Another Ignorant AGM Battery Question

[bijanjames]

I just purchased a Group 35 X2 Power Series battery from batteries plus, apparently a rebadged NorthStar, which I've read good things about. I'm trying to get away with running a fridge without getting a specific house battery. If it comes down to it, I'll bit the bullet and get the national luna power pack, but ideally would like to keep it as simple as possible. Anyway, my question is, has anyone done a field test to see how long a starter AGM battery will run a fridge before the volts get too low to start the vehicle? I've read numerous post regarding this and stating that there are too many variable to give an accurate answer. Other posts on this forum and others give answers ranging from 24hrs up to 72 hrs, with a smart fridge like an ARB or Engle.

 

[perkj]

it'll depend on environment temperature conditions, the brand of fridge how full/empty the fridge is, and the amp hours of your battery. All these contribute to how often the fridge will cycle and the amp draw of the fridge when cycling.

 

[Ducky's Dad]

there are too many variable to give an accurate answer

Color of truck, color of interior, where the fridge is sitting, ambient temps, orientation of parking place to sun, etc., etc., etc.,...

FWIW, my Indel B 50, white truck with light taupe interior and deep tint on back windows, fridge set on max cold for freezer, after five days of pretty steady driving on a 270 amp alternator, powered by a brand new Grp 34 Optima Blue house battery, went less than 24 hours in September So Cal temps. YMMV. You will need to test in your conditions with your eqpt.

 

[gwittman]

I can usually go 36 hrs or more with my old ARB refrigerator (very basic) unless the outside temperature is more than 90 degrees F. Then I can still get 24 hrs if it doesn't get much over 100. When I use my 100 watt solar panel to charge the battery, I have never run out of enough juice to start the engine. I run a group 34 Red Top Optima that is about 3.5 years old now. The refrigerator just sits behind the front seats and I try to keep direct sun from hitting it. I usually leave windows open when parked to keep it from getting too hot inside unless it is pretty cool out. If I have to lock it up only the rear window is open.

 

[bijanjames]

Thank you!

 

[travelman]

AGM Battery Reserve Capacity

As indicated earlier, there are too many variables for a correct answer. Solar will be your best friend when dry camping and running accessories. I used 1-Optima AGM Yellow Top (120 min reserve) in our truck for accessories only and never worry about the Dometic Freezer (like ARB units) in the back seat running the battery much below 11.5-12.0 volts during 24 hours of sitting. After installing a dual-battery isolator, it never became a consideration the truck would not start. Later on...2-Optima AGM yellow tops, one under the hood and one in the camper in parallel with 300 watts roof solar and battery charge is no longer a concern month after month. The isolator also allows 'reverse' charging from solar to the main start battery when accessories batteries are above 13.4 volts and shut off when voltage drops to 12.9 volts. If interested, you can look up; Dual Battery Isolation Kit with 140A Smart Battery Isolator.

 

[rayra]

There's nothing magic about an AGM, not in the way you are thinking it can provide more total current, anyway. It's design will allow a deeper drawdown with less potential damage to the battery. No pun intended. But that's not good, anyway.

Figure your power requirements and the ratings on your battery, that's what matters most in your 1 battery + fridge scenario. The kind of battery isn't going to solve your problem. For the same money btw, you can get two 'lesser' brand batteries and have your capacity and draw problem solved. It's all tradeoffs and deciding what the more important priorities are. Capacity or Ruggedness? Optima Fashionista or Good Enough? Redundant batteries in case your starter battery fails? Isolated 'House' battery so your vehicle battery is unmolested? Are there other aspects of the Optima that you'd really benefit from? Do you beat your vehicle up off-road? Are your power requirements such a high load that you'll be regularly drawing your battery down a great deal? If so an Optima isn't gonna solve that. if so, get a dedicated deep-cycle battery for your 'house' loads.

eta, missed that you'd just bought a regular Group35 battery. I'd probably get a second one, same type, and wire them up in simple parallel. I don't see anything about a vehicle in your post, if it's some form of truck or SUV there's often a factory option for a 2nd battery, which means an easy procurement of a tray for it and mounting in the engine bay.

 

[1Louder]

I reference this table all the time. Lots of folks smarter than me have already answered. My answer always is..... get a solar panel to supplement your power needs when parked for long periods of time with that you should be good for many days at a time.

http://www.arkportablepower.com/blo...reezer-and-battery-life-what-you-need-to-know