Hi Guys,
I am going to ask some very stupid questions so I'll apologise first and then move straight in to it. (sorry!)
So I have Type 1 Diabetes and use a Dexcom G5 Transmitter to monitor my blood glucose levels. The problem is that the Transmitters are NZD$750 each and only last 3 months (due to battery limitations) so I am very interested in trying to find a way to build a rechargeable one (or two to swap around when each needs to be recharged).
So what I know so far:
Each Dexcom G5 Transmitter runs on 2x RENATA 389 1.55v 80mAh batteries wired in series.
The PDF from RENATA tells me these are Zinc / Monovalent Silver Oxide batteries and a quite, quite small. I'm not sure if that is relevant or what its relevant to but maybe worth noting.
The batteries are concealed in resin to make the device water proof (showering, swimming, etc).
So - I can find some 3.7v 80mAh rechargeable batteries [55608303059 - VARTA - Rechargeable Battery, Robust, Single Cell, Nickel Metal Hydride, 80 mAh, 3.6 V, Button Cell | elem… ] - but I am not sure if the extra 0.6v will cause damage to the internal board (I assume I could add resistors to drop if required, assuming this doesn't affect the capacity of 80mAh). I also had a thought about using something like a Pebble Watch battery (also waterproof, with USB charging) but also not sold that will be the perfect fit..
Anyway I guess the questions I have are:
1) Is this project even really feasible?
2) Will there be any major effect moving from the Silver Oxide batteries to something like Nickel Metal Hydride in the link above
3) Will completely sealing this in resin once put together be an issue (do they need to 'breath' or anything?)
4) How do you build a recharging circuit - is it just a matter of connecting the USB power pins to the positive and negative terminals on the cell/battery? How do you prevent overcharge, etc?
Any help/guidance/advice would be greatly appreciated!
