When to change out batteries

[Blueskies123]

I have several flashlight I keep around the house. My Fenix has 2AA and they register about 1.41 volts. The ITP A3, about 1.39 volts in a AAA battery. I carry a ITPA3 and did not want it to die on my when I need it it to work. At what voltage will I still have enough power for half an hour.

 

[SilverFox]

Hello Blueskies123,

Welcome to CPF.

In order to actually get information like that, you have to do some testing. Many times the open circuit voltage of a cell is not a good indication of how much charge is left in the cell. Observing the voltage under a load is better, but it is still not perfect.

With alkaline cells you can run your light for awhile, let the cells rest, then look at the voltage. If you graph those results, you may be able to get a rough idea for the particular cell you are using. If you change brand or batches, the results may vary, but you should still be in the ball park.

The ZTS tester gives and indication based upon voltage under load. It is better than just looking at voltage, but it is far from perfect also.

In critical use, the best advice is to start with fresh batteries. When in doubt, change the batteries. However, this option is not the most economical choice.

Tom

 

[Milan]

Well, these are not very scientific method, but I use them where measuring voltages won't tell you much, such as with Heavy Duty Ni-Cl/Zn...

I use this old old old Light bulb connected to a wire and you can tell by how bright the bulb glows if it glows at all.

Or I just switch to 10A scale and short em trhoug MM and watch how much current they are capable to deliver.

 

[Glasstream15]

Lights that I use frequently get Eneloop rechargeables and replaced often with fresh charged cells. Lights and other things that don't get a lot of use I eother leave without batteries or I check open circuit voltage every 6 weeks and any cell that's below 1.5 volts puts all the cells in that device in the trash. That way I am always keeping an eye on the alkalines in some of my lights and tools and, hopefully, catching them before any leakers and being sure they are ready to go if I need them.

When I was inspecting rides at Universal in Orlando back in the mid 90s I used a 3D Mag, still works, and some rechargeable Ds that were actually NiCd AAs. Charged every day they would work well for a shift, 3rd, and the light was only half as heavy to carry around. I have used rechargeables in all my work/inspection lights since.