Follow the steps to know the right battery for your device:-
Things to be considered:-
1.Battery Voltage - can be 1.2V , 2.4V , 3.6V , 4.8V and so on...
You can find it by reading your old battery
2.Battery Capacity - 300 mAh , 1900 mAh , 2500 mAh and so on.
A higher capacity means more backup- hence a 5000 mAh battery can suit your product even if your product's old battery mentions 2500 mAh.
So it gives double backup - 2500 x 2 =5000 mAh
3.Battery Composition : Ni Mh , Ni Cd , Sealed Lead Acid , Lithium Ion and so on..
4.Battery Size : Measure your old battery's length and diameter in cm-use a small scale (compare this with image 2 of the listing in our site) it shows battery length. A variation upto 5mm is acceptable.