What batteries to use for outdoors project with solar panel

[abahler]

Hello,

I am building a weather station that will be powered by batteries. I have a 1.5 watt solar panel with an open circuit voltage of 22.25V that I would like to use to keep the batteries charged. The current draw will be about 2.5 - 3ma average & temps can drop to around -30C around here.

What batteries would you recommend in this situation?

I would like to use 4 AA NIMH batteries but not sure how they would hold up to being charged all the time.
My other option is to use a lead acid battery which is easier to charge and from what I know will hold up better in this type of app.

Thanks!

 

[kalbun]

If I remember correctly, NiMH capacity quickly drops under 0°C. They work below zero Celsius but with quite low efficiency.
Lead acid is heavy and cumbersome but could work better at low temperatures.
I saw devices similar to yours with a battery box at the base, and the box then embedded in the soil to limit temperature range

 

[abahler]

Burying the battery is an interesting idea. After searching around it seems that a lead acid battery is about the best battery for cold weather.

I've been looking at this one made by Hawker. Those cyclone batteries are supposed to work well below freezing.

My solar panel outputs 125mA max (C20) but will probably be less most of the time. Is that amount of current going to damage a 2.5A lead acid battery if applied continuously during the day? There will be a 3ma draw from the circuit during the night.