I Am currently looking for battery suggestions for use in one of my projects. My projects current consumption (calculated) is
- 360mA for the main rotor 2.5A stall Link (my exact part RK370SD-4045)
- 400mA for the Mbed uC
- tail motor ? unknown specs, N30 is the only part reference
- 3x servos Link unknown mA
- sensor 100mA or less
Voltage has to be 7.2V to 12V
What I would like to know is what are the pros and cons of each battery? This link gives some great info but i want real world recommendations and things I should look out for and any other pertinent information when selecting my new battery.
Currently I have looked for batteries and have come to this conclusion, Lead Acid batteries are not a choice in this project, which leaves me with Li-ion batteries, Li-Po, Nimh, NiCd. The original battery was a 9.6V 650mAh Nimh battery and the helicopter had about 20 mins of flight time with the original equipment.
Best Answer
For hobby flight applications, lithium polymer ("Lipo's") generally offers the best performance from a weight-to-power or weight-to-energy ratio. Compared with the theoretical energy density of most cells, Lipo's are quite close as they usually lack the steel casing of most other chemistries.
Their downside is a somewhat fussy nature about how they are charged (you must use a Lithium battery charger) and discharged (going below a certain voltage can severely damage the cells, turning them into a potential fire hazard when recharged), and their poor mechanical robustness, due to the aforementioned lack of a steel case.
An additional potential negative in using lithium batteries with a NiMH-designed circuit is that their voltage varies dramatically over their discharge curve, from up to 4.4 V when charging down to 3 V when fully discharged. To fall within a 7.2 to 12 V input, a 2 or 3-cell Lipo should work. They are usually charged at 4.3-4.4 V/cell, so a 3-cell's open-circuit voltage may be above 12 V. If the upper limit you cite is absolute, you would be stuck with a 2-cell Lipo, which will drift well below the lower limit.
So if you're looking for an upgrade from NiMH, Lipo is the way to go. Respect their hazards and they will provide much entertainment.