Lithium (Li) batteries, like the ones in your cell phone, will DIE if discharged to 0, so don’t let that happen! I think the iPhone shuts down when the power gets below a certain point. But your personal portable chargers that contain Li batteries also need to be carefully monitored. If they drain completely, they cannot be recharged. That even applies to those Li batteries in your expensive Harmony universal remotes.

There’s an 80-20 rule that applies to charging Li batteries. For best battery life and performance, stop charging at 80% and start charging at 20%. However, Li batteries can be charged to 100% without any side effects. It is just that it doesn’t take very long to charge to 80%, and it takes a LOT longer to finish charging to 100%.

Another consideration is temperature. Li batteries can deliver a charge below 32º, but you do NOT want to try to charge them if the temp goes below 32º. That actually damages the battery. If the Li battery gets too hot, it degrades the battery life. I don’t have any information on what is too hot, but probably letting a device sit in the direct sun (like your car dashboard or on the seat exposed to the sun) is definitely not a good thing. The iPhone shuts down when it gets too hot, and that’s a sign that you have just degraded the battery somewhat.

John Carter