How long do LiFePO4 batteries last?

Thread Starter


Joined Sep 24, 2015
I have a few cells that came out of solar garden pathway lighting. Their manufacturer date is 05/2014, making them over 8 years old. I'm wondering how long they remain viable. Looking on the web they seem to have a claimed 71,000 charge cycles, but I'm certain that varies by manufacturer. The ones I have were made in China. Yeah, I know, possible Chinesium.

I'm working on my welding helmet with auto darkening lens. It normally operates from a CR2032 coin cell battery. I thought about changing it to run off of a CR2450 but can't seem to find battery holders with wires. I also want to incorporate a switch so the battery doesn't drain over the years from non-use. I've replaced a couple 2032's because even though they're not being used, they have a draw, and thus, after about a year they go dead. Plus, they're not "User Serviceable". So I MADE mine User Serviceable. Using a 2032 holder glued to the inside of the helmet - it works well. But still, the batteries go dead after a while. So I decided to pull it from the holder and place a plastic insulating strip between the negative contact and the battery. But in so doing I pulled the holder lose from the helmet. It still works, but now I have a battery dangling in my field of view. So I'm considering alternatives to the coin cell. Being that the auto-darkening glass of the welding helmet operates with the 3V cell, use of a few NMh batteries or LiFePO4's with a switch installed would give me better user capabilities. When discharged the battery can be recharged. So 2 or 3 rechargeable batteries inside the helmet should work. I'd prefer to stick with the smallest batteries possible to reduce weight so I'm not walking around with a 20 pound weight on my head, so the CR2450 seems like the best option for the three situations - space, weight and longevity. But I HAVE LiFePO's on hand. Old, but on hand. They fit a 2X AA holder, which I have, and are not quite as big as a traditional AA battery.

So for now I'd like to know if I can depend on the batteries in hand or if I can depend on them to fail in short order.

Audioguru again

Joined Oct 21, 2019
8 years is a very aged LifeP04 battery cell. Solar lights charge then discharge each day they in 8 years they cycled 2920 times.
They will not die suddenly, instead their max current and capacity will slowly drop.