Hi all. I'm currently building a humanoid robot which uses 12 MG995 servos for its two legs. I tried using a USB power bank to power them but it obviously failed. But I read in some other forum that nimh batteries are good for powering hexapods, if so then also a humanoid. So, would these be able to power my robot? If not, please tell me what kind of power source can I use. I'm not really experienced in batteries. Thank you!
12 MG995s is asking a lot of any AA-size batteries. I’d go for C or sub-C high current packs like those sold for RC models e.g. https://hobbyking.com/en_us/turnigy-receiver-pack-sub-c-4200mah-6-0v-nimh-high-power-series.html looks like it would be good.
Alternatively Lipos are excellent but the voltages available don’t quite suit MG995s which are not really specified for 7.4V (though you MIGHT get away with it).
A good rule of thumb is that the power supply must be able to provide 1 Ampere per moving servo. If all of them are moving at once, 12 Amperes.
That is too much for NiMH AA batteries (good ones are rated at 4C), but you could divide the servos into banks and power each bank with a separate pack. Don’t forget to connect all the grounds.