Solar or not?

Bohemian scout · Nov 12, 2017

I have been trying to figure this out for 6 months... Studying, reading, watching videos. Before I came a regular on this forum I purchased a Dometic 18 / 12 volt fridge. I decided on a an AMG battery, had a friend who could get one at a discount and install it for free so I did that. He installed a battery isolator under my hood and said he was hooking up my battery to my extra 12 volt plug. I didn't really understand this but he was not one for explaining things. When needed I also run a 12 volt fan and charge devices. I don't want to ruin my battery or let the charge get too low so each day I start my van and let it run for 15 or 20 minutes when I'm camping. I figured eventually I'd get a suitcase or portable solar but now I'm not so sure after reading a posting on a forum that I can't seem to find now. It basically said that the solar would charge to slow and it would be better to just start my vehicle each day. I want to be able to stay out longer without worrying about starting my vehicle everyday. I'm not a permanent van dweller but go two to three months at a time. So, would solar be useful or feasible for me? What size / type solar panel would I start with? I'm also wondering if my AGM battery is powerful / big enough? My brain seems to have a hard time processing volts, amps, inverters, converters, charge controllers, Etc. I would appreciate any help but please keep it very simple. Thank you! I posted photos of my isolator and Battery.

highdesertranger · Nov 12, 2017

first off that AGM is not a deep cycle battery it's a starting battery. running your vehicle for 15-20 minutes will not recharge a depleted battery. it takes many hours to recharge a depleted battery. this is one reason solar works so well, because it's charging all day. you need to let that battery rest for a day(no loads and no charging) and take a volt reading. come back with the numbers and we can help you with the condition of the battery. highdesertranger

Bohemian scout · Nov 12, 2017

highdesertranger said:
first off that AGM is not a deep cycle battery it's a starting battery. running your vehicle for 15-20 minutes will not recharge a depleted battery. it takes many hours to recharge a depleted battery. this is one reason solar works so well, because it's charging all day. you need to let that battery rest for a day(no loads and no charging) and take a volt reading. come back with the numbers and we can help you with the condition of the battery. highdesertranger

How do I take a volt reading?

Bohemian scout · Nov 12, 2017

Bohemian scout said:
How do I take a volt reading?

Also, my van is not a daily driver so it has been setting, nothing plugged in. I try to drive it once A week. I do have a outlet splitter that I can plug into my 12 V that the battery is hooked up to and it has a voltage display. Would that work?

tx2sturgis · Nov 12, 2017

With what you have you can make it work but you will probably need about 200 watts of solar and a solar charge controller. 100 to 150 watts would suffice if you can always camp where the panels can be pointed toward the sun several times a day.

With that, you would rarely need to start the engine, maybe after several days of cloudy weather.

There are several options, eitther a portable suitcase style, or possibly 2 100 watt flexible panels wired thru the controller and attached to the battery.

With that isolator, you are not charging the battery as much as you might think when idling for 20 minutes, since they introduce a small drop in charging voltage to the batteries.

I peeked at the specs for that fridge, and it draws around 7 amps when running, and does have a battery monitor for voltage.

Look in your manual, find that section, and engage that reading. Tell us what the reading is, after you have had the cooler running for several hours.

It will be a number like 12.3, 11.8, something like that.

highdesertranger · Nov 12, 2017

take a multi meter and take a voltage reading across the battery terminals. everyone should have a multi meter, you can pick them up cheap at several places. get one and we will teach you how to use it. highdesertranger

Bohemian scout · Nov 12, 2017

highdesertranger said:
take a multi meter and take a voltage reading across the battery terminals. everyone should have a multi meter, you can pick them up cheap at several places. get one and we will teach you how to use it. highdesertranger

Ok, I will get a multi meter and would love to know how to use it and more about all this stuff! Thank you All.

GotSmart · Nov 12, 2017

Short answer. Yes. Solar will give you power to run your items without killing the battery.

HDR will set you straight. He has the knowledge to give honest advice.

wagoneer · Nov 12, 2017

I would not recommend using the starter battery for anything other than starting the car/truck or whatever. True deep cycle batteries/battery are essential to off grid life. if you have a lot of sun a good quality 100 will work, be frugal about your energy consumption.

Bohemian scout · Nov 12, 2017

Tx2sturgis, "I peeked at the specs for that fridge, and it draws around 7 amps when running, and does have a battery monitor for voltage."
I don't think my model of fridge has a monitor for voltage...just a switch for battery protection. There is no place for any kind of reading unless I plug in my 3 socket adapter, there a digital reading on that.

tx2sturgis · Nov 12, 2017

Ok, there are probably different versions and models of the Dometic 18. Some apparently have the monitor, and yours does not.

So, yes, you will need a basic digital meter, you can get them at Harbor Freight for less than $10.

There has been and will be negative advise here about you having a starter battery and not a deep cycle battery.

Your starter battery, that you already have, will work for awhile, maybe quite awhile. They will surprise you. But you just cant run them down as far, for as many times, as a true deep cycle battery.

This means it's even more important to keep it healthy and fully charged.

GotSmart · Nov 12, 2017

To be honest Tex, it could just as quickly die as keep going This is why you need to listen to HDR. He has the links to what works.

tx2sturgis · Nov 12, 2017

GotSmart said:
To be honest Tex, it could just as quickly die as keep going This is why you need to listen to HDR. He has the links to what works.

Yep. And I do too.

I run two starter batteries in parallel as combination house/starter batteries in my van, for 3 1/2 years now and they are still working fine. Granted, the occasional deep cycling is few and far between, and most of the time they are 'shallow cycled'...how's that for a new term?

BTW the Interstate Batteries are generally very good quality, and expensive, and I would not advise just tossing it and buying a new deep cycle battery while the Interstate AGM is still working fine, especially with no solar as of yet.

Also, Interstate Batteries have a good warranty, so if it should give up out there after weeks or months, hopefully she could get a full or pro-rated replacement, and a true deep cycle battery at that time.

akrvbob · Nov 12, 2017

While a starter battery for a house battery is not the best idea, it's what you have so you need to make the best of it--you've already paid for it, so you may as well get the most use out of it you can.

The best way to do that is to get as much solar as you can afford and, like tx2sturgis said, "shallow cycle" it. Deep cycles will very quickly kill your battery so you need to put as much power into it as possible, and take the very least possible out.

It's very far from ideal but it's the closest you can get to making lemonade out of these lemons.

Bohemian scout · Nov 12, 2017

I'm hoping I can make this battery work for awhile. I'll get a voltage meter and learn how to use it. The digital readout on the 12 volt adapter always reads in the high 11, 12. something range. I figure there's a bit more voltage when the fridge is plugged directly into the 12 volt plug. If I plug the adapter into my front 12volt plug it reads 13.3. I figure that is from the vans starter battery. When I have electric power I plug my fridge into it. I keep my fridge turned down, it doesn't come on much. Think I'll get a cover for the fridge too. If solar will help my battery last longer I'm interested. Thank you all!!! (It could be I have no idea what I'm talking about .....but I'm trying!)

Bohemian scout · Nov 12, 2017

tx2sturgis said:
Yep. And I do too.

I run two starter batteries in parallel as combination house/starter batteries in my van, for 3 1/2 years now and they are still working fine. Granted, the occasional deep cycling is few and far between, and most of the time they are 'shallow cycled'...how's that for a new term?

BTW the Interstate Batteries are generally very good quality, and expensive, and I would not advise just tossing it and buying a new deep cycle battery while the Interstate AGM is still working fine, especially with no solar as of yet.

Also, Interstate Batteries have a good warranty, so if it should give up out there after weeks or months, hopefully she could get a full or pro-rated replacement, and a true deep cycle battery at that time.

Bohemian scout · Nov 12, 2017

The battery says 48 month free replacement. What is "deep cycling" and " shallow cycling " ? How should I treat this battery to make it last longer? Would 200 solar be enough?

tx2sturgis · Nov 12, 2017

Bohemian scout said:
The battery says 48 month free replacement. What is "deep cycling" and " shallow cycling " ? How should I treat this battery to make it last longer? Would 200 solar be enough?

Well, deep cycle batteries will tolerate being discharged down more deeply, and more often. It has to do with how the battery is made. They were originally designed and marketed to the public for small fishing boats, where you wanted to run a very small electric trolling motor, with no way to recharge the battery while on the boat. Later, you would hook it up to a generator or a charger at the boathouse and get it back to full charge.

When I said 'shallow cycle', I just meant I try not to discharge the batteries much, and only use them for charging laptops and such during the day, when my solar is working. In other words, I conserve power.

Now having said all of the above:

IF somehow, you partially depleted that battery next week,

and took it back to an Interstate dealer, they might give you an allowance on the same physical size battery that is rated for deep cycle.

Its a thought.

For your stated use of that cooler you have, and making some assumptions about power use and boondocking locations, I think if you get a solar panel system with a good controller, you can get by with 100 watts, but 150-200 will be much better.

As Bob has said before many times, NO one EVER says, 'hey, I just have TOO much solar power now'...

tx2sturgis · Nov 12, 2017

Bohemian scout said:
Thank you all!!! (It could be I have no idea what I'm talking about .....but I'm trying!)

Miss Bo, you are doing fine.

Yes, you will get some conflicting information, like getting a second opinion from another doctor.

You have to sift thru all of it and decide what will work for you.

But I think most of us here would agree at least on this part: You should have some kind of solar power to replace what is being consumed by the little fridge, and constantly idling your engine to do that is wasteful and not good for the engine, the batteries, or your wallet.

Bohemian scout · Nov 12, 2017

I hate idling my engine, will be glad to not have to do it. Now, should I wait until I get to quartside/RTR to purchase solar panels and whatever else I need. I'll be looking at portable units, will someone help me set it up and understand what is what? OR should I figure out what I want / need and bring with? Tx, I thought about asking my friend who did the install and got the battery for me about an upgrade but if I get solar I won't have $$$ for an upgrade. Accidentally depleting a battery, yeah but I'd rather it be ligit.

Solar or not?

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