RV Solar Calculator

[ZachO]

Someday I'll learn more, because it can be really interesting to get serious about solar and what kind of things you can run. For now, my power demands are so small that I don't need anything fancy. Jim had me convinced and I was ready to buy flexible panels, when I saw a small discount on a 100W complete kit from Renogy with a rigid panel for only $150, if I remember right. Too good to pass up so I went with it.

High quality flexible panels with VHB tape right on the roof seems like a great install to me. I used VHB for my rigid panels...but I go back & forth on whether I'll put a couple bolts through at some point. It's one thing with a light panel stuck directly to the roof. A heavy, rigid panel with an air gap underneath has a lot more potential to start flying.

[Bhamm1]

Just for grins, and because I'm bored, I went out to my Bigfoot, and measured the current for my furnace. It is the factory {2005} unit. To my surprise, the draw when lighting was 0.3 amps, and the run current was 0.2. I do trust my Fluke 336, but was surprised with the numbers.
We dry camp a lot, like 20-25 days without hookup. I have those cheap Harbor Freight 300 wat panels, and they keep up just fine, with the occasional move.
Bob

[gordon2]

Originally Posted by Bhamm1

Just for grins, and because I'm bored, I went out to my Bigfoot, and measured the current for my furnace. It is the factory {2005} unit. To my surprise, the draw when lighting was 0.3 amps, and the run current was 0.2. ..

What is the manufacturer and model umber of the furnace? (I need one that efficient!)

[OCJohn]

Mine draws about the same in ECO mode. A Truma Combi – furnace and water heater.

[ThomasC]

Originally Posted by Jim Bennett

Here it is. I have found the 240W of panel does most of our needs and keeps the batteries topped up daily, often by noon. Only on a couple of heavy overcast and rainy days when battery was used a fair bit did I not get a full charge. If I was to worry at all, I would just connect my portable for good efficient charging.

As I have mentioned, I just love the out of site, clean feature of this method.

Solar Installation - Escape Trailer Owners Community

I want to thank you again for your post. It narrowed my search areas and yielded some good results. I knew nothing about ETFE until your post and have read that SunPower cells seem to be the best.

Your Lensun panels are the best constructed ones I have come across but Sunpower makes their own flexible panels however they don't get into the construction of them. Hmmm more reading.

I have not done your installation thread justice yet because the Escape forum is not letting view the photos for some reason. Maybe because I have never posted anything or an ad blocker...I don't know. Thanks again TomC.

[JonRaw]

Originally Posted by Bhamm1

Just for grins, and because I'm bored, I went out to my Bigfoot, and measured the current for my furnace. It is the factory {2005} unit. To my surprise, the draw when lighting was 0.3 amps, and the run current was 0.2. I do trust my Fluke 336, but was surprised with the numbers.
We dry camp a lot, like 20-25 days without hookup. I have those cheap Harbor Freight 300 wat panels, and they keep up just fine, with the occasional move.
Bob

.3 Amps including the blower motor? Wow, my vent fan over the stove and the vent fan in the bathroom both use at least 1 Amp.

[k corbin]

Originally Posted by Daniel W

This is a super awesome and timely post.


I'm in early of designing a solar system for our 25RQ.


I usually lean toward the overkill side of project designs.


I'm currently leaning toward a system...
-1020w panels (6 x 170w Zamp panels)
-500ah Battleborn Lith Batts
-either 2k or 3k Victron multiplus inverter charger
-appropriately sized Victron solar charge controller
-Victron monitors


Will be installing panels with 3M VHB tape.


Seems to be one camp of wiring panels in series...
...and another camp of wiring panels in parallel.


I'm probably going to wire combo series-parallel...
3 strings of 2 in series panels.


Interested in this audience's thoughts of series vs parallel panel wiring.


I am hoping that a series-parallel approach gives me both the benefit of minimizing shading impact (parallel advantage) and plenty of voltage to the charge controller (series advantage).
Thoughts and criticisms welcome.

VHB tape works IF you have enough square inches of it. The typical solar mounting brackets do not provide an adequate number of square inches to secure a panel in place relying only on the VHB tape. Plus most fiberglass travel trailers do not have a flat surface. VHB tape is for flat surface area mounting. If the surface is not completely flat then you won't achieve the bond that many inches it is rated for because it won't be making a full strength contact. Think it through..visualize what is happening. Do not just rely on what you read in a forum. You must engage your brain cells and do deep analysis regarding what is being posted.

[gordon2]

Originally Posted by k corbin

VHB tape works IF you have enough square inches of it. The typical solar mounting brackets do not provide an adequate number of square inches to secure a panel in place relying only on the VHB tape. Plus most fiberglass travel trailers do not have a flat surface. VHB tape is for flat surface area mounting. If the surface is not completely flat then you won't achieve the bond that many inches it is rated for because it won't be making a full strength contact. Think it through..visualize what is happening. Do not just rely on what you read in a forum. You must engage your brain cells and do deep analysis regarding what is being posted.

I got a better idea.. Go to the 3M web site and read all the technical information they have provided. There is much more to know than the number of square inches and relative flatness of the surface.

https://www.3m.com/3M/en_US/vhb-tapes-us/

[ThomasC]

Originally Posted by JonRaw

.3 Amps including the blower motor? Wow, my vent fan over the stove and the vent fan in the bathroom both use at least 1 Amp.

Yeah this doesn't sound quite right. I don't know what Bigfoot uses for a furnace but I do know they use a Suburban stove. Here is a link for a 12 volt 30,000 BTU furnace.

https://www.rvupgradestore.com/Subur...-p/79-1809.htm

It is supposed to draw 4.5 amps.

[gordon2]

Originally Posted by JonRaw

.3 Amps including the blower motor? Wow, my vent fan over the stove and the vent fan in the bathroom both use at least 1 Amp.

Originally Posted by ThomasC

Yeah this doesn't sound quite right. ... Here is a link for a 12 volt 30,000 BTU furnace....It is supposed to draw 4.5 amps.

Well, I was trying to be less direct, especially since he has a Fluke meter....

Originally Posted by gordon2

What is the manufacturer and model number of the furnace? (I need one that efficient!)

But I have to agree.. the claim that any furnace in a RV only uses 2 or 3/10th amp at 12 volts is, at the very least, worthy of further verification.

[ZachO]

If it's like the older Bigfoot trailers it has an Atwood Hydroflame. All the same, the 16,000BTU furnace in mine definitely draws more than that.

[ThomasC]

Originally Posted by gordon2

Well, I was trying to be less direct, especially since he has a Fluke meter....



But I have to agree.. the claim that any furnace in a RV only uses 2 or 3/10th amp at 12 volts is, at the very least, worthy of further verification.

I'm interested because he has a Fluke meter. I looked the meter up and it is a clamp on meter. Very nice. He is measuring at the bottom of the range but according to Fluke it is still supposed to be accurate at low readings.

One interesting point is he is about an order of magnitude off or one decimal place.

[Jon Vermilye]

I had an Atwood 8012II furnace in my Escape 17B, and as far as I know, it drew the least amperage of any fan powered RV furnace @ 1.8 amps. I do wonder if there is a decimal point error...

[MelH]

Below you'll find pics of the configuration and system I use and install for others. The things that I like a lot:
SAFE: LFP battery
MONITORED:Battery data, solar data, and load use all available on Bluetooth. No display panels to install or use. I'm able to maximize LFP lifespan by ensuring it stays above 20%.
EASY: With only two parts (not counting solar cell), it's easy and fast to install; usually 4 hours. This also makes it easy to move it to another camper when the time comes and restore previous one to sell.
Its proven VERY cost effective - Plug in sites cost me about $30 more per night than dry-camping sites. My system pays for itself every 100 nights off-grid.

I've described the battery and system a little more in the classifieds. I hope this helps on things to consider.

[John in Santa Cruz]

We called clampon amp-meters 'amp guessers'.

[Bhamm1]

Reply to Gordon 2, and all else who questioned me. I did too, but did not follow up. Specifically, my Bigfoot has an Atwood 8531-IV-DCLP furnace. It is rated at 12v, 7.8 amp. Therefor, my readings were off. We are going out for a few days, and the temperature now is about 33F, so will be using my furnace in a real-life way. I will do accurate measurements.
Just for information, I put 2 6v fork truck batteries in my trailer, and have a set of Harbor Freight 100 watt portable panels. We were out last year for about 3 weeks using these, and had no problem with power. We did not use AC, which has to have my generator, so faired quite well.

Bob

[Rzrbrn]

I still have not received the solar estimate/proposal from my RV Service shop. I will continue to update and will post the proposal here if or when I receive it.

[Raspy]

I just completed the installation of (3) 100 AH Battle Born batteries, MPPT solar controller and battery monitor in my friend's Oliver. It took us one day of leisurely work to get it all done and working, including a few custom things like battery spacers in the box, adding loom on the cables, making a nice stainless faceplate to mount the monitor in to cover the rough hole from the factory, and a lot of discussion about each step. It looked like they used a chainsaw to make the existing monitor hole at the factory. Back in 2015 and 2016, Oliver was definitely behind the curve on their electrical. I've uncovered a number of problems and traced their origins to somewhat disappointing answers.

A couple of the things that had to be discussed and justified were the compatibility of the Battle Born batteries, with the bulk and float voltages of the Progressive Dynamics charger already in the trailer, and the ability to occasionally get the batteries up to the needed 14.5 volts. Can't remember the specific voltages, but the Progressive Dynamics controller was close enough that we think the solar will top off the batteries sufficiently without modifying the PD charger. Battle Born makes a "drop in" part for the PD controller, for about $225., to make it a perfect match.

The Battle Borns, seem to settle in at a rested full charge voltage of about 13.1-13.3 and the float voltage is at about 13.2 on the PD controller. The solar controller wants to drive them up to 14.5 on each bulk/absorption charge, and do it on each new cycle if the solar has the capacity. This resets every day with the sun. Battle Born says they want the bats to reach this voltage twice a week. So the match with a smart MPPT solar controller, and the PD lead acid charger is pretty close for the lithiums. If I remember correctly, the strategy in the PD controller is not current based, to get through the absorption phase, but simply jumps from bulk to float once the 14.5 voltage is reached. So, if the trailer is continuously plugged in, the 14.5 volts from the PD charger will only be seen once and then remain in float forever. That means the solar is responsible for driving the voltage to 14.5 on it's daily reset and multi-step strategy.

When boondocking this might not occur very often, but when plugged in, the bats will be at or near full charge all the time and the higher voltage is easily reached by the solar. In other words, the batteries are already topped off, so the additional voltage, beyond fully charged, is easily reached. And therefore the batteries are meeting Battle Born's recommendation. At least while plugged in, and in the sun, or when unplugged and with low current demand. Even while out traveling, it is likely they will be plugged in once a week, or so, to dump and refill the tanks, etc. This will mean a reset on the PD controller too, and a full charge to 14.5.

The performance so far appears to be vastly superior to the Trojan 6 volt AGM "deep cycle" lead acid batteries. But the system Oliver installed never, from day one, worked right. I temporarily rescued it with a cheap PWM controller at Quartzsite, just to get them home. With that, the system worked better than it ever had.

The Trojan batteries installed by Oliver, I'm afraid, are not true deep cycle batteries. They say "Dual-Purpose" and list their performance in Cold Cranking Amps. One of them failed and another one seems weak just looking at it here at home while charging, after four years of never being able to run the microwave from day one. I suspect they are all nearly dead and I'm conditioning them now in preparation for a load test. They might make good door stops.

Another Battle Born benefit, besides being able to be more deeply discharged without damage, is their light weight of only about 35 lbs. When I'm ready for new bats, these may be the ones, and the conversion is easy, even if the onboard charger needs to be upgraded. In my case, it's just a different dip switch setting on the Aims inverter/charger. I am so tired of lead acid.

[Rzrbrn]

Thank you John, well done.

[Raspy]

More thoughts on the Battle Born upgrade:

We had to fit the new batteries into the existing battery tray. This is a specific size on the Oliver and fits (4) 100 AH 6 volt AGMs or (4) 6 volt T-105s. Also, we were able to re-use the existing well made load cables that go to the inverter and connect the batteries to each other. The cables are large and well made. At least the load cables are, but the charging cables/house cables are much smaller. They are #6 THHN or equivalent house type wire. I'm not a fan of this setup! Each installation will be different, just make sure your cables are large enough, made from the right type of wire, not corroded from their use around lead acid batteries, and routed such that they don't get in trouble.

So, the Battle Born batteries have a larger footprint than the stock AGMs, but three lithiums will outperform four AGMs. And three lithiums fit very nicely into the rack, with a small spacer on each side. Plus, the existing cables bolt right on and fit well. Excellent! We made a thin rubber mat to set the batteries on and made them very comfy.

Anyone doing work on an Oliver battery box should look carefully at two things. The rivets holding the frame to the fiberglass will pull out and should be upgraded, if not already done. The catches on early pull out battery drawers had a lot of play in them and would hammer the mounts while driving. This needs to be fixed, if it is loose, and can be fixed with a wood shim to take up the slack in the mechanism. I posted about this on the Oliver site and included pictures of the piece I made to "fix" it. At the time, a number of others found theirs to be loose too, and some have had the rivets fail and the tray come loose.

The Battle Borns come in various configurations. Two of these simply place the terminals in a different position on the same battery. This has no affect on the battery specs, but costs $100. more per battery. We used the ones with the more conventional terminal layout. The terminals on the same long side of the battery. This allowed three 12 volt batteries to be set in a row, long sides against each other, with the existing cables from four 6 volt bats re-used and arranged in parallel. The + and - house cables are set at diagonal corners of the array for even charging.

Three lithiums, with a deeper discharge capability, will outperform four AGMs of the same 100 amp hour rating. So, three fit where four were, and three outperform four. This is one factor that makes the conversion easy in an Oliver, for instance, and should help in other cases too. Where you might be replacing two AGMs with two lithiums, you will get a significant improvement in performance with nearly the same footprint. Then factor in the use of solar and you might not have to upgrade your charger, if it is a newer Progressive Dynamics model. This may be a controversial conclusion, so I am open to discussion about it and perfectly willing to be shown wrong about what we did.

The cost for all of our equipment was just below $3,000. This included three Battle Born 100 AH batteries, the MPPT solar controller and the system monitor with shunt and communication wires. No new battery cables were needed. We were all done easily in one day and looking for something else to do. The system communicates through Bluetooth too, on an app on a phone. This gives state of charge, solar performance, history of load and charge over a period of time, etc. It may seem silly, but you can sit comfortably anywhere near the trailer and study what is going on, or find out how much power you have, or identify potential problems, etc. Very cool.

This is not a hard conversion, but requires some thought and care to make it the best you can make it and understand what is going on with each piece, as well as the overall charging strategy. It is also an interesting exercise in upgraded technology and overlapping systems. You will also get the most out of it by understanding it the best you can. So, it's the kind of thing that is nice to do yourself if you can. At the very least, understand the voltages you see and what they mean. Simple voltage numbers, the rise or falling rate of those numbers, what they are while under load or rested, and when during the day it is all happening, can reveal a wealth of information. With lithiums, if the system gets to 14.5 and then falls back, in the afternoon, before the sun goes down, and is still at about 13 in the morning before the sun comes up, you are golden and have reserve power. Only look for accurate power levels with no load on the batteries and after they have rested for a while. Reading the voltage while under load is meaningless and misleading.