Input from solar panels
Submitted: Monday, Oct 20, 2014 at 11:47
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Krooznalong
How many volts should be going into a vehicle battery from a 140 w panel in full sunlight through a MPPT controller? I'm seeing low 13s which I suspect is not enough. Should I be getting closer to 14?
Thanks in advance.
Reply By: Gronk - Monday, Oct 20, 2014 at 12:18
Monday, Oct 20, 2014 at 12:18
Depends on the state of charge of the battery...
It may start off with low 13's, but then slowly climb to low or even mid 14's, then settle around 13.7 when the battery is fully charged ( float voltage ).
These figures are an AGM battery, but depends on if you have AGM or wet cell batteries and if you have/can adjust the controller to suit..
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Follow Up By: Krooznalong - Monday, Oct 20, 2014 at 12:24
Monday, Oct 20, 2014 at 12:24
Thanks Gronk
Battery would have been close to fully charged - driving most of previous day so had only run the fridge overnight and it was a cool night so it wouldn't have had to do too much work.
Battery is a normal lead acid - not AGM.
Controller is not adjustable - it's the one that came attached to the ebay panels so undoubtedly a cheapie.
I have never seen anything more than low 13s so I suspect a better quality MPPT controller is required.
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Follow Up By: garrycol - Monday, Oct 20, 2014 at 12:42
Monday, Oct 20, 2014 at 12:42
Krooznalong - sounds all normal to me for a battery that is near fully charged.
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Follow Up By: Nomadic Navara - Monday, Oct 20, 2014 at 13:59
Monday, Oct 20, 2014 at 13:59
Disconnect the panel after the days charge. Reconnect it mid morning the next day (or get someone else to connect it) whilst you are watching the volt meter. The meter should slowly rise to over 14 V, stay there for some time and then drop back to the float voltage. If you reconnect the panel with a fully charged battery it can go through that voltage cycle in less than 30 seconds so you have to watch the meter whilst reconnecting.
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Reply By: Travelling - Wednesday, Oct 22, 2014 at 16:26
Wednesday, Oct 22, 2014 at 16:26
An MPPT controller that WORKS correctly will cost you more than $200
Haven't yet tested an MPPT controller under $200 that works as
well as a good PWM regulator. They lock onto the wrong part of the curve and then stay at the incorrect point and don't resample the curve.
The regulator on the back of the panels is useless. The regulator needs to be within 1M of the battery with correct size wire and correct size wire from solar panel to regulator.
This is the cheapest MPPT solar regulator that functions as described
http://www.morningstarcorp.com/products/sunsaver-mppt/
and MPPT solar regulators from there go up on price.
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