Sizing a Solar Controller

[mfschu]

I'm going to purchsase a Victron Smart Solar Controller and need help determining the size I should purchase. I'm going to start out with a 350 Watt portable panel, but want to be able to add a panel or two on the roof at a later date. Is the Victron 100/30 the controller Escape uses for the 2 panel option, and will this controller work with 2 roof panels and also adding a portable panel? Thank You

[fudge_brownie]

I have a 300 watt portable panel and the 100/15 works fine. An important advantage my 300 watt panel has is that it is 24 volt. Since yours is portable, is there a way to configure it into 24 volt? Maybe it is already. Read up on the advantages. All the Smart Controllers from Victron will handle 24 volt.

[Greg and Kathy]

no the ratings are on the viltron site. if you stay with 12 volt you can only do 440 watts max or 700 with the 100/50.. that said if you configure to 24 volts then you can do more. not sure if it is worth it unless you are going really big on your solar.

[paul65k]

Victron has a nice configuration tool on their website.... I suggest you use this as it will be the most accurate.

For reference, I would suggest "Overpaneling" by about 25% but you MUST stay within the total voltage (eg. 100V on the 100/50).... never go over on the voltage and you can go over by up to 30% on the wattage.

Good luck!

[fudge_brownie]

My point to use a 24 panel is that you are planning portable. I am running 50 Ft of 11 gauge wire from panel to controller. I have the ability to add 50 more 12 gauge. There are National Parks where even that is not enough. The northern part of my state is heavily forested, hard to find viable campsites.

Using 24 volt panels reduces the energy loss with such long runs.

[Perry Butler]

On our Escape 5.0 we had the original 170 watt GoPower panel and I added three 100 watt Renogy Compact panels. Because I made sure the VMP of the two panel sizes was as close as possible I chose to run them in parallel, and the math gave us a potential of 463 watts. They ran just fine with our Victron 100/30 controller. The 5.0's roof is not flat but angled, so the rear three panels were angled to the rear, but the front panel was angled to the front. The most watts recorded by the 100/30 was 435 watts, slightly under the theoretical maximum of the controller.

Rich Solar makes 200 watt 24v panels. We currently have two of these panels on our Bigfoot with a flat roof. I was given bad advice by AM Solar (they knew I was purchasing 24v panels) and purchased a 100/50 controller in case we purchased another 200 watt panel. A 100/30 controller would have been just fine with 600 watts of 24v panels.

Our 100 watt Renogy portable has its own Victron 100/20 controller. I'd never buy another 100/20 controller because the wire bus is too small so 10 awg wires barely fit. The Victron 100/20 has recorded over 110 watts numerous times, with the highest reading at 120 watts.

I bought mounts and bars from AM Solar so we can angle our panels if needed, but they will mainly be used to get under the panels for cleaning.

Food for thought,

Perry

[BobG]

Originally Posted by fudge_brownie

.... All the Smart Controllers from Victron will handle 24 volt.

To clarify, do you have a 24 volt battery system?

[Centex]

Originally Posted by fudge_brownie

All the Smart Controllers from Victron will handle 24 volt.

Originally Posted by BobG

To clarify, do you have a 24 volt battery system?

Just to further clarify, all of the Victron controllers which will "handle" nominal 24V input from the PV array will also provide proper output for charging a 12V or 24V nominal battery array.

When referring to voltage that a controller will "handle" it's probably useful to distinguish PV input vs charging output to avoid potential confusion.

[BobG]

The current version of Victron 100|15 MPPT can handle input voltage up to 100 volts from the solar panels. It can put out up to 15 amps to the batteries.


If the battery is 24 volt then it can provide up to 15 amps x 24 volts = 360 watts. If the battery is 12 volt then it can provide up to 15 amps x 12 volts = 180 watts. These are approximate numbers. Since fudge_brownie has a 300 watt panel connected to the to the MPPT 100|15 I was thinking that he is running 24 volt batteries but wasn't sure.

[nicklee]

It is best not to exceed the voltage

[Dave Miller]

I’m building out my system now. I’m doing 24 volt panels and 12v battery. From what I’ve read, 24v panels do better when partially shaded. Also, the ETI pre wire for rooftop is 10 gauge so has a 30 amp max. So, I can support twice the watts with 24 volt panels. And less loss in the wires. Unfortunately There are fewer choices in 24v panels. Also, you need to be careful about using 12v in series as a single shaded panel will affect both.

I’m installing a 3000 watt inverter and considered a 24v battery but wanted to avoid a DC converter to support the 12V system, especially the compressor fridge. Because the battery is 12V my wattage is more limited on the Charge controller. I’m planning on two - 30 amp for portable solar and probably 50 for rooftop.

Also, the 2/0 welding cable to support the inverter is expensive and massive.

Bottom line when sizing the charge controller you need to look at PV voltage and watts and the wiring from the panels to the controller as well as the battery voltage and therefore Amps coming out of the controller.

[John in Santa Cruz]

I used a 360W home rooftop panel, rated for 100 MPH hurricane winds. its 40V peak PV, 36V typical PV, works great with a MPPT controller. I got my panel several years ago at deep discount because they were clearing out the 360's, newer ones the same size were 400W.

On an E21 classic, at least, if you remove the 'chimney' on the absorption fridge vent column, and cap the opening off flush, the 360W panel fits cleanly behind the A/C unit and doesnt stick out at all.





I mounted this on the original 160W panel's mounting rails, using another piece of extruded aluminum as a riser.



very clean look




this panel is 66.38 x 40 x 1.57 inch


edit: oh, I have the MPPT 100/30.