Introduction

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

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

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  • 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

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  • 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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  • Insert wisdom here.

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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.

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  • 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.

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  • 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 :)

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Conclusion

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

17 other people completed this guide.

Joern

Member since: 02/05/2016

508 Reputation

1 Guide authored

24 Comments

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 -

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 https://www.dremel.com/en-us/customerser... (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 cedias1420@gmail.com

Thanks.

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 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

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