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Help understanding power draw and battery usage


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I recently bought an Aluma Lite skid house and am trying to keep the weight down as much as possible.  I would really like to only have to run 1 battery in it.  The only things I want to run are lights, a small fan, XM radio, and the occasional phone charge.  

The fan will run all the time.  The lights will only be on when it is dark.  Radio and phone charge will be sporadic. I really don't know much about this stuff so here is where I am at....

 

I looked at the XM radio 12v plug in and it says 5v 1.5A.   The lights in the house are 12v and say about 0.6A with both lights on.  Not sure the Amps on the fan yet.  Not sure how much power a phone charge takes.  

Can I get by 2-3 days with a single charge on a 100Ah deep cycle battery?  Can somebody explain how to calculate an expected run time?

 

I am very intrigued by the idea of a solar panel as well.  I saw the build that Princeton did a few years ago (The Irish Pub Skid House) and that looked awesome.   But I won't be running a TV or stereo or WII or other things he had in there.

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Here is a calculator to help you figure out if 1 battery will work.  My suggestion is to get a solar charger and keep it on the battery so it has some type of charge.  naturally you need to draw the battery down from time to time to minimize the memory of the battery.  

 

https://www.batterystuff.com/kb/tools/calculator-sizing-a-battery-to-a-load.html

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I would suggest that you run through the calculator above.  We sat down and listed all the power requirements when we designed ours.   I also agree with the solar panel recommendation.  There are a number of kits available on amazon.  Here is one with a panel and and a charge controller that you can add panels to it latter and it only weighs 25 lbs.  https://www.amazon.com/WindyNation-Off-Grid-Controller-Connectors-Mounting/dp/B00JML23X0/ref=sr_1_15?ie=UTF8&qid=1486925146&sr=8-15&keywords=solar+panel+with+charge+controller

 

 

 

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Thanks guys!  That looks like a good little kit for the solar panel.  I ran across a different calculator on a different site.  It said with a 100Ah battery, I can run 3.1 A for ~32 hours.  Does that sound right?  

 

0.6 Ah per light (really only need 1 light in the house)

1.5 Ah XM radio

0.5 Ah for the fan

0.5 Ah for little speakers for XM

= 3.1 Ah

 

Princeton--  On your build you attached the panels to the house.  I will be trailering this house and moving on the lakes quite a bit.   We try to park the houses with the door on the downwind side, so that might not put the panel facing south every time.  Do you have any thoughts on putting the panel on a stand and bringing it in and out of the house so we can always face it south?

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The calculations sound about right.  What are you using for a heater?

 

You surely could put a disconnect on the outside of the house that you could plug the solar panel into, then you would have the freedom to orient the panel which ever way.  I would put it on  a corner so you have more options for placement.  One caution is that the panels are glass and they are really meant for permanent mounting.  I could see them getting cracked.  I have seen some RV mounts that have adjustability built into them but they can get spendy.  So far I have not had any issues with my door facing north.

 

I really like my permanent  mounted panels as you don't need to mess around with them and I always have power.  Even if they are not exactly south they still make a good amount of energy.  After 4 years I have yet to run out of power.

 

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An amp hour is one amp for one hour.   So if your battery is 100 amp hours, it can supply 1 amp for 100 hours, 2 amps for 50 hours, etc.  

 

That breaks down at high draw, probably can't do 50 amps for two hours.  

 

Whether a solar panel or a generator is a better solution to recharge or extend battery life is a good question, given the short days and low angles of sun in the winter. 

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One other thing on your radio is that it will have some type of draw to maintain memory unless you plan on totally disconnecting it rather than just turning off.  Also you have to figure in some loss for temperature.  I would figure 5 amps and then go down as you hook things up.  Good luck,  Jeff

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13 hours ago, lungdeflator said:

Thanks guys!  That looks like a good little kit for the solar panel.  I ran across a different calculator on a different site.  It said with a 100Ah battery, I can run 3.1 A for ~32 hours.  Does that sound right?  

 

0.6 Ah per light (really only need 1 light in the house)

1.5 Ah XM radio

0.5 Ah for the fan

0.5 Ah for little speakers for XM

= 3.1 Ah

 

Princeton--  On your build you attached the panels to the house.  I will be trailering this house and moving on the lakes quite a bit.   We try to park the houses with the door on the downwind side, so that might not put the panel facing south every time.  Do you have any thoughts on putting the panel on a stand and bringing it in and out of the house so we can always face it south?

If you want to save some energy I have used these dimmers in the past and can extend your run time if your willing to have dimmer lights. https://www.amazon.com/Dimming-Controller-Adjustable-Brightness-Zitrades/dp/B007V1B0W8

I don't see any reason why you couldn't also use one of these on the fan you want running or use a cycle timer like what is in a boat for the live wells something like this should work. https://www.amazon.com/LeaningTech-Newer-Version-Relay-Module/dp/B00P0TZ5CY/ref=sr_1_4?s=hi&ie=UTF8&qid=1486975739&sr=1-4&keywords=12v+cycle+timer

 

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17 hours ago, lungdeflator said:

Thanks guys!  That looks like a good little kit for the solar panel.  I ran across a different calculator on a different site.  It said with a 100Ah battery, I can run 3.1 A for ~32 hours.  Does that sound right?  

 

0.6 Ah per light (really only need 1 light in the house)

1.5 Ah XM radio

0.5 Ah for the fan

0.5 Ah for little speakers for XM

= 3.1 Ah

 

Princeton--  On your build you attached the panels to the house.  I will be trailering this house and moving on the lakes quite a bit.   We try to park the houses with the door on the downwind side, so that might not put the panel facing south every time.  Do you have any thoughts on putting the panel on a stand and bringing it in and out of the house so we can always face it south?

 

It is recommended to never discharge a battery less than 50% capacity to lengthen to life of a battery.  With that in mind, you would last for about 15 hours with one 100AH battery.  Also, your biggest draw appears to be coming from your XM radio and speakers.  Now, the nameplate may say 1.5A but that doesn't mean the it will constantly draw 1.5 amps.  Put a multimeter on it to see what it really draws.  65% of your power draw in your calculations is for music, maybe you could figure out something different.  Maybe like a Dewalt/Milwaukee boom box and a newer receiver?  Just a quick search of the SiriusXM Onyx shows that their MAX draw is only 0.5 amps. 

 

Here is the battery curve for an AGM battery for the depth of discharge vs cycles in a batteries life.  AGM batteries are far superior to most other technologies on the market right now so a regular lead-acid deep cell will even have worse performance than this. 

 

DOD.thumb.jpg.e75ed8edcaeeff608a0b902fa41d4dbb.jpg

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Thanks again guys.  Princeton- I put a Nu-Way propane stove in.  Probably not the most efficient heater out there but they are fairly cheap, have a small footprint, and don't require any power.  

Yetti- I got that 1.5A number for the XM off the 12v plug in....maybe it is a 1.5A fuse in it?  If max draw is only 0.5A then that is alot better.  

The music is nice, but not even close to necessary. Like stated above the radio and speakers are 50% of the current draw so maybe it is better to just load up the phone with music and play it through the phone without speakers.  Its a small enough space so it doesn't need to be very loud.  It would be nice to be able to listen to Hockey/Football games or ESPN radio without using data on the phone though.  

I like the idea of putting the fan on a timer.  I think if it is fairly warm outside, the fan won't need to be on.  But if it is cold and the holes are icing over, it would run alot to help keep them open.

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  x3 on the solar panel.  IMO perfect of your situation with the small amount of amp draw your using.

I don't like the stove you've chosen.   Instead of a sealed combustion chamber that draws outside air its air intake is an open bottom.    Your life is depending on the stove drafting correctly.   So you need to supply air for the stove to burn.  You open a vent.

What happens when the wind outside starts sucking air out the vent?   It;ll take it from the chimney.

No thanks.

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Definitely something to consider with the heater....I would think the vents that are in the house plus 2 windows would give us plenty of air to draw in.  I will most likely add another vent right behind the heater so there should be plenty of air moving through.  

Through work I have access to some 4 gas monitors so I will have O2 and CO detection.  

 

 

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