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Old 05-15-2016, 08:59 PM   #1
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Safe Minimum House Voltage?

What is the lowest voltage on your 12V system when dry camping before you set your generator to start? On my way to Alaska and may be doing a lot of dry camping with a residential refrigerator. Not knowing for sure, I usually run the generator probably before it's necessary to do so.
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Old 05-15-2016, 09:13 PM   #2
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Our NorCold refrigerator spec list indicates that it's controls need a minimum of 10.5 volts for proper operation while in propane mode.

Perhaps you should research your refers specs for similar info.
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Old 05-15-2016, 09:33 PM   #3
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Originally Posted by bobguigley View Post
Our NorCold refrigerator spec list indicates that it's controls need a minimum of 10.5 volts for proper operation while in propane mode.

Perhaps you should research your refers specs for similar info.
10 1/2 volts on a 12 volt battery is completerly dead. 12 volt is about 50% charge. Or did I not understand?
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Old 05-15-2016, 10:07 PM   #4
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12vdc is my minimum allowable level to allow for discharge. Which is about 50% charge level level. Not an exact number as it can depend on the current or recent load on the battery bank. But is a good rule of thumb IMHO. Has held me in good stead over the years as I have experienced good battery life with three coaches, several sets of batteries, and a moderate amount of dry camping.
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Old 05-16-2016, 10:07 AM   #5
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I sent my generator autostart for 12.0v. About 50% charge level with Lifeline AGM batteries.
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Old 05-16-2016, 03:04 PM   #6
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The question is, "safe" for what? There will be no harm to any appliances or lighting if the voltage drops below its minimum, and many of them will simply shut themselves off if the DC voltage falls too low (an inverter is a good example of that). At worst, the device simply stops working reliably. Of course, that means your fridge shut off (even if on propane), so that is not safe for your food.

Your batteries, on the other hand, dislike being deeply discharged. Some more than others, though. A typical marine/RV battery could lose a substantial portion of its useful life if discharged to 11.5v or less just one time, but a rugged golf cart deep cycle probably just shrugs it off. For best battery life, though, keep the voltage above about 11.9v. That is measured with no load on it, so somewhere around 11.6v under a modest load is probably ok too.
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Old 05-16-2016, 04:28 PM   #7
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The question is, "safe" for what? There will be no harm to any appliances or lighting if the voltage drops below its minimum, and many of them will simply shut themselves off if the DC voltage falls too low (an inverter is a good example of that). At worst, the device simply stops working reliably. Of course, that means your fridge shut off (even if on propane), so that is not safe for your food.

Your batteries, on the other hand, dislike being deeply discharged. Some more than others, though. A typical marine/RV battery could lose a substantial portion of its useful life if discharged to 11.5v or less just one time, but a rugged golf cart deep cycle probably just shrugs it off. For best battery life, though, keep the voltage above about 11.9v. That is measured with no load on it, so somewhere around 11.6v under a modest load is probably ok too.
Im happy you pointed out the difference between a marine/rv and true deep cycle (golf cart)... Most people dont know this(because it isn't advertised)... But the vast majority of deep cycles sold aren't actually true deep cycle's anymore. They are "hybrids" ... They for sure are more sensitive to a complete discharge ... As far as 11.9... To each their own. But I wouldn't want to go below 12.2 honestly ..For a while I had a car with the alternator out... Was running it off two large batteries.. Not marine, to be fair. Not sure if there are characteristic differences... But had an auto charger... If I recall correctly... 12.2 was actually about 50 to 60 percent charge.... And as you said.. If you go too low you can cause damage. So why even risk it. Now I understand if there are rules in that park about operating hours on the gen.. But whether you set the threshold for the gen to kick on at 70 percent or the threshold to be 40 percent. The generator wont run any more total time. It just runs to replace what you have used. granted it will have to do two starts vs 1... But I imagine a starter is cheaper than a bank of batteries.. Then you also have to consider.. Once a battery is damaged.. It doesn't charge as efficiently .. Thus creating more work for the generator... Oh and this is my first post lol..Broke my cherry.. I just now joined because I have a question.. But came across this before I found the spot to post my question
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Old 05-17-2016, 11:14 AM   #8
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As far as 11.9... To each their own. But I wouldn't want to go below 12.2 honestly .. ... If I recall correctly... 12.2 was actually about 50 to 60 percent charge....
12.2 is generally considered 60% charge, but there is a lot of windage when translating volts to percent of charge. At best it's a very gross estimate.

My Trojan AGM deep cycles don't mind going down to 35%-40% SOC and they have performed well for 8 years now. Yours may be less capable. Marine/RV and "trolling motor" batteries can only handle that deep of a discharge once or twice, if at all.
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Old 05-18-2016, 06:07 AM   #9
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I have it set to 12.2 V for my Lifeline AGM batteries. That's 50% SOC according to the Lifeline manual. I try to stay on the conservative side because the voltage-SOC curve is *very* steep. 11.9 volts is 25% SOC, and I don't really think voltage measurements are more than +-0.1 V accurate. These are not universal, so I would always get the information from whatever battery OEM you have.
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Old 05-18-2016, 07:06 AM   #10
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I think 50% SOC or 12V are safe but consider the other side of the equation. The deeper you discharge the longer it takes to charge to full or even 90%. Using a generator to get from 90-100% is not a good use of fuel on a normal basis.

I set my AGS to kick in at 60% SOC and shut off at 90% SOC. This may not be a perfect answer for every situation but for occasional overnight boon docking it makes a fair amount of sense.
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