Here is the link to the one i have. Solar battery charger is where I think everyone should at least start.
Solar battery charger. Recharge batteries with the sun!
Charges 11 different NiCd and NiMH battery sizes (AAA, AA, C, D, and 7 GUM sizes) Never be without power again!
Charges 2 pcs of NIMH or NiCad “D”/”C”/”AA”/”AAA” size rechargeable batteries
Adjustable top lid and bottom stand for optimal sunlight exposure
Blocking diode to prevent discharge