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Thanks, I did know that having the solar on the roof wouldn't increase what the alternator was doing when driving, particularly since my Defender's alternator isn't 'smart', but just operates at a fixed rate. However, I didn't say it well. Your explanation did explain it much better than I could have, so thanks for clarifying it.
Re: The Difference between a MPPT and PWM
I might be wrong here but I thought the main difference between the 2 is efficiency. The MPPT is more efficient than the PWM and therefore u would get more out of your solar Panels..... The MPPT is usually more expensive but it may pay for itself over time too through time saved in charging your systems up.....
There is some useful reading here: MPPT vs PWM Solar Controllers
or this one:
Which solar charge controller: PWM or MPPT?
I'm not convinced that MPPT controllers have enough advantages to justify the extra cost. My PWM controllers do everything I need.
The big difference between the two regulator types is what happens to the input voltage to the regulator. A MPPT controller will allow the panel voltage to climb well above battery voltage, then use a DC-DC converter to take the slightly lower amps and much higher voltage and produce higher amps at the battery charging voltage. This means you can efficiently use 24V panel sets to charge both 12V and 24V batteries as the regular adjusts everything automatically. You can use lighter cabling with two series panels than a parallel pair and lose less power.Quote:
Originally Posted by Robmacca
PWM regulators are simply wasteful of potential charging power by limiting regulator input voltage to battery voltage plus regulator voltage loss, which is much lower than the rated max power output voltage of the panel.
But if your set up does what you need, it's fine. Wait for a MPPT regulator to turn up on special if you want a few more amps without carrying more panels. [smilebigeye]