I use several low-end trail cameras for monitoring wildlife. All of them are powered with 4 x 1.5 V AA batteries. Replacing non-rechargeable cells in several trail cameras starts to generate more electro-waste than I like (and it also costs money). All cams have external 6 V DC input, so I am starting to think about options I have in order to get rechargeable source of 6 V. Regarding current, it only takes few mA (maybe les than 1 mA) in stand-by and this usually takes most of the battery life.
As first, I have asked a manufacturer of my recent trail camera (Suntek Mini300) about using 7.4 V (2S li-ion cells) as external power source. As I expected, they do not recommend it, because "the infra LED will not work" (no more details to this statement). So I will probably need source of 6 V. Below, I sum options I came with. There is a need to say, all of them will be really "external" - can not be fitted to 4xAA compartment in trail camera.
- 5xAA Ni-MH 1.2 V cells - probably the simplest solution, but re-charging 5 cells is really uncomfortable.
- 4xAA Ni-MH 1.2 V cells + step-up converter - I know very little about it, but stepping up 1.2 V might not be very efficient.
- Li-ion 3.7 V cell / 2P cells + step-up converter - I have no experience with li-ion cells in outdoor conditions + uncertain efficiency. 1 cell might not have enough capacity, and connecting 2 cells in parallel may be dangerous.
- Li-ion 2S cells @ 7.4 V + step-down converter - low voltage difference -> might not be very efficient (?)
- Li-ion 3S cells @ 11.1 V + step-down converter - voltage difference is higher, so conversion might be more efficient(?)
- Above mentioned with Li-po cells - no experience, aware of cold conditions
- 6V Pb cell - can have enough capacity, but is too bulky & heavy and especially not very eco-friendly.
- Lion 2S @ 7.4 v directly :) - should I try it despite the fact it is not recommended? It is needed to assume 8.4 V when fully charged.
- Other suggestions?
Personally, I mostly like first 2 options, but maybe I have not mentioned some obvious solution, that is why I am asking here. I will be very grateful for any suggestions or discussion of above stated options. thank you.