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AGM Batteries How long last until auto start
Hello,
A few months ago I replaced my batteries with 8 4D AGMs. Since it has cooled down and I won’t have AC running I decided to test how long they will last without shore power. I currently have my auto start at when coach reached 23.8 for fifteen minutes.
I have fridge running and other minimal items that keep the coach alive. This morning at 11 am the batteries read 25.2. This is the actual reading on the Trace inverter LCD monitors.
We will see how long it batteries will keep up before generator kicks on.
David Thomas
1998 Featherlight XL
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11 Replies
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I have bought 8, 8D’s for my Country Coach, then about six years later I bought 6, 8D’s for the same coach. They did so well I didn’t need 8 again.
My coach was 12 volt and it would run for a long time dry camping.
They all came from Tom Chilcote, he made me an exceptional price on them.
His company is TransSpecialest on the site here.
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Everyone needs to understand that the length of time between when fully charged batteries are without a charging source until they need to be recharged varies significantly from coach to coach and owner to owner.
There will be a great difference between that time span for a 3 8D battery Liberty Classic owner and an 8 8D battery Featherlite owner. But there also could be a big difference between 2 Liberty Classic owners based on what devices remain powered when dry camping begins or how low the voltage will get before recharging.
Some autostart voltages are adjustable so a 12 volt coach whose autostart is set for 11.9 volts is going to go longer than one set to 12.2. Similarly new batteries are going to go longer than older ones, especially if the older batteries have not received life extending charging practices.
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Hello,
An update to my experiment.. This is the time of year I love for camping, as not need to heater or AC.
Last night I left a few lights on TV on just as i would dry camping. This morning I made coffee.
11 am day two (24 hours of use). Meter reads 24.5
David Thomas
1998 Featherlight XL
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How do 8-4Ds compare to 4-8Ds capacity wise? (LifeLine AGMs)
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These are round numbers so go to the Lifeline web site for exact ones.
An 8D is 250 AH, and a 4D is 200 AH so a 4D is about 80% of the capacity of an 8D.
From the school of hard knocks after making the switch from 8D AGM Lifelines to 8D LiPoFe4 I found as a practical matter an AGM battery has about 50% of its rated AH available so if the number of hours of dry camping is to be a calculation that 50% has to be the basis, as compared to 80% to 90% available AH on Li batteries.
But even that is not the whole story. Conventional batteries have an operating range from their fully charged voltage of around 12.6 to 12.8 volts down to the point at which they have to be charged. As voltage goes down current draw increases so as an AGM is discharged the devices that are powered by the batteries are drawing increasing amounts of current accelerating the loss of charge rate.
That was a serious eye opener for me with the switch to Li because for 30 years I was accustomed to conventional batteries and their available power. What took me completely by surprise was with the higher voltage range of Li combined with its almost flat discharge curve all of the devices that are battery powered are drawing less current so it takes longer to discharge the batteries by a significant amount, and when I see battery voltages at 12.6 or thereabouts the Li battery available amp hours are very close to being used up.
So If I had to stick with AGM I would look for the greatest available AH in a given space and then I would follow the manufacturer’s manual on when and how to recharge them paying very close attention to making sure they are fully charged. Driving all day does not fully charge batteries.
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Hey Dick, how are things in WI.
4D Battery at 25amp draw will last 390 min. 20 Hour rating is 210 amps.
8D Battery at 25 amp draw will last 550 min. 20 Hour rating is 255 amps
The 8D and the 4D both weigh 124lbs. Did not believe that but their site shows that.
I don’t know the price difference between the two cause I have never bought any 4D’s.
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Things in WI are pretty good Buddy. Thanks for asking.
So 8-4Ds provides much more power than 4-8Ds.
I’m surprised they weigh the same.
Hope all is well! I worry about you, Tommy, and Brady every time a hurricane heads into the Gulf.
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That’s fuzzy weights you ole Cajun, Lifeline 4D’s are 135 lbs and the 8D is 162 lbs.
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You are correct Oh Battery Guru, my apologies.
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Unless an owner wants to reconfigure the coach battery area (if possible) it is likely a coach can work well with fewer batteries, but maybe not quite as long without charging, but it is unlikely adding batteries or going to a larger size will be practical. If the storage of additional power is needed then the only way I know of to increase the power available from a given amount of cubic feet is to go to Li technology.
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Over 22 years, having personally changed my Lifeline 8D’s three times, I promise you, all eight of my 8D’s weigh 162 lbs. – EACH !
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