Every once in a while I learn a valuable lesson.  Sometimes that lesson is more valuable because it actually costs me money.

Today's lesson is that, even though these three batteries look the same on the outside, and all three fit into the same holder, one of them is very different in where it can be used.

The white one has a model number that starts with "IFR".  The pink one starts with "ICR".  The other one doesn't have either of these designators on it, but it is an ICR type also.

As you can see in this chart from some charger docs, the IFR runs at 3.3 volts, but the ICR runs at 3.7 volts.  That means if you put the ICR battery in a device meant for an IFR battery (like my $50.00 LiFePO4wered/Pi+) you can let the magic smoke out and you will be sad.

So, learn from my mistake and be happy!