MPPT controller sizing recommendation

[Tomthumb62]

Sorry that was a typo - I meant 5.0v. And what I meant was that since the Victron MPPT controller requires battery voltage +5.0 volts, let's say it will typically require ~18 volts (~13.x + 5.0) of input before it will start charging the battery. The tow vehicle's alternator will never put out more than about 14.5 volts (and then quickly settle to something like 13.8v). Since this will never exceed the ~18v required by the MPPT controller, the input from the alternator of the tow vehicle would essentially be ignored. I hope that makes more sense this time - I was using too much shorthand before.

And the MPPT will be looking for a Maximum Power Point, found in a solar array, but an alternator isn’t likely going to provide that pattern. Which means that even if the MPPT could function at 14.6v, it’s not going to get the kind of electrical pattern it’s expecting. In other words, who knows how the MPPT would react if you connect your alternator to the MPPT input.

 

[chrisski]

As A User of the Victron 75/15, I’d recommend getting data off the 75/10 and the 220 watt panel With what you have now and then use this to decide what you really need.

I use mine for a 24 volt battery bank and it maxes out at 420 watts, so a 75/15 in a 12 volt system would push 210 watts.

To get this much wattage, I overpanel my Victron SCC by quite a bit. I run 100 watt panels 3S 3P so that I have an East, South and North Facing arrays when I need it to push 300 watts for hours on end from sunup to sundown. There is around 9 amps coming into the SCC and with the voltage conversion, 28 volts and 15 amps goes into the battery.

When your system grows, it could be to 24 volts, or you could want to get a new series of panels run by a seperate SCC. My RV has three SCCs on it.

 

[rickst29]

All this info has been super helpful so far - thanks everyone for your input. now you have me thinking about "future-proofing" the system and I'm on the hunt for something that would allow for 2x220 panels in order to maximize my power production. I see that its a big step up to the Victron MPP 100/30 and then I also see a Renology unit that also supports DC-DC charging from an IGN port which could be good for the car charging input..

There are many reports of problems with less complex Renogy components on this board, and the usual summary is "friends don't let friends buy renogy". Their DC->DC controllers have had numerous "issues" reported, and their MPPT controllers have had even more problem reports. That unit combines both functions, I feel that combination is therefore even more problematic.

The Victron units are first class and more configurable, but they are far more expensive.