DIR- Generic When to change batteries in backup lights?

[dray_gnv]

I use replaceable alkaline C batteries in my backup lights. Full charge is 1.5 volts. One now has batteries at 1.3 v and the other at 1.2 v. Looks like <1.0 is considered dead. When do you change?

 

[Tanked Monkey]

I replace my backup light's batteries every year, or if I use the light. Whichever comes first. Write the date on the batteries when you put them in.

At 1.3v, throw them out. Alkaline batteries are cheap insurance.

 

[crofrog]

Same as above annually or when used for an extended period of time.

 

[eightytwenty]

I swap mine at 1.3V.

 

[rjack321]

under 1.4V. Although I havent used an alkaline battery backup in ages.

 

[Sascha314]

You may google "alkaline discharge chart" to find some measurements. So roughly at 1.25 to 1.3V you have only about half capacity left.

Now think of the burn time and burn chart (lux vs time) of your backup. You want to have it properly for some time.

So I would regularly check the voltage before a dive (then you also check for water inside) and swap at latest 1.3V, better 1.35 to 1.4V. Earlier if used in cold water.

 

[Lorenzoid]

I have a circa-1975 analog multimeter, and I can't even distinguish the needle position between the marks on the scale at 1.5V and 1.4V. Nothing back then required such precision. When the needle is "clearly" below 1.5V, I replace the batteries. Regardless, I change them any time I use the backup light or, if I don't use it, twice a year.

 

[Capt Jim Wyatt]

I haven't used an alkaline battery backup in ages.

Me either.

 

[gmerick]

Alkaline batteries have a bad habit of leaking if left in a partially discharged state. I never leave alkaline batteries installed. I remove the batteries anytime I won't be using the device for more than a week. If the device has not been used, I keep the batteries until next time, otherwise they go in the trash, no matter what the volt meter says.
At less than $2.00 per battery why risk damaging a $100 light.