In the series configuration, we could shut down when any single cell is discharged.
That one's interesting, but I'd put it down to a bad cell. I'm not too worried about cheap knockoff cells being used, that's a training issue.
Indeed..
I have about 10 of the 2 cell lights, I use them a lot. No issues, but I don't mix my cells, and I don't buy from grey market sources.
And putting them in backwards isn't?
[...]-- John Devereux
"dbvanhorn"
Thought about it, but it doesn't solve the problem of getting half the life with 1 cell backwards,
** It certainly eliminates the explosion risk.Monitoring the voltage drops on each PTC will allow a user alarm feature ( beep beep) to work.
** The value of the trip current is irrelevant to this job- as there is a large difference between the normal and fault conditions.also an issue, but not a huge one.
** The user alarm obviates this one.Better still - change the STUPID design mistake YOU have built in by using loose cells in parallel.
...... Phil
No, not backwards. Cells in different states of discharge-- whether from use or self-discharge--in series, then run down together, is a known deadly combination, even for top-quality cells.
I believe I've also seen single-cell instances of venting-with-flame involving top-quality cells, but I can't speak for the conditions-- high to abusive discharge rates may apply.
But then that's what happens if you parallel mixed cells--the strong cells slam charge into the weak, damaging them, and starting their "spontaneous flame timers."
Cheers, James Arthur
The >So, I'm looking for a solution for protecting my system against
[...]-- John Devereux
Right, right, to prevent a nasty mishap he described. I thought you meant to imply the mishaps--vent-with-flame cell failures-- were strictly limited to cases of backwards insertion, and hence a training issue.
Cheers, James Arthur
Dude, you're THINKING too much. Look at a CR123 cell, it IS asymmetric (positive terminal is an outie, negative terminal is an innie). Battery holders that won't contact the terminals on backward insertion are the easy fix. Battery holders that won't ACCEPT the cell inserted backward is harder, though, depending on how strong your users are... does the battery-insert have to happen in the dark?
Sorry, I've been off on other things for a while..
In the dark, in the rain, while people are shooting at you. It's not just a training issue.
I agree that better battery holders would be a solution, but given that it's got to "just work", I'm thinking now that the FET bridges are the best solution, since having to find out which of three cells is reversed under the above conditions, would be pretty nasty.
As to other comments about "stupidly using three loose cells", that's what the users tell us they want. They tell us LOUDLY, and FREQUENTLY. Special battery packs would solve all these problems, but create the problem that when you're out of special battery packs, you're done.
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