This guide will show you how to replace the dead batteries of a Dexcom G4 "slim" transmitter.

The Dexcom G4 features a molded plastic body encasing two coin-cell batteries. Replacing the batteries will require grinding away the plastic over the cells, cutting them out, and refilling the excavated plastic with epoxy.

Be very careful not to damage the battery cells when grinding!

  1. Take a marker and paint two circles at this position.
    • Take a marker and paint two circles at this position.

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  2. Use the 2-3mm cutter and grind slowly down to the batterries.
    • Use the 2-3mm cutter and grind slowly down to the batterries.

    • Be careful not to grind away the contact plates.

    Made a mistake here so I grinded too much on that contact plate area so they snapped off in step 3.

    kakoni - Reply

    Mine did the same thing

    Jghake - Reply

    • Lever both contact plates carefully with the screwdriver.

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    • Use a 0.5mm cutter and grind around the batteries. Be careful not to grind too deep. This process is only for loosen them and make space for the screwdriver.

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    • The lever part is easy but be careful with the lower contact plates. They are sticking at the (-)pole. Use the edge of the screwdriver and lever it carefully left-right-left ... till it's detached. Then push the contact plate down.

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    • The original batteries are Maxell SR1120W (391) with a capacity of 55mAh. I suggest that you use the same ones because of the profile form inside of the transmitter. If you prefer to use another brand i can suggest Energizer 391 (60mAh) and Renata 391 (50mAh). First you have to scratch the contact plates with the screwdriver.

    Is it a bad thing if the contact in the middle *under the batterie* breaks?

    derksinge - Reply

    No. Just add a conductor filler, like aluminum. (I'm did the same thing…I broke a top contact too.)

    necessaryevil74 -

    • Use superglue and sprinkle it at three points in the battery hole sidely. Then insert the new battery and push it down for 2 minutes. Same with the second battery. After this the (-)poles of the batteries should have contact with the lower plate.

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    • First you have to scratch the upper sides of the batteries with the screwdriver. Then add a small amount of superglue under the plate and push it down for 2 minutes. Same with the other battery.

    I could not get the top contact to glue down with continuity. Is there a way to solder it?

    Sam jarczynski - Reply

    • At this point, the transmitter should work again. Let's check it out and take the multimeter. Set it to 2000mV and add the measuring pens on the sensor contacts. It should show you 019. If yes ... congratulations! You can move to the next but one step. If not, there's a contact problem. First check the upper contact plates. Set the multimeter to ..

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    • ...continuity. Touch one pen on the plate and the other on the battery. 000 should be displayed. If not, you have found the problem and have to remove + clean + re-glue it. If both plates have continuity you have to check out the lower contacts and remove the batteries again.Maybe pull up the lower contact a little bit before attaching the battery

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    • Slip on some latex gloves and add some 2K-Epoxy glue on a piece of plastic, glass or something else. Mix it about 2 minutes with a toothpick.

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    • Use the toothpicker to add the epoxy glue on the batteries and seal the grinded holes completely.After 2Std it's dried about 80% and you can insert it into your sensor pod. Wait 24hrs before showering. All done and have fun with your new transmitter. It should last now approx. 1 year again. After that ... you now know what to do. Cheers :)

    So all done with replacement have 19 but it's not connecting to my receiver? Am i missing something this is my first time . Thanks for any info

    heather - Reply

    So I have mine done with a positive 19. But I can't get it to sync with my receiver. Take any help I can get.

    heather - Reply

    Hi heather @g4type1girl - it cannot work on dexcom’s receiver, you have to use xDrip+. I believe you must have reached that conclusion already. Good luck.

    Azar Ali Zain - Reply


To reassemble your device, follow these instructions in reverse order.

28 other people completed this guide.


Member since: 02/05/2016

794 Reputation

1 Guide authored


Thanks for posting Joern!

timthornton - Reply

Awesome! Thank you for the guide.

John Vilburn - Reply

I'm wondering which model of dexcom G4 this is? Apparently one has a dual pc board structure with the batteries sandwiched between. I don't want to cut from the top as you've done if I'll cut thru the top pc board. Thoughts?

ortho - Reply

It's the slim model. You can check this by measuring it's height. 6mm - slim, 8mm - the old one (sandwich PCB).

Joern -

Excellent post Joern. The batteries were exactly as you described. I am up to step 7 and just ordered my batteries on eBay. I will post an update once I get the batteries installed. To do the surgery, I mounted the transmitter in a vise and then went at it with my Dremel. I used the multi-purpose cutting bit (561) and the engraver tool for the fine work.

My only setback was when I bent back one of the top contact plates and it broke off. I will need to solder it back in but I am not too worried.

I found this posting after I paid out of pocket for a new unit but I really want to see if I can get my old one back up and running.

If anyone has any dead units they want to donate to science please contact me. I would like to see if I can do an even finer job.

Scott S - Reply

Well, its done and working. The only thing I have yet to do is test it on an actual sensor. I did things a bit differently after step 7. I tried gluing the top contact to the battery but the superglue would simply not adhere. So I soldered the contact to the battery with the smallest amount of solder. I followed with a coating of epoxy as Joern outlined. I am getting 19 on the multimeter so I am confident all will work well.

Scott S - Reply

The Maxell SR1120W is silver oxide and the SR 1120 is Lithium ------- would Lithium not be better?

George Davis - Reply

All SR batteries are silver oxide. You mean the LR1120. They are not better because of less voltage (1.5V) and less capacity.

Joern -

SR is silver oxide, LR is Zinc Manganese. The voltage difference (1.55V vs 1.5V) is negligible, but the capacity of LR is 1/3 less than SR for this size (60mAh vs 40mAh). You can't get a lithium cell in that form factor, and even if you could it would be the wrong voltage (3V nominal).

tml4873 -

2K-Epoxy glue I'm not finding this epoxy and the gorilla epoxy sounds pretty hazardous to have that close to me for long periods of time is there an epoxy you recommend or a link to the 2k

jmeesenburg - Reply

2K means 2 components epoxy. So you can use the gorilla suringe. The epoxy doesn't have contact with your skin.

Joern -

I had a lot of problems with my first one. I just couldn't get the reading I was suppose to get after gluing everything together. Eventually I broke a contact plates while trying to grind the glue off. I also tried soldering but my battery got too hot and swelled. The second one I tried I wrapped all the contact plates in the smallest wire I could find. It made the batteries (don't worry I replaced the swelling batteries) stick up a little higher, but I got it to work on the first try. Now I'm just waiting on the epoxy to dry before I hook it up and give it a go.

Chad Reeves - Reply

Hi Joern, I think this guide is great and I am hoping to be able to experiment a bit with a dead G4 thin transmitter soon. What tool is a 2-3mm cutter? Is it something I could purchase from a hardware store?

Matt Pulford - Reply

I used dremel cutter myself with 2mm cutter tip, you can see it in here (part number 193)

kakoni -

What do you think of fixing the repalcement batteries with electroconductive glue

Svet - Reply

Our battery replacement procedure went fine. I used grinding file bits to be able to more precisley open some space above the batteries and the finest file bit to cut a little deeper around the batteries. What I saw as most difficult was to secure a good contact between the plates and the replacement batteries.

What do you think of fixing the repalcement batteries with electroconductive glue.

Only a very small amount. When applying the glue on the (-) pole it would be enough to just put e very tiny film dot and also to leave the glue for a while in order to avoid spils and short circuit. Applying the glue on the (+) pole would be much easier and safer. The glue that I found is designed for fixing electronics and has following characteristics:

- specific resistance: 0,004 ohm/cm

- current load: up to 1 A/mm2

- temp. range: -30 ...+80 C

Svet - Reply

I think if you are not able to successfully make a good contact with superglue only, conductive glue (wire glue) or silver will help as a second step after the superglue has dried. It is only needed for the upper (+) pole because the bottom (-) pole has a direct contact with the contact plate without superglue on it.

Joern - Reply

wow, i've been hoping for one of these, i will get the batteries, cutters & sealers & give it a whirl.

trudijolene - Reply

The procedure for the thicker G4 battery replace was so much harder. I cannot wait to try this. I will be getting a dead G4 thin soon. Right now I am on the G5, which has the software problem. Looking forward to the xdrip G5 solution, which is in Beta.

jonathanj36m - Reply

Hi all, I'm paying out of pocket for the dexcom g4 transmitters, I tried to replace the battery on the thicker version, didn't work. Anyone willing to donate an used unit? It can be the slimmer or thicker version. Please email me at


Carlos Dias - Reply

one of the tabs from the bottom of the battery came off, is there any chance of saving it?

Daniel Powell - Reply

You should be able to solder a small wire on the broken piece. Maybe have to grind a little bit to see it.

Joern -

great idea, but how many times can you replace these batteries?

Bill Barishman - Reply

I just started my second replacement. Used a dremel tool to remove the epoxy. Popped out old batteris and installed new ones.

Scott S -

i was planning to figure out this repair myself. thanks for the write up with pics! i just ordered the specified sr1120w batteries, and some sr1130 batteries, and intent to test this out with the thicker batteries, which obviously have higher capacity. i'll try to post back with an update once i get to work on it, but i hope to boost the battery life this way

josh hurley - Reply

attaching wires to the contact points and using epoxy to seal the wires to the transmitter and then soldering the wires to battery holders makes more sense, as u can replace the batteries whenever they run out.

jcstone - Reply

Thank you for the guide. All worked !!

Tomas Andersson - Reply

Tell me where I can buy a G4 Transmitter with the batteries already installed. I have a slim installed in my G4 now that has replacement batteries installed and it is in its 5th month working fine.

Leon Ullrich - Reply

I tried this operation on a used G4 Transmitter

My sensor has a chip and a circuit board in these 2 locations, the batteries are deep within, I think I'm out of luck.

Claude Quenneville - Reply

Fantastic job. I would like to criticize Dex-Com. IMHO the company is nothing but Greedy. Making a unit to change batteries is not difficult. If and when they read this I have no doubt they will make it even more difficult to change the batteries. Probably an Epoxy unit that would be destroyed if trying to open. I will Boycott Dex-Com for now.

Robert Allocca - Reply

Great post - all found exactly as described. One small tip. How to hold the transmitter still while working on it with a Dremel... I used an old sensor pod glued to a piece of wood with epoxy. The wood can then be clamped, a firm hold and no risk of damage to the transmitter from a metal vice...

Charles Brett - Reply

wow, that's pretty awsome. i have about 5 of the G4 sensors lying around and two G5 sensors that i hate. all are dead and may really be going head first into this replacement. thanks for the steps. i'll post back once i get it going.

Robert Vela - Reply

Just to let you know: I changed my batteries according to this guide. More precisely: I used the directly predecessor of this guide, which I found on another platform. I used the Maxell 391.

Yesterday it was the batteries first birthday: Since 20th of April 2016 (!) the transmitter is running perfectly without any problems or breaks. The value for "Transmitter-Battery" today is 213.

Hooray, hooray and once again: Many thanks.

Minda - Reply

This is way too difficult. What is needed is induction charging that is used in some of the new cellphones. No grinding needed.

avagts - Reply

This solution is far too difficult . What is needed is the new induction charging used in some new cellphones.

avagts - Reply

Anyone having trouble with the receiver saying it out of range but you have power on the transmitter? I'm getting 19-21 on the meter but we start the sensor and it says out of range.

jcheney.sdcc - Reply

Are you getting the error from the beginnig after you did the battery replacement? Mine was working fine for several months but recently I started getting this error more and more, together with low batteries warning - but I knew it was not true. I figured out that problem was weak contact between plates and the battery. Quick solution was that I pressed the transmitter against table quite strongly so I put them together again... let's see how long it will last ☺️ So maybe you have also weak contact, but it does not show up when you do the measurement because it's in different position as when it's attached to the sensor.

Adam Tisovsky -

Can the G5 batteries be replaced?

Miles Denson - Reply

Great instruction. But not working, I have the same issue as jcheney.sdcc , volt reading on meter looks correct but the receiver is saying out of range. Have stopped and started, cleaned contacts on bottom, verified sn of transmitter is the same as the one listed in the meter. Anyone have any ideas on fixing this?

Robert - Reply

Same issue . I will try disconnect one of the batteries and then reconnect it again.

Andrei Rusei - Reply

Thank you for this post. The replacement has been working fine for at least 4 months. The only problem seems to be the contact between battery and plates which is getting unstable. I am considering to use some conductive glue instead of superglue. And I used melt glue instead of epoxy ☺️

Adam Tisovsky - Reply

Please can I pay you to do this for me?

Lindy Seabrook

Lindy Seabrook - Reply

I have no idea what these item are and would be happy to pay you to replace batteries for me

Lindy Seabrook - Reply

Lindy, look for “Dexcom G4 transmitter“ on Amazon. There is a seller who will replace batteries for you for around $85.

Dmitry K -

Yes, a fine topic and I'm just about to try it after getting my second “low transmitter batte” warning.

All looks straightforward but I'd like to ask some questions …

1. Once I Superglue the top contact onto the + battery face and then cover everything above and around with epoxy, how on earth can I excavate the battery cavity next time? Won't it be impossible to free the top contact from the battery and surrounding epoxy?

2. If I used the Maxell SR1130 for its considerable extra life, would there be enough epoxy thickness above it to provide the required survival strength?

And many thanks Joern for helping us all make the very best of our G4s!

Brian Littlewood - Reply

Now i grind down the whole body to the batteries and make a full seal layer over both batteries with epoxy after replacement. Then it’s easy to unglue it with a screwdriver - stap into the edge of epoxy and move it up and down. The complete layer will plop away then.

Joern -

Great Post. How hard will it be to remove all the glue and 2K-Epoxy next time?

Thanks Carmen

Carmy C - Reply

To remove the epoxy, simply take a tiny screwdriver and stab into it at the edge. Then move it up and down and you will see that the whole layer will unglue and comes up.

Joern -

Very good post. I also incorporated some tips from and

One of my upper + terminals broke off. Took multiple attempts to solder some wire onto the terminal and was afraid I’d overheated the circuits but all seems good. For gluing, my initial stage was to coat all of the top BUT put a #6 nut over the + terminals and used large binder clips to clamp the terminals securely to the batteries. will remove nuts and fill in holes left by them after glue is cured. Next time around I am considering shaping a lid that can be clamped & glued over the batts while clamping the lid which will also be pressing firmly against the contacts.

I saw the the G5 uses Renata 389 which is an 80 mAH battery and is only 1 mm thicker. Will probably use the 389 next time to get up to 33% longer life with the negligible additional height.

John - Reply

Yes, i would prefer Energizer 389.

Joern -

I was using a re-batteried transmitter for 11 months before getting Low Battery warning and 3 days later it ceased to function. Perhaps it is a failed transmitter but I am reading 0.192 VDC on the sensor contacts and therefore wondering IF the 0.19 reading is a valid measurement to test the transmitter batteries???

John - Reply

The only way to test the batteries: xDrip+ Android app.

Joern -

Thanks for posting this. Broke off both bottom contacts trying to remove the batteries. Used a dot of silver-loaded conductive epoxy to fix down the batteries onto the lead to the missing bottom terminals, and then also used the conductive epoxy to reattach the top terminals to the batteries. Then potted with regular epoxy. The replacement batteries I was able to find were Renata 391’s, and they turned out to be slightly larger in diameter than the Maxell batteries I removed. To compensate, I used an aluminum oxide grinding bit in the rotary tool to enlarge the cup into which the batteries sit. Also of note, the output voltage on my transmitter after replacing the batteries was 214mV. So far so good - the receiver now shows the battery status as “ok” and the sensor is going through its two-hour start up with everything behaving normally.

Stephen Streiffer - Reply

I am going to attempt to just extend water-proofed wires to an external battery holder that can be taped beside the G5. This way when I need to replace the batteries it can be done without re-grinding the epoxy etc. I also use Tegaderm water proof tape over the sensor so slipping the battery pack under that will be fine.

jcstone - Reply

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