blalew
Active Member
...halfway through a show one of them died after charging over night.
Just a problem with capacity. That's the "Amp-Hour" (sometimes mAh, milliAmp hour). In my opinion, you need something on the order of an alkaline. Rechargeable 9volts have only recently (last couple of years) had the capacity that the alkalines do.
I'm sure there are others but the iPowerUS batteries are the only ones I'm aware of that have 500mAh or more.
DC9V-500mAh_Li-Polymer_Battery -- iPowerUS.com
Also, some rechargeable 9volts have a higher initial voltage that some devices don't like them, and some have lower initial voltages so that the battery gauge looks low, but still works.