A couple of possible points on battery life...
1. There are lots of fake 18650 batteries around, they need to be sourced from reliable sources. In the UK, I bought my 3400mAh from Torchy.
2. When running, there should only be an occasional flash from the iSpindel at the time it transmits a data batch. If the LED on the gyro is constantly lit, that will seriously reduce your run time. The simple way to prevent that, is to simply snip through the middle of the LED with some small snips to break the component, rather than attempt to desolder.
1. This is very likely. All the parts were bought from AliExpress EXCEPT the batteries and the whatever he had on hand. The batteries were bought on Amazon from who knows where? Oddly enough, or not surprisingly, old link to these batteries doesn't have them as a product anymore, which further suggests this is the problem.
2. Yeah the LED is never on constantly so I don't believe this is an issue. I have a feeling this all pointed back to the battery.
It honors your mate that he soldered this together "the old way".
Haha I'm sure he'll dig this.
You have the right one and it seems to operate in the right manner like switching it off when it gets down to 2.5V. However, there seems to be no solder at all at B- that could be a problem.
I have one left with the resistors and diode already soldered on to them and I am happy to send it to you but as I am EU based and I dove in to this I thought "I'll put it in an envelope and send it which will cost 4 euros" but it isn't allowed anymore to send goods in an envelope and frank it as a letter. They will just confiscate it, the US wants to know what is in it before it is send and I should send it as a package with a customs declaration form CN22, and that costs 11 euros(about 13,50USD). And then to think I had these made in the US a couple of years ago at pcbs.io.
Thanks for the kind suggestion. Probably no need to send it. In regards to the lack of solder at B-, I may investigate the battery side first before looking at replacing the PCB.