12 volt Batteries for Camping

If you are camping away from mains power then a good battery and charging set-up is essential. Many people simply do nothing more than use the battery provided in their caravan/RV/camper trailer with little understanding of the characteristics of the battery – how much power can it deliver and for how long. A worst case scenario sees a battery becoming fully discharged with a high chance of irreparable damage being done to it. This article will hopefully provide some useful information on batteries, their use and care.

First off, different battery types. There are three main battery types that I will address here, wet cell starter batteries, deep cycle, and a variation on deep cycle that is AGM. It is important to appreciate the differences because they are all made for a specific purpose.
12 volt Batteries

The starter battery is one that we are all familiar with under the bonnet of our vehicle. This type of battery is used to provide very heavy currents to a starter motor for short time periods. Because of this requirement, and thus its construction, it should not be deep cycled as its lifetime will be shortened as the plates will deteriorate rapidly.

A deep cycle battery is one that is NOT designed for short heavy loads but IS designed for the occasional discharge below the 50% threshold (a rule of thumb is that batteries should not be discharged below about 50% of their capacity if you want to get a reasonable life out of them). Deep cycle batteries can be wet cell, but tend to be constructed with the electrolyte more of a gel so that the battery can be “sealed”. Sometimes they are called “maintenance free”, but what this means really is that you CANNOT maintain them because of the sealed nature. In reality, wet cell deep cycle batteries are better in hotter climates because at least you can test the cells and top the electrolyte up with a regular maintenance pattern. Most batteries perform better in colder climates.

AGM (Absorbed Glass Mat) batteries in my opinion are the best choice for camping. Yes they are more expensive, but for the advantages they offer it is worth it. An AGM battery can tolerate the occasional discharge below the 50% level – some people even say down to 20%, but personally I wouldn’t do that. You see batteries LOVE to be charged. They HATE being discharged, and regular excessive discharge is where the damage can be done. AGM batteries tend to charge faster and take more charge, up to close on 100% of charge (did you know that your car alternator is only capable of charging your vehicle battery to around 70-80%?). Because AGM batteries were developed for the military they can take the punishment too. Their sealed nature means that you do not have to vent these batteries to the outside. You can store these batteries inside your car or caravan and even store them on their sides if you have to, and if you leave an AGM battery in storage, unattended for an extended period you can recharge it again without any deterioration or loss of efficiency.

OK, if you are not convinced about the benefits of AGM yet, how about this:

Lifetime of a standard cranking battery is generally up to 4 years
Lifetime of a deep cycle battery is generally up to 6 to 8 years
Lifetime of an AGM battery is up to 10 years

Now of course all this depends on how the battery is used (or abused) and is a general assumed figure if the battery is well cared for. The more you look after your battery the longer the life.

Now on to capacity. The capacity of a battery is usually given in terms of Ampere hours. The best way to explain this is as follows:

You have a 100 Ampere hour battery and you are going to run just one light taking 1 amp from the battery. In the utopian world that light will remain on for 100 hours. However, remember the 50% rule – the battery will best be protected if you run the light for only 50 hours. If you want to calculate the length of stay your battery will reliably sustain you for you need to list all your appliances, their current draw and how long they are used each day. For example if you use two lights drawing 1 amp each for 3 hours per day then your drain is 2×3 = 6 ampere hours.
Then compare your calculations against your battery capacity. As an example, if I work out that all my appliances require 20 ampere hours each day and I have a 120 ampere hour battery then I should be OK for three days. If I have an AGM battery, maybe a little bit longer. Personally I have two 120 ampere hour AGM batteries connected in parallel so I know I have at least 120 ampere hours (the 50% rule), with a bit in reserve. I have tested this on site for three days and used lights, radio, water pump, TV, and experienced no problems at all. I might add here that I also employ a battery voltage monitor to see the state of charge at a glance.

Now how about charging your battery(s). If you have spent good money on quality batteries then please spend a bit more on a quality charger, and the best type is a smart multi-stage charger that will not only charge your battery faster and to a higher charge, but will also ensure a longer battery life with more capacity than if it was charged with one of the constant voltage chargers – you know the type – they sell for around $20.

Where you place your battery(s) depends on their type of course but as I use AGM batteries I have one in the built-in bay in my camper trailer connected in parallel to another that sits in a battery box in the boot of the camper trailer.

If you do use more than one battery, when you connect then together, make sure you use properly sized cable. This is a common mistake made by many people – undersizing the wiring, and then they wonder why their batteries are not delivering. Remember, the smaller gauge the wire, the more voltage loss; and the longer the run, the more voltage loss again. If in doubt, get advice. There is a lot more information on the Internet.

Coming soon – information on Lithium Iron Phosphate batterries for camping.

For more information on dual battery systems (including wiring diagram) for your caravan or trailer see this blog post.

See more smart ideas here.

And for other products to answer your camping battery needs see this page and search for batteries.

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11 Responses to “12 volt Batteries for Camping”

  1. Larry Jay - May 15th, 2010 at 6:09 pm

    Hi:

    Can you advise me as which type of baterries I need for my camper. It takes two. The camper is a 2005 10.5E Bigfoot.

    Thank you,

    larry

  2. Terence - May 16th, 2010 at 7:50 am

    Hi Larry,

    This is not something I can categorically answer – it’s a bit like, “how long is a piece of string”. You need to consider many things before you buy. We have settled that it is 12 volts and that you have space for two. You also need to decide how long you are likely to stay away from mains power and how many home comforts you just cannot sacrifice. I believe the Bigfoot range come with Radio/CD player, on demand 12 v water pump, LCD TV to name just a few. Batteries are rated in ampere hours – that is how much current they can deliver over how many hours BUT, with any battery you should only run them down to 50% of their full charge. This prolongs their effective life. So let’s take for example the LCD TV. This draws about 3 amps at 12 volts. And let’s say you have just one battery rated at 100 ampere hours. This gives about 50 ampere hours of charge to be safe. OK 50 ampere hours means 1 amp for 50 hours, so with the TV drawing 3 amps, you can run it for 16/17 hours. Now take how long you would watch it each day – 5 hours? Now you are down to just over 3 days viewing !

    I have been very simplistic about it all to indicate how it is not that easy. In my camper I have just about the same services you have. I have two 120 ampere hour AGM batteries wired in parallel. Applying the 50% of charge rule (though AGMs can take the occassional discharge below 50%), I have 120 ampere hours. I have easily spent three days bush camping and used the lights, water pump, listened to CDs during the day, and played DVDs or watched TV at night. No problem. I do realise though that if I wish to spend longer in the boondocks then I need to look at solar or a generator to charge the batteries.

    My advice would be to talk to your auto electrician. Make sure the physical size is right, then personally I would go for the 120 ampere hour AGM batteries. You pay premium dollar but the life expectancy compensates. One thing you must insist on is a DEEP CYCLE battery. AGMs are deep cycle but they offer many more advantages over standard sealed deep cycle batteries.

    Sorry I couldn’t ‘nail it’ for you but I hope this helps.

    Regards

    Terry

  3. danny - March 12th, 2011 at 9:17 pm

    This is some really excellent information. I'm shocked by the quality of your blog

  4. Earlean GKarte - January 5th, 2012 at 8:41 am

    Very instructive and good bodily structure of written content , now that's user pleasant (:.

  5. Paul - September 29th, 2012 at 7:11 am

    I am considering buying an 80 watt solar panel. I would like to know if 80 watts will properly charge two 12 volt AGM batteries and if two batteries would be sufficient in hunting camp. We run a small frig in the daytime, lights at night, tv, satellite and on occasion a small hot water heater.
    I'm probably way off on what I need to accomplish this, so any advice would be appreciated.
    Thanks

  6. Terence - September 29th, 2012 at 4:11 pm

    There is no quick answer to this. You need to do some math. But, whatever your solar panel puts out will certainly charge the batteries but to what capacity depends on many factors:

    A quoted 80 watt panel will actually put out usable power of around 70-75% of that stated – in your case 60 watts, and that is under ideal sun conditions.
    If we assume that and assume that you can get five hours of full sun, then your kilowatt hour output will be 300 watt hours.

    Now you need to find out the power requirements of your appliances and then multiply that by the number of hours you want to run them for. Take an example of lights. I have three lights in my pop-up camper rated at 12 watts (12 volts at 1 amp each). That makes 36 watts for lights. Now let's say I use all the lights for four hours per day. I then need 36 x 4 or 144 watt hours for the lights alone without drawing on my battery's reserves.

    See what I mean? I will not be OK saying, "Yeah you'll be right with that.", because I am sure you won't be.

    So find out the power requirements first, then multiply by the number of hours of operation, and then size your solar panel. I would recommend you consult with an auto electrician first too.

    Regards Terry

  7. Brad - August 14th, 2013 at 4:06 pm

    Hi All.
    Like many I am kind of new to this type of thing and we've just purchased a cheap camper and have heaps of things to fix and improve. We are about to go on a 4 week trip from Sydney through to Cook Town and will obviously need to look at power. We have a 160W portable Solar system to use to power up the battery when at camp, but just wanted to see what others have used when travelling to maintain the battery ie – DC-DC charger or a straight charge from the car's alternator?
    We’re only sunning a 80L 12v fridge/freezer, LED lights, water pump for sink so not using a lot of power.
    Also wanted to know how people monitor their battery/ies and if anyone has tried any cheap ebay led monitors or built their own system up (not wanting a system that will cost the earth! or that asks for a pee sample to see how many electrons just left my body! ) I am thinking that we will just needr something to tell me the charge going in (from solar mainly), what charge state the battery is in and possibly something to warn when charge drops too low
    Really appreciate any ideas, suggestions and corrections with my thinking
    Thanks Brad

  8. Terence - August 28th, 2013 at 11:44 am

    Hey Btad,

    Sorry in replying a little late.

    It sounds to me like you have your power requirements pretty much covered. A 160 watt solar system is great and the fact that you are using LED lighting is a good idea too. You may want to consider another battery if you intend a fair bit of time "off grid".

    I explain a lot of this kind of stuff on the web site – in particular http://www.camperscircle.com/624/dual-battery-system/ There is also a comprehensive illustrated guide you can purchase for just $12:97 too. Lots of people have bought this and provided positive feedback.

    As far as battery monitors go, my experience is that the cheaper models do not give a complete and accurate picture of battery state. Believe me it is worth while paying out around $250 for a good battery monitor unit. I review mine on this blog page http://www.camperscircle.com/12289/installing-a-battery-monitor/

    Hope these articles help.

    Regards

    Terry

  9. Peter. Raethke - November 24th, 2013 at 2:26 pm

    Thank you. I read your comparison, I found this very helpful. I am building a teardrop van, so I want to be on 12volt power only using a 1500 pure sine inverter. I found this info quite easy to take in, as it is one of my problems, there is so much info out there, believe me it does get a bit annoying at times. So thanks, you answer a lot of my questions. Cheers Peter

  10. Bob Davis - March 9th, 2014 at 12:34 am

    Thanks for your guide; some very useful information.
    However, technology just keeps rolling along and I'm wondering whether Lithium batteries have made most of this info redundant. Lithium batteries are much lighter, totally maintenance free, the entire capacity is usable (eg 60 Amp Hours = 60 actual Amp Hours), much faster and more efficient charging and they have a much longer life. The only negative appears to be cost, but over a reasonable period this is easily justified.
    Does you article need an update?

    Regards, Bob

  11. Terence - March 11th, 2014 at 3:08 pm

    Thanks for the information Bob. I certainly will update the article with a link to a companion article that I am obtaining rights to. When I have it I'll put a link here too. http://www.camperscircle.com/12555/lithium-iron-phosphate-batteries-for-camping/


 

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