I am working on a project that requires a very tiny amount of power and will be used fairly infrequently for short periods. As such, I'd like to experiment with making it entirely self-contained by connecting rechargeable batteries to solar panels, allowing it to recharge from ambient light.
According to my research, sealed lead acid batteries can be subjected to a charge at a constant "float" voltage for extended periods, but are generally reserved for high-power applications due to their weight and bulk. LiPo and Li-ion batteries are extremely finicky.
According to this question, NiMH batteries "don't have a float voltage, so constant voltage charging doesn't work, as you've likely discovered". However, I'm having difficulty finding a resource explaining what "doesn't work" means, precisely. Other pages say that as long as a battery is subjected to a voltage greater than its current charge level, it will charge. I take this to mean that NiMH batteries can be charged at constant voltage, but in charging them to their full potential one runs the risk of overcharging them due to temperature-dependent fluctuations in their charge and discharge curves.
So my question is: can a NiMH battery be safely charged for an indefinite period of time using a "dumb" charger which supplies a constant voltage below the battery's maximum? i.e. if my application requires 3.6 volts, can I power it using a 4.8 volt NiMH battery that is deliberately charged to only 3.6 volts?