Solar Battery Charger suggestions Needed...

[iONic]

I am hoping to build a "Universal" Solar NiCd, NMH, and Lithium Ion Battery Charger to charge anything from a AAA Battery to a 12V/35HA Scooter Battery.

Thus I am looking for suggestions on the Solar capacity needed to charge the batteries in a reasonable amount of time. For example... to charge the scooter
battery in a couple of sunny days.

Circuit design ideas are also welcome!

Any reference material (websites) would also help.

Thanks

 

[Sceadwian]

There are several ways of approaching this. The solar cells are going to have to generate at least enough voltage to drive your control electronics and then you're going to have to use a switch mode converter to adjust the final output voltage to the charging voltage. 1.5 to 13 volts is a pretty wide supply range. It could be as simple as using enough solar cells to generate the charging voltage and making sure they can supply enough current to change the batteries, no circuitry needed, but that's not going to be universal. The amount of current you need to supply depends on the number and type of cells in the battery and the amp hour capacity of the pack. Lipoly's need a relatively intelligent charger so you should think about starting with a 5-12 volt solar array that can handle the current requirements. Micro controllers are going to be the easiest solution, as the circuitry required to intelligently charge a battery is a bit difficult to do purely from analog parts. Suggestions would be easier if you could supply more information like the normal use for the charger, their capacity and your experience.

 

[ericgibbs]

hi,
If you just considered your 12V/35Ah battery, which you want to charge in 2 days.
Electrical charge conversion efficiency, say 70%, [48AHr required] this means that it would require 2amps charge for 24 hours.

Say 15V at 2amps for 24 hours of sunshine.

So if you get 12 hrs sunshine a day it would require 2amps * 2days *12hrs

This means that output of the solar panel 14/15V at 2amps = 30watts.

 

[audioguru]

12 hours of STRONG sunlight per day? Where? Bermuda?
You are lucky to get strong sunlight for 2 hours per day. Then the other hours don't have much power.
Clouds? Then good-bye sunlight and good-bye charging.

 

[Sceadwian]

Mind you that's charging the battery from completly empty. Not something one usually does. The solar arrays are supposed to constantly trickle charge the battery.

 

[HarveyH42]

12 hours of STRONG sunlight per day? Where? Bermuda?
You are lucky to get strong sunlight for 2 hours per day. Then the other hours don't have much power.
Clouds? Then good-bye sunlight and good-bye charging.

2 hours? Not everyone lives in Canada, yet... Unless we have a huricane passing through, usually clear skys most of the day. Raining right now, but it was hot and sunny until about 5 o'clock.

Anyway, 12/35Ah is going to take a pretty good size panel, not exactly portable. Seems like a lot to pack into a single project, three different charging circuits crammed together.

 

[audioguru]

You are almost on the Equator when the sun is the most powerful. Not many people can stand the heat, the hurricanes and the crime. (I think the Cubans and Mexicans who sneaked in love it).
Florida has hot and cold alligators and some very nasty people.

 

[Krumlink]

solar panel charging is near impractical in michigan. There are less than 100 days of the year in michigan that has a clear sunny day.

 

[HarveyH42]

At least the alligators do knock over trash cans like your polar bears...

 

[audioguru]

I have seen polar bears in Canada only at the zoo. Alligators are also there.
It is the racoons who knock over garbage cans.

The racoons know how to move a big heavy rock off a garbage can so they can make a huge mess.

 

[dannix]

This maybe of interest, It is what I made to charge a 12Ahr battery. Calculation provided to adjust parimiters

**broken link removed**