I have a Silver U Max that uses a nine volt battery..I was thinking of going to rechargeable 1 1/2 volt batteries Then buying or building the English modification add on..for 6 1 1/2 V batts.What kind of battery type do I want to buy, and can anyone suggest a solar charger? I have a friend in Central America that could use a Silver with the ability to recharge batteries. Some of the festivals have been going on for hundreds of years in the same grass filled squares..Cordially NAD