Hope I don't confused anyone too much, I get muddled with all the numbers, I'm by no means proficient in this, so looking for advice.I currently have 2 solar arrays. One is 2x325w 72 cell panels in series feeding a Victron 100/50 MPPT. Not planning on touching that one. The other array is a single 250w 60 cell panel feeding a separate Victron 100/30 MPPT. Current total wattage is 900w.I have room on the roof for 1 more large panel that I was planning to wire in series with the single 250w panel. Ideally I would have preferred to avoid replacing the existing MPPT, but the max wattage for the 100/30 is 440w @ 12v. The unit is able to handle wattage above maximum, but it would be wasted (manual states "If more PV power is connected, the controller will limit input power."). So here's the question - if I stick with the 250w panel and add another one in series, then am I correct in assuming that I should stick as closely to the rated amperage of the installed panel (8.24A) with any new one (i.e. no point in going to a 300w panel)?The end objective is to add enough solar to reliably power a residential fridge and get off of propane. I have 600 A/H of LifePO4 (500 A/H usable). The primary consideration is not price (but is a secondary one), it is reliability of the system as we plan to leave the trailer at a remote location for extended periods and I don't necessarily want to worry about propane running out when we're away.Thanks for your input.

IMO you have plenty of solar panels. 1100 watts+. Solar panels don’t “power” fridges. Panels and controllers charge batteries. With adequate batteries you can power a residential fridge.

In a similar situation, I added a third controller to go with the added panel. I have three controllers for three arrays on the roof all controllers in parallel to the battery bank, all set to the same voltage so they add their amps. Works great.I got it that way from taking the solar sets from my previous RVs and using them with this RV so it seems like a hodge-podge, but it actually works as well as doing it all in one from scratch.Generally, if there isn't enough sun for a bunch of solar to get it done, then adding more wattage won't help much. No sun is no sun. As in if there is no wind, hoisting more sail won't help.It could make a difference in some scenario with lots of "dependings"

i do have a spare old 30A MPPT lying around, forgot about that (an old tougher than nails Rogue MPT-3024). That's an idea!More work but less $ and more flexibility for another panel.Not worried about not enough sun, with the batteries I figure I'd be good to run the fridge for a few days without much of a problem, more looking for enough wattage to quickly bring them back up when there is.EDIT: on 2nd thought, looking at the Rogue's charging profile it doesn't seem well suited to LifePO4 batteries, no way to disable absorption phase...

The series panels should have the same (almost) amps and they must not exceed the controllers Voc rating across the temperature range. I figure 67% efficient for flat panels (if that is what you have) and hence your panel wattage is close to the controller so you won't waste very much IMHO. If you travel south in the summer with the higher sun then more watts can be generated and wasted. And when hot are do you need AC for A/Cs etc?So good to go.

phemens wrote: The other array is a single 250w 60 cell panel feeding a separate Victron 100/30 MPPT. I have room on the roof for 1 more large panel that I was planning to wire in series with the single 250w panel. So here's the question - if I stick with the 250w panel and add another one in series, then am I correct in assuming that I should stick as closely to the rated amperage of the installed panel (8.24A) with any new one (i.e. no point in going to a 300w panel)? the trailer at a remote location for extended periods and I don't n .I would simply add another 250 watt 60 cell panel. Panels in series are limited to the smaller amperage of two.I would consider retro fitting a compressor cooling system to the existing fridge.

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pianotuna
Nomad III
Jun 09, 2020
phemens wrote:

The other array is a single 250w 60 cell panel feeding a separate Victron 100/30 MPPT.
I have room on the roof for 1 more large panel that I was planning to wire in series with the single 250w panel.

So here's the question - if I stick with the 250w panel and add another one in series, then am I correct in assuming that I should stick as closely to the rated amperage of the installed panel (8.24A) with any new one (i.e. no point in going to a 300w panel)? the trailer at a remote location for extended periods and I don't n .

I would simply add another 250 watt 60 cell panel. Panels in series are limited to the smaller amperage of two.

I would consider retro fitting a compressor cooling system to the existing fridge.
CA_Traveler
Explorer III
Jun 09, 2020
The series panels should have the same (almost) amps and they must not exceed the controllers Voc rating across the temperature range.

I figure 67% efficient for flat panels (if that is what you have) and hence your panel wattage is close to the controller so you won't waste very much IMHO.

If you travel south in the summer with the higher sun then more watts can be generated and wasted. And when hot are do you need AC for A/Cs etc?

So good to go.
phemens
Explorer
Jun 09, 2020
i do have a spare old 30A MPPT lying around, forgot about that (an old tougher than nails Rogue MPT-3024). That's an idea!
More work but less $ and more flexibility for another panel.
Not worried about not enough sun, with the batteries I figure I'd be good to run the fridge for a few days without much of a problem, more looking for enough wattage to quickly bring them back up when there is.

EDIT: on 2nd thought, looking at the Rogue's charging profile it doesn't seem well suited to LifePO4 batteries, no way to disable absorption phase...
BFL13
Explorer II
Jun 09, 2020
In a similar situation, I added a third controller to go with the added panel. I have three controllers for three arrays on the roof all controllers in parallel to the battery bank, all set to the same voltage so they add their amps. Works great.

I got it that way from taking the solar sets from my previous RVs and using them with this RV so it seems like a hodge-podge, but it actually works as well as doing it all in one from scratch.

Generally, if there isn't enough sun for a bunch of solar to get it done, then adding more wattage won't help much. No sun is no sun. As in if there is no wind, hoisting more sail won't help.

It could make a difference in some scenario with lots of "dependings"
Lwiddis
Explorer II
Jun 09, 2020
IMO you have plenty of solar panels. 1100 watts+. Solar panels don’t “power” fridges. Panels and controllers charge batteries. With adequate batteries you can power a residential fridge.

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