Earlier this week I was on an activation, calling CQ with about 13.5v left on my 4x18650 battery pack, when I lost all power. Investigation at home showed 3 cells at3.2v and the 4th showing 0v, infinite resistance, and refusing to take any charge, even under ‘battery recovery’ charging.
The batteries are LG HG2 - INR chemistry batteries. The slightly shorter of the two 18650 formats I have (65 vs 66.5mm), and - to my understanding - no protection or control circuitry internally.
Am I wrong and INR batteries do include protection circuitry - which has presumably failed - or are there other ways a lithium INR cell can fail ‘instantly’ to a zero voltage, high-impedendence state? The radio/battery pack was stationary at the time, so no physical forces applied, and the FT818 was transmitting (SSB) so moderate, variable power draw was occurring.
OK. Further reading:
Looks like there is some protection in all 18650 cells, even the shorter ones without the ‘internal protection circuit’.
Still welcome opinions though as its unclear whether either of these devices could result in the behaviour seen.
If you’ve got 0V and infinite resistance across the cell, I’d say that it has somehow become internally open circuit - poor connection eventually completely failing etc.
If there is current limiting the device used for that has presumably failed. Fuse?
I’m NOT suggesting or recommending you do any of this but you might find this video of interest:
Something triggered the CID. Heat? Resetting it takes skill and knowledge. Note at the 29 minute mark in this video that rising temp after a reset indicates a short. Run for the hills. Better to just tear open another discarded laptop battery or rob the piggybank to buy one.
I have already ordered a couple of replacement sets. These were a couple of years old and have earned a goat and a bit already!
Just more curious as to what (beyond mechanical failure) could have failed to open-circuit under low-load conditions. And whether my understanding that there was no protection in these cells was correct (in which I’ve sort-of answered my own question!).
Will certainly watch that video when I get home.
Curiosity - not lack of willingness to buy a replacement!
My guess is that there is no internal protection in your cells. Most 18650 cells are made as cheaply as possible and incorporating some protection costs money and makes the cell longer unless capacity is sacrificed by shortening the active cylinder. This in itself would mean using a non standard manufacturing process. $$
I have been shown cells where internal connections failed. No solder or weld apparent, just enough contact to work for a while. Because of the huge volume of production, even at a very low failure rate of one in a million quite a few failures will still show up. You got lucky,?
Do you know anyone who has a Tesla car? They are stuffed full of 18650 cells. Just saying.
You’d have to reconfigure it to 3s or 4s, but it would run an FT817 for about 6 months.
The CID or the tab weld could be likely failure points.
I assume that the CID is kind of a click-dome type thing. It is easy to imagine that you have at some point lightly overcharged one of the cells, and it now has internal gas pressure, but not enough to click the CID. Some time later during an activation, the temperature (and thus pressure) rises, and the CID clicks.
Aside from pressure build up, perhaps it can pop spontaneously from other stresses too.