low battery indicators in lights

[2manybikes]

I have a couple of 2x 123 lights I use primarys in. Each light is supposed to flash when the batteries get low. Are the odds pretty good that I will not over discharge a cell before the low battery indicator goes on? I'm guessing that no one really knows.

Since I take the batteries out of my lights in the daytime anyway, I check them with a ZTS tester. I have found a couple of cells that were not reading on the ZTS meter paired with a cell that was 40 or 60 %.
I also have found that a couple pairs of batteries came out of the lights in the morning at 40% and 60% when left unused for two days one cell would not register on the meter. The other would remain the same.

I'm guessing that when used at low power settings the batteries do a certain amount of self balancing, and when left alone the weak cell drains and the good cell remains the same. I have yet to use the low battery indicators on either light, before finding one low cell. I wonder if I used the light on low if some of these cells would balance the pair out enough to be safe before I set the light on a high drain setting?

 

[SilverFox]

Hello 2manybikes,

Primary lithium cells do not self balance.

The low battery indicator will kick in when the combined voltage of both cells drops below a certain point. It is still possible to over discharge a cell, if you start with unbalanced cells.

I don't think it is a good idea to run a cell that does not register on the ZTS with one that is showing 60%. I have seen cells come out at 40% and 60% after some use, but I usually match them with other 40% or 60% cells rather than using a mismatched pair.

If you start off with cells that don't register on the ZTS, I would recommend running the light for 30 seconds, or so, then checking the cells again and using a pair of cells that test equally after this exercise.

It would be interesting to know the brand of cells you are using...

Tom

 

[2manybikes]

Hello 2manybikes,

Primary lithium cells do not self balance.

The low battery indicator will kick in when the combined voltage of both cells drops below a certain point. It is still possible to over discharge a cell, if you start with unbalanced cells.

I don't think it is a good idea to run a cell that does not register on the ZTS with one that is showing 60%. I have seen cells come out at 40% and 60% after some use, but I usually match them with other 40% or 60% cells rather than using a mismatched pair.

If you start off with cells that don't register on the ZTS, I would recommend running the light for 30 seconds, or so, then checking the cells again and using a pair of cells that test equally after this exercise.

It would be interesting to know the brand of cells you are using...

Tom

Thanks. That's a big help.

I use have only used Panasonic, and I have some new Duracells not used yet. I always test new cells before use. They go into the light at 100% each.

They typically come out at 40% and 60% after some use, but twice the 40% cell did not register on the meter a day later, but it was 40% in the morning after the light sat all night. I've been doing what you do I guess, throwing out the low cell (the ZTS minumum indication is 20% so it may not be dead) and putting aside the good one to match to another cell later.
Do you think I can learn anything else using the voltmeter?

I'll try your suggestion, it sounds like a good one.