my readings. Also, I found I mis-spoke when I said both mice were the same model... the white one is a M-RR95 and the black one is a M-RAU95. Other than the color, they do look identical, although I have not pulled the circuit boards to examine them side by side for any minute difference. The back label on both states "Rating: 3.0V 100ma".

Using a Fluke series 73 digital mutimeter, I measured a mere 5 ma standby and 30 ma in-use current draw. That was with the 3.7 volt battery in the white mouse. I threw a couple of AA's in the black mouse and measured 7 ma standby and 50 ma in-use! Well, that's counter intuitive. Hey, Mice! did you forget about Ohm's Law? To be sure, I hauled out my old Simpson model 240 analog meter, and it confirmed the readings.

So.... what? Do my batteries suck? Could be. They are fairly old. Maybe they have a lot of self-discharge? They are not the most expensive around. Matter of fact, several are chinese eBay cheapies. I use a Vanson "Speedy I Charger Ni-MH & Ni-Cd" and usually use the slower, lower current setting even for the Ni-MH's, in which they barely get warm to the touch.

As usual, I'm left with more questions than answers. *sigh*

FrozenKnight (author)Davetech2011-03-11

I just thought I'd add my 2 cents. Mice don't use Ohmic devices in them. Granted they still need to use ohm's law in individual areas, but over all what you said makes perfect sense well from a transistor point of view
Since the processor in a mouse is transistor based I'll try to explain it so you understand it. Transistors are not perfect linear devices. So an increase in voltage may not have the result you expect. Transistors have three basic states, well at least as far as digital devices are concerned. These states are full on, full off, and gain. (The name is different depending on the type of transistor, so I've used terms that are close to what you might see commonly used between all the types.) Digital devices don't really like this gain state. it's where the transistor is switching and not fully on or off, this period of time is usually very small, but it's during this period where the transistor draws the most power. Depending on the transistors design they will hit fully on or fully off at a specific voltage.

What this means in your case is that that extra .7 volts is causing your transistors in the mouse microprocessor to jump to the fully on and probably the fully off state faster. This means that the transistors will be in their gain state for a shorter period of time. Since they are drawing current high current for a shorter period of time they will consume less current.

Please note there are may be other reasons for this as well, such as limiting inductance, or capacitance. Just be careful when using mods like this, transistors (especially MOSFETS) don't always like too much voltage and you can easily let out the "Magic smoke" of your mouse IC. And not all battery power devices have a voltage regulator in them to prevent this. (voltage regulators consume power and in battery powered devices this isn't always a good thing) If you really wanted to see what was going on you would need an Oscilloscope. Which is not a small investment for a Hobbyist moder.

Davetech (author)FrozenKnight2011-03-12

Hi FrozenKnight, thanks for your input.

I have a B&K dual trace 'scope but what I don't have is a schematic of the mouse.

It used to be that circuits were easier to figure out before so many components were miniaturized and combined (integrated). I wouldn't be at all surprised to find mosfets in there and that's why it was a bit of a shot in the dark whether the mouse would work or "go poof!" with the higher voltage.

"Since they are drawing high current for a shorter period of time they will consume less current." -- I think you might have nailed it right there.

CyberBill (author)Davetech2011-03-11

Actually, the higher drain on lower-voltage batteries makes complete sense. The mice themselves don't care about amperage, either way they go through a voltage regulator and draw equal amounts of power.

5ma * 3.7v = 18.5mW (idle)
30ma * 3.7v = 111mW (in use)

In a perfect world, with 2 1.5v AA batteries, you should see:
18.5mW / 3.0v = 6ma
111mW / 3.0v = 37ma

However, since you're using NiMH AA batteries, you're only getting 2.5V (NiMH have nominal voltage of 1.25V, rather than 1.5V)
7ma * 2.5v = 17.5mW
50ma * 2.5v = 125mW

Accounting for measurement errors and stuff, since I doubt it was actually reading exactly 30ma and exactly 50ma, and since the batteries aren't going to have exactly 2.5 volts, it seems to me like its drawing the same amount of power either way.

technosasquatch (author)Davetech2011-03-10

I just use duracell or energizer alkalines in mine

pandyaketan (author)2011-03-11

You can use light sensors, like ones on my I'Bles (click my name) instead of a switch as well as a 9V battery, if u want!

"May the good belong to all the people in the world.
May the rulers go by the path of justice.
May the best of men and their source always prove to be a blessing.
May all the world rejoice in happiness.
May rain come in time and plentifulness be on Earth.
May this world be free from suffering and the noble ones be free from fears"
---- Vedic blessing

speedsterharry (author)2011-03-10

Funny. I have exactly the same wireless mouse and added the switch to save up on consumption. I didn't think about using Li-ION though !

Davetech (author)speedsterharry2011-03-10

If you went to the trouble of adding a switch, am I correct in assuming your mouse was eating batteries too? Wondering if I just have sucky batteries.

pandyaketan (author)Davetech2011-03-11

You can use light sensors, like ones on my I'Bles (click my name) instead of a switch as well as a 9V, if u want!

"May the good belong to all the people in the world.
May the rulers go by the path of justice.
May the best of men and their source always prove to be a blessing.
May all the world rejoice in happiness.
May rain come in time and plentifulness be on Earth.
May this world be free from suffering and the noble ones be free from fears"
---- Vedic blessing

speedsterharry (author)Davetech2011-03-10

Yes, it was a real chore and expensive business to change batteries all the time. I managed to put a really small 2 position switch in the mouse casing -> dremeled the case a bit. I'm quite happy with the result.
Logitech disappoint me a little by not putting this switch at design stage :/

_Vyper (author)2011-03-09

just need the additional step of the induction charging and this would be mega sweet

caarntedd (author)2011-03-09

Nice work. Very useful.

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