I have a cell phone that isn’t charging - and no new batteries are available. I’m going to try to jumper through the case via a long wire that I can connect indirectly to an external charger. It’s 800ma. I am planning to use a second battery as a terminus and place that in the charger as needed or even long term as the charger has over-charge protection. I expect the original battery voltages to be lower - but I think the innate resistance of the original battery will prevent over-charging, and an equilibrium balance will just find itself without any rush of current, b/c al the potential max voltages are safe, all the potential max charging amperages are safe, and nothing evil can happen. The power genie is safely bottled up. I only expect the new battery to heat up based on current draw from phone as it does normally.