Battery dimensioning


For a school project I'd like to put a "fit pc 2" (a RaspberryPi-like) on a flying device.
As the fit PC2 is supposed to be directly plugged to energy, I'd like to buy a battery to let it work in the air.

I have the folowing information written on the fit pc 2 box :

Input: DC12V (9V to 15V tolerant)
Adaptater: AC100-240V -> 12V 1.5A

I found the flowing battery :

It says "NX – 12V – 2.9Ah – 98.5x79x55.5mm". As far as I understand this would work and let me use the computer for a theoretically 2hours.

Is this right ? Should I only care about making it 12V and n*1.5 Ah (n being how much hours I want the battery to last) or is there any other characteristics I should take into consideration ?

Needless to say I'm far from being good in Electrical Engineering… 😉

Best Answer

The other option you have are 3-cell LiPo batteries. These tend to have a fully charged voltage of ~12.6V, with a typical voltage of ~11.1V. When fully discharged they will drop down to about 9V. All of that is within the spec of your computers input - you say it is tolerant of 9-15V.

LiPo's will be far lighter for a given energy density which is why they are frequently used in RC Helicopters and planes. For example a 6Ah LiPo weighs about 400g, vs the 1.2kg of the 2.9Ah battery in your link - twice the capacity, 1/3 of the weight!

The thing with LiPos you have to be careful of is to include protection circuits for over discharge - many have this built in - and over charge. Charging is usually done with a special balance charger to ensure all cells get an equal charge.