I replaced the original 4 12volt coach batteries a couple of months ago oN my 2014 378. We are full timers and have always been plugged in. Today we lost power. I immediately checked the voltmeter. They read 12.9 volts. We left the coach with only the residential fridge and fantom draws (like alarms & inverter) running. Returned about four hours, voltage read 12.2. Used a few LED lights and voltage was down to 12.1 when the power was restored, a total of about five hours.
We have never dry camped even at Walmart, but now I am nervous about making it overnight (10+\- hours) without dropping below the 50% level of 11.9 We were planning several such stops this summer. Can we make it thru the night without turning on the generator in the middle of the night? How critical is it to stay above 11.9?
Do I simply test again perhaps start in the morning so I have all day to monitor? How long will it stay at 12.1?
If you recall. I am an OEM in another industry that deals with these issues all the time. First the RV industry has it ALL WRONG. Plugging in 100% and leaving a charger on KILLS batteries.
The required minimum voltage for many (not all) items is 12.25 Vdc not 11.9! The AH use is NOT LINEAR. Any amp draw above rated numbers drops usefulness exponentially! A 200 AH battery bank is actually 160AH and of that 58 AH is usable. To get full use (down to 10.5 Vdc dead battery - no one gets there!) would be with a 8 amp draw for 20 hours. So for 58AH usable, you would at best get 7 hours with a brand new cycled battery bank. The typically battery bank, especially one always plugged in and charging would probably be around 2-4 hours then stuff start not working - voltage is below 12.0.
13.2 Vdc 100% fully charged
12.25 Vdc apx 50% discharged
12.0 Vdc MAKE SHURE CHARGER IS ON!
Lower - Don't do it unless emergency and no other choice
Good to know. But not great news. So how do folks dry camp even overnight with an inverter and residential fridge? Do I turn the fridge off until it begins to lose temp and then run back cold? Any techniques are appreciated. Obviously I can run the genset every couple of hours, but trying to avoid that.
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2014 Georgetown 378 XL
Toyota Prius on dolly.
Full time since 2014
How many amp hours are your batteries? Most batteries labelled as deep cycle are not true deep cycle, but are "dual use". I would think with 4 true deep cycle batteries at full charge you would not have any trouble running the fridge for 10 hours +. Check to see the power requirements for your fridge and you should be able to easily calculate how long your batteries would last.
I was told when I made my TT "Dry Camp" ready that it reduced its value because "NOBODY does that they all plug in"! It took everything out and transferred it to my RV. That is all I have done in both - from tailgating to National parks, .... no power is available.
In the marine environment, unless you are dockside, you better bring it or make it. So I do both. My previous battery banks were between 800-1200AH. My current RV has 800 that works fine, but miss the larger a few times - only allows multiple days vs single day between charging. My batteries are true deep cycle.
BTW, FYI, if after a full charge, your battery bank is only 12.9Vdc, the battery condition (life) is apx 80% used (20%dead)
I replaced the original 4 12volt coach batteries a couple of months ago oN my 2014 378. We are full timers and have always been plugged in. Today we lost power. I immediately checked the voltmeter. They read 12.9 volts. We left the coach with only the residential fridge and fantom draws (like alarms & inverter) running. Returned about four hours, voltage read 12.2. Used a few LED lights and voltage was down to 12.1 when the power was restored, a total of about five hours.
We have never dry camped even at Walmart, but now I am nervous about making it overnight (10+\- hours) without dropping below the 50% level of 11.9 We were planning several such stops this summer. Can we make it thru the night without turning on the generator in the middle of the night? How critical is it to stay above 11.9?
Do I simply test again perhaps start in the morning so I have all day to monitor? How long will it stay at 12.1?
Anyone with more experience with this?
I think you are fine, you're seeing the effects of how the Inverter is designed to provide 120v power when no other power is available... and it performed very well for you.
Most of us experience different times when it comes to how 'long' can I go on my inverter while dry-camping, since we all use electricity differently, the weather is different(temps, especially), the fridge temp is different(some like it 'really' cold!), some of us open the fridge door more often, have more stuff in there, etc., and actually use much more within our coach than we 'think' we do - phone and device charges are a simple example, along with watching tv,etc. Lights, while not on the inverter, certainly use 12v battery power, as well as the water pump.
I believe that under the best of conditions, at least during the warmer months, 5-6 hours without the generator is doing well. Some may get 10-12 if conditions are right, and they are really without all other electrical uses, and some may get less, like us, because we want to continue to have all the 'luxuries' that our coach is designed for, and that we expect, even when dry-camping, such as tvs, sat receivers, computers, device charging, water pump, furnace fan, electric fans, etc., etc.,... so our AGS(automatic generator starter) is the way to 'manage' when the batteries need attention, at around 11.9 volts, and wakes up the generator to handle that. It runs about 30 minutes at the time, and may run several times overnight, but not that much. I can sleep and not be concerned, plus our LBCO(low battery cut out) setting of 11.5 will keep the batteries from being overdrawn by the Inverter, cutting it off, if so. The SHORE button on the inverter panel tells the Charger how much amperage to use, which we set to 40 or more, for overnighting.
Use your generator, don't be scared to, it's your 'power source' for your batteries. We all like quiet, but we all like our 'lectricity, too! Use them both.
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The Turners...
'07 Rockwood Signature Ultralight...
two Campers and two Electric cars : )
Flybob.. so if just the fridge is running g (no other fantoms) how long does that calculate to? The fridge supposedly only runs 15-20 minutes per hour right?
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2014 Georgetown 378 XL
Toyota Prius on dolly.
Full time since 2014
Flybob.. so if just the fridge is running g (no other fantoms) how long does that calculate to? The fridge supposedly only runs 15-20 minutes per hour right?
Modern residential refrigerators run ALL THE TIME! The power draw varies but they never draw zero since they have their own inverter powered compressors. My really big Frigidaire (French door with bottom freezer) will draw and average of 100 watts continuously through the inverter. So, 4 hours at 100 watts (about 8 amps) will pull 32 AH out of the bank. Your bank has a capacity of around 300 AH but only 150 to 50% discharge.
Scott... My fridge is the same model. So if I have 150 amps/hours available and I draw 32 per hour.... 150/32 = about 5 hours, yes? So the answer really is to get an auto gen start for safe overnight dry camping....
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2014 Georgetown 378 XL
Toyota Prius on dolly.
Full time since 2014
if you minimize opening fridge, why not leave it off overnight? Surely it will stay cold...
I never run with my fridge on and after an 8-10 hour day on the road I open the fridge and ice is still frozen and drinks still cold.
__________________ "nothing can now be believed which is seen in a newspaper. Truth itself becomes suspicious by being put into that polluted vehicle." Thomas Jefferson to John Norvell pg. 2, June 11, 1807 2014 Shamrock 183
2014 RAM 1500 Bighorn Crew Cab, HEMI, 3.21 gears, 8 Spd, 4X4 TST TPMS
Scott... My fridge is the same model. So if I have 150 amps/hours available and I draw 32 per hour.... 150/32 = about 5 hours, yes? So the answer really is to get an auto gen start for safe overnight dry camping....
You don't draw 32 per hour...you draw 8 per hour! 32 was for 4 hours. I run overnight all the time as it will only take out 64 AH for 8 hours which is safe for a 50% discharge. The problem comes when I run the furnace which draws about 7 amps when running. I charge before bed and charge in the morning while I make coffee and breakfast.
Don't sweat it. You should be fine. An AGS is pretty pricey and for your use not really worth it. Start it yourself but when you do, you really have to run for a couple of hours at a minimum. I also added a charge wizard pendant on my converter so that I can force it into boost mode for the whole charging cycle. If you are really concerned, install a Victron or Trimetric and then there will be no guessing. I love my Trimetric.
Using published numbers ( from ID plate) will generally provide max numbers. If you want good actual numbers, I suggest something like this. Comes in handy for many applications. https://www.amazon.com/P3-Internatio...+power+monitor
Using published numbers ( from ID plate) will generally provide max numbers. If you want good actual numbers, I suggest something like this. Comes in handy for many applications...
Maybe, but not for a modern reefer which has loads all over the map. Measure it in the low load state and you will be really happy...and then disappointed much later when you look at your SOC after more than a few hours.
Here is a long term measurement log for a big residential reefer:
After four years full time and many hours on this forum, I still am amazed and grateful for the help and non judgemental advise I get from my fellow rvers. Thanks.
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2014 Georgetown 378 XL
Toyota Prius on dolly.
Full time since 2014
Not to take away from the inexpensive outlet monitor, but consider a whole system battery monitor. The price has dropped significantly in the last year or so from $400 to $150-200. Then you know everything about your battery system all the time. I have 2 installed. 1 for FR lousy 200Ah battery bank and 1 for my 8ooAH system I installed. The first one also monitors the engine battery - voltage only.
Here is the type of information available from 2 different companies. They are "battery fuel gauges" - no one should leave home without one.
BTW, FYI, if after a full charge, your battery bank is only 12.9Vdc, the battery condition (life) is apx 80% used (20%dead)
Not true. 12.6-12.7V is a 100% charged FLA or AGM battery after the surface charge dissipates after 45 minutes. Measuring the battery battery right after pulling off the charger means nothing.
BTW, I worked on electric vehicles back when they first started with FLA batteries.
More info....
Turned off power at pedestal. With inverter and fridge on, voltage is 13.3
NAPA advises my 4 deep cycle batteries have amp hr specs of 79.4
The fridge (Frididairre with ice) label shows an 8.5 amp rating.
The inverter is a Xantrex ProWtt 2000 - draw is ??
That help?
When you pull your batteries off the charger, measuring the voltage at that point means nothing as I noted in the previous post. To really see at what SOC the batteries are at, you need to have ZERO load and wait for the surface charge to dissipate.
If you have 4 79.4AH batteries, your 50% SOC draw is approx 160AH. Try not letting your batteries get below 12.V which is the 50% SOC level.
You should really invest in a battery Monitor like the Xantrtex mentioned earlier or the Victron ones. I just bought the BMV-712 which allows you to access all the numbers with your smart phone using Bluetooth.
With a residential fridge, in order to get meaningful consumption numbers, plug it into shore power and attach a Kill-o-watt meter on it and monitor how much it draws in 24 hours while opening the doors like you would normally use it. That will give you a good idea how much power will get drawn off your bank while using the inverter.
Personally, 4 batteries is too small of a bank for a residential fridge, especially the size you have. If you had 4 group 27 or 31 100AH batteries, you would have a little more margin.
Out of curiosity, which model batteries do you have?
Linear Mode
