I need a 5V charge controller to be used with solar panel.

All the Lipo type charge controller I found... comes with 4 connectors (current in and battery. but it missing connectors for the load.)

What I need is something like this one (it has 6 connectors) but lower voltage and power... hopefully smaller in size. Anybody can point me to a circuit diagram to make one of this controller in lower voltage? or a commercial product in smaller size and in the similar price range.

Here is what I need,

Input: 0 to 8V
Input current: 0 to 2A
Output: 5v
Output current: 500mA
Battery: 3.7v Li-Ion ( I can make it 7.4v adding 2 battery, if that simplify the circuit a lot for not having step up circuitry)

output should be consistent as much as possible. and automatically/continuously charge the battery whenever higher input current is available.

Thanks!

 

Might take some design changes to convert to that voltage but might give you some ideas and they have available explanations to satisfy your thirst for knowledge.

I've built and installed two of these and they work. http://www.cirkits.com/spc3/

 

Thanks wmodavis!

Although the circuit looks moderately complex (and it might not be easy for me to convert it to different voltage/current config) but that is something exactly what i needed. Except for the price! the kit priced $54 !!

on my link as you can see you can find a 10amp controller for $8. as per my requirement 500mA controller should be even chipper (as you know in the system like this high amp rectifier, ic, and cooling system drives the price higher).

i'm looking for a solution under $15. I have to make couple of these so... I think if i can a design little-more IC dominated... then it would be cheaper and simpler. for such low current its certainly possible to cover most of the functionality within the IC.

 

any other ideas... anybody?

BTW, can anyone tell me what would happen if I forget all these... and just connect the load parallel to the battery to one of those lipo charger?

idea is, power the lipo charger by the solar panel through a step down voltage regulator... then connect the load parallel to the battery through a step-up voltage regulator. so after connecting the load

would that actually power the load and charge the battery at the same time when the higher current available and add up from battery when lower current in the source?

one problem i can with this approach is that efficiency would go down by a lot because of up down converter... but is there any other problem that i would be aware of ?
things like over charging the battery or reverse flow to source should be taken care by the charge circuitry. but what would happen to the battery? if the power in the source fluctuate rapidly... is that going to trigger rapid charge discharge cycle... and kill the battery soon? or anything worse that i'm even seeing...?

 

You might find a charge controller that can accept a range of input voltages, to eliminate one block on your diagram and possibly increase the range of operation at which power can move from your panel to your battery/load.

 

Tell us some more about your solar panel. How many watts? Max voltage, max current.