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Old 10-08-2019, 01:46 PM   #1
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Default how long can I run the refrigerator an/or Fantastic Fan on House battery

I used my refrigerator for the first time on a road trip yesterday. I was surprised at how well it worked. The van sat for 7 hours while having some work done at a shop,...and the fridge kept drinks cold.

Im looking for some feedback on how long I can run the fridge and/or the Fantastic Fan when camping without risk of damaging the battery. It is a lead acid battery, Thinking it is a 100 amp hour, and probably about 2 years old,

I realize there are lots of variables like size and health of the battery, so, lets assume a healthy or new 100 amp hour battery.

EDIT:
1)-The battery is rated at 490 CCA at 0 degrees F.
2)-The fridge is rated at 3.1A when operating on 12 volts

Questions:
1)--Using the recommended guideline of no more that 50% battery drain for lead acid batteries,...Can I run the fridge for one or two days safely if nothing else is used? Longer?

2)--Would a permanently installed volt meter be a good indicator of approximate level of battery state of charge,....or is there a better way to monitor state of charge?

I will be installing Solar panels in the future,...but need some guidelines on usage until I get them installed.

Brian
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Last edited by bcolins; 10-09-2019 at 06:14 AM.
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Old 10-08-2019, 05:40 PM   #2
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Default Re: how long can I run the refrigerator an/or Fantastic Fan on House battery

You haven't given us enough info about the fridge ... different models/capacities (and ambient air temperature) vary wildly.
My little Engel 40 liter chest box averages 2 amp hours per hour of operation, so a "100 Ah battery" can safely run it for 50Ah/2A=25 hours. (70 F ambient).
Your fridge may have a 24-hour "watts" or "watt-hours" rating that can be converted to fit the equation.

Why 50 in the numerator? Because you shouldn't draw more than 50% of an AGM's rated capacity. Thus 100 Ah*50%= 50 Ah.

The MaxxFan draws different currents depending upon speed: at full speed, it's 4.5 amps. At slowest it's around 0.25 amps.
So full speed would consume your battery in 50Ah/4.5A= 11 hours, minimum speed would be 50/0.25= 200 hours.

All of those "timings" are "perfect world" estimates. The world is never perfect, so knocking 30% off them is a good idea.

--dick (who gets by with a 67 Ah battery and 200 watts of solar ... the solar easily handles the fridge during the day)
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Old 10-08-2019, 07:44 PM   #3
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Default Re: how long can I run the refrigerator an/or Fantastic Fan on House battery

Quote:
Originally Posted by autostaretx View Post
You haven't given us enough info about the fridge ... different models/capacities (and ambient air temperature) vary wildly.
My little Engel 40 liter chest box averages 2 amp hours per hour of operation, so a "100 Ah battery" can safely run it for 50Ah/2A=25 hours. (70 F ambient).
Your fridge may have a 24-hour "watts" or "watt-hours" rating that can be converted to fit the equation.

Why 50 in the numerator? Because you shouldn't draw more than 50% of an AGM's rated capacity. Thus 100 Ah*50%= 50 Ah.

The MaxxFan draws different currents depending upon speed: at full speed, it's 4.5 amps. At slowest it's around 0.25 amps.
So full speed would consume your battery in 50Ah/4.5A= 11 hours, minimum speed would be 50/0.25= 200 hours.

All of those "timings" are "perfect world" estimates. The world is never perfect, so knocking 30% off them is a good idea.

--dick (who gets by with a 67 Ah battery and 200 watts of solar ... the solar easily handles the fridge during the day)
Its the stock fridge for the Gulf Stream Vista Cruiser,....hence why I posted it in that section. May try to pull the fridge out and see if it tells me anything on the back of it.
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Old 10-08-2019, 07:48 PM   #4
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Default Re: how long can I run the refrigerator an/or Fantastic Fan on House battery

Quote:
Originally Posted by autostaretx View Post
You haven't given us enough info about the fridge ... different models/capacities (and ambient air temperature) vary wildly.
My little Engel 40 liter chest box averages 2 amp hours per hour of operation, so a "100 Ah battery" can safely run it for 50Ah/2A=25 hours. (70 F ambient).
Your fridge may have a 24-hour "watts" or "watt-hours" rating that can be converted to fit the equation.

Why 50 in the numerator? Because you shouldn't draw more than 50% of an AGM's rated capacity. Thus 100 Ah*50%= 50 Ah.

The MaxxFan draws different currents depending upon speed: at full speed, it's 4.5 amps. At slowest it's around 0.25 amps.
So full speed would consume your battery in 50Ah/4.5A= 11 hours, minimum speed would be 50/0.25= 200 hours.

All of those "timings" are "perfect world" estimates. The world is never perfect, so knocking 30% off them is a good idea.

--dick (who gets by with a 67 Ah battery and 200 watts of solar ... the solar easily handles the fridge during the day)
Thanks for showing me the math side of that Dick. The more I look into this whole off grid and solar conversation, The more I see that math can answer all questions,......the only catch is that,.....you have to know WHAT math to use and where to find your data.

Brian
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Old 10-08-2019, 07:56 PM   #5
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Default Re: how long can I run the refrigerator an/or Fantastic Fan on House battery

Quote:
Originally Posted by bcolins View Post
Its the stock fridge for the Gulf Stream Vista Cruiser,....hence why I posted it in that section. May try to pull the fridge out and see if it tells me anything on the back of it.
Try googling the refer model number to download the manual and specs.
100 amp hour Lead battery is really only 50 amp hour of usable power. 50 amp x 12 volts is 600 watt hours of usable power or you can operated a 100 watt light bulb for 6 hours.

Now you can do your math and add up any open power drains to calculate how long you can run them. Also understand that this is just an estimate as you will have power loss due to voltage drop from resistance in wire length, poor electrical connections, and phantom drain.

Also your battery rated amps are at 72 deg F. As a lead battery gets colder is greatly losses it's ablity to provide power. So this means it is best to get a good battery monitor like a Victron BVM712 that can also compensation for battery temperature.
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Old 10-08-2019, 08:00 PM   #6
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Default Re: how long can I run the refrigerator an/or Fantastic Fan on House battery

Quote:
Originally Posted by bcolins View Post
Its the stock fridge for the Gulf Stream Vista Cruiser,....hence why I posted it in that section. May try to pull the fridge out and see if it tells me anything on the back of it.
The fridge is running on propane correct? If so, it consumes abooot 1-1.5A per hour continuously....
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Old 10-08-2019, 09:32 PM   #7
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Default Re: how long can I run the refrigerator an/or Fantastic Fan on House battery

Sorry I didn't provide better data guys. I just went out and looked around with a flashlight and think I found the info needed to do the math.

It says:
CCA @0 degrees F = 490
CCA @ 32 degrees F + 610
then says: 175 RC

How do I determine CCA at 72 degrees and how does CCA translate to amp hours?

The fridge also had a sticker INSIDE with some info:
Norcold Fridge and freezer 120/12/24 V
DC 12/24V 3.1/1.55A

So, assuming that this means I draw 3.1 A (12volts)
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Old 10-08-2019, 10:48 PM   #8
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Default Re: how long can I run the refrigerator an/or Fantastic Fan on House battery

am pretty sure the formula is CCA / 0.60 = AH (but cant remember)
uhhh... maybe not (still trying to find good info)


check this out:
https://batteryscout.com/how-many-am...0-cca-battery/

and here's some real math/science to figure it out:
https://sciencing.com/how-8681870-co...amp-hours.html


but... there's a number of different calculations for AH, with the most common being the

'20 hour drawdown rate' at appx 5% of rated capacity (at 77degF)

read: 5a for 20 hours = 100 ah

and if a battery is rated in CCA, then it's most likely NOT a 'deep cycle' type


here's some more discussion:
https://forum.solar-electric.com/discussion/3421/cca-ah
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Last edited by outbound; 10-08-2019 at 11:04 PM.
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Old 10-10-2019, 07:30 PM   #9
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Default Re: how long can I run the refrigerator an/or Fantastic Fan on House battery

Starter Batteries are not designed for constant discharge. CCA (cold cranking amps) sounds like a starter battery. Deep Cell and starter batteries are constructed differently as the both do different operations. Starter Batteries have a lead sponge and deep cell have solid thick lead plates. Don't use starter batteries for your house unless you want to replace them monthly.
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Old 10-10-2019, 11:20 PM   #10
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Default Re: how long can I run the refrigerator an/or Fantastic Fan on House battery

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Starter Batteries are not designed for constant discharge. CCA (cold cranking amps) sounds like a starter battery. Deep Cell and starter batteries are constructed differently as the both do different operations. Starter Batteries have a lead sponge and deep cell have solid thick lead plates. Don't use starter batteries for your house unless you want to replace them monthly.
Yes, prior comments got me pointed in that direction. The current battery was installed by the prior owner,.....the same one that blew a radiator hose and kept driving until the engine gave up.

So, deep cycle or maybe Lithium batteries are on the list for my solar build.

Brian
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