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Creating a cheaply built (mostly out of slaughtered parts) mppt


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What I need is a circuit That will transfrom my 17V DC into something with quite a bit of frequency, I know if it's a capacitor based solution I might end up with higher voltage spikes, but on the output end I can smooth things out with capacitors again :P so I can feed it through a transformer to be stepped down and current gained. Background on the idea is below. Short version DC through transformer efficently as possible to gain charging current. mpp.jpg

Terramir
Background:
I got solar panels, catch is they deliver around 17V and lets say at one given point in time 5A (can be anywhere from .1A to 6 eventually .1A to 9 When I put my third panel up. mmpt's are expensive and not that efficent when it comes to 12V systems.
So I had an idea, instead of constantly measuring and losing alot to electronics inside an mppt, build a transformer based system.
Well thinking to myself, Use a transformer which I rewind so it has a nice 17V input and the secondary windings have have several taps that of which only the voltage needed at the current moment get's switched on.  Latching relays steered by a pic should do the trick, hey and that pic circuit will use virtually no power except for like the measuring, which won't cost much, the sleep inbetween, and the big real power usage (5V maybe 25 mA=.125W) will only happen when the logic decides it needs to switch relays, maybe once every two three hours lol for like a min maybe .02Wh a day.
Catch is I need some way to convert my nice little dc looking like this:
--------------------
into something that looks like this: v^v^v^v^v^v^v^v^v^v^v^v without losing any power (well sub 1% loss would be nice plus the loss I will get from the transformer (hoping to keep that low) and then after it's transformed and comes out I'm thinking of hanging some 1000 micro F capacitors to smooth the voltage back into a nice -solid line :D like this ----------------------------------- Heck I even have one 25V 4700 micro farad capacitor this way I could get more power out of my solar panels ironically the lower the batteries will be at the time the higher the gain will be, but even at a 17V to 14.5V ratio (when the batteries are pretty full) mathematically I could gain like 17% mathematically at a 12.5V output a 36% gain. But even a 15% overall gain after losses would be better than doing nothing.  ;D

terramir

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A switched-mode charger doesn't use switched relays. It uses Pulse-Width-Modulation. The power is switched with Mosfets.
17V at 9A is a power of 153W. There must be a powerful switched-mode charger circuit somewhere on the internet, designed forr solar cells as the source.

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Not looking for pwm  :( pwm wastes energy nothing else Matter of fact used one of them screwed up my lead acid batteries! Also I'm not trying to lose power here but gain it. There is a theoretical possiblility of using pwm and create a second rail that catches all the pwm dropouts and op-amps em back into the circuit, however the efficency of that is questionable at best. Solar panels are fail safe designs they are rated let's say 100 W but that's around 17V 5.9A however a 12V battery is mismatched so the battery will pull the voltage down to 12Vx5.9A =  70.8W well there's the greatest loss.
Trust me my design is solid, except for how I'm gonna put this DC into a transformer most mppt's use audio frequency for it 20 to 80 khz to keep transforming losses down.
PWM is great for charging on the grid, it will take the power it needs and well burn some excess in the process, however when you want to squeeze every mA you can get in charging current out of it pwm fails miserably.

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