Im designing a product which needs around 5 to 7v. I need to power it from a rechargeable battery.
It spends most of the day in an off state, consuming about 0mA. Sometimes is powered by the user, draws 40mA for 4 seconds and 200mA for 1 second, then it shuts down.
The peculiarity of the project is that it needs to run without any charging for 5 months a year. It will be subjected to ambient temperatures up to 50°C.
I've excluded, for one reason or another, pretty much every type of battery i know:
- lithium based batteries are not happy to stay at full charge and almost full discharge for such long time
- nichel based ones seems to have a big self discharge
- lead acid batteries seems like the more suitable type, but it also seems that they are very heat sensitive. I understand that there are also some "deep cycle" ones, that would be more suitable for my application, but are pretty rare.
I don't have any weight or space constrain (well... As long as they are reasonable)
At this point I'm quite lost, i hope for your help. I'm not an expert on batteries, some of my considerations can be wrong.