Solar Charge Controller

Under full sun conditions the MOSFETS got a bit warm and the whole unit radiated a lot of RFI.  This design uses a set of relays - one for each panel.  If the controller decides the battery voltage is too low, it engages another relay; if its too high, it drops one out.
This tends to 'float' the voltage at about 14 volts as long as sufficient sunlight


The controller also implements a network style interface (open collector TTL, 9600 baud).  This makes it possible to 'tweak' the charge settings using a terminal program and an RS-232 to TTL interface (coming to this web site soon).  If you choose to duplicate this device, you may leave out the network stuff and 'hardwire' the charge settings in software.

Here is the Schematic diagram: 


  1. Hello:

    Very interesting design, I like it. Can you tell what PIC controller you used for this. Is the software written for this, and can I use BASIC. Can I control the circuit from an online source possibly by my smart phone. Of course I would have to have an IP address I imagine.

    1. Source file has been uploaded you can get it by clicking on given above link.......for further detail please check schematic diagram of circuit.

  2. OMG! This is really very critical to understand but yeah i want one solar charge controller in delhi for my home if any supplier u know over tehre...just pls let me know...

    thank u in advance