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Old 01-13-2021, 09:37 AM   #1
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Join Date: Nov 2020
Posts: 10
Another battery Q

My Trailer has what all of you call the cheap interstate deep cycle marine(85 AH).
Iam going to travel from Miami FL to Las Vegas NV at the beginning of february
My plan is to stay 10 days on the road, finding places to stay at night,no hookups.
1.Is this battery enough for this kind of trip,minimal use,water heater(gas) fridge(gas),one or two lights(led) at night,plus the normal fantom draw,no way of charging the battery,only from my truck,i dont even know if that is possible,2019 Chevrolet Colorado diesel,some people say yes some say no,

2.What do you think of this battery,Interstate Batteries 12V 110 AH SLA/AGM Deep Cycle Battery,top of my budget for a battery,$249 amazon prize.
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Old 01-13-2021, 10:09 AM   #2
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Posts: 25,506
You can pick up a 105 AH Gp 31 deep cycle battery from Sam's club for less then half that.

You can pick up 2, GC2, 6volt, 205 AH capacity batteries for less then $200.

The first battery is maintance free and the GC 2 batteries need water checked every few months.

AH is AH weather its from AGM or flooded lead acid type battery.

If you don't have a charge line, or generator, I don't think your going to get 10 days of dry camping out of a typical battery bank.

If you have a working charge line, your present battery may be all you need. That, you can test in your driveway. Spend the night in it.

My money would go to the charge line before new batteries. Any vehicle can have one, the trailer and its plug will be setup for it.
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Old 01-13-2021, 11:05 AM   #3
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Posts: 177
FYI, two 6v 205AH batteries wired in series gives you the equvalent of a 205AH 12V battery, not 410AH. AH don't add when batteries are in series. AH only adds when batteries are in parallel.

6V 'Golf Cart' batteries are better deep cycles than 12v Marine Deep Cycle. Marine Deep Cycle are not true deep cycle as they are also intended to be a start battery in addition to a storage battery.

Your furnace can use a surprising amount of battery on cold nights, the blower pulls a good amount of power. A buddy heater would help save a lot of battery power, make sure to properly ventalate the trailer for fresh air if you use one.

IMHO you'll want more than 95AH if using the furnace. I 2nd the comment to install a battery charge line from your tow vehicle if you don't already have one. Depending on use, even with the charge line you may not get the house batteries fully charged before stopping for the night.
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Old 01-13-2021, 12:32 PM   #4
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Location: Beaver Dam, Wisconsin
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How long can you go?

Good advice above!

The battery amp hour size gets you from one charge cycle to the next. However, if you do not have enough charging, it does not matter how big the battery is. It will be drained sooner or later.

85 amp hours is enough for one night, maybe two, of lights and frig controls, etc. 110 amp hours will get you two or three nights. 200 amp hours will get you 5 to 7 days. Running a propane furnace that has a big fan will cut that almost in half in cold weather.

In all cases, you need to replace substantial charge before the next dry camping event. Periodically you need to do a 14 to 18 hour full clean charge to keep the lead acid battery healthy. Maybe once per week.

Assuming the engine does not charge the TT battery, and you do not run the furnace, you could stay at a camp ground using shore power every other night. With a bigger battery you could delay the campground hook up another night or two.

A robust charge from driving 6 or more hours a day would keep even an 85 amp hour charged enough for dry camping every night. Running the furnace may or may not work out after a couple of nights. Test it to find out.

I recommend you get a cheap digital multi-meter from your local hardware store. Use it to monitor voltage at the battery terminals until you know how the charging and discharging is performing.

You can measure tow vehicle charging of your TT batteries by measuring current and voltage while the engine is running. Some tow vehicles need to be running faster than an idle to charge. Do this at the connector between TT and TV. Measuring current is not the easiest thing to set up, but it would be the best way. You will need a 40 amp current meter for this.

Measure voltage on TT batteries first and then start the engine. It should be below 12.4 volts for this test to start with. Discharge to 12.4 volts or less first if necessary. You should see 10 to 30 amps flowing. Voltage should slowly rise in an hour or so. 30 amps would be an excellent charge rate for an 85 amp hour battery. Less than 10 would be a problem.

I assume you have a 7 pin tow connector. Increase the size of both ground and positive 12 volt pin and engine alternator to increase current flow. Check for loose or corroded connectors. There will be a fuse or circuit breaker in the positive side of the circuit. I used 8 gauge multi-strand wire for mine.

If you canít or wonít measure the current, you can easily measure terminal voltage. There are three basic voltage profiles for lead acid batteries. They are: Charging, Discharging, and Static. Charging profile tells you how the charging device (your engine alternator) is performing. Static profile will tell you what the current state of charge is in the battery. Use a chart to convert voltage to percent of charge or use the percent charge meter in your TT. Static means not charging or discharging for 4 hours or more.

Discharging profile will always have a voltage lower the Static.

Note, checking the voltage in the tow vehicle works for the engine start battery. It is often not accurate for the TT house battery. Check at the house battery terminals for more accurate results.

Start at home. Measure the battery terminal voltage. Start with the battery terminal voltage below 12.4 volts. Hook up the tow vehicle and start the engine. The voltage should slowly rise to more than 13.3 volts. It may take 4 hours or more. Final charging phase should be 13.6 volts or more. At this point the battery is not fully charged. It takes 14 to 18 hours to do a full clean charge. Voltage will stay the same for the remainder of the charge. This is the charging profile.

If the voltage does not rise at all, then the engine alternator is not charging the battery. If the voltage is not above 13.3 after four hours, the charge is below optimum. Increase the size of both ground to 7 pin and positive 12 volt pin to engine alternator to increase current flow. Check for loose or corroded connectors.

I wish you good luck and happy trails ahead!
Paul Bristol
Kodiak Cub 176RD
Nissan Pathfinder 2015
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Old 01-13-2021, 12:57 PM   #5
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The operation of a furnace isn't mentioned. Not sure of your intended route but guaranteed once you get to these parts you're going to want some heat at night. Even parts of Texas is into the 40's at night, here in ABQ it's been in the 20's.

LED lights, water heaters and fridges on propane draw very little 12V power so it's not a stretch to think with those loads alone you might make it. I would measure the actual draw and come up with a power budget. Part of this exercise I would do a measured test of your existing battery to know it can do what you think it does.

I can't think of any reason you couldn't do some degree of charging from the vehicle while underway. It may not be a quick or complete charge by just connecting directly to the house battery but it sounds like many hours on the road, so you've got the time. If you wanted to assure a charge my vote would be to buy/borrow an AC inverter you run from the truck and power the converter in the trailer or an AC outboard charger with an extension cord.

Mark B.
Albuquerque, NM
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Old 01-13-2021, 02:03 PM   #6
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I had the small group 24 battery in my trailer. I towed from Columbus Ohio to the southern part of S. Carolina in December. I pulled into a rest stop on a cold 34 degree night. I got into my trailer and fired up the furnace set to 72 degrees and went to bed around 11:00pm. I woke up at 4:00am cold. The small group 24 battery was dead. I got into the truck to get warm. I could not sleep so at 5:00am I got on the road to Florida.

That experience taught me to get a group 31 battery and my truck does not charge the battery very well.
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Old 01-13-2021, 02:38 PM   #7
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Thanks to everybody,I think Ive been tryng to find an answer that is really hard to get,to many variables.
I think the best way is to find out on the road,if i have to get a campground for a night or two of the 10 days so be it.
Hoping the worst is that i damage the cheap battery
Checking the wearher i think i wont be using the furnace but you never know
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Old 01-13-2021, 07:05 PM   #8
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I think if you don't use the heater, you'll make it 2 or 3 days without charging. If you drive 6 hours a day and the truck is charging the battery, you might make it. If you run the heater, no way. I have a group 24 plus a group 29 on my TT and the heater really eats into power. I have 270 watts of solar and have never had a problem. Personally, I'd buy a new group 31 from Sam's club and small generator and run the generator as needed an hour or two at a time.
My first experience with a TT was dry camping in a rental in Yosemite. The single group 24 was nearly dead on day 2 after a night with heater on and regular incandescent lighting. Managed to get through the week by buying another battery (better/new) and running a generator about 40 minutes every day. I almost had to fight a few campers over the generator one day. When I got my TT, I added the Solar Immediately and have never had to run the generator but I always take it just in case.
2017 RAM 1500 4x4 5.7 HEMI
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Old 01-14-2021, 07:42 AM   #9
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I bought a group 31 deep cycle from batteries plus for 150 and it was more than enough on my way to Florida. I stayed three nights on a farm in Tennessee where it snowed and the nights were in the 30s. My initial battery was the interstate same as yours and it was worthless. I got up every morning after the furnace ran all night and it was down to 50 percent. I did have a generator to recharge the battery each morning. If I was only staying one night as you I never would have bought the generator. Iím sure the 6 hour drive would have recharged the battery but donít know for sure 100 percent, but thatís my sense of it. I have no plans to dry camp again but you never know. If it was going to be a regular thing then multiple batteries such as golf cart type is good advise. Iím not in the camp that wants to buy the expensive gel batteries. The old fashioned deep cycle work just fine as long as you take care of them. Good luck.
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Old 01-14-2021, 08:52 AM   #10
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Location: Lake Jackson, TX
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I bought a 21.5'. TT 2 years ago to go to hunt tests with my black lab. Lots of hunt tests let handlers dry camp on the hunt test property, so I needed to be able to boondock for 3-4 days at a time. I eventually went with two 6 volt, 200 AH batteries with 200 watts of solar and a trimetric solar controller. I bought a small gen set for backup. I also bought a Magnum inverter/charger because I could. Before I got the solar, the furnace ate my lunch on cold nights. (I had a junk battery that came with the TT, Walmart brand I think). They do make gas space heaters for small areas that can be used indoors if you have some ventilation, then you would not need to use the furnace. I haven't been able to use the TT as much as I hopped, as I got sick after using it just a few times, and am still recovering. The small solar system helps a lot. Good luck.
Bill Tobler
Lake Jackson, TX
2002 R-Vision TrailLite 7212/ 21.5'
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Old 01-18-2021, 02:15 AM   #11
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Ditto on previous comments.

Your battery charging through the trailer plug will not get you a full charge while driving (probably around 70%), but might get you enough if you don't use the trailer furnace.

I use two 6V golf cart batteries to make 12V. If I don't use the furnace and am frugal with battery use, I can easily go a full week without an external charger. If the batteries are new, a few days longer.

Spend a night or two in the driveway and find out. Figuring it out on the road is frustrating. If you find that you need to stop at an RV site with electricity to charge every couple of days reservations might be necessary. COE and state park campgrounds are usually the least expensive, cheaper still if you only get water & elect.

There are a couple of options. Most are somewhat expensive or require some expertise.

A small generator around 2000 Watt (16.6 amp) minimum will run your trailer battery charger when you stop. Get a 3000 watt (25 amp) and you can run your air conditioner too.

DC to DC Battery Charger will cost you about $250 plus install.
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