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Old 20-03-2011, 00:32   #1
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Can MPPT make use of low voltage

hi

i know MPPT charge controllers can make optimum efficient use of voltages above the charging voltage of the batteries by doing a DC to DC conversion.

Can they also make use of lower voltages to upconvert DC to higher voltage DC to allow some charging in low light conditions?
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Old 20-03-2011, 00:40   #2
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Re: Can MPPT make use of low voltage

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Originally Posted by west coaster View Post
hi

i know MPPT charge controllers can make optimum efficient use of voltages above the charging voltage of the batteries by doing a DC to DC conversion.

Can they also make use of lower voltages to upconvert DC to higher voltage DC to allow some charging in low light conditions?
Some have sync converters, most have buck converters, so you have to read the specs.

It shouldn't make much difference for low light conditions, look at the IV curves for solar cells, even at 200 W/m^2 the voltage comes up above 12, it's the current output that decreases. This is probably why most don't bother with sync converters.





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Old 20-03-2011, 01:09   #3
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Re: Can MPPT make use of low voltage

Almost all are buck converters so they cannot boost voltage. Many of the MPPT controllers recommend you hook the solar cells up in series, this gives them the potential to charge better in low light conditions, but in practice it produces little gain. Hooking the cells in series also creates the downside that there is a disproportionate loss in power and MPPT point when one panel has partial shade. With a typical boat installation partial shade on one panel is very common so the losses (from having the cells in series) generally out way the gains (from having a higher solar voltage)
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Old 20-03-2011, 11:14   #4
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Re: Can MPPT make use of low voltage

thanks

very helpful - going with 3 x kyocera KC85T 85 W panels (3 x smaller panels due to geometry constraints) in parallel with morningstar 20A non-MPPT controller.

cheers!
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Old 24-03-2011, 17:44   #5
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Re: Can MPPT make use of low voltage

FYI, you will get better average output by using (smaller) MPPT controllers, one on each panel, than you will by running them all to one bigger controller. With individual controllers each one will optimize the output for it's individual panel shading condition.
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Old 24-03-2011, 17:56   #6
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Re: Can MPPT make use of low voltage

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Originally Posted by west coaster View Post
thanks

very helpful - going with 3 x kyocera KC85T 85 W panels (3 x smaller panels due to geometry constraints) in parallel with morningstar 20A non-MPPT controller.

cheers!
Why parallel, that defeats the purpose of using an mppt controller...just curious.Been using several different ones for 8 years now.
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