Victron 100V/20A MPPT Charge Controller

[DrShotsPHD]

Hello,

I have a Victron 100V/20A MPPT Charge Controller that I'm planning on putting 3x Renogy 100W Flexible Solar Panels on. I've been reading that it's best to wire parallel so a partially shaded panel doesn't affect output wattage as much but I've also read that running in series with the increased voltage results in better efficiency.

My question is as follows, is it advisable to just put all 3 panels in parallel, or could I put two panels in series and then tie in the third as parallel? Not sure if this is advisable or not seeing that one half of the parallel hookup will be half the voltage although if my math is correct I would end up with about 56.7 Vmp and 10.29 Imp which falls below the charge controllers limits.

 

[gnubie]

No, that series / parallel configuration would seriously degrade your system's performance effectively throwing away half the output of the two series panels. Even if you used blocking diodes to assist with this the large power difference between the two strings would likely result in the MPPT controller deciding to stay at the voltage of the higher string and as a result drawing little, if any, power from the lower.

When doing parallel strings (or panels) you should have the same or close to the same Vmp on each string.

I'm guessing you have a 12V battery so assuming your array ever hit full power, it probably won't, you'd be at ~25A on the output of the Victron with the panels in series or all in parallel. That's not a problem as the Victron will current limit at 20A on the output. Remember to ensure that the current from the Victron is suitable for your battery, 20A into a 2Ah battery (silly extreme example) wouldn't end well.

I'll also guess those are 12V class panels. The voltage window will be slim but the Victron will still see enough voltage difference between the battery and array Voc to start charging - 5V and then be able to continue charging - 1V. Personally I'd like to see higher voltage and that would mean 4 panels arranged as 2s2p.

*edit to add more*

 

[DrShotsPHD]

No, that series / parallel configuration would seriously degrade your system's performance effectively throwing away half the output of the two series panels. Even if you used blocking diodes to assist with this the large power difference between the two strings would likely result in the MPPT controller deciding to stay at the voltage of the higher string and as a result drawing little, if any, power from the lower.

When doing parallel strings (or panels) you should have the same or close to the same Vmp on each string.

I'm guessing you have a 12V battery so assuming your array ever hit full power, it probably won't, you'd be at ~25A on the output of the Victron with the panels in series or all in parallel. That's not a problem as the Victron will current limit at 20A on the output. Remember to ensure that the current from the Victron is suitable for your battery, 20A into a 2Ah battery (silly extreme example) wouldn't end well.

I'll also guess those are 12V class panels. The voltage window will be slim but the Victron will still see enough voltage difference between the battery and array Voc to start charging - 5V and then be able to continue charging - 1V. Personally I'd like to see higher voltage and that would mean 4 panels arranged as 2s2p.

*edit to add more*

Thanks for the quick response, I guess I'm now back to deciding if I want to do 3 in series or 3 in parallel. I'll be charging a Battleborn LiFePO4 100Ah 12V battery. I have some branch connectors coming in so I guess I can try both ways to see how output looks prior to tidying up all the cabling on the roof of the camper.

 

[BoloMKXXVIII]

Can you fit another 100 watt panel? If so, I would suggest doing so and make ti 2s2p like gnubie advised.

 

[DrShotsPHD]

Can you fit another 100 watt panel? If so, I would suggest doing so and make ti 2s2p like gnubie advised.

I can fit another but it appears the Victron 100/20 is limited to 290W at 12V, so the 4th panel and $180 would be wasted to some extent in full sunlight.

 

[BoloMKXXVIII]

$180 for a 100w, 12v panel? I have never paid more than $89.
Keep in mind you will not get a true 100w from a 100w panel. That is only going to (possibly) happen in lab conditions. Also, your panels aren't going to be tracking the sun. At best, you are likely to get 85w per panel. 4 panels would help keep you stay near max charging for longer periods of time during the day. Just my $0.02

 

[GMB]

I can fit another but it appears the Victron 100/20 is limited to 290W at 12V, so the 4th panel and $180 would be wasted to some extent in full sunlight.

This is a good thread to read regarding over-paneling a Victron controller.

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