Anyone ever try a rechargeable battery in the G5 transmitter?

Was thinking about what to do when it comes time to replace the batteries in one of my G5 transmitters. What would be great is to remove the need to ever have to replace the batteries in the future.

This battery seems to meet many of the requirements:

  • Small enough to fit
  • Enough juice to run for a good amount of time (110mAh)
  • Rechargeable

The issues, so far, are:

  • Would need to add a load sharing LiPo charging circuit, with 3.3v? regulation. Haven’t been able find anything off-the-shelf that’s small enough.
  • Would want charging port to be waterproof. (Use something like this on whatever charging circuit used, and epoxy everything in?)
  • Would the LiPo run cool enough, especially when charging?
  • Would the Lipo handle being encased in epoxy? Would it eventually expand and crack the epoxy?
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The G5 transmitter runs on 2 Renata 389 batteries wired in series. 1.55v/80ma each. I am still looking for something rechargeable as it is a very interesting proposition. Personally I have used JB Weld 2 part epoxy and Sugru as a sealant. The both can be ground off fairly easily for repeated battery replacements. I generally get 5.5 months per transmitter on XDrip+.


@jkiel, welcome! What an intriguing idea!

That will be a challenge.

For us, swimming is a big part of the day, so waterproofness makes a big diff.

@elver, I had no idea you did your own battery replacements for the G5. Kudos!

I don’t know if you read the very long G4/G5 battery replacement thread:

The battery I linked above is 110mAh @ ~3.7v, so maybe similar to 2 389’s? However, looking more closely over its specs, it’s probably a little too long to be able to fit it.

There’s an even smaller one:

This is about the same thickness and width as a 389, and just over the length of two 389, so could fit? (Provided the charging circuit + connector can be kept small enough, and the resin between the two 389’s on the transmitter can be removed.)

But, it’s only 40mAh, so certainly wouldn’t last even close to 2 x 389 button cells. That said, if a charging connection could be made convenient enough (charge while in-use), would it matter if you had to charge it once or twice a month?

The problem then comes down to the charging and regulator circuit that would need to be integrated and epoxied in with the battery. Probably would need to be a custom circuit.

Oh well, I’ll likely just swap out the 389’s with new ones for now…

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Yeah, I really don’t think it would be worth doing if it couldn’t be waterproof. Even for non-swimmers, I assume most of us like to take shower.


I found this rechargeable G5 transmitter, but don’t have facebook acct for additional details. Looks interesting.

G5 Transm