Solar chargers

[Greg_Nuspel]

I was wondering if anyone has ever tried a solar battery charger. I'm going on a bike trip this summer and would like to be able to charge some AAA batteries for my GPS unit. So if anyone has some recommendations please share them.

[ericmark]

Many years ago I used both solar and wind power in the Falklands. The problem with both was voltages cab sore unless some regulator is connected and to charge batteries often the step charge method was used which means it starts with constant current then as a threshold voltage is reached goes to a high voltage (14.8 for 12v lead acid battery) and when the current drops it then switches to a lower voltage (13.2 for 12v lead acid battery) this could be a problem for charging AA cells both as cells could become disconnected and building the charger could also be a problem.
With the normal charger once the charge is completed it stops drawing current however with both wind and solar when output is no longer required it turns energy into heat and never removes the load.
My son is about to install some solar cells and he will just connect direct to main domestic batteries should they produce more power than required which is unlikely then the batteries will gas but with 400AH of batteries this is unlikely to cause a problem however with small batteries you can easy have problems.

If the cell is sold for charging AA cells then it will have the required safe guards but if just getting a solar cell I would have it charge caravan, car, or camper battery then use a car cig lighter charger of AA cells.

It's the problem of not being able to turn off the sun. The procedure of covering the solar cell before removing any cables is important.

We made nice charger from a cycle front wheel with hub dynamo (alternator really) and we changed rim for aluminium loop and wound tape around spokes to make into wind charger. Did not do anything to turn into wind as in a valley and wind always either up or down valley and did not matter if wheel went clockwise or anti-clockwise through diodes charged two 6 volt batteries which then powered lights in toilet block. Simple is best!

So how about a hub dynamo? Do remember although we call them dynamos really they are alternators so you will need some diodes to turn into DC.