Solar Questions

[BeerBrewer]

I'm interested in adding solar power and lithium batteries to our trailer, but I'm getting lost in the weeds.

For starters I calculated what I think would be our worst case power need (without using AC) if we went go off grid. First, it is just my wife and I, so no kids. We we wouldn't be using the Microwave, hair dryers or electric coffee pot when off grid. I calculated our power load to be about 120 amp hours a day. We wouldn't winter camp off grid, but I did assume that we may need the heat on for a couple hours, just to remove the chill. We'd only use the batteries for LED lights, to run the frig, charge up cell phones & tablets, run fans, to run TV and DVD player a couple hours at night and of course the other parasitic loads. Does my 120 amp hour estimation sound logical?

Assuming that my power swag is somewhat correct, I was thinking that we'd need two 100AH lithium batteries. Sound about right?

As for solar panels, I read that you can get approximately 30 amps from a 100 Watt solar panel, so I'd need four 100 watt panels or 400 watts worth in total. I know that I need more "stuff but does my plan seem logical so far?

[BFL13]

2 amps for TV/DVD is very low. I measured a couple of 32" TVs a few years ago in the 5er and got:

Samsung- Movie 70w, Standard, 80w, Dynamic 120w so divide by 10 for the amps.

Another TV (LG?) was: Vivid 8.2 amps, Standard 7.4 amps, Cinema 6.0 amps

The latest TVs might be fewer amps, don't know. It does show how your picture choice can matter.

[StirCrazy]

BFL13 wrote:
Inverter time does add up. 10 minutes of MW at 125 amps is 21AH. Add some movie time 3 hours at 8 amps is 24 AH.

We do pig out on 12v stuff. I read somewhere that the average RVer uses about 50AH a day.

Furnace time!

Ah, see I don't use the microwave when dry camping, and my TV/dvd is under 2amps. we started out with a tent trailer with two "car batteries" then went to a trailer where I put the four 6v batteries on it and converted everything to "power efficient" versions and the habit has carried on with the 5th wheel. with the trailer (no solar) I could go camping for a week in the Island winter on 475 amp hours, with the 5th I am not sure now as I have 480 watts of solar and I have never seen the batteries down when I go to bed in the evening. haven't taken the 5th winter camping yet though as we live in Kamloops now, but I have done late September in mid Alberta and in Banff with no power concerns.

Steve

[BFL13]

The OP said no winter camping (for now anyway) but here is an example with the 5er with six batts doing four nights with temp near freezing in January:

After two nights, next morning 12.1v (50%) and down 292 AH. (146/day)

Recharge with gen/charger (no solar) for two hours --constant 150 amps for 0.5 hr and 1.5 hrs tapering now down 78AH, restored 214AH. Figured that meant at 87% SOC of 584AH full. (Not new batts down in capacity near freezing)

So do third night, now down 227AH so 227-78 = 149 used. Now need another night, and 227 + 149 = 376 down, so would be at 208/584= 36% SOC. Oops, have to recharge again to top up to stay above 50% next day before going home.

The Trimetric monitor being very useful!

So can't continue with every second day recharge. Can restore 214 in the park gen time 9-11am and using 149/day, so can keep going if recharge every day.

You do get an extra 10% AH the first day from starting at full before going into 50-90s which can help on a weekend trip.

[BFL13]

Inverter time does add up. 10 minutes of MW at 125 amps is 21AH. Add some movie time 3 hours at 8 amps is 24 AH.

We do pig out on 12v stuff. I read somewhere that the average RVer uses about 50AH a day.

Furnace time!

[StirCrazy]

BFL13 wrote:

BeerBrewer wrote:
Unfortunately the amps that I used for each appliance came from the electrical load rating table in the manual for the trailer. I estimated the number of hours of use for each. For instance the manual claims the Frig uses 3 amps of DC power and 6 amps of AC. I assumed that when using propane there is no AC usage, but I was stuck with the DC. Since the frig runs for 24 hours per day that equated to 72 amp-hours and yet others have said that it uses only 17 to 20 amp-hours. So I TOTALLY agree with you that my numbers look high, but unfortunately I've got nothing else to go on. If you folks have more realistic numbers I'd appreciate it.

You numbers aren't that crazy. Your WH figure can come down, also the pump--you will run out of water pumping that much--take Navy showers.

Your 180AH minus ( fridge 72-17) 55 is 125 and minus 48 furnace is 77AH, which is like the 75 we use approx. Furnace is extra and it depends on ambients and rig insulation, etc.

Two 6s at 230AH down to 50% is 115 and you want 160 for two days of no furnace camping between generator recharging two hours( a 50-90 = 40% = 92AH) so you need an extra 45AH/2 = 22.5AH from solar daily to do that or else gen charge every day
)

do you use a lot of inverter time? I even find your numbers high, living in Victoria camping for new years eve out at Jordan river I had the furnace running 24/7 couple hours of movies every night, water heater and fridge on propane and so on in a 39 foot 5th wheel and only used about 45ah/day and it was chilly and windy.

Steve

[BFL13]

BeerBrewer wrote:
Unfortunately the amps that I used for each appliance came from the electrical load rating table in the manual for the trailer. I estimated the number of hours of use for each. For instance the manual claims the Frig uses 3 amps of DC power and 6 amps of AC. I assumed that when using propane there is no AC usage, but I was stuck with the DC. Since the frig runs for 24 hours per day that equated to 72 amp-hours and yet others have said that it uses only 17 to 20 amp-hours. So I TOTALLY agree with you that my numbers look high, but unfortunately I've got nothing else to go on. If you folks have more realistic numbers I'd appreciate it.

You numbers aren't that crazy. Your WH figure can come down, also the pump--you will run out of water pumping that much--take Navy showers.

Your 180AH minus ( fridge 72-17) 55 is 125 and minus 48 furnace is 77AH, which is like the 75 we use approx. Furnace is extra and it depends on ambients and rig insulation, etc.

Two 6s at 230AH down to 50% is 115 and you want 160 for two days of no furnace camping between generator recharging two hours( a 50-90 = 40% = 92AH) so you need an extra 45AH/2 = 22.5AH from solar daily to do that or else gen charge every day

To do a 50-90 in two hours on 230AH you need a 75 amp charger and a 2200W inverter gen to run it.

So it's Friday and off you go on a sunny weekend off-grid. You need to do a 50-90 on Sunday and Tuesday unless you go home on Tuesday and plug in for a full battery recovery.

Add some furnace time and you can do some gen time every day instead of every second day. You can get more battery bank if you decide to camp in the winter so you can run the furnace at 100AH a day.

If you do camp in the winter off-grid, expect hardly any solar, so it is all up to generator recharging. You can still do 50-90s every second day if you have more of a battery bank and charge for a longer time each session if it is not too cold out. Four 6s would be good.

Another thing is that 230AH is 15% less at 32F, so your bank is 195 now, and a 50-90 is only 78AH. So you need those four 6s instead of two for sure. Two for the normal 77AH and the other two for the furnace, and a 50-90 every day.

(Which is why you can camp in February and have the whole Provincial/State park almost to yourself 🙂 )

[ScottG]

Your fridge draws about an amp while running on propane. It draws close to 3 amps AC when running on 120V - maybe that;s where you got the 3A from .

[StirCrazy]

BeerBrewer wrote:
Unfortunately the amps that I used for each appliance came from the electrical load rating table in the manual for the trailer. I estimated the number of hours of use for each. For instance the manual claims the Frig uses 3 amps of DC power and 6 amps of AC. I assumed that when using propane there is no AC usage, but I was stuck with the DC. Since the frig runs for 24 hours per day that equated to 72 amp-hours and yet others have said that it uses only 17 to 20 amp-hours. So I TOTALLY agree with you that my numbers look high, but unfortunately I've got nothing else to go on. If you folks have more realistic numbers I'd appreciate it.

is it a 3 way fridge? if it is 2 way I could see that 3 amps while it is doing its lighting and such but would expect it to drop to much lower after it is lit and only run once and a while depending on temp. if it is a 3 way on DC it will be a hog, never use that LOL

Steve

[pianotuna]

BeerBrewer,

Get a Kill-a-watt meter.

Plug rv into meter

Plug meter into 15 amp outlet.

Measure the consumption for 3 days.

[BeerBrewer]

Unfortunately the amps that I used for each appliance came from the electrical load rating table in the manual for the trailer. I estimated the number of hours of use for each. For instance the manual claims the Frig uses 3 amps of DC power and 6 amps of AC. I assumed that when using propane there is no AC usage, but I was stuck with the DC. Since the frig runs for 24 hours per day that equated to 72 amp-hours and yet others have said that it uses only 17 to 20 amp-hours. So I TOTALLY agree with you that my numbers look high, but unfortunately I've got nothing else to go on. If you folks have more realistic numbers I'd appreciate it.

[StirCrazy]

BeerBrewer wrote:


TV & DVD = 30.3 AH (using and inverter for 4 hours)
Misc Lights = 5.0 AH
Furnace = 48.0 AH (4 hours at 12 amps)
Dometic Frig = 72.0 AH (24 hours at 3 amps)
Water Heater = 6.0 AH (6 amps for 1 hour)
Water Pump = 7.0 AH (7 amps for 1 hour)
Power Vents = 5.0 AH (5 amps for 1 hour)
Misc loads = 7.2 AH (LP and smoke detector, power awning use, antenna booster, etc)

Total: 180.5 AH
!

I think your numbers may be a little out to lunch. 😉

if you have a new trailer the manuals will have the actual running amps of each piece of equipment. a fridge will ramp up with it lights then drop off to almost nothing just for the control system, a furnace does the same but had a fan draw, and water heater is the same as a fridge. the furnace is probably closer to 3 ah/hr a fridge running on propane will be about 1.7 ah only when its running so depending on temp that may be 4 hours a day to about 12 hr/day, water heater same thing, almost no draw as its only the ignition then its propane . if you install LED lights and don't have them all on at the same time you could drop that down to 1 or 2 ah. as for your inverter you need to take the power consumption of what you are powering and add a few percent for the efficiency of the inverter. I only use about 70 ah/ day in a 39 foot fifth wheel and that's about 2 hours of running the converter for the coffee pot and 2 hours for the kids to watch a movie and the furnace in auto all day in September up north here.

I have 480 watts of solar and four, 235ah 6v batteries and I never have to worry about power.

Steve

[Boon_Docker]

BeerBrewer wrote:
Sorry I made a typo....Boob Docker, you are correct, I read that you can get 30 AMP-Hours per day and not 30 Amps from a 100 Watt panel.....my bad. Is that a realistic assumption?

Yes, 30 ah with a 100 watt panel on a good day is a realistic assumption.

[PatJ]

In my small class C, I have always roughly ball-parked 20AH per day minimum for fridge on gas, WH on gas, CO and propane detectors, charging phones, and factory night-lights for 12 hours. It has gotten me close.

My 40" LED TV and Sony blu-ray take very little through my tru-sine inverter. I want to say off the top of my head they are like 50w combined while running, and about 400ma from the inverter while it is idling with TV off (I turn inverter off when not using.) I might be off track there though, going from memory.

One thing I am sure of is my wife and I and one kid use 60-65 AH per 24 hour period dry camping real-world when we are running hog wild and not trying to conserve and it is cold enough to need some heat at night. If we don't watch any movies and are stingy on lights and heat it is more like 30 AH per day. With two crappy 12V LA in parallel that means fire the gen daily if you are liberal with your power, fire it up every other day if your are stingy. We don't have solar because we are always in the woods.

I am a weekender with kids, and generally not trying to be stingy with power

[mordecai81]

I have a 120 watt portable panel. The most I have ever gotten from it in one day is 40 a/hrs, and that was by repositioning it about 20 times late in the day just to see by how much I could break my old record of 28 a/hrs. 15-20 with no repositioning is more typical.