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Old 05-21-2018, 05:53 PM   #1
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Roughly how long do 2 12V batteries last?

Hi, I know this is a "it depends" question, but I'm looking for any kind of rough guess here. We are first time RV'ers, new 233S, lots to learn. We are going out for first trip this weekend. 3.5 days, 3 nights. No hookups. I saw a video showing that 2 12V batteries with a constant 5A drain (3 led lights, a small fan, and a small stereo) lasted 17 hours. I guess that seems short to me! We will of course try and not use lights, won't need the heater, but will use the water pump, refrigerator, some cooking (gas), some light usage at night but we will bring lanterns, etc. I guess I just have NO IDEA what to expect as far as how fast our 2 12V batteries will drain! Was sort of hoping that they would get you through a long weekend and get the slide back in! Any feedback is appreciated. Thanks!

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Old 05-21-2018, 05:58 PM   #2
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Guessing that they are dual purpose batteries(not true deep cycle batteries)and you don't use the furnace, 3-4 days if they are fully charged on arrival. That's what we would get.

But that was just the two of us and we are long time dry campers.

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Old 05-21-2018, 06:05 PM   #3
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lasted 17 hours. I guess that seems short to me!
You might be surprised that this quote is close to being correct.

You might make it 3-4 days with light (not constant ) usage...

You need to pack a cheap VOM to measure voltage and not drop those batteries to less than 12.1 to 12.2 VDC ( 12.7+ VDC is nominal @ full charge)... and then quickly (within 24-36 hours) charge them back up otherwise you will permanently compromise the batteries... that is you will never be able to get them back to 100% capacity again.

ASSUMING you are boondocking and not within a good earshot of your camping neighbors... I would get to a Harbor Freight and pick up one of their cheap $100-$120 generators (900 watts) and charge the batteries for 8 hours (about 1 tank of gas) at least once during your trip. Be sure to get a dogbone adaptor ( 30A to 15 Amp) for the TT hookup or get a separate charging appliance to hook to the batteries.

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Old 05-21-2018, 06:08 PM   #4
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The high tech guys will tell you that you should never run batteries down more than 50%. The low tech guys (like me) don't hesitate to run them flat, so I'd just isolate one battery and run whatever you want on the other. If that battery dies you'll know how long you 'should' go with two, and will also have a spare to bring that slide in when you break camp. I'm sure you'll also hear from the solar crowd - personally, I'm a generator kind of guy.
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Old 05-21-2018, 06:11 PM   #5
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Originally Posted by Wprather View Post
Was sort of hoping that they would get you through a long weekend and get the slide back in! Any feedback is appreciated. Thanks!
The instructions for my RV say to use the slide either under generator power, or under 30 amp plug in power. It indicates not under the house batteries only power. I would consider it under an emergency situation only, not a routine procedure.
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Old 05-21-2018, 06:15 PM   #6
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If you check to see how many amps each of your batteries are you can use the chart in the link below to guestimate your amp hour usage. Like some of the others stated above I never run my 2 12v batteries down below 50%.

RV Converters and Amp Draw - RV Information (RV Maintenance)
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Old 05-21-2018, 06:23 PM   #7
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Run the refrigerator on GAS. Charge the batteries up and practice in the driveway. That will give you a good guess as to how long things will go.

If you doo buy a generator, read up on them in the search box. If you gonna boondock often I'd buy a Honda/Yamaha/Champion 2000 inverter/generator.

If one doesn't do it for you, you can buy a 2nd and run them in parallel. 4000 Watts. 1- 2000 will run your AC but not leave you for much else.
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Old 05-21-2018, 07:19 PM   #8
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No idea how long your batteries will last.

We're former tent campers, so we bring solar/battery powered lights, fans,radio, and a solar charger and charged battery pack for the phones.

Critical is keeping that battery up for the electric ignition for the refrigerator on propane and the water pump. I'd leave the lights off inside at night unless absolutely necessary. Your lanterns should do the job.
Happy Camping!

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Old 05-21-2018, 07:28 PM   #9
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In a pinch you can also plug into your tow vehicle and run it for a time. Works for retracting slide and/or awning.
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Old 05-21-2018, 07:53 PM   #10
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The math is easy.
Find the available amps on a battery. Likely a dealer installed battery is 85. Divided by two is about 43 available. 8 hours at 5 amps. 16 hours for two. No day two and three.

If you run them down more it damages them. I. E. They hold less. Should last 6-8 years or 18 months. Your choice.

Get a table with usage by item. Easy.

My solution is 4 six volts. 520 amps. 260 usable. Makes 3 days easy. We have 85 a day.

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