My new solar system for my "new-to-me" Kustom Koach KC280

The parts:

4 Unisolar us 64 panels (total 256 watts) shade tolerant with diodes between each of the 22 cells . This means that if one cell is shaded I lose only 1/22 of the voltage on the panel. Most other panels if even one cell is shaded output drops to near zero.

1 blue sky 3024i charge controller with battery temperature sensor

1 2500 watt cobra inverter modified sine wave.

The wiring:

I added a new 115 volt outlet in the waste water valve hatch as I boondock at extremely low temperatures.

I added a cord from the rear of the RV where my generator lives on a rack to the shore power box. This will be used in hot weather to power the air conditioner.

The RV was prewired for solar with a #10 wire (too small imho).

The panels are wired in two banks of two in series using #12 wire that is twinned (i.e. four wires for each panel–two for the negative and two for the positive) to a combiner box under the fridge hood. Two panels are at the rear with 11 feet of wire, one is behind the air conditioner with 4 feet of wire and one is beside the air conditioner on the drivers side of the coach with 7 feet of wire.

The #10 goes from the fridge hood to the charge controller.

I used #8 wire from the charge controller to the battery

The wires are twinned to the inverter using #4 (because that was the maximum size the inverter terminals would accept) and there is a catastrophic failure fuse rated at 350 amps at the positive battery terminal

The inverter output is sent via a #10 wire to a plug in the shore cord box. When I disconnect from shore power I simply plug the shore power cord into that outlet. Before I turn on the inverter I manually trip the breaker that operates the stock converter for the RV.

The batteries are what came with my RV. They consist of two 105 amp hour 12 volt batteries–and another one that doesn't' match and may be of lower capacity. I intend to change them in the future–but I want to see just how much energy I can draw from them first before getting replacements.

The results:

The "overhead" for running the inverter is about 1 amp. It is a cobra 2500 modified sine wave–chosen because of space limitations. It "lives" behind the driver's seat which allows a cable run to the house batteries of less than four feet.

It was interesting to note that the stock converter only brings the batteries to 13.8 volts.

A side bit of information is that I found out the charging voltage from my solenoid based isolator is 14.2 volts. So while I'm driving the solar panels will boost that up to the correct float value.

On day one I was trundling down the road and had my 1120 watt water heater on (by accident not design). I gathered about 84 amp hours (nominally 1000 watts) from the solar panels.

Charging from the solar panels started at 6:15 am and was 0.2 amps. It rose to a peak of 17.2 amps. The morning was cloudy, so at noon I was gathering only 6.5 amps. The afternoon turned sunny and I had solid readings of 13 amps from 1 pm. to 4 pm.

I found out that even trees bare of leaves dramatically reduce the output from the solar panels. Thank goodness I got the shade tolerant type!

Day 2 started with the batteries at float charging (not completed but showing 14.8 volt). 85.9 amp hours were gained from solar. The vacuum, hot water heater, the microwave (one minute only, for testing purposes) and a small portable electric heater were in use, on and off during the day. Later in the day as it got warm the fantastic fan was used on high to suck air out of the RV. I also used solar power to drill 68 holes, and drive 68 #6 1.25″ screws.

The lowest battery voltage reading I noted was 11.5 volts, but when I turned off the inverter that bounced back to 12.2. Final battery voltage was 12.3 at 8 pm.

I had a 14.9 volt reading with the temperature at 10C–so I know the temperature compensation is working! It is in an inverse relationship–as temperature rises voltage drops by 10 millivolts per 1 degree Celsius. The 3024i is preset to 14.4 at 20 C–but from what I'm observing it takes it to 14.8 (@20C) then allows voltage to sag back to 14.4.

If I'm standing still I think I'll have over 1000 watts (100 amps) on a sunny day to charge and power the RV–with a reserve of 1500 watts (without dropping below 50% charge state) from the batteries.

I've been waiting for an overcast day–which finally appeared May 8, 2009. At high noon output was 8 amps (or ~115 watts), and at 4 pm. it was still 3 amps (or ~40 watts). I'm quite favorably impressed with those numbers. Perhaps 500 watts on a totally overcast day.

All in all, I'm extremely happy with the new system–it certainly will be of great use to me as I frequently boondock–and I try as much as possible to avoid propane use. I'll be running the fridge on 12 DC, and the water heater from the inverter. I'm a bit of a rolling stone and rarely spend more than two days in one spot, so I think that my system will produce enough energy that I can boondock and not worry about conservation at all. I have led bulbs to install from my old RV–but I've simply not gotten round to moving them over. I'll likely do that this weekend.

I'll have more results tomorrow.

May 16 report:

10:00 AM voltage 13.1, charging at 10.1 amps. Sky was clear This represents a C 30 charge rate which suggests batteries are about 65% of capacity.

Kill-o-watt meter reading was 630 watts over a 24 hour period or 26.25 watts per hour

3:00 PM voltage 14.8 and 3024di (charge controller) indicating float charging at 7.0 amps. Sky was cloudy. This represents a c 42 charge rate which suggests batteries are at 115% of capacity

I'll not be doing another report for a week as I'm off in my old RV with my brother who is now the proud owner.

Hi all,

The batteries were full up today and I'm preparing for my trip in June, so I decided I'd "play" and see how things went with running the air conditioner from the inverter with the engine on the RV *not* running.

I started the fan first on low–and my kill-o-watt meter suggested a draw of 175 watts. Then I tried high fan and wattage jumped to 225.

I put the fan back to low, turned the thermostat up to 100 degrees, switched the thermostat setting to cool, and slowly slide the temperature indicator down to where the air conditioner compressor cut in.

The inverter didn't even burp and the draw according to the kill-o-watt meter was 960 watts. (I suppose about 80 amps).

I'm pleased as punch!

Are there any concerns I need to worry about if I'm trundling down the road and wish to use the roof air conditioner? The alternator is rated at 130 amps and I get about 12 to 14 amps from the solar panels.

Hi all,

I did the "draw" on the block heater and the results are making me smile from ear to ear.

It takes 584 watts–which means I can run it for over 3 hours without using more than 50% of my current house battery capacity! That is without the solar panels providing any energy at all as well!

That's enough time for the block heater to reach "steady state"–so no more dragging the generator over in very cold weather for this RV'er!

The generator will be relegated to those few times where I wish to take the RV somewhere and *not* move for a week or more.

Hi all,

Well I'm back from a 9000 kilometer trip–lots of boondocking.

My panels put out 20.8 amps at one point–which is higher than their rated output. I'm very pleased to say the least.

I was able to run the Fridge on 110 volt from the inverter and the panels were able to handle the load. As a side light I also found out that when the Fridge thermostat cycles that the demand in watts drops way down.

Hi all,

Hurrah! I have my four extra batteries installed.

I decided against welding a rack under my RV and gave up one storage compartment (there happened to be one of suitable size right beside the existing side out battery tray).

My cousin did the work. He welded a support brace under the compartment so that it would be much stronger than the original construction. He placed a piece of 3/4 inch plywood in the bottom of the compartment and secured the batteries with a wooden "frame" to keep them from shifting. He also added an "air hole" so that there can not be a build up of explosive gases.

The four batteries are tied together electrically by two copper bus bars. The positive one is covered in tape insulation.

The original solenoid had only blown a fuse–so that fuse was replaced with a 50 amp fuse. (all he happened to have)

A second solenoid was added–tied into the starter battery and fused at 60 amps.

This should give me a combined charging amperage of 120 amps–10 amps less than the maximum output of the alternator.

This also gives me "redundancy" if either solenoid or fuse decided to "pack it in".

The original solenoid was factory designed to connect once the engine was running. This has been changed to a manual switch with an led indicator light built in so I can control it. The new solenoid also has a similar switch. This has the side benefit that if I turn on the ignition key and flip the switches that power will flow from the house batteries to the starter battery. This means if the starter battery is low I can recharge it from the house batteries. It would take a few minutes for this to build up a sufficient charge in the starter battery, should it happen to be low. When starter is engaged the house batteries are disconnected. It's not a perfect system–but far better than the original design which did not allow any connection until the engine was running. The solenoid switches are disabled when the ignition key is in the Aux or Off positions.

Each battery bank can be charged from the alternator via the two switches–so I can avoid over loading the charging capacity.

Each battery bank has its own 100 amp disconnect switch to the inverter, so I can run 3 or 4 or 7, or if I really desire to do so 8 batteries (flipping the solenoid switches on with the ignition turned on {a poor idea, imho}). Running all 7 would give the best Peukert results, while protecting that all important starting battery.

The solar panels are able to charge either bank–again via a set of two switches. The switches are rated at 25 amps and are fused–and have lovely led lights in them to let me know whether they are "on" or "off".

One downside to that is that if the inverter is running on one bank–and the solar switches are both turned on the system can "back feed" through them and burn out a fuse. The way around that is, of course, to have both disconnect switches in the "on" position, and only one solar panel switch turned "on". That still allows the solar to add to the energy available without any back feed being possible. A diode could have been added–but that would have "cost" 3/4 of a volt, a sacrifice I was not willing to make.

All in all, I feel it is a brilliant piece of work and allows great flexibility.

Hi all,

My next "mod" will be fairly straight forward. On my next visit Stateside I'll replace the three old tired deep cycle batteries with brand new 12 volt units from Walmart. They sell a battery that is 105 amp hours for $75.00, ($225 in total), and I've had wonderful service from the ones I bought for my previous RV six years ago.

I'll also replace the dinky toy sized starter battery that Village RV of Regina "gave" me when I purchased the Kustom Koach. I know that with the system I have that is perhaps money I don't need to spend–but a 650 cold cranking amps battery on a Ford Triton V-10 seems to me to be undersized.