Solar configuration

Camp20144 · Mar 3, 2023

I anticipate two situations for the solar side of my portable system. One where I would have 800 Watts of solar (rv roof mount + ground). The other, where I’m only able to have 400 Watts of solar (ground mount only, e.g. camping from boat). I’m looking at Rich Solar 200 Watt panels. My question, would I use a Victron 150/60 SCC, and just have two or four panels connected, or would I be better off with 2 Victron 100/30s (2 panels each)? The price is pretty close either way. The picture is the Rich Solar panel I’m looking at.
Thank you,

Camp20144 · Mar 3, 2023

The solar side will be feeding two 100Ah Battleborn batteries. Power usage based upon charging capacity. Main use - cpap

littleharbor2 · Mar 3, 2023

Those high watt solar panels really need to be series wired and ran through an MPPT controller due to the higher than normal voltage for 12 volt, nominal, panels. Good thing you are going the MPPT route. Using a PWM controller would end up wasting a lot of power.

Are you going with a 12 or 24 volt battery bank?

Camp20144 · Mar 3, 2023

I’ve been thinking 12Volt because my use(s) are 12Volt, but I’ve also considered a 24V/12V dc converter to drop to 12Volts. Don’t understand if the trade-offs are there to make 24volt or 12Volt better at this size of system. If my system was larger I understand 24volt or 48volt is better.

rodrick · Mar 3, 2023

Camp20144 said:
I’ve been thinking 12Volt because my use(s) are 12Volt, but I’ve also considered a 24V/12V dc converter to drop to 12Volts. Don’t understand if the trade-offs are there to make 24volt or 12Volt better at this size of system. If my system was larger I understand 24volt or 48volt is better.

If you plan to run a inverter off this system anything over 1000-1200 watts should go up to 24 volt system

littleharbor2 · Mar 3, 2023

With a 24 volt system you get the same load covered with half the current. You can double the maximum PV wattage with the same controller in the event you want to expand your system. Typically you can use smaller wire between your battery bank and inverter for like sized inverters and wiring design for your battery bank is simpler.

Camp20144 · Mar 3, 2023

Thank you,
@rodrick & @littleharbor2 Okay, I wasn’t sure if my system was large enough to consider 24volt. I haven’t purchased SCC(s) or panels yet, so doable. I will always have the two batteries in the system, so no problem there. I have a Victron BMV-712 and it senses battery voltage so I’m good there.
Where I know I will have times with two 200 watt panels and times with four 200 watt panels, how do I best configure for SCCs? Two SCCs, one each for two panels a piece, or one SCC that would have two or four panels connected?

Factsmanmp · Mar 3, 2023

littleharbor2 said:
With a 24 volt system you get the same load covered with half the current. You can double the maximum PV wattage with the same controller in the event you want to expand your system. Typically you can use smaller wire between your battery bank and inverter for like sized inverters and wiring design for your battery bank is simpler.

How would you wire 12 v batteries or would you buy a 24 v battery?

Camp20144 · Mar 3, 2023

I have two 12Volt 100Ah batteries, connecting them in series would give 24volts, for a 24 volt system?

littleharbor2 · Mar 3, 2023

Personally, I would go with a single controller, panels series wired two at a time. so 2s2p with a 4 panel setup 2s1p for two panels.

Always have the battery connected before you connect the panels.

Camp20144 · Mar 3, 2023

littleharbor2 said:
Personally, I would go with a single controller, panels series wired two at a time. so 2s2p with a 4 panel setup 2s1p for two panels.

Always have the battery connected before you connect the panels.

Yes, and as this is a mobile system requiring connecting system components, I plan on having a list of setup steps to follow.

Here are my calculations - please let me know what I missed.

The numbers for Rich Solar 24volt 200 Watt panels are:
Voc = 45.4V
Isc = 5.83A

2s2p = 90.8V, 11.66A
2s1p = 45.4V, 5.83A

Record low temp for my area is -25F, correction factor 1.23. Voc corrected = (90.8V)(1.23) = 111.68V

111.68V is greater than 100V therefore need SCC rated higher than 100 Volts and Amps greatest at 2p is 11.66
A Victron 150/35 meets this criteria.

littleharbor2 · Mar 4, 2023

All good except for one calc. When you add the second string in parallel the current adds but the voltage stays the same.
2s2p = 45.4V, 11.66A x 12 volts = 45 amps. (rounded up)
2s1p = 45.4V, 5.83A
You will need a 45 amp controller for a 12 volt system. If you decide to go 24 volts you can get away with a 25 amp controller.

Camp20144 · Mar 4, 2023

littleharbor2 said:
All good except for one calc. When you add the second string in parallel the current adds but the voltage stays the same.
2s2p = 45.4V, 11.66A x 12 volts = 45 amps. (rounded up)
2s1p = 45.4V, 5.83A
You will need a 45 amp controller for a 12 volt system. If you decide to go 24 volts you can get away with a 25 amp controller.

Thank you for catching my adding the volts a second time on my 2s2p string.

Camp20144 · Mar 4, 2023

@littleharbor2 I’m confused, where am I going sideways?

littleharbor2 said:
All good except for one calc. When you add the second string in parallel the current adds but the voltage stays the same.
2s2p = 45.4V, 11.66A x 12 volts = 45 amps. (rounded up)
2s1p = 45.4V, 5.83A
You will need a 45 amp controller for a 12 volt system. If you decide to go 24 volts you can get away with a 25 amp controller.

The numbers I used in post #11 are for the 24 Volt 200 Watt Rich Solar panel (for my 12V batteries wired in series for a 24V system)
Voc = 45.4 Volts
Isp = 5.83 Amps

For 2s1p, there are 2 panels total, the 2s (2 panels in series) adds the voltage of the 2 panels = 90.8 Volts
For 2s1p, the amperage is non-additive therefore stays at 5.83 Amps
So for 2s1p, I end up with 90.8 Volts, 5.83 Amps

For 2s2p, there are 4 panels total, 2 sets of 2 panels in series, so there are 2 series strings in parallel.
The series strings are 90.8 Volts, 5.83 Amps (series adds volts values)
Setting the two series strings in parallel makes 90.8 Volts, 11.66 Amps (parallel adds amp values)

This gives me
2s2p 90.8 Volts, 11.66 Amps
2s1p 90.8 Volts, 5.83 Amps

Thank you,
Mark

littleharbor2 · Mar 4, 2023

The first time I looked up Rich Solar 200 watt panels I got this first panel. Now I see they have 2 different 200 watt panels. Just goes to show it really is important to list all specs of your components to get accurate, correct answers to your questions. I had assumed the lower voltage panel in a few of my previous answers. My bad for assuming what equipment you are working with.
12 volt version / 24 volt version specs below
Wattage: 200W
Type: Monocrystalline 12 volt/24 volt
Operating Voltage (Vmpp): 20.4V / 37.6V
Open Circuit Voltage (Voc): 24.3V / 45.4V
Operating Current (Impp): 9.80A / 5.32A
Short Circuit Current (Isc): 10.2A / 5.83A
Size: 58.7" x 26.8" x 1.38" 26.5lbs

Camp20144 · Mar 4, 2023

littleharbor2 said:
The first time I looked up Rich Solar 200 watt panels I got this first panel. Now I see they have 2 different 200 watt panels. Just goes to show it really is important to list all specs of your components to get accurate, correct answers to your questions. I had assumed the lower voltage panel in a few of my previous answers. My bad for assuming what equipment you are working with.
12 volt version / 24 volt version specs below
Wattage: 200W
Type: Monocrystalline 12 volt/24 volt
Operating Voltage (Vmpp): 20.4V / 37.6V
Open Circuit Voltage (Voc): 24.3V / 45.4V
Operating Current (Impp): 9.80A / 5.32A
Short Circuit Current (Isc): 10.2A / 5.83A
Size: 58.7" x 26.8" x 1.38" 26.5lbs

Yes, I agree, I apologize for the confusion on my part. Is my math good for the 2s2p (4 panels) and 2s1p (2 panels) setups?
Please help me understand how you arrived at the 45 amp controller (scc) for 12 volt system and 25 amp controller for a 24 volt system. I know when you go from 12 volts to 24 volts you divide the amps in half. Where I’m looking for assistance is the 45 amp controller size for the 12 volt system. Wouldn’t the 12 controller be figured from (2)(Isc) = (2)(10.2A) = 20.4A? for 2s2p 12V 200 Watt panels?
Thank you,
Mark
[Edit] For the 12 Volt, are you setting the panels all in parallel, (4)(10.2A) = 40.8A (rounding up = 45A controller)
Thank you again,
Mark

littleharbor2 · Mar 4, 2023

I used your numbers which are actually Voc. volts. This gave me higher wattage than it should have.
Take rated watts divided by nominal battery voltage.

400 / 12 = 33 1/3 amps, 35 amp controller 400 / 24 = 17 amps. 20 amp controller
800 / 12 = 66 2/3 amps, 70 amp controller. 800 / 24 = 33 1/3 amps. 35 amp controller.

Camp20144 · Mar 4, 2023

littleharbor2 said:
I used your numbers which are actually Voc. volts. This gave me higher wattage than it should have.
Take rated watts divided by nominal battery voltage.

400 / 12 = 33 1/3 amps, 35 amp controller 400 / 24 = 17 amps. 20 amp controller
800 / 12 = 66 2/3 amps, 70 amp controller. 800 / 24 = 33 1/3 amps. 35 amp controller.

Thank you again for your assistance. It is very much appreciated!
Mark

Pi Curio · Mar 5, 2023

Camp20144 said:
I anticipate two situations for the solar side of my portable system. One where I would have 800 Watts of solar (rv roof mount + ground). The other, where I’m only able to have 400 Watts of solar (ground mount only, e.g. camping from boat). I’m looking at Rich Solar 200 Watt panels. My question, would I use a Victron 150/60 SCC, and just have two or four panels connected, or would I be better off with 2 Victron 100/30s (2 panels each)? The price is pretty close either way. The picture is the Rich Solar panel I’m looking at.
Thank you,

Camp20144 said:

I have two 12Volt 100Ah batteries, connecting them in series would give 24volts, for a 24 volt system?

Click to expand...

Camp20144 said:

Thank you,
@rodrick & @littleharbor2 Okay, I wasn’t sure if my system was large enough to consider 24volt. I haven’t purchased SCC(s) or panels yet, so doable. I will always have the two batteries in the system, so no problem there. I have a Victron BMV-712 and it senses battery voltage so I’m good there.
Where I know I will have times with two 200 watt panels and times with four 200 watt panels, how do I best configure for SCCs? Two SCCs, one each for two panels a piece, or one SCC that would have two or four panels connected?

Click to expand...

Camp20144 said:

Yes, and as this is a mobile system requiring connecting system components, I plan on having a list of setup steps to follow.

Here are my calculations - please let me know what I missed.

The numbers for Rich Solar 24volt 200 Watt panels are:
Voc = 45.4V
Isc = 5.83A

2s2p = 90.8V, 11.66A
2s1p = 45.4V, 5.83A

Record low temp for my area is -25F, correction factor 1.23. Voc corrected = (90.8V)(1.23) = 111.68V

111.68V is greater than 100V therefore need SCC rated higher than 100 Volts and Amps greatest at 2p is 11.66
A Victron 150/35 meets this criteria.

Click to expand...

Camp20144 said:

I’ve been thinking 12Volt because my use(s) are 12Volt, but I’ve also considered a 24V/12V dc converter to drop to 12Volts. Don’t understand if the trade-offs are there to make 24volt or 12Volt better at this size of system. If my system was larger I understand 24volt or 48volt is better.

Click to expand...

Just to be certain, do you plan to build a single portable system that will be used in both, the 400W/800W scenarios?

What's the biggest load you anticipate you'll ever possibly run on this system?

Do you have an inverter in the plans, or do you plan to power 12v devices only?

Best,
D.

Camp20144 · Mar 5, 2023

Daxo said:
Just to be certain, do you plan to build a single portable system that will be used in both, the 400W/800W scenarios?

What's the biggest load you anticipate you'll ever possibly run on this system?

Do you have an inverter in the plans, or do you plan to power 12v devices only?

Best,
D.

I’m thinking of building a single portable system.

I would have my 2 100Ah LiFePO4’s with me. With 400 watts of solar I would be in a pickup canopy, similar low volume accommodations, or boat access beach camping, where I only want to deal with 2 solar panels. My power usage at this level would be 1st priority cpap and then if I have enough power buffer, cell phone recharging and possibly minimal LED lighting. When I have my slide-in camper I would carry the 4 200 Watt panels. Again 1st priority is cpap, then phone charging, some LED lighting, I may add microwave usage (2-3 minute reheat prepared from home food) with the addition of a 1200-1500 Watt inverter. My microwave is 800 or 900 watts. I’ve seen people write on here that you should have more inverter than intended use. Therefore the 1200-1500 watts.

Most cooking, coffee etc. is propane in the camper. Most of this type camping is “off season” so cooler possibly some around freezing so water will be in containers so I don’t have to worry about water pump or re-winterizing the camper. It won’t be that cold so warmth is maintained through proper clothing layers.

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