question

kolopop avatar image
kolopop asked

Solar output increases with caravan lights turned on?

I have noticed that my Solar panels double in output when my caravan lights are turned on (running on battery). I have a solar panel, fuse then directly into the MPPT and then from there into another fuse and on to the battery terminals. There is no connection to the lighting system although the wires do run near each other.

Does anyone who is smarter than me have any idea why that might happen? Solar output is 8 Watts with the lights off and 20 with them on. The panel is on my roof.



Any help would be greatly appreciated

Thanks a lot

MPPT SmartSolar
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2 Answers
gazza avatar image
gazza answered ·

I assume the lights are being powered by the DC system that the solar is charging?
My guess would be, without further details, that the battery that you are charging (at the time the lights are switched on), is full... ie in float mode? So, the MPPT is throttling back the power from the available solar, because there is nowhere else for it to go (when the battery is full). When you turn the lights on (or any other DC powered device) then there is an extra load to supply, so if the solar is available... the MPPT will allow more through to satisfy the load, which is exactly how it should behave.

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kolopop avatar image kolopop commented ·
Thanks a lot for the reply, you are correct with everything you say regarding float etc. Looks like it was just me not understanding how it throttles it down.

Much appreciated

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gazza avatar image gazza kolopop commented ·
Glad it helped to clarify.
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ako avatar image
ako answered ·

The same will happen while in Absorption , quite often our system will be allowing in just a few watts then the washing machine will spin or wife will turn on some gadget in the kitchen and suddenly we have up to 2400 watts coming in and MPPT is still in either absorption or Float . The only time you wont see that is when the charger is in Bulk because its already using everything the panels can produce .

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kevgermany avatar image kevgermany ♦♦ commented ·
Even in bulk it happens, especially with AGMs.
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