Continuing Solar build for RV.

Re: Continuing Solar build for RV.

Nvreloader wrote: »

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),

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= 1.5Ahr used
CO Detector = .11amps (constant on/24 hrs per day),

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= 2.65Ahr used
LED lite panels (2/panels per lite fixture) = .33 amps

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= 10.5Ahr p/nite use
Furnace= 9.1amps for 5 minute cycle, comes on once per/hr x 8 hrs (nite time use= 72Ahr)

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Total = 104 Ahrs used per 24hrs

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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):

http://rredc.nrel.gov/solar/calculators/pvwatts/version1/US/Nevada/Elko.html

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

Re: Continuing Solar build for RV.

Nvreloader wrote: »

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.

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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

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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

Re: Continuing Solar build for RV.

Nvreloader wrote: »

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

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.