Why do different batteries of the same voltage have different results and which battery would i choose?

Question

I want a power a homemade robot that uses an arduino and 4 small dc motors and a few sensors. Ive used pp3 energizer 9v batteries to power it in the past and they worked well, i used 9v again after they died but a different brand and learnt that not every 9v is the same as it wasnt strong enough for the bot to make turns. Why do different batteries of the same voltage have different results and some are stronger than others? is it because of internal resistance because 9v use the same chemicals i couldve sworn?

I want to use a nimh rc battery now that will last long and be strong enough for the robot and was wondering if amp hours means capacity and if was to use 2000mah battery, it wouldnt damage the arduino. I have my eyes set on this battery and charger and was wondering if they would work together too?

Answer 1

The PP3 Energizer battery has lithium-based chemistry, which usually have much higher discharge rate than other types (alkaline) of small 9V batteries. And yes, it is related to the difference in internal resistance. However, even with the same chemistry, the internal design of a battery might differ between manufacturers and battery design target. Apparently your homemade robot has pretty high demands for current.

As long as your MCU controller has a regulated internal power, and the 9.6V input doesn't exceed its input limit, your arduino won't be damaged.

Regarding the particular battery and particular charger, they appear to be completely compatible, since the charger has user-selectable charge rate. You just need to select the right current to your battery of choice.