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Old 08-18-09, 03:32 PM   #1
jlinstrom
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Default Solar MPPT

Solar arrays have a power curve with a maximum power point and the device that sets this point is called a Maximum Power Point Tracker. It's the electrical equivalent of a variable speed transmission - it's got nothing to do with pointing the array at the sun, strictly electrical charging.
Many places sell MPPTs, I've built some using a circuit idea from EDN, Dec 5, 2008. It's the cheapest, most foolproof I've found, but you have to be (or know) a EE who can help with component values. As time and work permits, I want to design an MPPT circuit board to handle charging 12V batteries at say 5-10 Amps and make the circuit boards available to the 'solar public'.

2 things -
an MPPT is NOT a diverter (which shuts off charge power when it's had enough).
this circuit is adaptable so, for instance, a 6V array can charge a 12V battery -it all depends on the charging IC.

Befriend a geek, ask them.
johnl

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Old 08-18-09, 03:44 PM   #2
Daox
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First off, welcome to ER!

Woooo, very interesting. I was just reading and thinking about MPPT charge controllers the other day. Its great technology that can boost your panel output up to 15%. I'd love to see something for smaller applications.

Do you have any circuit diagrams you'd be willing to share?
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Old 08-18-09, 06:42 PM   #3
jlinstrom
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Default MPPT circuit

I tried to attach the EDN article as a .pdf <alas!> Here it is.
Solar-array controller needs no multiplier to maximize power - 12/5/2008 - EDN

It is available on the EDN (Engr Design News) site; my design used the LT1316 from Linear Tech, but that part is user choice. That's the neat thing about the circuit, it's a P&O (perturb and observe) that only controls the normal feedback pin on a switch mode controller. You pick the controller and switch electronics from milliamps and low V up to mega-amps and big volts. This circuit does the equivalent of the kids' game - you're getting warmer, you're getting colder... and centers around the max power point!
The designer is a regular circuit contributor and bright fellow.

Gals to be here, good site.

johnl

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