Is this sensible: Portable Solar / Controller for RV

[dkoldman]

I am wondering if it makes sense to have a solar controller that is portable meaning it would be used temporarily, and could be moved from one battery bank to another?

Context: I have a new Portable Power Station with 200watt MPPT Solar panels on the way (12 volts). The Power Station is to address other needs that may not be RV related, i.e. just having 1,152wh of electrical power in my SUV or any vehicle or simply power where none otherwise exist.

New Project: Given I have the MC4 Connectors on the 200 watt / 10 amp portable panels on order, I am thinking what if I had a solar controller (Lithium & AGM) that I could connect to any battery bank via Alligator clamps? If so, I could keep that panel and controller in the RV, and if I ever wanted to utilize the sun to keep house or chassis battery charged, I could get more value out of my panel investment.

Other need to know mitigation factors:

1. I have a Victron Orion XS 50 amp controller; so I will never need solar while driving
2. I have a Victron Smart Shunt, so this makes me lean toward some Victron Solar Controller with Bluetooth
3. I have single 300ah Lithium battery & FLA Chassis
4. I also have two 125ah AGM batteries that use to be in the RV that is now in storage shed. I am thinking of adding an inverter and using the solar panels to charge it when not be used in RV. Maybe run the power in the shed and cut off from grid completely?

What are the thoughts and any suggestions on sizing for solar controller? I think 200watts / 10amps of solar panels is all I need and that is already on order, but 400 watts / 20amps is for sure the maximum I could ever use.

i.e. would a Victron Energy SmartSolar MPPT Solar Charge Controller (Bluetooth) - 75V, 15 amp, 12/24-Volt do this job or do I need 100V, 20 amp?

 

[dkoldman]

So without guidance I bought the Victron SmartSolar 75v / 15 amp.

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If I follow, based on solar panels I have I will never go over 10 amps. 12 volts if one 200 watt panel and 24 volts in series if I were to in future double up to have 400 watts.

I made a low balled offer for a brand new unit on ebay and the seller surprised me by accepting.

If it works, my goal is to have it where it is not permanently mounted. I will make alligator clips on one end so I can connect to house or chassis, I will need to change the profile in the Victron Connect app.

 

[ducksface]

How can a regular guy use your system to their advantage?

 

[dkoldman]

How can a regular guy use your system to their advantage?

If I follow the question, they would not be able to do so unless they happened to have use for a Power Station and it's accompanying Solar Panel.

I found a great deal on Power Station after years of watching. In the mist of tariffs I am seeing some of the best prices ever. Having 1,152wh and 1800watts of power in a portable box allows me to do some things like plug in my electric AC power dethatcher anywhere in my lawn versus having to run excessively long extension cords with worry about overheating wires over the distance. It also brings life to all of my electric tools that I kind of replaced because I have their battery equivalents, like my really nice Chicago Electric impact drill that's basically sitting in favor of the Ryobi.

With that said it is the portable solar panel that I bought that I am crowing about for the RV. It folds up nicely, and I can put it almost anywhere as it has nice stand. For the regular guy that upgrades to Lithium, if they keep or kept their FLA and have a spare inverter around ( I don't) then you can do things like have a setup in storage shed completely off grid. When you wish to take a trip you can simply take the solar controller and solar panel with you for backup just in case. Note: If this works I may buy one of those cheapo China made solar controllers to be dedicated for the shed.

But for the RV, it is really about me being able to just say I can do it. I want to be like all of the people who have solar panels all of the place. Some even put those panels on their roofs!!! Hey I may even buy a Winegard if I get really restless. When I come to AZ and I find that Behemoth; the first thing I will do after I get my Woolford Reserve off your top shelf: I am gonna say excuse me Duck.... or do I call you Bill..., I got to go hook up my solar panel outside before it gets dark, so I can get my SOC back to 100% from the 99.9 SOC since I cut the engine and killed the Victron DC to DC charger

 

[ducksface]

I just this week gave away one of the early hf three panel solar set ups.
I came with the controller and 12v outlet and a 300a inverter.
It ran a shed light, then my greenhouse, then I had he opportunity to give it away.
I decided to run an extension cord to the greenhouse so I could run fans and mister and such.

I guess I built my own little power station.
A big ol' Walmart battery in a box with the inverter and controller.

 

[dkoldman]

I just this week gave away one of the early hf three panel solar set ups.
I came with the controller and 12v outlet and a 300a inverter.
It ran a shed light, then my greenhouse, then I had he opportunity to give it away.
I decided to run an extension cord to the greenhouse so I could run fans and mister and such.

I guess I built my own little power station.
A big ol' Walmart battery in a box with the inverter and controller.

I have two of the vMax Tanks AGMs 125ah each and one OEM Aux14 stop/start battery that all work fine but nothing to use them for. I did not trade them in. I think the Aux14 can run the lights in shed solo. But the vMax tanks should power any AC tools I have grid free. I may only need to charge once a month or longer depending upon usage.

You know the expression, build it and they will come. That is how I got here. I was just wanting to get confirmation on what size controller I needed. I don't see myself in such a need for power that I would need two panels, but if I am somewhere off the grid, if I have the time I can setup and get 10 amps sent to the House or Chassis battery if needed. I don't think I will even bother to have inline fuse. I believe the Controller has a 20 amp fuse anyway.

I am thinking of buying the exact same Yitranic 2200 watt inverter I bought last year for the RV. It is working really well and I love the remotes. If I make the 2nd one portable for shed etc., it would be plug and play backup for the RV, but with the new power station, I don't need that much power from inverter in the shed. I just wish to put those batteries to use.

 

[Chateau_Nomad]

Since you already bought a controller, it's probably moot... but there's online calculators you can use. The thing about charge controllers is you don't want to be constantly pushing the top amperage rating or you'll shorten the controller's life... amps = heat and all that.

Note that it's the total panel open circuit voltage (Voc) which determines the controller max voltage (in your case 75 volts). Typical 200 watt panel Voc is usually around 22 volts, so three in series still puts you well under 75 volts.

For the amp rating, use the panel Short Circuit Current (Isc), which is probably in the neighborhood of 11 amps. Adding any more than the one "like panels" (200 watt) in PARALLEL would exceed the controller's 15 amp rating... probably why the seller didn't balk. A 100/30 would have been my suggestion. Regardless, if you ever get frisky and want to expand... stick with series anyway. You can use common 10 AWG cable. The (minor) drawback of series is if shade hits one panel, the entire string suffers. Not so with parallel... but to me the system amperage increase (and more expensive cable) for parallel isn't worth any efficiency advantage.

Now let's do the math:

For amperage, a typical 200 watt panel maximum amp output is in the neighborhood of 10 amps... that's maximum rated output. The MOST amps I've ever seen from my 3 x 200 watt panels was around 25 amps @ 12 volts in Colorado... that's 8+ amps per panel.

Let's say you get a nice sunny Texas day... no clouds and you can tilt the panel directly at the sun, which is ideal. Depending on the quality of your panel you "may" get 10 amps... but probably something less. Add a few passing clouds and everything gets messy. But let's just say you get an AVERAGE of 8 amps per hour.

Now take the amount of energy you need to recharge your battery. Obviously a 100Ah battery @ 50% SOC requires 50 amps. So... simple math says you'll need 6.25 hours in those conditions to add 50 amps of energy back into your battery.

Multiply that 8 amps by 3... 24 amps per hour = just over 2 hours. Quite a difference.

Now... the "pain-in-the-ass" factor. A single panel is pretty easy... kind of like setting up a ground base Starlink dish. Unroll the cable and string it across the ground... prop up the panel, clip the alligator clips on the battery and wait... and wait... sometime tomorrow your battery should be charged... IF you had perfect sun.

But you want to speed things up, so add two panels. Now you have THREE panels and the associated cables in series to set up. The payoff is a quicker charge... but you'd be surprised how much real estate those panels consume. It's fun for awhile...

Takeaway... there's a functional reason Thor started putting SINGLE solar panels on RV roofs. They refer to them as a solar "starter package". I call them a trickle charger for the batteries.

P.S. Many inverters, especially when you start talking 2k -3k consume a fair amount of energy at idle... sometimes as much 30 to 50 watts, or 2 to 3 amp-hours. Doesn't seem like much, but when you take 2 or 3 amps away from the 8 (or so) you're getting from your single solar panel... you see my point. Check the inverters idle power usage, keep it off when not needed or fire up the generator!

 

[dkoldman]

Great information, this is what I was seeking. Based on what I just learned I may have bought the Victron 100 / 20 unless a 100/30 fell in my lap with good price.

I did speak with Bluetti and may have got some misinformation. He was saying that if I wired two of the 200watt Solar panels in series, I would have 400 watts, but still the panels would output only 10 amps? Sounded odd because I was trying to figure out how the batteries would charge faster if amperage stays the same. My uneducated guess is that if I had two panels 400 watt capable, I would not exceed about 210 watts in any circumstance as long as I had the 75 / 15. That would only go to 280 watts if I had the 100/20.

Regardless, getting a 2nd panel is not likely for me, and and having 3 panels is out of the question. It is not beyond me to sell my brand new yet to receive 75 / 15 for a brand new 100 / 20 if it makes sense? It would probably cost me $40 more. I listen for thoughts? You may recall I bought a 30amp Renogy DC to DC and before I received it; I sold it on ebay because I ran across the Victron Orion XS 50 amp and fell in love with it. I paid about $100 more for the Orion XS and it was a good decision.

Since you like the numbers, here is my real scenario. I have 300ah of battery capacity. If I run all day doing what I do with the fridge on propane, the next morning I am at 83% SOC. So I have consumed about 50 amps. Using your projections with my single panel, I may get 8amps out of my Solar Controller; so I should be back at 100% by 4:00 PM next day (Day 1). With the overlap of usage and solar charging on 2nd day, I should be back to 100% by noon on 2nd day. I am not likely to spend a 3rd day anywhere in same spot; so I will be on the move and my Victron 50amp DC to DC will finish off what may be needed.

If I followed what you said, if I ever do get a 2nd Solar Panel and wire in Series. Then I may get 15 amps Max out of that 75 / 15 which means I could go from 83% to 100% SOC in about 3 hours. That sounds good, but I doubt if I would buy a 2nd Panel for that. However, it is possible I may get a 2nd panel for other reasons and that would be an option.

Great point on energy consumption of Inverter while idle if I put a solar controller and solar panel to feed it. I saw some really cheap $10 30amp controllers for FLA batteries. My inverter in RV has a true wireless remote, if I bought one like it for shed and as a contingency backup for RV, I could easily turn it ON/OFF and keep it off unless needed AC. I could use the Load output on the solar controller to connect a Switched DC light; so I could open shed door, turn the DC light on, find the remote, turn on the Inverter and then turn on the main AC powered light for shed and have 125ah of capacity for tools.

 

[Chateau_Nomad]

Briefly, look at Ohm's Law. In simple terms, by wiring in series you're just swapping higher voltage for lower amps... just to allow use of thinner cable. BUT you still get the same available watts at the controller.

In SERIES, the more panels you add increases VOLTAGE... which eventually requires a higher rated controller

In parallel, it increases AMPERAGE... which necessitates thicker cable.

Either way, watts is determined by the number of panels in the string.

Although it's geared toward deep cycle batteries, the math is the same. Here's a little primer:

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[dkoldman]

Briefly, look at Ohm's Law. In simple terms, by wiring in series you're just swapping higher voltage for lower amps... just to allow use of thinner cable. BUT you still get the same available watts at the controller.

In SERIES, the more panels you add increases VOLTAGE... which eventually requires a higher rated controller

In parallel, it increases AMPERAGE... which necessitates thicker cable.

Either way, watts is determined by the number of panels in the string.

Although it's geared toward deep cycle batteries, the math is the same. Here's a little primer:

KT Cables - Automotive, Electrical & Industrial Wiring Accessories

KT Cables keeps your workshop running smoothly with rugged, reliable automotive, electrical, and industrial wiring accessories. From quality cables and connectors to terminals and heat shrink, find everything you need to get the job done right — every time.

ktcables.com.au

I got lost here, the more I read the deeper I sunk.

In simple language. I am gonna always have 12volts on my actual batteries. When you say available watts at the Controller, it is implied that will be up to 200watts at my controller based on efficiency of panel and direction of sun.

My cable is 10awg; so I don't I have any issues with wiring sizes.

So the confirming part is if I were to add one panel in series... that means I would have 400 watts. I follow the open circuit voltage going from 24volts to 48 volts. Not an issue as I have capacity for 75 OCV on controller. Which leaves the question as to what is actual amperage (LSC) Short circuit current?

Based on the Bluetti Solar Panel specs. A panel is 10.24lsc. If in series; my guess is that that value would try to go to 20.48lsc?, but since I have a Victron Solar Controller, it will safely max out at 15amps lsc? Am I getting this right?

Again, I am not planning to get a 2nd panel, if I get 10amps out of the solar panel, then it means I can go from 83% SOC to 100% SOC in 4 hours. In my view that is good. I am never gonna want to hook up the portable solar anyway unless I know I am gonna be parked somewhere in Sun for 6 hours or so.

See my specs on Solar panel. Looks like I may have lucked out and got what I need for one 200 watt panel? Remember the one panel I have is actually for the Power Station 1,152wh. I will just use the Solar Panel (NOT THE POWER STATION) in the RV just because I have it available to help recharge with no SO or generator. The price I paid for the Victron Solar Controller was very cheap for a brand new unit, especially compared to cost of the new Victron DC to DC and Smart Shunt

 

[dkoldman]

I got my Portable 200 watt Solar Panel today. Hooked it up to my 1,152wh Power station that was down to 1% SOC. In 2 hours I was up to 22% SOC, but clouds kicked in. I thought when you bought Solar the Sun always stayed out? Well, I didn't want to get my Solar Panel wet; so I shut it all down and brought into house.

The max watt reading I observed was 152 watts. Bluetti says that is normal and that I may hit 160 watts when it breaks in. Not sure how the efficiency work because they say 23.4% efficient?

 

[dkoldman]

Why do I always read to set Solar Panel up faces south when what I see is Sun setting on the West / Northwest sky? Maybe midday is just a tad South but mostly straight up overhead?

I am playing with my new 75/15 Victron to direct charge any battery with Alligator clips. It is cloudy and I have 6 seen 6 watts from the panel for 15.5vdc on the battery. Not much current but it is charging the battery and it is almost dark.

 

[dkoldman]

Also, which comes first when reading the Watts on a Solar panel?

The amount of watts the panel can extract from Sun, or the amount of watts or power the controller will pull from Solar panel based on actual voltage of the panel, or something else.

Trying to understand how to have 200 watts of panel but will never get 200 watts and how watts can be so slow but still put of over 16vdc?

 

[16ACE27]

Also, which comes first when reading the Watts on a Solar panel?

The amount of watts the panel can extract from Sun, or the amount of watts or power the controller will pull from Solar panel based on actual voltage of the panel, or something else.

Trying to understand how to have 200 watts of panel but will never get 200 watts and how watts can be so slow but still put of over 16vdc?

I believe the solar panel industry "wattage" is the theoretical maximum the solar panel can provide.
A 100 watt panel will never produce 100 watts in real life.
At best you may get 65 - 70 watts. The rest is lost in resistance/heat in the panels.
Almost any power supply has a voltage droop. So with no current drawn, no load applied, the voltage will be maximum. So a solar panel not connected to anything may put out 20 volts, but since there is 0 amps there is 0 watts.
As you add load to the solar panel, the current increases and the voltage decreases but the watts produced with be the product of the voltage and current at any point on the curve. So if you are pulling 5 amps and the voltage has dropped to 15 volts you are getting 75 watts.
If the sun starts fading both the voltage and current will decrease as well as the watts produced.

 

[dkoldman]

As you add load to the solar panel, the current increases and the voltage decreases but the watts produced with be the product of the voltage and current at any point on the curve.

This might be what I needed to learn. When you say as you add load to the solar panel.....

Today I had a simple 12v AGM battery that started with 12.47vdc. I made a connector cable with MC4 on one ends to plug direct to my 200watt Bluetti Solar Panel while the other end was direct connected to the VIctron Solar Controller.

It looked like the solar controller was controlling the load ( or amp draw) based on profile to not over charge the battery so 6 watts to 8 watts was about all I could see. I could not tell if the wattage was low because of no sun or because the Victron did not want to exceed the threshold of the profile based on actual battery voltage?

 

[dkoldman]

A 100 watt panel will never produce 100 watts in real life.
At best you may get 65 - 70 watts.

I am kind of disappointed the @Real Solar Fanatics don't chime in more here. I always read about the number of watts in solar panel they may have, but no one ever comes clean to say my 400 watts is actually only 240 watts.

My 200 watt Bluetti portable solar panel seems to max at about 130 watts. I have it direct facing the sun, no could and perfect angle. I am damn near blind for lining up the dam panel.

I saw 150 watts but that was with the Victron Controller on a battery; not on the power station.

I am trying to get perspective if i should accept the panel as it is as normal or try to have Bluetti replace or just return for a refund? I know enough about the 200watt panel that I will never buy a 2nd panel to have 400 watts. As long as my 200watt is normal, I will live with it, but I don't know the true normal.

 

[Chateau_Nomad]

I am kind of disappointed the @Real Solar Fanatics don't chime in more here. I always read about the number of watts in solar panel they may have, but no one ever comes clean to say my 400 watts is actually only 240 watts.

My 200 watt Bluetti portable solar panel seems to max at about 130 watts. I have it direct facing the sun, no could and perfect angle. I am damn near blind for lining up the dam panel.

I saw 150 watts but that was with the Victron Controller on a battery; not on the power station.

I am trying to get perspective if i should accept the panel as it is as normal or try to have Bluetti replace or just return for a refund? I know enough about the 200watt panel that I will never buy a 2nd panel to have 400 watts. As long as my 200watt is normal, I will live with it, but I don't know the true normal.

If you think solar panel manufacturers are being disingenuous, consider your venerable trusty generator. Your "Onan 4000" generator is technically only an "Onan 3600". Sure... it will handle a SURGE of 4,000 watts, but it's continuous rating is only 3,600 watts. So you're getting cheated 10% in the name of misleading advertising.

So I had to put 600 watts of solar on my roof to make up for that shortfall.

See what I did there?

 

[dkoldman]

Nah. I got a 5500 watt generator and I run everything no questions.

But tell me what is realistic for 200 solar? Should I accept 100 - 130 watts as normal? If that is the answer I can live with it. I am only asking to see if I need to be anal about and try another one?

 

[16ACE27]

Nah. I got a 5500 watt generator and I run everything no questions.

But tell me what is realistic for 200 solar? Should I accept 100 - 130 watts as normal? If that is the answer I can live with it. I am only asking to see if I need to be anal about and try another one?

Yes. I explained this to you earlier. 100 watt solar equals 65-70 watts AT BEST.

 

[dkoldman]

Yes. I explained this to you earlier. 100 watt solar equals 65-70 watts AT BEST.

Yeah you did, but I want a professed Solar Expert to tell me. I feel like I have been hoodwinked for 6 years, part of some vast conspiracy to make me an others invest in what appears to be a vastly inefficient system. I can't even figure out the efficiency thing, my panels crows 23.5% efficiency and is suppose to be one of the best in the industry, but I don't see how it translate to a 200 watt panel doing 130 watts.

The other thing I have noticed,it seems like if I did need solar, putting it on the roof would be even more inefficient. On a normal day, I see readings as low as 5 watts and as high as 130 watts to recharge the power station (no solar controller involved). I have to move the panels at least 3 times a day to keep optimum wattage flowing in. If I had on my roof I may barely get 30 watts on average.

To force myself to learn and use the panels, I have on used 120vac to charge my power station once. I use the power station in the house and when it drains downs, I play with the panels to recharge. Last night I used one 125 ah AGM Vmax tank wired to my bluetti with special cable I mady and I only get 71 watts max. The Bluetti when from 14% SOC as the low point to 28% before the AGM was down to 11.79 volts. Granted ny VMax tanks may be useless, but I wanted to know what it can do. I have since wired both vMax tanks in parallel next to my storage shed. This weekend I intend to drain power station down, and try to recharge with both VMax tanks? Maybe I can get SOC up 30%. Even so, what a bunch a crock, I have been hoodwinked on solar.