After about 4 years using a PWM solar charge controller with our 80W solar panel on our caravan I have just upgraded to a MPPT solar charge controller.
We have an 85 AH leisure battery in our van, LED internal lights throughout, and a motor mover ( fitted within about the last 12 months and before the MPPT controller ).
In use, the PWM controller has served us well during the past 4 years and we have often spent over 2 weeks ( sometimes 4 ) away on site without EHU during the warmer months and usually without any power shortage at all.
We watch, quite often, about 3 hrs of TV per night late evening/early morning.
Our caravan TV is LED back-lit and 24 inch.
Within the past month, and during one trip, we attended two THS sites over 6 nights without EHU and during the first 3 days the sky was almost permanently cloudy.
This caused power shortage problems after about 2 days.
During the second 3 day period at another location the problem wasn't so bad as it was not as cloudy.
The leisure battery was fully charged before we set off and is charged during driving time.
The power shortage during the first 3 days in cloudy weather and with a low sun angle at this time of year prompted me to buy the MPPT controller.
Low power, true MPPT controllers are not commonly advertised on the net.
PWM controllers masquerading as MPPT controllers are there at MPPT prices and I was aware of that.
This is what I bought:
http://www.ebay.co.uk/itm/3221347291...%3AMEBIDX%3AIT it is true MPPT not fake.
It arrived today and I am currently testing it off the van.
The price difference between PWM and MPPT controllers is quite substantial ( about 300% ).
My original 4 year old PWM controller was about £25.
I will report findings once testing is complete.
Colin