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general question on battery chargers

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killfire

New Member
I have a solar battery charger that I built, it's pretty simple, just a solar panel, a charge controller, and a set of batteries...

Originally I built it (off of directions, mind you) with 8 AA batteries in series- so 12 volts- but I would like it if it could be run with only 4 AAs...

what, if anything, would I need to change (do I need something to step down the voltage?) to make it work with this.

Ideally as simple and small as possible, the entire thing is inside a waterproof box of limited size....

thanks,
Daniel
 

Klaus

New Member
Hi Daniel,
You are expecting us to be able to visualise your project but give us very little detail :cry:
Since you mention a charge controller of sorts why not reconfigure it to cater for 4 batteries?
I cannot suggest how since I have no idea what kind of controller you use nor what kind of solar panel nor what kind of battery.... :?

Klaus
 

killfire

New Member
sorry for the lack of detail...

let me try again:

the solar panel is rated at 16.5 volts, 0.3 amps.

the charge controller is a black box- it is epoxied so you cant get at anything, or reconfigure it in any way. all it has is two ins for the panel and two out (rated at 12volts) for the batteries. model: morningstar sunguard solar controller, rated 4.5A 12V (SG-4 is written on the bottom inside)

the batteries are AA, 8 of them. as they were, were in one of those simple black holders, where all the batteries snap in and at one end you have two metal tabs, hot and ground.

I'm sorry if there isn't too much detail, but that's all there is... any reconfiguring of the controller will have to happen outside of the controller, as it is impossible to change it itself.

with that in mind, any advice?

daniel
 

justDIY

Active Member
8 rechargeables is not 12 volts, not even close?

8 batteries X 1.2 volts = 9.6 volts

4 batteries will only yield 4.8 volts

what is your end goal, do you only need 4.8 volts, or do you want to save money and not have to buy 10 batteries? you might want to look at the MAX712/713 ... it's a flexible charge controller for 1 to 16 cells (batteries)

**broken link removed**
 

killfire

New Member
justDIY said:
8 rechargeables is not 12 volts, not even close?

8 batteries X 1.2 volts = 9.6 volts

4 batteries will only yield 4.8 volts

what is your end goal, do you only need 4.8 volts, or do you want to save money and not have to buy 10 batteries? you might want to look at the MAX712/713 ... it's a flexible charge controller for 1 to 16 cells (batteries)

**broken link removed**


it must have been 10- sorry, I don't have that container any more....

no, what I want is to take up less space and weight- this is something that I am using to travel- and I by no means need to be able to charge 10 cells, 4 would be just fine (actually, 2 would be fine)....

about the MAX712/713: how big is this? I have a waterproof case and the entire thing is around 3x5x1.5 inches (7.5x12.5x3.75cm)... ideally it can hold the batteries and the charge controller....

the other charge controller itself is waterproof- is there a 4 or 2 cell solution that is waterproof?
 

williB

New Member
killfire to charge rechargeable batteries with a solar panel, you dont even need a charge controller since your panel is small .
my advice is to leave out the charge controller, and charge the batteries directly with the panel...i hope that it has ( and probably does ) have a reverse blocking diode built into the panel, if so , you will get much more charging power out of JUST the panel if you hook it directly to your four batteries. or even two.
i have done this for three years now ( i use the batteries for my walkman) with the same batteries ( i alternate)..
the solar panel output voltage will AUTOMATICALLY adjust itself to the battery voltage.
ie.to charge 12V you may get 15mA , but to charge 2.4 V you may get 100mA....
 
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