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post #2 of Old 03-07-2008
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I think you're a bit confused.

MPPT stands for Maximum Power Point Tracking, and has nothing to do with the movement of the sun and the angle of the panel to the sun...and they could care less about boat movement... they're purely electronic devices that alter the voltage and amperage of the solar panel output to more closely match the charging needs of the battery bank and reduce the amount of electricity spent as waste heat. In general, using an MPPT charge controller will increase the efficiency of your solar panel/battery bank setup by anywhere from 10-20%, depending on the size of the panels, type of battery used, etc.

Here's an example: A solar panel will generally put out 17 volts or so.

Say one panel puts out 10 amps at 17 volts. A 12VDC battery during bulk charging phase only requires 14.6 volts. Without the MPPT charge controller, you'd be charging the batteries at 10 amps @ 17 VDC, and if they're wet cells, boiling off some electrolyte in the process.

Now, let's add an MPPT charge controller. The charge controller takes the solar panel output of 10 Amps @ 17 VDC and will change it to 11.64 amps @ 14.6 VDC... effectively giving the battery 16.4% more charge for the same time period. The charge controller uses a tiny bit of the solar panel's output to transform the output to the batteries—on a good MPPT charge controller, this is less than 2-3% of the power going from the panels to the batteries.

AGM batteries are really require to maximize the benefits of an MPPT charge controller, since they have much higher current acceptance rates.


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Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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Last edited by sailingdog; 03-07-2008 at 01:18 PM.
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