I have three different devices, I’m having trouble figuring out witch ones support monitoring the battery voltage.
My goal is to turn this solar light in to a repeater node and I’d really like to be able to send a message once an hour with the battery voltage.
Hi Spor7biker 
I think the last board the ttgo tbeam would work voltage detection (although I don’t know which version is the tbeam).
That’s according to the pin definition
The first board is a heltec but which is the second one? Is it a ttgo lora Vx?
I think it is a ttgo lora32 v1 ^^
I assume those lights are just charging an 18650 battery. On the TBeam ©, I would solder some wire leads to where that battery holder was. The TBeam can measure the voltage directly that way. As for the TLora32, I remember seeing a post somewhere where someone built a voltage divider to measure the battery voltage. If I can find it, I will re-post a link
Found it,
Yes. The solar light charges an 18650. There is actually room for two in several lights I’ve taken apart. It’s not ideal (much bigger than needed) but the light does provide a case with a clear front. I ordered some weatherised momentary switches so the buttons can be used while it is all closed up. For a repeater I think this will be really cost effective.
If you do more then 1 cell, you might need to buy the 18650 with the protection circuit built in. Or add one seperate to keep the cells balanced.
I have a battery tester and was planning on matching cells closely. I was disappointed (but not surprised) that cheep batteries from amazon are not any where close the the rated mAh ratting.
Can anyone recommend an affordable source for 2500 mAh (or better) 18650 batteries?
I used cells from my drill battery. 1 cell died and rendered the whole pack useless. They are a Samsung brand. They might be designed for high current but they seem to get the same runtime that is being reported by others. I think there was 20 in my pack, leaving 19 good 18650s
Great idea! Thanks. 123
This is great! I am trying something similar with a smaller all in one light and a board like “B” above. The t-beam is too large for this case. It came with a 1200mah 19650 in it, but I put in a recycled 2200mah battery from an old laptop pack. I put it outside yesterday in the < 20F weather with little sun and it only made it to 3:30am. I would love to get a voltage output too!
Nice! I have a goal of eventually making a how to guide and video. Some of the reasons I like my light is I think I can fit a tuned dipole antenna in it as well as an information card that will be visible thought the original led light window in addition to the display. The solar panel is separate so the radio side of things can be places ideally as well as finding a good place for the solar panel. They both have little adjustable mounting brackets.
Those are great ideas. I was going for something that is stealthy, looks like it belongs, and is still functional for it’s original purpose. I believe the solar panel is insufficient in this case so I may look at your solution with the split panel/light.
I love this project! My kids and I use it as our ‘spy network’ right now. We will use it for camping in the summer time for comms.
If you are willing to do some disassembly you can score used battery from batteryhookup. There 2200mah batteries are actually 2200ish. If you can find some NCR gray cells they are usually at least 3000mah. They will not support high current draw, but that’s fine for this sort of project. I lucked out and found some in a dell laptop pack.
