rctestflight solar plane v2 is using http://genasun.com/all-products/solar-charge-controllers/for-lithium/gvb-8a-li-lithium-solar-boost-controller/

have seen solar charge controller(mppt) but the one that suits my project(genasun mppt) costs 10k so im going for some other alternative
any suggestions ?
i'm trying to finish this project as low as possible

This one of the most interesting projects I have seen on RCI! Congratulations on a successful flight and all the best for a successful solar-powered flight as well  .

I can't comment on anything to do with the aerodynamics of the plane, being a multirotor guy myself, but I had a couple of questions/ ideas about the electronics. What exactly is the role of the buck/ boost converter is here? Is it to maintain a steady voltage from the cells? Another thing to consider is that the diode will drop your voltage by 0.6-0.7V. Since LiPo charging is pretty tricky, involving both a constant current and a constant voltage phase, I would advise against attempting to charge your LiPo in-flight, unless you are using proper charging circuitry. One idea that came to my mind is to use the LiPo as a backup power source and use a relay to switch between the solar cells and the battery. You can use a receiver control switch (Shameless plug - like the one I posted on my blog) to turn on the relay. The LiPo will be connected to the NC pin and the solar cells to NO, allowing you to switch between them easily.

so what spec are you looking at?

yes the diode(rectifier diode) i have consumes 0.3watt .3v@1amp  -bought schotty diode (need to test)
i hve used buckbooster for two reasons
1-to get a steady voltage
2-to convert power either into a 2s or 4s

i did consider that charging a battery at 12v @2c charging rate would require-5.2amps -at less than 5amps my charging rates will be less than that

relay switch i hve heard from my electronics faculty-need to try one

@sahilkit

i hve some schotty diodes,
LTC3780 -buck booster

40 watt is my avg consumption for leveled flight
my pannels(if every thing works well) will give atleast 60watt(max 79watt)
so my battery would be charged at 20 watt --ie 12v @1.6 amps

if im running the plane for 6 hrs -i hope my current config will charge the battery with in 1hr but then i dont know how to stop charging

im looking for something similar to thermostat(im from mechnial) where it charges the battery when less than 12v and stops charging when above 12 v automatically

LTC3780 looks good as it allows VIN (solar panels) above, below or equal to VOUT, assume 12.6v or 12 v is used. Configure your solar cell to a Vmax of below or equal to 33volts with 3volt buffer (Wide VIN range: 4V to 36V Operation).

Assuming you have solved charging and cutoff please consider a cell balance charger circuit for safety and battery health.

Sahil

i will post some layout later.

thanks 

FYI http://www.linear.com/solutions/5195

tested solar cells-(between -11-12.30pm)
12..8-13.1v
3.8-4.2 amp

The cells are heating fast and due to that my sheeting got attached to cells and due to the extreme heat it started to shrink too
all these happened in a span of 10-20 mins

so decided to test only with some cooling(table fan maybe)

any suggestions?

have been testing solar cells past three day from morning 8am-5pm
greater than 40 watt for more than 6 hrs
peak 67 watt with just the wing
peak 47 watt with motor running

@aneesh.p,
Excellent.
Forget the lipo and fly on solar.
Try a 5 minute test flight.
It may turn out to be a flight of 2-3 hours!
I'm a believer...

Sir, i did run my plane today from 9am to 3 pm at 45 watt rating. Its a success  

well done Aneesh.

solar power alone

@manojswizera
  Thanks

Wow ! Supreb sir !

@aneesh.p,
Waiting eagerly for test flight on solar power alone.
You can consider a small lipo and BEC to power the rx and servos, while the motor is on solar.
Regards.

@k k iyer
Sir, im searching for for good fields nearby to fly but so far i didnt find any. Moreover its my review time, so im too busy with documentation, signs etc etc.
Yes sir im using bec for rx and servos, u can see that in the last video i hve posted.
i will update once my review is done

Regards
aneesh.p

cant help but notice the solar panels on the roof on post 113 photo. is that your inspiration? anyways seems like the success is like a meter away and havent seen anyone from india going this far.. Good luck !!

Thanks !
those panels are used to power our dean's room-and no thats not my inspiration
i felt its more of a challenge to test my experience and knowledge gained over past 2 years in my team
and definitely Solar Impulse 2 added a bit to it 

Regards
Aneesh.P

@aneesh.p,
Can you contact karthick ashwath via PM?

He thought of this project before you, but he is only 12 years old, and has no access to materials.

Your experience will be of great benefit to him.
Please help him if you can.
Regards.

Sir
   I have contacted him over facebook even before i started this topic here ,but no reply yet
   will try here

@Aneesh.P

Sorry for the long period of inactivity. I have replied on fb.