Hi tim32!
Frankenstein looks really funny!
But it will derange you by wearing it, doesn’t?
You have to push in the slimmer 365er batteries.
I’ve managed to push in an original 391er in the front area.
This area is a little bit flexible ;).
Just remember : With 2 x 365er you will get a low battery warning every day which can be ignored.
With 1 x 365er + 1 x 391er you will get battery state: OK
Check it out …
Cheers
Ah, that makes sense now! Wish I did not buy a large pack of 391! 
Its larger, but not too bad, I got use to it quickly and it does not get in the way. But after 3 weeks I found the extra weight was causing the adhesive to give way - will secure it down better next time.
The front replacement battery (Maxell SR1120W) was lasting 4.5 months. I have replaced it again.
Now i’ve inserted a Energizer 391. The rear battery (Renata 365) still works and no need to replace.
Cheers
Hi Joern, sounds like you’re from Germany - me too. And it sounds like you’ve been quite successful in replacing the flat batteries of the G4 Transmitter. Mine just died on me after 12months usage. Would you be willing to try replacing my batteries as well if i (of course) cover all the costs for labour, materials, shipping etc ? That would be simply awesome after seeing the current price increase from Ninatmed…
Thanks !
Hi. Is there anyone in Europe who is willing to replace the batteries of my G4 Transmitter? Of course i would cover all the incurring costs + a little extra. And of course i do understand you wouldn’t be able to guarantee that it will be working afterwards, but that’s totally fine with me - as i’m sure i would damage my own device anyway.
If so feel free to contact me on billabong125 [at] gmx [dot] net.
Thanks !
Hello Joern,
I saw some instructions from you recently on how to change the batteries on the newer G4 slim transmitter at: insulinclub.de However, this page is coming up blank now. Do you have them posted anywhere else (ideally in English, but I’m happy to use google translate if not). My G4 is on it’s last legs, so I’m keen to get it done soon!
Many thanks for your help and great work in this area.
Tim
Hi Tim,
yes i know. There is something going strange.
I will post the instructions on another platform the next days and
edit the link … stay tuned.
Perfect! Thanks Joern. I hope to put them into practice in the next couple of weeks.
Is there someone willing to do this to one of my old transmitters? I would be willing to pay of course. Am I correct in assuming that once you have a hacked transmitter, you can just replace the batteries over and over again after removing the epoxy?
If nobody can do it for me is there at least a video or something?
Thanks!
The RECEIVER eventually looses (rechargeable) battery life, and the receiver dies. Rather than buy a new receiver - you can change the batteries. . .
I would be interested in the same thing, but I’m assuming that the cost of someone ‘doing this for others’ would probably make it not worth doing??? I can’t do it myself. I’m just not mechanically inclined. . . .
Has anyone tried opening the G5? Is it possible just to cut off the upper part, like a cap, or is everything inside glued together as well?
I guess that the recent G5 has the same layout as the old G4 one.
That means, that you can’t simply open the cap because of it’s sandwich
PCB layout. If anyone has a dead G5, send it to me and i can examine it
for a battery replacement procedure. Leave me a message.
I agree it’s most likely to be another sandwich design. The Dexcom CEO said on a podcast that future versions would be slimmer than the current G4 slimline, so I think we should wait for that to be released and hack that. The difficult part will be resetting the reed switch I guess.
I’m not using a G5 yet, but I have contacts that are. If a dead one becomes available, I’ll send one out.
@Joern, did you re-post the instructions for the slimline G4 hack somewhere? Thanks, Tim
so, I cut open a G4 transmitter and am a bit confused about how to slice into the existing batteries and insert a new one. I may have obliterated one of the batteries, the rear one as it wasn’t obvious where the battery was, per se. I cut low, then started cutting upwards then started cutting in again. I guess I haven’t lost anything because the transmitter was useless now anyways.
I’d recommend folks cut the front battery first as it’s easier to find.
Time to put it down and visit it again tomorrow.
Thanks for the work, guys.
How’s the automated process going? I’m starting to look at possibly purchasing a G4 for my 12-year-old - his numbers are just awful, and sucking it up and paying for a CGM might be the best thing we can do for him. I’m in Ottawa, so I guess we’re practically neighbours. 
I wish the technology had existed when I was 12. I’ve got a collection of the thick transmitters and I’ll probably do my last batch when my schedule slows down in May/June.
Hi Joern,
Please email me at tampaone@gmail.com and I will send you my old G5 to examine.
Thanks
Anthony
If anyone else has dead transmitters please let me know. I want to move beyond doing the thick units and build a screw top battery holder for the thin transmitters. I’ve got 8 to do right now so I’m going to do a production run of them soon. Email is hackish at gmail.
Hi Hackish… great info - thanks a ton. My G4 is going to be failing soon and I want to replace the batteries myself. I’ve seen the process here as well as on the ifixit.com site. Silly question but it looks like the new slim transmitter is the one on the ifixit site (uploaded by Joern) and the batteries have been cut out by a top down approach (ie: there isn’t the sandwich pcb design). Is this your finding as well? I don’t want to cut into the top of my transmitter only to hit the pcb. I’ll admit my G4 looks like the one Jaybyrd posted on Dec 14 (post 40/79) is a matte finish not shiny. The thicker one is the dual pcb design correct?