Expected solar output.

[CanuckRV]

I'm thinking of installing a 200w solar kit from Renogy. What could I expect in the real world, (semi-shaded site and horizontal panels) in the way of solar gain? 20amph a day? more? less? just trying to see if it makes sense to do the installation.

[booster]

Originally Posted by CanuckRV

I'm thinking of installing a 200w solar kit from Renogy. What could I expect in the real world, (semi-shaded site and horizontal panels) in the way of solar gain? 20amph a day? more? less? just trying to see if it makes sense to do the installation.

It will all depend on how shady the site is and how much of the panels is in the shade if spotty.


The normal things that most people see would be in the range of, per 100 watt panel:


Good sun in the late spring, summer, early fall no shade 30ah per day per 100 watts


Same time of year but spotty shade or sunny some off the day, probably down to the 10ah per 100 watts you state or anything up to 30ah.


Full shade or full clouds it could be under 5ah per 100 watts. We have seen this personally a couple of times in very cloudy weather.


There are so many variables that is extremely hard to predict solar harvest when not using full sun conditions. At the right latitude and time of year we have heard of over 40ah per day being seen from 100 watt panels, but you can't count on that especially if you like to camp in the cooler northern regions like we do.

[CanuckRV]

Thank you for replying so if I sort of say 20 ah for the 200 system that would be a good standard to budget with?

[booster]

Originally Posted by CanuckRV

Thank you for replying so if I sort of say 20 ah for the 200 system that would be a good standard to budget with?

Unless you are rarely out of deep shade, you should be able be able to average that with a 200 watt system. Usually there are occasional trips to the store, sumpstation, attractions, trailheads, etc so the solar gets a chance to be in the sun for a few hours every day or two.

[Davydd]

Originally Posted by booster

Unless you are rarely out of deep shade, you should be able be able to average that with a 200 watt system. Usually there are occasional trips to the store, sumpstation, attractions, trailheads, etc so the solar gets a chance to be in the sun for a few hours every day or two.

If you are out for a few hours every day or two then your alternator will charge more than solar. A second under hood alternator would make no need for solar or Onan generator in my experience and you can have more batter capacity that will charge batteries completely that no amount of optimum solar on a Class B is capable.

[CanuckRV]

Usually, we have no issues charging only with the alternator but last weekend we were parked for two nights for our thanksgiving with temps getting close to freezing the heater was running and with coffee and toast etc we ended the weekend at 50 ah left on our 200 ah lifepo4 battery 20 or 30 more would have been more comfortable for me.

[N147JK]

https://www.classbforum.com/forums/f...ing-13592.html

[N147JK]

Originally Posted by Davydd

If you are out for a few hours every day or two then your alternator will charge more than solar. A second under hood alternator would make no need for solar or Onan generator in my experience and you can have more batter capacity that will charge batteries completely that no amount of optimum solar on a Class B is capable.

There doesn't seem to be a perfect solution. Each one has it's pros and cons. Living and typically camping in the north, I don't think solar will work for us. But that second alternator is intriguing. How are they assembled into the typical engine compartment?

[CanuckRV]

Another alternator is not much good parked.

[booster]

Originally Posted by N147JK

There doesn't seem to be a perfect solution. Each one has it's pros and cons. Living and typically camping in the north, I don't think solar will work for us. But that second alternator is intriguing. How are they assembled into the typical engine compartment?

They are just a second alternator put onto the engine like has been done for a long time to get more output. Not too hard to do and some run on the same beltline with a longer belt and some add a drive at the front of the engine and separate belt.


A lot depends on if the bracketry is made for your particular engine. Sprinter, Transit, Promaster and the Chevies have them available but never have heard of an install on the old Dodges, so unknown if you can get them or would have to make them, which can be difficult because of the need for the line up of the beltline and squarness to the beltline.


If you have an internally regulated alternator on the van, you can parallel the two alternators, but it is good to have them as close to identical as possible. If you have the more modern PCM controlled alternator you would setup as a standalone for the coach only. We have a 250 and a 280 amp alternator setup in parallel on our Chevy. It works very well.

[booster]

Originally Posted by CanuckRV

Another alternator is not much good parked.

If it is allowed, you can idle for 20 minutes and have a couple of days of moderate use power so definitely possible in an emergency. If we ever got to the point of needing it, we would probably just go to the dump station or store, maybe a trailhead to hike and be good. Solar normally covers our use without issue.

[@Michael]

Originally Posted by CanuckRV

Another alternator is not much good parked.

I hear 'ya. I'm not a fan of idling for long periods, especially when there are other campers within earshot.

I think you'll find that panels will help a lot in a few cases, some in most cases, and very little on cloudy days.

For example, I'm at 45deg north, the day was half cloudy with a few hours of full sun, temps in the 40's. My 200w of panels, laying flat on the roof, whose peak output probably has degraded to around 180 watts, peaked at 82 watts combined and generated 160wh of power - roughly 12 Ah.

They obviously do much better under ideal conditions.

[SteveJ]

When trying to collect solar in tough conditions an MPPT controller versus the cheaper PWM controller with the panels wired in series you will get a significant increase in AH collected. It could be as much as 50% depending on condition.

Have you thought of portables? I use them and it works out quite well. I'm currently camped at a place that has almost zero son for roof panels but my portables are set up about 60' from the Trek collecting lightly for most of the day but I am getting just over two hours of full sun. I am down near Bristol, TN. With 240 watts of panels and a Victron SmartSolar 100/30 MPPT controller I collected 320 watt hours of electricity, about 25 AHs. This according to the Victron app. Some light cloudiness mixed with mostly full sun. I'm having to run the furnace so I'm falling more behind each day. I'm staying for a total of two weeks so some genny time will accrue.

[Davydd]

With my second alternator, I can idle for 3 minutes to charge my batteries with 12ah.

[Davydd]

Originally Posted by CanuckRV

Another alternator is not much good parked.

Though I don't use it that way, I have the ability to Autogen or automatically have my engine start at high idle to produce at a rate 220ah (270+ah driving at 55 mph). When the battery reaches 20% of charge or a certain percentage I set of charge it will start automatically and run for 2 hours or fully charged batteries and then shut off. I have 552ah of battery or set at 80% usable = 442ah. So I can fully charge my batteries within 2 hours.

I don't bother to use the Autogen feature because as Booster said, "Usually there are occasional trips to the store, dumpstation, attractions, trailheads, etc " and with 552ah of battery I could sit in one spot 3 days anyway which i usually don't do. As I said 3 minutes of idle will produce 12ah battery replenishment cited by @Michael, or 6-7 minutes to replenish 25ah produced by 300 watts of solar panels as cited by SteveJ. Less than a 1/2 hour of driving usually replenishes an overnight battery use.

I had 460w of solar panels on my former van which was a 24 ft. Sprinter and that was the maximum I could get on the roof. I found it was useless when I had 800ah of battery and the second alternator. Now I have a 19 ft. Sprinter and more on the shorter roof (2 skylights, Maxxfaln, antenna, AC) so I opted from real experience to forego solar. Maybe I could have gotten a 100w panel, but why? Vanity? Feel good? Being a good citizen? Eventually you do have to drive a Class B. Carrying a portable solar panel takes up valuable space which I can find a more practical use for.

If you have 100-200 ah of battery you might have a use for solar that you can justify. More than that I think you have to look at other options. Solar panels simply don't make sense to me on limited capacity of Class Bs. I've opted for more battery capacity (lithium) and the more versatile second alternator over an Onan generator.

[booster]

We all need to remember that davydd uses a lot more power than many/most of the rest of us on the forum so the solar couldn't provide a meaningful part of it, especially on the short Sprinter. He also has a good cushion of battery capacity to wait for the drive.


Many with a gas frig can get by on 20ah a day, with a lot of that going to the detectors. We have a compressor frig so we use 40-60 normally when we throw in some microwave use and laptop charging and use. In hot weather with fans going all day and the frig using more we might get to 75ah per day. In decent sun we can get close to 100ah per day from the solar so unless weather is very bad we can keep up on 300 watts of solar. We also have 440ah of battery so a few days is not a big consequence for us as by the time we use up the battery plus what solar we get in bad weather, we need to go to the dump station anyway (about 5 days usually).


Everybody's use patterns are different as are their camping styles and how often they drive so all every one is going to be somewhat different. That is why we always stress that a careful power use vs all three charging sources, if you have all of them, is necessary before you start trying to figure out if you need solar, a second alternator, or neither of them.

[GallenH]

I agree with booster. It's all about how you use the power. Not so much about how much battery capacity you have.

My anecdotal case: gas fridge, no tv, no coffee maker, no microwave. I use very little power in a day. When I camp in the winter in Cibola, AZ near the CO river, I'm stationary. I don't drive anywhere (friends we camp with have a jeep that is our transportation). My 100W suitcase panel gets my battery back to 100% by noon. My experience at the Arches in Utah for 5 days was exactly the same.

Unless I'm missing something, it doesn't really matter if I have a single 100AH battery or 400AH of capacity. I'm simply replacing, via solar, what I've used.

It would also seem to matter how your trip was arranged. For example a higher power user might not be able to fully replenish via solar the result being that the battery pack would slowly diminish over days. But a night at a campground with electrical hookup could solve that issue.

Bottom line: what booster said.

[avanti]

IMO, solar is for storage, not for use. If you never store your rig where there is no shore power, you probably don't need it. But if you do, it can be an important part of the recipe.

[CanuckRV]

I have thought of a suitcase but we have no place to store one they are all just a little bit big to go under the beds or behind the driver's seat. I also worry about them walking away while we walk the dogs.

[Davydd]

I worry about a lot of things when I away from the van. A private campground with seasonal RVs is the worst. You can get stripped of chairs and anything you leave out. I use to think my Smartplug cord was safe when no one had one (I was the first installation in 2014 at ARV) but now I disconnect it and put it away as more people have them. I've had a door mat taken.