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Old 02-15-2020, 02:56 AM   #1
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Default Multiple Batteries

Hello, All. I want to know how to extend the battery power life for the house electricity on my van. Right now I have 1 battery that charges for house power as the engine runs. Is it possible to extend battery power life on my van by connecting another battery to the one already charging as the engine runs??

If this is not the correct set-up, please correct me or, if there is a better or safer way to do this, please let me know.

Look forward to receiving your feedback!
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Old 02-15-2020, 05:28 AM   #2
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First learn how to better use the one you have. Install a battery monitor then a DC to DC charger. When you get that done then you can install a second battery. Just an opinion.
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Old 02-15-2020, 12:22 PM   #3
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We really need more information to answer your question. How are you using your camper (travel style and duration)? What are you running off the battery? How long do you go between recharging? Are you using any other methods to recharge (shore power, solar, generator)? How old is your battery? Has it been abused (repeated discharge below 50%, stored in a discharged state, low water level)? Do you have a battery monitor? How old is the coach and charging system? What is your level of knowledge and experience with RV 12V systems?

In general, first priority is reducing your power requirements. Second priority is improving your recharging capability (solar, for example). Last priority is adding battery capacity.

Short answer is yes, it’s possible to run two 12V batteries wired in parallel, but they should generally be matched in terms of size, age, and condition (kind of like tires on the same axle). And there are other ways to upgrade your system that might work better for your travel style and power needs. You don’t want to throw good money after bad.
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Old 02-15-2020, 03:51 PM   #4
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We really need more information to answer your question. How are you using your camper (travel style and duration)? What are you running off the battery? How long do you go between recharging? Are you using any other methods to recharge (shore power, solar, generator)? How old is your battery? Has it been abused (repeated discharge below 50%, stored in a discharged state, low water level)? Do you have a battery monitor? How old is the coach and charging system? What is your level of knowledge and experience with RV 12V systems?

In general, first priority is reducing your power requirements. Second priority is improving your recharging capability (solar, for example). Last priority is adding battery capacity.

Short answer is yes, it’s possible to run two 12V batteries wired in parallel, but they should generally be matched in terms of size, age, and condition (kind of like tires on the same axle). And there are other ways to upgrade your system that might work better for your travel style and power needs. You don’t want to throw good money after bad.
^
This.

Running two group 24 batteries is doable, place one of them in the side box. You will have to go the AGM route or get creative with venting for a lead acid. Also, watch your side box weight limits if going this route.

I could run for two full days on a group 24 battery in good condition, but I only use about 20AH per day without help from solar.

There are a lot of ways to skin this cat but without more info you are just shot gunning parts at it, hoping something will work.

Check the condition of your current battery.

LED lighting helps a bunch.

As an aside, assuming your LP tank is set up like ours with the fill hose in the way to battery access, remount the LP fill connector to the far side(but not too far) of the opening from the battery. This also allows access to fill without removing the trailer hitch draw bar.
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Old 02-15-2020, 04:10 PM   #5
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Default Thanks!

A bit more info:

I have a ‘97 RTChevy200Versatile.

House battery was new June 2019, as was the rest of the house battery setup (ie. All wiring from engine to fuse box). LED’s have been installed and I have both propane and a generator on board. I’d like to use as little fossil fuel as possible, just cuz I don’t like going so quickly through the tiny tank of propane that’s on this RT.

I stop most often at places without hookups, so I’m using house battery power for lights, devices, small plug-in heater or the roof fan, but could use more If I weren’t concerned about running the battery down in the overnight. I don’t know exactly how much power I’m using. The battery monitor I’m using is the same on the panel installed by RT. Is something beyond adviseable?

I run the fridge during the day’s driving off of battery power, again, so I’m not using all my propane. At night, I tend to stay out of the fridge, so I don’t have to run it. If it’s too hot, I lean into the propane a bit more.

I investigated solar, but was told the cost benefit comparison made it senseless. I was told I’d be better off increasing battery capacity. Thus,...
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Old 02-15-2020, 04:28 PM   #6
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A bit more info:

I have a Ď97 RTChevy200Versatile.

House battery was new June 2019, as was the rest of the house battery setup (ie. All wiring from engine to fuse box). LEDís have been installed and I have both propane and a generator on board. Iíd like to use as little fossil fuel as possible, just cuz I donít like going so quickly through the tiny tank of propane thatís on this RT.

I stop most often at places without hookups, so Iím using house battery power for lights, devices, small plug-in heater or the roof fan, but could use more If I werenít concerned about running the battery down in the overnight. I donít know exactly how much power Iím using. The battery monitor Iím using is the same on the panel installed by RT. Is something beyond adviseable?

I run the fridge during the dayís driving off of battery power, again, so Iím not using all my propane. At night, I tend to stay out of the fridge, so I donít have to run it. If itís too hot, I lean into the propane a bit more.

I investigated solar, but was told the cost benefit comparison made it senseless. I was told Iíd be better off increasing battery capacity. Thus,...

I am a bit surprised that you go through a lot of propane, as AFAIK you have the typical Roadtrek 30# propane tank and we don't hear about that a lot unless in the very cold with the furnace running. How often are you filling the tank?


You are running an electric heater off of a single battery? How many watts does it use?


The suggestion to get a battery monitor so you actually know how much power you use and have left continuously is a very good idea, even with an increase to two batteries. Depending on how far you drive and the voltage making it to the batteries, you may or may not even be getting the fully charged a lot of the time.


Solar can be pretty cost effective these days if you do the labor yourself, as that is where the cost runs up pretty quickly. Hiring it all done can get quite costly.
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Old 02-15-2020, 04:31 PM   #7
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I have to fill it after every weekend trip. I usually cook outside and use the RT stove for tea making. The fridge uses a lot, so I’ve stopped using propane and only use the fridge when Im driving and can fuel it with battery. I was told its a 10# tank, which I also thought was very small. It was meant to be that size, I expect, as theres no additional space for a larger tank.
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Old 02-15-2020, 06:26 PM   #8
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I have to fill it after every weekend trip. I usually cook outside and use the RT stove for tea making. The fridge uses a lot, so Iíve stopped using propane and only use the fridge when Im driving and can fuel it with battery. I was told its a 10# tank, which I also thought was very small. It was meant to be that size, I expect, as theres no additional space for a larger tank.

There has got to be some issue with the frig, I think, as that is truly a really short time. When we had an absorption frig, we didn't even have to fill our tank once a year in most cases. The 1997 shows a 30# tank but it is in the generic section so might not be right. Later years show 200s with a 52# tank.


I think you have something wrong with the tank or the filling as you should have a tank that is 10 gallons or more so 2-3 ft long and over a foot in diameter. How many gallons or pounds are the actually getting in to the tank, they should know because that is how they charge you. Might even be on the receipt. If you really can use that much LP in a weekend, you would have to see the frig throwing huge amounts of heat out the vents.
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Old 02-15-2020, 07:25 PM   #9
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The dimensions you give for the 10# tank are consistent with whats under my van. I’ve watched the fill and they typically put in +/-8lbs. With that, the gauge reads full.

Given what you say, I must have a leak! I’ll get under and see if I can find anything. Thanks for the tip, as I just assumed this was to be expected with such a small propane tank. that said, my grill tank at home give me longer use than this van tank. Thanks again, for the tip.
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Old 02-15-2020, 07:28 PM   #10
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Originally Posted by BigBee View Post
The dimensions you give for the 10# tank are consistent with whats under my van. Iíve watched the fill and they typically put in +/-8lbs. With that, the gauge reads full.

Given what you say, I must have a leak! Iíll get under and see if I can find anything. Thanks for the tip, as I just assumed this was to be expected with such a small propane tank. that said, my grill tank at home give me longer use than this van tank. Thanks again, for the tip.
Hi BigBee,

Your leak is possibly large enough to smell?

One of the most common places is the regulator, thus some soapy water for example. You'll find it.

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Old 02-15-2020, 08:22 PM   #11
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My 97 Pleasure Way has an 8 gal. LP tank which I believe translates to about 34#. We were just out for a long weekend using LP cooktop in RV, LP furnace (nights got into the high 30s), and absorption fridge. Our propane gauge indicated that we used about an 1/8th of a tank (1/2 full to between 1/4 and 1/2). I'm not sure why your usage would be so high.

There must be specs for your specific RV in the owners guide/manual. If you know how many gallons it holds, see how many it takes on the next fill. If I'm on 1/4 tank and fill to 3/4, I should only take 4 gallons of LP. If I was only able to take, say, 1 gallon, I would suspect the gauge.
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Old 02-15-2020, 09:12 PM   #12
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Not the most elegant solution for a battery monitor system but they(you'll need two, on for each direction) will set you up with all of the info that you need.

The gauge on the wall from RT is a joke.

On the LP side, something is not adding up. According to the math the fridge will run for about 160-170 hours on one gallon of propane.

If you truly only have a 10# cylinder somebody has messed with it. Replacement tanks are quite expensive so it could have happened. According to the brochure https://www.roadtrek.com/brochures/ you should have a 7 gallon(30#) tank. My 2000 200 has the bigger 52# tank mounted in the rear with the fill port concealed by the license plate that flips up to fill it.

It seems as if there may be a number of differences from a '97 to a '00 model.
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Old 02-15-2020, 09:42 PM   #13
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Agree with all that's been said. You want to use propane for heat and refrigeration, and you should be able to get anywhere from a couple of weeks to a month off the tank unless you're doing some serious winter camping (don't confuse gallons and pounds). Heat is the biggest user; the fridge has a tiny flame. Running an absorption fridge on 12V is the least efficient mode. Electric heat is simply not realistic off-grid with a conventional battery system.

If you really want to ditch fossil fuels, you need a high tech lithium battery system with a roof full of solar panels and all-new appliances designed to use 12V power efficiently. With a 20-year-old coach that would indeed be throwing good money after bad. Better to make the most of your old-school system.

It wouldn't hurt to find out just how much your alternator is actually recharging while you drive. It may be less than you think. It depends on the alternator output, what else is using power (chassis and/or coach), and the gauge of the charging line from the chassis to the coach. If you're running the fridge on 12V, there may not be much going to the battery.

As to solar, you should be able to get 100W with a controller and connector for well under $200. If you spend more time driving, a rooftop mount is best; if you spend more time parked in camp, a portable suitcase setup allows you to optimize placement for maximum output. Portable simplifies the installation.

So... get the LP issues resolved and switch off-grid heat and fridge to propane. Install a battery monitor and get a handle on your actual usage. Make sure you have enough recharging capability to keep up (alternator and/or solar). Once you do all that you may find a single large 12V (group 31) does fine.

Bottom line... ten batteries isn't enough if recharging can't keep up with usage.
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Old 02-15-2020, 10:18 PM   #14
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Default Extremely Helpful!!

I’d just assumed my experience was usual, so each of you has been extremely helpful. I’ve learned 2 important things:
i) get my lingo straight! (My 30lb propane tank holds 10gallons of propane. I’ve been purchasing +/-8Gallons, rather than #s. Doh!);
ii) my van’s propane use is not normal;
iii) check for propane leaks, asap, as patching such a leak and using onboard resources as they were meant to be used (Propane for fridge) could help to resolve power usages concerns, not to mention $$ spent on over-frequent propane refills.

Identifying and addressing gas leaks will be my first priority.

Thank you!
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Old 02-15-2020, 11:28 PM   #15
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Unless I'm in error here (someone correct me!) 1# of LP = .236 gal or, from the other side, 1 gal of LP = 4.23#. So my 8 gal tank would hold 33.8#. My experience filling LP is that I get charged per gallon not per #.

But I fill only to the 3/4 level. I believe that's what is recommended (again, others chime in if this is in error). So the most I would put into my tank, if it was completely empty, would be 6 gallons.

If I did put 6 gallons into my (empty) tank, filling it to the 3/4 level on the gauge and returned after a weekend with a tank on 1/4 I would fill it again to the 3/4 level and see if it took c.4 gallons (the amount needed if the gauge was accurate). If it did, I would check for leaks.

I do a leak check on a yearly basis as routine service. Probably not necessary but it gives me peace of mind. I take it to a RV service place where they put a gauge on the main LP line (with the tank valve open), note the reading and come back hours later to see if it has changed......indicating something is leaking somewhere in the system.
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Old 02-16-2020, 05:49 AM   #16
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Agree with all that's been said. You want to use propane for heat and refrigeration, and you should be able to get anywhere from a couple of weeks to a month off the tank unless you're doing some serious winter camping (don't confuse gallons and pounds). Heat is the biggest user; the fridge has a tiny flame. Running an absorption fridge on 12V is the least efficient mode. Electric heat is simply not realistic off-grid with a conventional battery system.

If you really want to ditch fossil fuels, you need a high tech lithium battery system with a roof full of solar panels and all-new appliances designed to use 12V power efficiently. With a 20-year-old coach that would indeed be throwing good money after bad. Better to make the most of your old-school system.

It wouldn't hurt to find out just how much your alternator is actually recharging while you drive. It may be less than you think. It depends on the alternator output, what else is using power (chassis and/or coach), and the gauge of the charging line from the chassis to the coach. If you're running the fridge on 12V, there may not be much going to the battery.

As to solar, you should be able to get 100W with a controller and connector for well under $200. If you spend more time driving, a rooftop mount is best; if you spend more time parked in camp, a portable suitcase setup allows you to optimize placement for maximum output. Portable simplifies the installation.

So... get the LP issues resolved and switch off-grid heat and fridge to propane. Install a battery monitor and get a handle on your actual usage. Make sure you have enough recharging capability to keep up (alternator and/or solar). Once you do all that you may find a single large 12V (group 31) does fine.

Bottom line... ten batteries isn't enough if recharging can't keep up with usage.
Good info.

Although, due to the way the battery placement is set up on a 200, putting in anything larger than a group 24 is not doable without re-engineering or relocation.
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Old 02-16-2020, 01:41 PM   #17
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Good info.

Although, due to the way the battery placement is set up on a 200, putting in anything larger than a group 24 is not doable without re-engineering or relocation.
Aah... My 190 holds 2 large 6V GC2 batteries. Still, a G24 should be enough to run some lights and the furnace blower for a night or two. With enough recharging capability, it can last indefinitely. That’s all I have in my Scamp travel trailer.

Seems like an undersized system, though, even by standards from 20+ years ago.
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Old 02-16-2020, 02:26 PM   #18
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Aah... My 190 holds 2 large 6V GC2 batteries. Still, a G24 should be enough to run some lights and the furnace blower for a night or two. With enough recharging capability, it can last indefinitely. Thatís all I have in my Scamp travel trailer.

Seems like an undersized system, though, even by standards from 20 years ago.
I found that we could last two overnights unless it was quite chilly. killing battery capacity as well as running the furnace.

I'm currently running a group 29 "maintenance free" flooded battery that adds a day to that, mounted in place of the defunct Onan.

Due to the factory location of the battery refilling a flooded battery requires removal of the battery for filling unless a filling system is installed(possible but not straight forward)
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