Solar - Upgrade or replace outright?

The new-to-us coach has a small solar panel system. I would like to upgrade it to the point where I could reasonably hope to capture 50 or 60 amp-hours per day in light conditions that are less than ideal. I assume that to achieve this, I will probably need a system sized to produce 25 or 30 amps to get a real-life average of 5 or 6 amps for 10 hours. I’m not sure if any part of the current system can be salvaged for use in an upgraded system. Or if I should plan to replace everything.

Current system: According to the 1997 Safari brochure, it would appear that I have the 25 watt solar panel, plus the optional 75 watt panel. The build sheet lists only a “Siemens M65-BLK, CLA” panel. I have been unable to find specs for that on the internet.

On the roof of the coach, there are 2 panels. I see a Siemens label on the larger panel on the roof, but I see no model number. Probably it is on the bottom and the panel is fixed mounted. The large panel measures 47.25 inches by 20.75 inches and appears to have 36 cells in 4 rows of 9. The smaller panel has no visible identifier and measures 13.5 inches square. I’m sure the smaller one is a throw-away at this point. I’m not sure if the larger one can be incorporated into an expanded system.

The solar controller is labeled ASC Specialty Concepts, Inc., but has no visible model number or amperage rating. It’s not much bigger than a pack of playing cards. I expect that it, too, is a throw-away.

Although I know little about solar, the wire seems inordinately long. It comes down through the refrigerator vent, then forward about half the length of the coach to the controller under the hood on front. The battery bank is behind the rear wheels. The wire at the controller is AWG 10 THHN. I don’t know much about DC wiring, but this seems small for such a long run if it is expected to carry much power at 12 VDC.

The plan: What I envision is solar panels on the roof totaling 300 to 400 watts, with allowance for future upgrade, wired to produce 24 volts (which I assume would result in less loss over the run to the controller compared to 12 volts) to a 4-phase MPPT controller, which I would probably locate on the wall adjoining the refrigerator to keep the run as short as possible. From there it is also a relatively short run to the battery bank in back. Still, I would expect to need larger gauge cable to minimize current loss.

Does this seem a reasonable plan? Does this make all of the components of the current system obsolete? Or can anything reasonably be used for the new system?

I will appreciate the thoughts of those with more experience with solar!

Wayne

38 Replies

jrnymn7
Explorer
Nov 30, 2014
mena661 wrote:
pnichols wrote:

Yep ... how else you gonna (finally) run your RV air conditioner without a generator ... of course you may have to tow something to do it:

http://www.renovagen.com/?services=rollarray-trailergen
THAT is friggin cool!!!

And the kids could use it as a slip'n'slide when it rains! :)
pianotuna
Nomad III
Nov 30, 2014
Hi,

Victron makes a cheaper and possibly better amp-hour counter than the Trimetric.

Empty Nest, Soon wrote:
and probably a Trimetric battery monitor, I think I will have a much better idea of how much power I need to replace and can better figure what I can reasonably achieve with solar. Wayne
mena661
Explorer
Nov 30, 2014
pnichols wrote:

Yep ... how else you gonna (finally) run your RV air conditioner without a generator ... of course you may have to tow something to do it:

http://www.renovagen.com/?services=rollarray-trailergen
THAT is friggin cool!!!
Empty_Nest__Soo
Explorer
Nov 30, 2014
I have no aspirations of eliminating generator use. I just hope to reduce it by a reasonable margin by using some solar.

When I do use the generator for charging batteries, it figures to be the little Yamaha portable running the 40-amp VEC-1093-DBD charger. It is quieter and saves some money on fuel. But the main reason for this is that I like to stay out in the forest for maybe a month at a time and the big Onan generator can empty the propane tank at the rate of about a half-gallon an hour. I wish the Safari had a bigger propane tank.

After I get the DC ammeter I ordered today, and probably a Trimetric battery monitor, I think I will have a much better idea of how much power I need to replace and can better figure what I can reasonably achieve with solar.

Wayne
MrWizard
Moderator
Nov 30, 2014
its been raining all morning
right now we have heavy over cast and light rain
i just checked the watt meter and we are getting 3.3 amps of solar charge
from 505w of thin film unisolar poly panels
my laptop uses that or more.. the fridge cycles etc..
so naturally the generator is running
going to bake a YAM in the MW and heat up some ham...LUNCH
for us..Solar is an addon..it reduces genset time but NOT eliminate it
if i had 1500w on the roof, i could maybe eliminate most genset run time (but not all)

we do have a residential fridge..which was my main reason for adding the solar and increasing the battery bank

i think if we had a propane fridge, we would only need the generator for cooking and for bad weather
Empty_Nest__Soo
Explorer
Nov 30, 2014
CA Traveler wrote:
Cost wise the Trimetric is a good choice. I have the 2025 RV and would get the 2030 RV model today. . .

Thanks! And nice work mounting the shunt.

I've ordered a clamp-on DC ammeter as a first step. I'm curious to see how much parasitic load I have. I'm not sure what the parasitic baseline is, even before I start turning things on. I won't be surprised if it turns out to be many times what I had in the little TT.

The Trimetric will probably be the next step. I don't plan on camping off-grid again until springtime.

I've been reading a lot on portable solar, and for my situation that seems to make the most sense.

Wayne
CA_Traveler
Explorer III
Nov 30, 2014
Here’s a picture of my battery shunt installation. You can use a piece of copper or just a short cable. The copper shown is a flattened piece of 3/4” copper tubing.

The cable on the battery post is connected to a second parallel battery and not any loads. Hence all current passes through the shunt.
The Trimetric 2025 is connected to the display with 5 strand light small gauge cable. It the cable runs along other power cables then you might need cable with 3 twisted pair conductors.
CA_Traveler
Explorer III
Nov 30, 2014
Empty Nest, Soon wrote:

Is there a good, cost-effective choice to the somewhat pricey Trimetric monitor? I’m thinking of something that can reliably tell me how many net amp-hours I’ve used. If not, which Trimetric model do you recommend?
Cost wise the Trimetric is a good choice. I have the 2025 RV and would get the 2030 RV model today.

For me the cost was well worth it for the capability to understand loads, usage and charging. Among other things you can turn your lights, TVs, any 12V item on/off and the difference in amps is what it draws. Knowing the battery SOC, etc is very useful and it's all done inside the rig. The only downside is that you do have to install a 5 conductor cable from the battery to the monitor and you need a common ground on the batteries to install the shunt.

You can do as BFL13 suggests but about all you'll have is rough overview of your usage. You can buy very good glass hydrometers that help. But you will be outside with them and how many different days are you going to be making volt, amp and SG measurements? At least my usage varies day to day depending upon a lot of factors. And voltage measurements to determine SOC are very inaccurate unless you remove ALL loads and wait several hours for the battery to stabilize. To me what was suggested is cheaper but a battery monitor is much move valuable.

My Trimetric paid for itself on the last rig and I could say the cost is now $0.
pianotuna
Nomad III
Nov 30, 2014
Hi,

Some people have "great expectations" from solar systems that are too small to possibly be effective. This ends up giving solar a black eye.

It is quite possible to design a system to meet the needs of a user. But, they need to do their homework to know how much energy they use per day.

Their camping locations, length of stay and their style need to be considered and the size adjusted to the worst case situation they find themselves in.

Since one of the sure ways to commit "batteracide" is to never equalize a bank, my own personal belief is that is the minimum number of watts that should be considered.

It is more than possible to eliminate generator use for battery charging purposes.

For folks who full time it is a bit harder to calculate the wattage needed, especially if an air conditioner is going to be run. I have noted that wattage drawn varies between 1200 and 1900 depending on out door temperatures and how many hours the air conditioner has been run. Depending on the size of the roof it may not be possible to meet all the energy requirements. Adding panels on the sides may make an RV wider than the legal limit, so that leaves only the rear end of the RV available for more wattage.

Pay back for a full blown system capable of running a roof air conditioner is unlikely unless campground fee savings are counted against the costs.

Those of us who drive self propelled RV's do have a "back up" way to charge the battery banks without the purchase of a generator. It is much more annoying for other types to arrange to charge batteries "in a pinch".

This whole issue reminds me of water use. Some folks can "stretch" 60 gallons over three weeks, others use that much in three days.
Snowman9000
Explorer
Nov 30, 2014
BFL13 wrote:
Some people seem to think the whole idea of solar is to not ever have to run the generator. So they specify a whole football field full of solar. Others just want some extra time between recharges using their generators, even to the extent that they can do a long weekend or even a week and recharge at home when plugged in.

For the latter you can do some actual figuring using AHs and the anticipated scenario for that location and time of year. Then if the weather does not co-operate, they can always run the generator as required--no big deal.

We need to establish what the various OPs are really trying to achieve in their scenarios before automatically telling them they need the whole football field full of panels when all they want is to do a long weekend. :(

You (we) can do a week and a half off-grid with no solar at all. After that "some solar" is required. How much is "some?" That "depends." :)

I agree completely.
100W of portable solar made all the difference in the world for us.
I've added some to the roof now, but I can't see covering the roof with panels.

We still run our genset when we need the microwave etc. For me it's not worth the expense and installation bother of a huge inverter and a big solar panel system, just to eliminate that occasional genset usage.