Battery Bank

[PRZNBUS]

Trying to figure out what I want to do for off grid stuff and while traveling. With a battery bank of six to eight AGM batteries, about how long would that run a 10 cubic foot fridge, a couple LED lights an AC? I know this is a fairly vague question with tons of variables but wondering about going from campground to campground or home if the batteries would last long enough to keep the fridge cold. I plan to also have a generator which would fire up when needed but I'm really ignorant on electrical stuff.

Bruce

[Darkspeed]

Depends more on the fridge..

You can get 8.1cf super insulated fridges that run on 60W DC with a Dan Foss Compressor

but an elcheapo fridge will use a lot of power

My favorite being this one > http://www.suremarineservice.com/DP2600IBD4-F.aspx

Average fridge runs 40% of the time so thats only 24w per hour..

[eagle19952]

Depends more on the fridge..

You can get 8.1cf super insulated fridges that run on 60W DC with a Dan Foss Compressor

but an elcheapo fridge will use a lot of power

My favorite being this one > http://www.suremarineservice.com/DP2600IBD4-F.aspx

Average fridge runs 40% of the time so thats only 24w per hour..

two 8d AGM will run incandescents, tv, limited microwave, and 12 cu/ft residential fridge in my coach for 10-14 hrs...

[pennuja]

I have four 6V GC2 batteries from Sams Club, I can run my Haier Stainless Apartment Sized refrigerator, Wifi Router, 2 18" Samsung TV's, WDTV, an Amazon Fire Stick and Fantastic Fan (on and off) on the low setting for over 30 hours before going below 50%. That is continuous use, and includes opening and closing the Refrigerator at least once an hour. I tested this a few times to make sure that I have enough power.

Now when I go dry camping I run the generator for an hour at night and an hour in the morning to keep up on the batteries (I also have to run for hot water) I just went 4 days like this.

I also have a 70 amp charger that gets the batteries to 90% in less than 2 hours, it is made by Progressive Dynamics.

I picked up my stainless Refrigerator at Lowes on sale for $320, I wanted a Danfoss compressor model but this was so cheap I couldn't see paying more for what I was going to use it for. If I was dry camping for weeks on end I would go that route and get some solar panels.

I should mention that the first time I went camping I used a lot of battery power charging my electronic devices, this should be done when the generator is on, since each device pulls at least 2.5 amps, and between us and the kids we have four iPads and three phones it doesn't seem like much power but they all add up to a lot when you charge them at once or use them while they are being charged.

[belfert]

You mention AC.  Are you trying to run air conditioning on battery?  You won't run an air conditioner for too long on batteries.

I used to be able to run my 15 CF Energy Star rated fridge by itself for two to three days on six AGM batteries.  They are not a standard group size, but each weighs 100 pounds.  I can get maybe 18 hours on batteries when the fridge is going along with lights and other loads.  My bus often has three laptops up and running much of the time.  My run time is down significantly right now as the batteries on on their last legs.

[Oonrahnjay]

You mention AC.  Are you trying to run air conditioning on battery?  You won't run an air conditioner for too long on batteries.  ...

   Yeah, Brian, when I read that he wrote "a couple LED lights an AC?", I wondered if he meant "a couple LED lights *ON* AC?" as versus DC current.  You're right, of course, unless you're looking at extraordinary conditions, an air conditioner will only run on batteries for minutes.

[PRZNBUS]

   Yeah, Brian, when I read that he wrote "a couple LED lights an AC?", I wondered if he meant "a couple LED lights *ON* AC?" as versus DC current.  You're right, of course, unless you're looking at extraordinary conditions, an air conditioner will only run on batteries for minutes.

I told you I'm an electrical idiot, I did mean air conditioning. Fortunately, I have a friend who is an electrical genius but he's gone for a bit when I was thinking about this question.

As I understand the responses, it should be no problem going from shore power to a destination and be able to use a fridge and a few other small items (I understand now obviously not the air conditioning) for a reasonable amount of time.

Thanks

Bruce

[belfert]

Some run one air conditioner while on the road by feeding power from the alternator through their inverter.  You usually need to have a DN50 or other large alternator to make this work.  A few here can run their A/C off battery for several hours at a time, but they have big battery banks like eight 8D AGM batteries and usually A/C units that use less power than rooftops.

I have an 8KW diesel generator and I just run that for air conditioning when not on a pole.  (Only been on one pole ever while away from home.)

[bevans6]

Bus electrical in a nutshell - batteries are rated in amp-hours.  That's how many amps they can supply for an hour, if they are being discharged fairly slowly.  You can count on half the amp-hour rating as available to do stuff with.  So if you have 200 amp-hours of battery, you can get 100 amps out before it needs to be recharged.

Things use power, and you can usually find out how many amps they use when they are running.  Things like LED lights use almost no power, so you don't have to worry about them.  Fridges use a lot of power, and air conditioners use a ton of power.  To estimate how many 120 volt ac amps you are  pulling from your 12 volt battery through an inverter, just multiply by 11.  If your fridge uses 2 amps of AC power while it's running (a really efficient, smallish fridge), it will use 22 amps of 12v.  If it runs half the time, it will use 110 amps of 12v power in 10 hours.  If you have a 200 amp hour battery bank you can run that fridge for a little under 10 hours.  If you have 400 amp hours, you can run it for a little under 20 hours.  Then you need to charge the battery.

An air conditioner might draw 10 - 15 amps while it's running, depending on how big it is.  That works out to 110 amps to 165 amps of 12V power.  You can see that your 200 amp hour bank is going to be out of juice after less than an hour of running, not to mention that you can damage batteries by discharging them that fast.   That's why people say it's difficult to run air conditioners on batteries unless you have a really big battery bank.

Maybe this helps you understand a bit better

[flynbanjo]

we use 4 Lifeline 8D AGM batteries and our dorm room size fridge will run for 2 - 3 days without a problem.  

[John Z]

I have 4 6v golf cart batteries for the house. This is linked by relay to the bus. So whenever I'm driving, the house battery is getting charged. I can run a smaller house size fridge, lights, tv, fan, for 36 hours easy. We run our genset in the morning for an hour and half. If we need air, we run the genset. Our Progressive Dynamics charger/maintainer is on whenever the genset is on, or we are on a pole. This keeps everything going.

[PRZNBUS]

Bus electrical in a nutshell - batteries are rated in amp-hours.  That's how many amps they can supply for an hour, if they are being discharged fairly slowly.  You can count on half the amp-hour rating as available to do stuff with.  So if you have 200 amp-hours of battery, you can get 100 amps out before it needs to be recharged.

Things use power, and you can usually find out how many amps they use when they are running.  Things like LED lights use almost no power, so you don't have to worry about them.  Fridges use a lot of power, and air conditioners use a ton of power.  To estimate how many 120 volt ac amps you are  pulling from your 12 volt battery through an inverter, just multiply by 11.  If your fridge uses 2 amps of AC power while it's running (a really efficient, smallish fridge), it will use 22 amps of 12v.  If it runs half the time, it will use 110 amps of 12v power in 10 hours.  If you have a 200 amp hour battery bank you can run that fridge for a little under 10 hours.  If you have 400 amp hours, you can run it for a little under 20 hours.  Then you need to charge the battery.

An air conditioner might draw 10 - 15 amps while it's running, depending on how big it is.  That works out to 110 amps to 165 amps of 12V power.  You can see that your 200 amp hour bank is going to be out of juice after less than an hour of running, not to mention that you can damage batteries by discharging them that fast.   That's why people say it's difficult to run air conditioners on batteries unless you have a really big battery bank.

Maybe this helps you understand a bit better

Dang it, if you keep explaining electrical this well I'll become dangerous thinking I actually know something. Thanks

Bruce

[gumpy]

You indicated going from campground to campground or home. So I assume you'll primarily be parking at a power post with occasional boondocking.

If you put in a crossover from your coach batteries to your house batteries and they are the same voltage, you can run indefinitely while traveling,
with the proper equipment. That includes air conditioning.

I have 8 trojan T105s in my bus (on the 11th year with the same set). I have a crossover so they charge when driving. I can run the basement air conditioner
while going down the road just fine. Just completed a trip to CO and WY where I did just that.  We can also boondock for 24 hours with no power
conservation. I run the generator for a couple hours each day to recharge.

Anything is possible with money and the proper setup.

[PRZNBUS]

OK, what's a crossover. That sounds like what I'd like to do.

Bruce

[digesterman]

Have an automatic switch device that connects the house batteries to the coach batteries anytime the engines charging system is working