Rechargeable AA battery
If you own few of AA or AAA rechargeable battery, this info might be useful to you.
1. Fully charge your batt before the very FIRST use.
2. Label them before the very FIRST use..... how? why? If the device gonna use 2 AA batt, then use permanent market to mark both of them such as 1, 1. For me I have 6 AA rechargeable batts, I label them as 1,1,2,2,3,3; and always use them as a pair..... remember "do not use half drain batt with new batt together". This is to prevent damage to the batt and get the best result out of it!!
I learn this lesson the hard way.... because I fucked them up yet they are expansive!!!!

Cheers!!