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Twistedlarch

Cottage Grove, OR.

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Posted: 04/12/20 11:24am Link  |  Quote  |  Print  |  Notify Moderator

I'm trying to determine whether my current solar system is adequate or if I need to add more panels/batteries.

Currently I have 2 6 volt lead acid batteries.
I have 300 watts of panels
40 amp controller

I'm curious as to how many Amp hours my trailer uses.

Small 3 way fridge running on LP
CM detector
Stereo on standby mode
Water pump

I usually try to use battery powered lights at night.

The kids also watch a movie to unwind at night, the TV and DVD player run on a separate small battery hooked to an inverter. Small battery will be charged during the day from the panels.

We keep water use at a minimum.

I also have two dual USB charging ports.

Heat is set at 60. Night time outside temps can dip down into the high 30's in Spring and late Summer where we usually camp

Our usual camping area is at 4,500-5,000+ altitude with pretty intense sun in the afternoon.


Thanks
Brian

Lwiddis

Mono Basin National Forest Scenic Area

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Posted: 04/12/20 11:49am Link  |  Quote  |  Print  |  Notify Moderator

Separate batteries for lights and separate batteries for kids to watch TV. Trying to limit water pump use. What a PITA! Two six volt batteries doesn’t tell us their AH rating. 300 watts of solar can feed batteries with 300 AHs under “good” conditions. Do an energy survey. Determine your AH needs and multiply by 1.5. Buy batteries with double that storage capacity. Then you can determine how many solar watts are necessary and if your present controller is up to the task. Make sure your wiring is adequate to keep losses minimal.


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Lwiddis

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Posted: 04/12/20 12:00pm Link  |  Quote  |  Print  |  Notify Moderator

All this solar/battery math and surveying should have been done prior to you mounting any panels as you posted on March 27.

Camper8251

Big Sky Country

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Posted: 04/12/20 12:34pm Link  |  Quote  |  Print  |  Notify Moderator

Nobody will be able to answer this for you. Way to many variables.
Need a meter or something else..

Kind of like saying what is may cars MPG without telling anyone want type of car what size motor etc etc


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jdc1

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Posted: 04/12/20 12:34pm Link  |  Quote  |  Print  |  Notify Moderator

The only killer usage is the heater motor. Use a "Mr Buddy" heater and you're fine. Change out all the light bulbs to LED's too (Amazon...least expensive)

Bigbird65

Arlington Texas

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Posted: 04/12/20 12:39pm Link  |  Quote  |  Print  |  Notify Moderator

My suggestion would be to buy a digital DC current meter. Fully charge the batteries, clamp the meter over the positive lead and turn all the DC items you mentioned. Amazon has several to select from. Good investment.


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CA Traveler

The Western States

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Posted: 04/12/20 12:41pm Link  |  Quote  |  Print  |  Notify Moderator

Furnace is your main draw. You can use a DVM to measure voltage (battery has to be completely at rest) hence look up SOC and then Ah used. There are inexpensive volt/amp measuring devices on up to better battery monitors.

I use to just check voltage and based on prior experience with the rig I was an adequate "battery monitor".


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RickLight

Washington

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Posted: 04/12/20 12:52pm Link  |  Quote  |  Print  |  Notify Moderator

There are 2 main ways to determine how much you use.

1. Get a battery monitor and let it measure actual use. There are hundreds of discussions here on battery monitors.

2. Try to figure out how long you use each device and multiply that by the load. This can get pretty hard and very detailed as your uses will vary. The CM detector and fridge electronics are easy, measure them if you can't find the load printed out. Water pump and USB will probably vary widely day to day. Furnace fan is a huge load, but dependant on temps, insulation and how often you open the door! There are some spreadsheets around to get you started (not sure if they are here or on other sites) but the more info you can get from your rig and your use the more accurate the estimate. Guesses by others will be all over the map!

I suppose there is one other method. I assume you have run out lately. If you can charge up what you use in a day, then you have enough solar and more battery is needed. If you only run dry at the end of a trip then more of either will help.

My solution to all this is a small generator to fill in as needed. More solar = less generator time. More battery = less frequent generator time.


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time2roll

Southern California

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Posted: 04/12/20 01:01pm Link  |  Quote  |  Print  |  Notify Moderator

If the idle voltage is 12.2+ when you get up in the morning you are good to go.


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theoldwizard1

SE MI

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Posted: 04/12/20 04:43pm Link  |  Quote  |  Print  |  Notify Moderator

Camper8251 wrote:

Nobody will be able to answer this for you. Way to many variables.

Correct !
Abiut the only thing we can guess at is your two 6V batteries. About 220Ah @ 12V


RickLight wrote:

1. Get a battery monitor and let it measure actual use. There are hundreds of discussions here on battery monitors.

Not as good as QUALITY battery monitor (like Victron) but less money is a multi-meter with an "amp clamp", like a Unit-T UT210E.

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