# Continuing Solar build for RV.

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• Solar Expert Posts: 5,182 ✭✭✭✭
Re: Continuing Solar build for RV.

NVR you have left the time factor off your numbers.. eg the first one would be 3 Ahr not 3A
and the last one has me confused 72Ahr per day? from a 9A instantaneous reading?

and the voltage used is important so that you can talk in Watts as well as regardless of voltage a watt is a watt...

hth

KID #51B  4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
• Solar Expert Posts: 71 ✭✭
Re: Continuing Solar build for RV.

WB
Here is what I did, and how I came up with these figures, I am NOT sure I figured the amp hrs used correctly,
Unplugged the TH from the shop electrical panel, Running on the 2-12v battery power thru/from the convertor,

Water pump,
Turned on the wp, it cycled about 5 sec? untill the pressure was reached in H20 lines, shut off wp,
then turned on the facuet and ran it untill NO water came out, then shut it off,
TURNED on the WP and the clamp on meter read 3.0amps for the approx 5 sec it took to repressure the water line.
I figured that the total time used for the day/night (24 hr period) would be approx 1 hr total time, which would = 3 ahr used?

Reefer
Reefer was running and showed 2 amps per meter,
I figured that 12 hrs of run time for a 24hr period, which would = 24a hrs used?

LPG Detector,
Was running and showed .05 amps, which would equal 24hrs x .05 = 1.2 ahrs used?

CO Dectector,
Was running and showed .11 amps x 24hrs would = 2.64 ahrs used?

Radio, disreguard, fused pull, don't use at all.

LED lights,
2-50 lite led panels per light fixture, showed .33amps x 8 lights used per night,
approx 4 hrs (assorted places) would equal = 1.65 ahrs used?

Furnance,
Started furnance, meter showed 10.5 amps at start up, then leveled off to 9.1 amp for the 5 minutes it ran and shut off by itself,
furnance runs/comes on in about 1 hr cycles, which would equal about 72 ahrs used for night time use of 8 hrs??

Water Pump = 3 amps (during it's run cycle), used 1 hr max/per day? = 3Ahr used
Reefer = 2 amps running on LPG, (don't know the cycle times yet),---= 24Ahr used
LPG Detector = .05 amps (constant on/24 per day),
= 1.5Ahr used
CO Detector = .11amps (constant on/24 hrs per day),
= 2.65Ahr used
LED lite panels (2/panels per lite fixture) = .33 amps
= 10.5A p/nite use
Furnance = 9.1amps for 5 minute cycle, comes on once per/hr
x 8 hrs (nite time use=
= 72A
Total = 104 Ahrs used per 24hrs
This is what I have come up with from my panels:
IMP rating from Panel = 7.52a
7.52a x 4 panels = 30.08a total produced x 5 hrs p/day of sun = 150a total p/day produced
75% = 115a actual amps total put back

The above figures DO NOT include any bonus I will get from MPPT CC and the tilt angles etc,
usually there is CLEAR/SUNNY and COLD weather during this time period,
temps normally run 20* to -20*, with several inches of snow on the ground etc

We normally stay about 2-3 wks per site, Oct thru last day of Feb,
I would tilt the panels to get all the sun power I can get.

Where am I making mistakes?

Tia,
Don
Re: Continuing Solar build for RV.
Water pump,
Turned on the wp, it cycled about 5 sec? untill the pressure was reached in H20 lines, shut off wp,
then turned on the facuet and ran it untill NO water came out, then shut it off,
TURNED on the WP and the clamp on meter read 3.0amps for the approx 5 sec it took to repressure the water line.
I figured that the total time used for the day/night (24 hr period) would be approx 1 hr total time, which would = 3 ahr used?

Pump may use more current (running at pressure through faucet at ~30 PSI vs repressurizing line from zero to 30 PSI or so).

On the other hand, you would probably empty the water tank in 10-20 minutes (2 gpm * 15 minutes = 30 gallons of water usage). So, the AH used per day/tank of water is probably less.
Reefer
Reefer was running and showed 2 amps per meter,
I figured that 12 hrs of run time for a 24hr period, which would = 24a hrs used?

Yep--Hot weather runs longer, cold weather less.
LPG Detector,
Was running and showed .05 amps, which would equal 24hrs x .05 = 1.2 ahrs used?

Sounds right--Lower power/current draw for your model vs others.
CO Dectector,
Was running and showed .11 amps x 24hrs would = 2.64 ahrs used?

Go to Mega Hardware and by a 4xAA powered CO detector. Should run ~1 year on a set of batteries.
Radio, disreguard, fused pull, don't use at all.

Probably two "hot wires". One is the "ignition/acc switch wire"--Larger current draw. There is probably a second battery wire for clock/memory--should be low draw.
LED lights,
2-50 lite led panels per light fixture, showed .33amps x 8 lights used per night, approx 4 hrs (assorted places) would equal = 1.65 ahrs used?

Sounds good.
Furnace,
Started furnace, meter showed 10.5 amps at start up, then leveled off to 9.1 amp for the 5 minutes it ran and shut off by itself, furnace runs/comes on in about 1 hr cycles, which would equal about 72 ahrs used for night time use of 8 hrs??

Not sure I understand your "cycle time per hour". Some examples:

If the furnace runs 5 minutes every hour:

9.1 amps * 5 min/60 min per hour * 8 hours = 6.1 AH per night

If the furnace runs 30 min per hour:

9.1 amps * 30 min/60 min per hour * 8 hours = 36.4 AH per night

If the furnace runs continuously:

9.1 amps * 60 min/60 min per hour * 8 hours = 72.8 AH per night
Water Pump = 3 amps (during it's run cycle), used 1 hr max/per day? = 3Ahr used
Reefer = 2 amps running on LPG, (don't know the cycle times yet),---= 24Ahr used
LPG Detector = .05 amps (constant on/24 per day),
= 1.5Ahr used
CO Detector = .11amps (constant on/24 hrs per day),
= 2.65Ahr used
LED lite panels (2/panels per lite fixture) = .33 amps
= 10.5Ahr p/nite use
Furnace= 9.1amps for 5 minute cycle, comes on once per/hr x 8 hrs (nite time use= 72Ahr)
Total = 104 Ahrs used per 24hrs
This is what I have come up with from my panels:
IMP rating from Panel = 7.52a
7.52a x 4 panels = 30.08a total produced x 5 hrs p/day of sun = 150a total p/day produced
75% = 115a actual amps total put back

The above figures DO NOT include any bonus I will get from MPPT CC and the tilt angles etc,
usually there is CLEAR/SUNNY and COLD weather during this time period,
temps normally run 20* to -20*, with several inches of snow on the ground etc

We normally stay about 2-3 wks per site, Oct thru last day of Feb,
I would tilt the panels to get all the sun power I can get.

Where am I making mistakes?

The furnace and the refrigerator are the big current hogs for R/Vs generally... So it is no surprise to see that here. However, until you get some better numbers for those two items, I am not sure I can give you accurate numbers. I think the furnace is high (by 2x at least?) and the refrigerator is probably close enough for now--However, if you keep the trailer fairly cold, it will probably cycle less (keep just above freezing to keep water tank from turning to ice, etc. during day when you are not there).

The other major question I would have is the 5 hours per day of sun... You can use PV Watts for Elko Nevada (or similar):

But, for deep winter, December averages from ~3.5 to 4.5 hours of sun per day (fixed at ~41 degree tilt to full 2 axis tracking). If you go with ~4 hours per day average for December with 55 degree fixed tilt:

104 AH per day * 12 volt battery bank = 1,248 WH per day
1,248 WH per day * 1/0.61 typical DC system eff * 1/4.0 hours sun per day in December = 511.5 Watt array minimum fixed array in December "break even"

Your calculations came up with ~530 Watt array... Similar answer using different modeling/assumptions.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 71 ✭✭
Re: Continuing Solar build for RV.

BB

Thank you for the info,
I see where I messed up, left off the time figures (again),

The TH was running on LPG, for the reefer/Furnance and Hot water heater, during the testing and 12v supplied power from the convertor.

Questions,

Water Pump,
What would be a better way of checking the amp draw, let the WP run/pumping water and then check the draw?

Reefer,
I could shut off the reefer for several minutes, then start it up and check the draw.
As far as how many times it cycles (on/off) per 24hr period is a SWAG, I can hear the LPG come on,
if I am standing outside next to the exhaust, but cannot hear it inside.

LPG/CO Detectors
I will be looking into getting the replaceable type battery's detectors,

Radio, disregard, don't use, pulled fuse.

LED lites
Not really worried about them, as ALL were changed out, etc

Furnance
"If the furnace runs 5 minutes every hour":
9.1 amps * 5 min/60 min per hour * 8 hours = 6.1 AH per night"

This is the correct info (above), the last few nights has been hovering around 20* during the night time,
I am not sure how to figure out the amp hr draw during COLDER temps,
I would SWAG about 10 minutes for the Real cold temps,
so the amp hr useage would be approx 13.5 AH p/night.

Hot water heater, (almost forgot),
have to find the wiring to get the readings??

As for the sun hrs on the panels, I did an average of these hrs acording to the locals where we normally stay,
was hard to get correct info as I had to use other areas/states info, as NO info was provided,
except the couple of areas that were 50+ miles away from our spots.
Again a SWAG, so I'll use the 4.0hrs of sun hrs for the panels, to be on the safe side and anything over is a +.

Why is the derating .66% and yet when figureing out the amp hr used the rating is 73%???
Kinda confusing to me.

I am planning/building for a total of 3% loss or better in my system, if possible.

So, at this time I am using 47ah per/24 hrs (SWAG) untill better info can be obtained

Info from my 220W panels:
IMP rating from Panels = 7.52a
7.52a x 4 panels = 30.08a total produced x 4 hrs p/day of sun = 120ah total p/day produced
75% rating = 90ah total put back into the battery bank of 400ah
90ah used out of a 400ahr battery bank, would = 4.4 days use to 100% DoD,
2.2 days use for 50% DoD,
or just over 1 day of use at 25% DoD, intended target percentage.

My intended battery bank was 4-220 GC battery's,
but I have the room to extend the amount of GC battery's to 8 very easy and can go bigger, if needed.

Does everything look OK?

Tia,
Don
Re: Continuing Solar build for RV.
Water Pump,
What would be a better way of checking the amp draw, let the WP run/pumping water and then check the draw?

I would just measure the current with the fixture running water--But, I believe this is going to be a small amount of your overall energy usage.
Reefer,
I could shut off the reefer for several minutes, then start it up and check the draw.
As far as how many times it cycles (on/off) per 24hr period is a SWAG, I can hear the LPG come on,
if I am standing outside next to the exhaust, but cannot hear it inside.

Using a battery monitor and/or standalone AH/WH meter is going to be more accurate and easier to use to totalize your AH/WH usage on the DC side.
LPG/CO Detectors
I will be looking into getting the replaceable type battery's detectors,

The LPG detector--You probably have the lowest power unit you will find (at least when I did a quick looik). The CO detectors, inexpensive AA battery powered units are common (in California, they are required in many buildings).
Furnace
"If the furnace runs 5 minutes every hour":
9.1 amps * 5 min/60 min per hour * 8 hours = 6.1 AH per night"

This is the correct info (above), the last few nights has been hovering around 20* during the night time,
I am not sure how to figure out the amp hr draw during COLDER temps,
I would SWAG about 10 minutes for the Real cold temps,
so the amp hr useage would be approx 13.5 AH p/night.

A good start--If it runs 6min/60min for 60F internal vs 30F external (30F differentiation), it will run 12m/60 if the temperature differential is 60F (as I recall--been a long time since I have done that math). Of course, windy weather/poor weather stripping/leaky windows will make a difference.
Hot water heater, (almost forgot),
have to find the wiring to get the readings??

Depends... A simple RV water heater may use a pilot light and thermal pile to run the thermostat/LPG valve ("wasting LPG") or electronic ignition (draw energy while sparking, possibly while monitoring). I tried to find specifications, but did not find much with a quick search.
As for the sun hrs on the panels, I did an average of these hrs according to the locals where we normally stay, was hard to get correct info as I had to use other areas/states info, as NO info was provided, except the couple of areas that were 50+ miles away from our spots.

Again a SWAG, so I'll use the 4.0hrs of sun hrs for the panels, to be on the safe side and anything over is a +.

Solar power is variable... within 10% is pretty much as accurate as you can plan to (i.e., 4.0 hours +/- 0.4 hours).

Given that you cannot control the weather, and your exact power usage, you have choices... More power (larger solar array), cut power usage during dark weather, use a genset, etc...
Why is the derating .66% and yet when figuring out the amp hr used the rating is 73%???
Kinda confusing to me.

I am using rules of thumbs that are "close enough" to get us quick back of the envelope answers. The deratings for a PWM vs MPPT controllers are different because of the differences in how they operate... However, the overall derating works "close enough for government work". Turns out that for correctly designed solar power systems, on warm days, PWM and MPPT systems are about equal overall "efficiency".

For below freezing operations, an MPPT controller can give you 10% or more power than a PWM controller--But it really does not matter much (back to within the ~10% variation due to weather, etc.).

Roughly, for MPPT controllers, the deratings are:
• 81% off of Solar Panel name plate wattage in warm weather
• 95% eff for MPPT controller in average conditions.
• 80% eff for Battery Cycling of Flooded Cell under typical usage (can be >90% for controlled cycling, 90% for AGM to ~98%)
• 85% efficiency for DC to AC inverter
For PWM controllers the 81%*95% efficiency split is "different" and due to variations in battery charging voltages. But still 0.81*0.95=0.77 overall panel+controller derating.

For your DC power system derating:

0.81 panel * 0.95 charge controller * 0.80 battery eff = 0.615 ~ 0.62 (or 0.61) DC solar power system derating

You can "play" with how you use power... For example if you use power when the sun is up, then you don't have the 80% battery cycling losses. If you run 120 VAC power, you have another 85% derating:
• 0.81 panel * 0.95 charge controller * 0.80 battery eff * 0.85 inverter eff = 0.52 AC solar power system derating
Anyway--It is always a game playing off needs against capabilities against costs.

And why we really work on power needs first as a two small system is useless--And a too large system is a waste of money and can be costly to maintain (battery bank replacement, etc.).
I am planning/building for a total of 3% loss or better in my system, if possible.
For the moment, ~61% overall efficiency for your DC system (from solar panel Rating to useful DC power), is close enough. Once you have the basic system designed--You can always go back and revisit the assumptions. But 3% "error" is in the noise.

So, at this time I am using 47ah per/24 hrs (SWAG) untill better info can be obtained

Info from my 220W panels:
IMP rating from Panels = 7.52a
7.52a x 4 panels = 30.08a total produced x 4 hrs p/day of sun = 120ah total p/day produced
75% rating = 90ah total put back into the battery bank of 400ah
90ah used out of a 400ahr battery bank, would = 4.4 days use to 100% DoD,
2.2 days use for 50% DoD,
or just over 1 day of use at 25% DoD, intended target percentage.

My intended battery bank was 4-220 GC battery's,
but I have the room to extend the amount of GC battery's to 8 very easy and can go bigger, if needed.

OK, you can do this in AH or Watt*Hours--I prefer Watt*Hours because it is "voltage agnostic". 1 amp at 12 volts is different than 1 amp at 24 volts, etc. 12 watts is the same at any voltage.
• 47 AH * 12 volts = 564 WH per day (that is a smallish system--But can be done)
The size of the solar array based on battery bank AH capacity and 5% to 13% rate of charge (assuming 2x 6 volt @ 220 AH batteries for a 12 volt @ 220 AH battery bank for an ~55 AH per day load--2 days of storage to 50% maximum discharge):
• 14.5 volts charging * 220 AH * 1/0.77 panel+controller derating * 0.05 rate of charge = 207 Watt array minimum (weekend use)
• 14.5 volts charging * 220 AH * 1/0.77 panel+controller derating * 0.10 rate of charge = 414 Watt array nominal
• 14.5 volts charging * 220 AH * 1/0.77 panel+controller derating * 0.13 rate of charge = 539 Watt array "cost effective" maximum (typical maximum)
And then sizing the array on the amount of sun... Assuing 4.0 hours of sun for good winter weather:
• 564 Watt*Hour per day * 1/0.61 DC system derating * 1/4.0 hours of sun per day = 231 Watt array minimum (based on power used per day)
Does everything look OK?

If you want to double your power usage--Then just double everything above. Don't get to wrapped up on exact losses right now... +/- 3% here and 5% over there is not really worth worrying about right now. Getting your power usage and sun in the areas/seasons you want to be right is going to be the first.

500 Watt*Hours per day is a minimal amount of power usage. ~1,000 Watt*Hours per day is a goodly amount of power (assuming no electric refrigerator, no well pump, etc.).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 71 ✭✭
Re: Continuing Solar build for RV.

Ok Guys, I am back again,
I had a complete G-bladder Blow up with removal on the 24th/Dec with some problems after the surgery,
Just starting to feel like doing some thing without a lot of pain,
Sorry for the delay,

Here is the NEW updated info from my useage etc,

I have listed the Make/Model of the OEM installed equipment tested and any other pertentant info,
like Outside temps for the furnance running times/cycles etc.

Make: Desert Fox
Model: 2009 28KS
Furnance
Make: Subruban
Model: SF30F 30,000 BTU

Amp hr draws with the inside (analog) thermastat set at 55*, lowest setting possible,
Turned on the furnance and the reading was 10.5A, then leveled out to 9.1A during running cycle.

40* Outside air temps,
Run time= 5 min on
Off for 50 min's, then recycled
9.1 amps * 5 min/60 min per hour * 8 hours = 6.1 AHr used for 8hrs per night
30* O/S temps
On time = 5 min
Off time = 40 min, then recycled
9.1 amps * 5 min/40 min per hour * 8 hours = 7.3 AHr per night
20* O/S temps (N wind blowing solid 10mph, gusts to 20+mph, DID not figure Wind Chill effect)
On=5 min
Off= 30 min, then recycled
9.1 amps * 5 min/30 min per hour * 8 hours = 12.1 AHr per night
10* O/S temps,(N wind blowing solid 10mph, gusts to 20+mph, DID not figure Wind Chill effect)
On 5 min
Off 10 min, then recycled
9.1 amps * 5 min/10 min per hour * 8 hours = 36.4 AHr per night
0* O/S temps, (N wind blowing solid 10mph, gusts to 20+mph, DID not figure Wind Chill effect)
On 5 min
Off 5 min, then recycled
9.1 amps * 5 min/5 min per hour * 8 hours = 72.8 AHr per night

I did NOT HAVE the weatherproof skirting installed during this test, will install the skirting and retest ASAP etc.
I know from prior useage, the skirting will reduce the cycle times up to 50%, with the extreme Cold weather etc,
Refer
Make: Norcold
Model: N-821 (2 way, Elect/LPG)
Amp draw = 0.6A x 24hrs= 15Ahr per 24hrs- Running on LPG,
Hot Water Heater
Make: Suburan
Model: SW6DE
Amp draw = Attempting to get measurements, has electronic igniter/running on LPG
Make: Kewwood
Model-KDC-138/CR
Amp draw
Full on = 10.9 A
Off at switch = 4.0 A
Have pulled the fuse, don't use
LED Lite panels
50x50 diodes
1 panel = .17 A, (have 4 panels per light) = .68 A per light used x number of hrs used
Water Pump = 3 AH when running/pumping water, total useage time = 2 hrs?
Amp draw per 24hrs = 6.0Ahr
LPG Detector
Make: CCI
Model: Pro-Tell 22
Amp draw = .05 A x 24hrs= 1.5Ahr
CO Detector
Make: CCI
Model: ??
Amp draw = .11 A x 24 hrs = 2.64 Ahr
Phamtom Draw, still chasing down,have some but can't find where yet, may be the PD9260 CC ??

So, the tally stands at these amounts of Amps used, (so far), will update when NEW info is found,
Don't know how to figure out a standard for the furnace draws yet, all depends on the outside weather temps,

Minimum useage:
Furnance= 36.4 Ahr?? (10* OS temp)
Refer= 15 Ahr
Hot water heater=??
Led lites= 6 Ahr = 6hrs avaerage use per night
Water pump= 6 Ahr per 24/hrs
LPG/CO Detectors= 5 Ahr/24 hrs

Rounded off figures = 70 Ahr used/24 hrs = 840 W/hrs per day

Will use 4-200A GC batterys= 800A, (can add more battery's if needed)
880 W panels installed and with MS 60 MPPT CC used,

Some thing don't look right here?? Whats wrong??

Tia,
Don
Re: Continuing Solar build for RV.
Rounded off figures = 70 Ahr used/24 hrs = 840 W/hrs per day

Will use 4-200A GC batterys= 800A, (can add more battery's if needed)
880 W panels installed and with MS 60 MPPT CC used,

I believe you are staying with a 12 volt battery bank? If so, 4x 6 volt @ 200 AH Golf cart batteries. Two 6 volt batteries in series for 12 volt. Two parallel strings for 2x 200 AH = 12 volt @ 400 AH capacity (not 800 AH @ 12 volt capacity--batteries added in series add voltage. Batteries added in parallel, add Amp*Hour rating).

I think that is where you went wrong.

Charging 5% to 13% rate of charge:

400 AH * 14.5 volts * 1/0.77 panel+controller derating * 0.05 rate of charge = 377 Watt array minimum
400 AH * 14.5 volts * 1/0.77 panel+controller derating * 0.10 rate of charge = 753 Watt array nominal
400 AH * 14.5 volts * 1/0.77 panel+controller derating * 0.13 rate of charge = 979 Watt array "cost effective" maximum

So, your 880 Watts of panels are nice. Are you going to tilt them during winter (near vertical?)? Where will the system going to be used/installed to calculate typical available power?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 71 ✭✭
Re: Continuing Solar build for RV.

BB,
Thanks,
I keep forgetting that the GC battery's are 6V..............not 12v. :grr

Hunting season, (Oct/Nov)
I plan to tilt the panels when we are set up for more than a couple of days,
I am attempting to figure out the correct tilting angles for the panels, kinda confused on the angles they show,
I hope they mean 90* is straight up and 60* is off that angle etc.

We normally spend 10 days/2 wks at a time at each camp spot, most of the time it is the Northern half of NV/OR/ID,
depending where we draw or have tags for etc.

During trapping season,
We will be within 50+ miles of NV's North border, all the way across the state, for/during the months of Dec/Feb.

Would there be anything to add/change to my solar setup to get the most from it,
as it stands now, seeing how it is going to be used?

Tia,
Don
• Solar Expert Posts: 5,182 ✭✭✭✭
Re: Continuing Solar build for RV.

Just make sure there is NO SHADE , just a little bit will cut your production by as much as 50%! Don't ask...

KID #51B  4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
Re: Continuing Solar build for RV.

You can use PV Watts to get an idea of what would work. Assuming Winnemucca NV, tilted 41 degrees from horizontal (some programs use degrees from vertical):

Month
(kWh/m 2/day)

1
3.76

2
4.40

3
5.41

4
5.98

5
6.00

6
6.49

7
6.92

8
7.00

9
6.82

10
5.65

11
3.97

12
3.54

Year
5.50

56 Degrees:

Month
(kWh/m 2/day)

1
4.00

2
4.53

3
5.27

4
5.53

5
5.28

6
5.54

7
5.96

8
6.35

9
6.57

10
5.75

11
4.18

12
3.81

Year
5.23

90 degrees (vertical)--Probably does not include reflection from snow field in front of array (90 degrees, panels can be mostly self clearing, if high enough off ground):

Month
(kWh/m 2/day)

1
3.69

2
3.90

3
3.93

4
3.52

5
2.91

6
2.77

7
3.02

8
3.75

9
4.64

10
4.75

11
3.78

12
3.60

Year
3.69

If you assume a minimum (long term average) sun of 3.81 hours per day, and a 70 AH per day @ 12 volt load:

70 AH * 14.5 volts * 1/0.77 panel+controller derating * 1/0.80 battery eff * 1/3.81 hours of sun per day = 432 Watt minimum array (based on loads)

Based on the panel size for a 400 AH battery bank in the earlier post:

400 AH * 14.5 volts * 1/0.77 panel+controller derating * 0.05 rate of charge = 377 Watt array minimum
400 AH * 14.5 volts * 1/0.77 panel+controller derating * 0.10 rate of charge = 753 Watt array nominal
400 AH * 14.5 volts * 1/0.77 panel+controller derating * 0.13 rate of charge = 979 Watt array "cost effective" maximum

I would be suggesting 432 Watt minimum array... And if you don't want to run a genset very much, 753 Watt or larger array would be very nice. Looks like a pretty sunny area (as far as winter goes). Of course, when you have a storm moving through--Almost no practical sized solar array will produce very much useful power when the weather has blotted out the sun.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 71 ✭✭
Re: Continuing Solar build for RV.

BB,
Thanks for the info,

As it stands now, the following will be what is used/installed:
880w of panels,
400Ah of battery's,
Daily useage will be around 70Ah/840w of power,
MS 60 MPPT CC,

HD sized cables used in all the correct places for battery/CC etc,
Average of 4hrs of available sun light, (I know it will be closer to 5+hrs available),

Solar panels will be tilted to gain the best from the sun angles, around 60* (as a swag at this time)??,
I have to figure the angle of the RV domed roof, 6" rise/center height in 102" of width,
panels will be mounted/tilted from the bottom of this roof edge/angle,

Normally, there is clear,bright/sunny days with Cold temps of 10* to -20* average temps,
Normally with 2+ inches of snow on the ground,
Storms normally last 2-3 days,
41* tilt = 4.26hrs of sun (average)
for the months of Jan/Feb/Oct/Nov/Dec,

56* tilt shows = 5.56hrs of sun (average)
for the months of Jan/Feb/Oct/Nov/Dec,

90* tilt shows = 4.93hrs of sun (average)
for the months of Jan/Feb/Oct/Nov/Dec,

If you assume a minimum (long term average) sun of 3.81 hours per day, and a 70 AH per day @ 12 volt load:

70 AH * 14.5 volts * 1/0.77 panel+controller derating * 1/0.80 battery eff * 1/3.81 hours of sun per day = 432 Watt minimum array (based on loads)

Based on the panel size for a 400 AH battery bank in the earlier post:

400 AH * 14.5 volts * 1/0.77 panel+controller derating * 0.05 rate of charge = 377 Watt array minimum
400 AH * 14.5 volts * 1/0.77 panel+controller derating * 0.10 rate of charge = 753 Watt array nominal
400 AH * 14.5 volts * 1/0.77 panel+controller derating * 0.13 rate of charge = 979 Watt array "cost effective" maximum"
It would appear that I have enough to work for what I want to do, with a 880 watt system,
plus this is not factoring in anything gained for tilting/cold weather effects etc?

I am attempting to figure out the "rate of charge" formula for my system,
A swag of 11.5 % of charge for 880 Watt array??

Where do I go from here?? There has to be another "Monkey wrench" waiting for me!!!!!!

I greatly appreciate ALL the time/help you, and all the others that was provided to me with this project.
For some reason, this solar stuff gets me confused. :grr

Tia,
Don
• Solar Expert Posts: 71 ✭✭
Re: Continuing Solar build for RV.

West Branch,
Thanks,

I have already planned for/figured out the best loctions for the panels, using cardboard sized panels tilted to approx angles needed,
during these last months with NO shadows on any panel, RV set on a East/West angle approx, the radio ant caused a shadow,
but will be moved to a better location, since it is not used at this time, can't recieve any signals out in the Boondocks, :grr fuse pulled !!

Tia,
Don
• Solar Expert Posts: 71 ✭✭
Re: Continuing Solar build for RV.

Guys,

Have some more questions,

Do I have a fairly balanced system, with the 880 watt/400A battery system, MPPT CC, what could be better?

What would the "rate of charge" be for this system?

As a SWAG, in your opinion, what % could be gained for tilting/cold weather effects etc?

Tia,
Don
Re: Continuing Solar build for RV.

And you have a 12 volt battery bank....

880 Watt array * 0.77 typical panel+controller derating * 1/(400 AH * 14.5 volts charging) = 0.117 ~ 11.7% rate of charge

Remember that Rate of Charge is just one factor in a "happy" battery bank (5% to 13% usual recommendation).

If you have loads during the day, each load takes amps/watts from the array that is not not available for charging the battery bank.

Also, number of Watt*Hour/Amp*Hours per day needed vs month(s) of the year... If you pull more energy from the battery bank than the array can return--Either you need a genset, need to reduce loads, or have higher stresses on the battery (i.e., running them towards dead).

Don't focus on one parameter... You need to understand the entire operation (loads, amount of sun, seasons, using backup genset, etc.). Certainly, the more solar panels you have, the less you have to worry about your loads/random poor weather conditions. But, of course, you cannot just simply toss any and every load at the solar power system--It does have its limits.

We can use PV Watts (and other tools) to estimate the "average" solar array/system output. And, of course, the amount of avialable stored energy in the battery bank (we have forgotten to talk about battery temperature--Batteries >40F will perform better than batteries below freezing. And discharged batteries with low specific gravity will freeze at warmer temperatures (100% charged, below -70F freezing. Near dead, near 32F freezing).

Have talked about backup power (genset, using vehicle alternator to charge, etc.). How much fuel, willing to use a Honda eu2000i + XX gallons of fuel for backup power (during cloudy weather, availability of backup fuel within reasonable drive of camp, cutting power usage, cutting trip short, etc.).

Setup for backup genset/power source if bugging out of camp due to genset or solar power system failure is not a good option, etc...

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 71 ✭✭
Re: Continuing Solar build for RV.

BB,

Thanks for the reminder, 12v and the formula,

I also forgot, there will be a Trimetic battery moniter for the batterys, all of them and a gage for the MS 60 MPPT CC set up inside the RV for complete monitering of this system.
Normally we leave camp and are gone for the whole day, so there won't be much useage from the system, we normally set everything to the minimum settings (furnance) and shut off all equipment not being used etc, if the better half stays in camp she always runs the OEM 4000w gen set when cooking/heating etc, there is also 2-Honda 2000w gensets for back up, along with the 2-12v tongue batterys from the OEM setup.

The 4 battery/solar rack will be mounted underneath the RV Toy Hauler, tucked up inside the frame rails, there will be a heat duct from the furnance for heating this battery area, which will be semi sealed and insulated, along with the weatherproof outside skirting that wraps completely around the RV, this skirting holds the heat underneath the RV. I also have a portable temp gage setup underneath to moniter the temps and is part of the weather station we use to check for pending weather conditions for hunting/fishing/camp use etc.

We have seen several times that the snow, (several inches deep) we setup on underneath the RV has disappeared after several days of setup using the skirting etc. This will help keep the underneath battery rack above the 32* mark or higher. I don't think (at this time/unknown factors with underneath RV temps) that I can provide the IDEAL temp of 70*, but the temps should be around 40+* due to the skirting use, once set up.

Is there anything else I am missing or forgetting??

Tia,
Don
Re: Continuing Solar build for RV.

Nope--Sounds like you are off to a good start... I am not sure I completely understand your daily WH/AH loads--But, if you have room, you can add a couple more panels if needed (and to support you through bad weather a bit better).

I have seen a few RVs that were short of roof space install solar panels on a frame and use it as an awning. But that is a project in its own right (picking panels, how to make frame/mount and still be light and strong enough for the job).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 71 ✭✭
Re: Continuing Solar build for RV.

Bill,

After conducting several electrical useage audits, and finally getting reliable results,
this is the amount of electrical useage for the RV, for these items/equipment,

Minimum useage:
Furnance= 36.4 Ahr?? (10* OS temp)
Refer= 15 Ahr per 24/hrs
Hot water heater=?? pending
Led lites= 6 Ahr = 6hrs average use per night
Water pump= 6 Ahr per 24/hrs
LPG/CO Detectors= 5 Ahr/24 hrs

Rounded off figures = 70 Ahr used/24 hrs = 840 W/hrs per day

The ONLY BIG UNKNOW VARIABLE will be the night time outside temps, for the furnance running/useage, which will change the useage amount,
I took a SWAG at the usual/average night time temps at 10 degree for 37Ahr useage.

See below useage at the different outside temps,
The minimum furnance useage will be= 6.1 Ahrs, 40 degree night time tempatures,
and the maximum furnance useage will be=72.8 Ahrs, 0 degree night time temps.

Furnance
Make: Subruban
Model: SF30F 30,000 BTU

Amp hr draws with the inside (analog) thermastat set at 55*, lowest setting possible,
Turned on the furnance and the reading was 10.5A, then leveled out to 9.1A during running cycle.
With NO skirting installed.

40 degree- Outside air temps,
Run time= 5 min on
Off for 50 min's, then recycled
9.1 amps * 5 min/60 min per hour * 8 hours = 6.1 AHr used for 8hrs per night
30 degree- O/S temps
On time = 5 min
Off time = 40 min, then recycled
9.1 amps * 5 min/40 min per hour * 8 hours = 7.3 AHr per night
20 degree-O/S temps (N wind blowing solid 10mph, gusts to 20+mph, DID not figure Wind Chill effect)
On = 5 min
Off = 30 min, then recycled
9.1 amps * 5 min/30 min per hour * 8 hours = 12.1 AHr per night
10 degree- O/S temps,(N wind blowing solid 10mph, gusts to 20+mph, DID not figure Wind Chill effect)
On = 5 min
Off = 10 min, then recycled
9.1 amps * 5 min/10 min per hour * 8 hours = 36.4 AHr per night
0 degree- O/S temps, (N wind blowing solid 10mph, gusts to 20+mph, DID not figure Wind Chill effect)
On = 5 min
Off = 5 min, then recycled
9.1 amps * 5 min/5 min per hour * 8 hours = 72.8 AHr per night

I am not sure how to figure out the furnance useage amounts because of the unknown outside night time tempatures, etc.

So, at this time, the minimum Ahr useage can be, 39 Ahr and or a maximimum of 105 Ahr, all depends on the furnance running time etc.

Tia,
Don
BB. wrote: »
• Solar Expert Posts: 140 ✭✭
Re: Continuing Solar build for RV.
BB. wrote: »
I have seen a few RVs that were short of roof space install solar panels on a frame and use it as an awning. But that is a project in its own right (picking panels, how to make frame/mount and still be light and strong enough for the job).

-Bill

That sounds like an application for which the Renogy 100W bendable panels would be a good fit, given their light weight of only 4 pounds each.
• Solar Expert Posts: 71 ✭✭
Which would be the best wire construction type,
Meaning number of wire strands/ wire strand diameters to use from the battery bay to the MPPT CC, in 4/0 size?

Heavy thick wire strands, (Welding cable), 5000+ fine wire strands, 10,000+ wire strands?

Which type of copper lugs, closed end or open end to use?

I have 12 ton and 20 ton hydrolic crimpers, to crimp with, and will have a good coating of dieletic grease and glued type heat shrink coverings, for the terminal ends etc.
I will have less than a 10' run for these cables, from the battery rack underneath the TH to the electrical bay/CC location.
Tia,
Don
ps, you changed the forum formatting, took me a while to figure it out.

• Solar Expert Posts: 5,182 ✭✭✭✭
Don, when I did my analysis of useage I did up a spreadsheet and plotted my use for each hour of the daytime and lumped the nightime loads together we I added everything up, as well I looked at the day in 3 periods, Morning, when there is a peak in use, midday and evening when supper is made, to see just what peaks I might have... doesn't change total consumption but you see things a bit differently by looking at the periodicity of use.
hth

KID #51B  4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
• Solar Expert Posts: 71 ✭✭
West Branch
You have lost me, are you replying to my post #80 about the wire types??
Or another post???

Tia,
Don
• Solar Expert Posts: 5,182 ✭✭✭✭
response is to #78 where you list all loads over the day

KID #51B  4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
• Solar Expert Posts: 71 ✭✭
WB
Thanks for the info, that clears up the confusion of your post.
That response #78 was to help explain what the approximate useage would be, but do to the unknown temps, it would be hard to get an exact figures etc.
Tia,
Don
• Solar Expert Posts: 5,182 ✭✭✭✭
err to the high side in planning and if/when you are running and use less it is a bonus..:D.

KID #51B  4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
• Solar Expert Posts: 71 ✭✭
WB
+ on that info, that is what I have been attempting do, all thru this build, within reasonable limits.
I only want to have a good system for our use etc and build it once.

I am going on to the battery cables/wiring section now,
have several types/choices to sort thru (meaning # of wire strands types), welding cable, or 5000+ strands or 10,000+ strands of wires, all is pure copper material, just not sure which one to use etc??
Thank you for your time and trouble,
Tia,
Don
I would only use fine strand (high flex) cable if you need it... Battery bank cables are nice if high flex, but fine cables also have a lot of air gaps and small strands--The small strands and gaps can attract moisture and electrolyte. Heavy strands hold their shape and be a bit more rugged in stationary applications... Plus most NEC type wire clamps hold coarse and solid stranded and pretty much fail at clamping/holding fine gauge welding cable.

If you can get the correct lugs to crimp the fine strand welding cable (and the proper dies), of course, this would be good too--Especially for battery cabling.

Insulation type can be an issue--Pulling welding cable through conduit may not be easy if rubber type insulation vs the slick/hard type insulation.

Our host, NAWS has this information:

http://www.solar-electric.com/installation-parts-and-equipment/wiring-cables-and-connectors/hardware-wire/bainca.html
Note: We are currently transitioning from using welding cable to using MTW UL listed cable for all of our battery/inverter wiring. Many solar companies sell welding cable for use with batteries and inverters. There's no safety issue when using welding cable, but it can cause problems with some electrical inspectors. Technically, welding cable is only meant to be used on welding machines. When welding cable is used on anything but welders, it violates the national electric code (NEC). This is why we've started using MTW listed cables. MTW stands for "Machine Tool Wire" and it's essentially the same thing as welding cable, but with a more versatile electrical listing. This means it's approved for many more uses than standard welding cable. If you would like to learn more about cable and wire listing and use, please read this article entitled "Clarifying Confusing Cables" from Home Power Magazine. All other cables are welding cable, unless otherwise specified.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
From my experience open-ended connectors were preferred because they had inspectable cable ends.

Closed end connectors could not be inspected to ensure all strands made it through and are crimped.

My two cents.

-Bill

P.S. I have also seen closed end connectors with small inspection hole so you can see the cable is fully seated before crimping.
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 228 ✭✭✭
Three other heating possibilities that are more efficient a a catalytic heater, an Eberspacher/Espar diesel heater, http://www.eberspaecher-na.com/ (Espar here in the US), and Propex propane heaters http://http//www.propexheatsource.co.uk/heaters/hs2000 also available in the US.
• Solar Expert Posts: 1,218 ✭✭✭✭
Just a reminder to folks that this thread is a very good lesson to always tally your loads in watt hours. Using amp hours is a mistake for three reasons.
- system voltage is a variable in the design stage
- battery terminal voltage can vary depending on how heavy the load is.
- brings the numbers into a universal language that all can understand without translating to system voltage.

Then, the final piece is to make it Wh/day, and then you are set. That involves knowing:
-  how many watts each device uses,
-  for how long,
-  on a typical day.

Once you have that, then you have a good handle on your loads, and have the best chance of having a balanced system.

1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
http://zoneblue.org/cms/page.php?view=off-grid-solar