question

Peter avatar image

Do I need a DCDC charger using just a solar MPPT?

Do I need a DCDC charger using just a solar MPPT?

4WD canopy and I want to try 100% solar charging without using the car alternator

Battery is a single 110ah lithium battery

Solar panels have yet to be purchased but I want to buy a single fixed panel approx 350W, hardwired, and a 180W blanket. When I run them both, via a switch I expect to run them in series as I understand this is the most efficient option for unbalanced panels.


Is there a 'perfect' sizing for a Victron MPPT and panels?

mppt smart solarchargerssolar sizing
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You cannot combine 2 different spec panels on a single mppt.

Peter avatar image Peter klim8skeptic ·

That's new.... I was told it will be fine in series but in parallel takes the smaller panels values. Is this not the case?

For panels in series, the Imp (working current) needs to be similar.

For panels in parallel, the Vmp (working voltage) needs to be similar.

Peter avatar image Peter klim8skeptic ·

Makes life easier.... thanks

3 Answers
dazey77 avatar image
dazey77 answered ·

Just thought I would chuck in another option thats in the middle (for the DC-DC, not the solar which I think others have covered)

Rather than do DC-DC you can just use the Cyrix-LI to allow from alternator charging in emergencies. If you put a main switch in the line you can run off solar alone most of the time and have a backup. The Cyrix is not expensive or large (but won't work with smart alternators and wont give the perfomance of DC-DC)

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spanner avatar image
spanner answered ·

Nope - you can run on solar MPPT alone if you want



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michelg avatar image
michelg answered ·

Hi Peter : "Solar panels have yet to be purchased but I want to buy a single fixed panel approx 350kW, hardwired, and a 180kW blanket. When I run them both, via a switch I expect to run them in series as I understand this is the most efficient option for unbalanced panels. "

You mean 350Wp and 180Wp I presume. Consider the voltage of your battery and PVs as these need to be at least 5VDC over the battery voltage, in order to have the mppt working.

In my opinion, you could use the panels in parallel, as in serie being different you will lose part of the power (at least this is what happened in one of my testing setups).

To avoid unexpected surprises, I think you should contact a Victron Dealer, and telll him precisely what you want. Mixing alternator and PVs on the same mppt is not a good idea.

Michel

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I don't want to use the alternator. If I do I will get a seperate DCDC charger.... yes you're right about the 350W and 180W