Without getting too technical let’s take our setup of batteries in the caravan which is:

3 x 12 volt AGM Deep cycle batteries. Each battery is 120ah (amp hour). (update 2019 - we now have 360ah of lithium batteries in our van but for the purpose of this original post we will leave the right up indicating a AGM setup)

 The key to a battery is the ah reading. Ah is short for Amp hours. So for simplicity reasons, a 100ah battery means you can use 1 amp of electricity from that battery for 100 hours before the battery is totally flat. Connecting batteries in series doubles the voltage but keeps the amp hours the same. Connecting batteries in parallel maintains the voltage and increases the amp hours. Refer to google if you want to know more but in general for caravans you’ll be connecting in parallel.

Caravan’s use AGM deep cycle batteries (or better like the recent  Lithium 12 volt battery). They do not use the  standard lead acid starter battery that you use in your car. There’s a reason for this that I won’t explain here but for now just be aware that there is a difference.

​Connecting batteries


Having 3 x 120ah batteries connected in parallel gives us a total of 360ah of current we could use. however, a deep cycle battery does NOT like to go less than %50 charge or else the life expectancy of the battery drops dramatically. There’s a chemical reason for that which I won’t go into either  but feel free to read the battery university website if your curious. Therefore our 360ah battery system is effectively 180ah "useable" amps.  Which means in one day if we used 180amps of electricity, our batteries would be %50 flat. That’s as low as we would want them to ever be, which equals 7.5amps per hour usage.



Like everything its up to the individual to decide what's right for your needs. To help guide you in your decision try entering different battery AH ratings  in the below excel spreadsheet and see what results you get.
Since writing this post we have now upgraded to lithium batteries which allow us to utilise down to %20 charge instead of %50. Lithiums also have alot of positives to them such as weight, a better power. However they come at a hefty price tag.

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Leave a Comment

    • Laz
    • February 25, 2018

    Here’s a comment

    • Rebecca Muller
    • March 23, 2018

    We have two AGM house batteries (120 i think) in our MH. How many hours would you be able to run a TV ? Thanks so much for your help.
    KInd regards

      • Laz
      • March 24, 2018

      Hi Rebecca thanks for the question. That question depends on how much electricity your TV uses. They all vary so would pay to have a look at the back of your TV and find out what the amp’s (normally reads like 3A or 3Amps) or wattage (W) of the TV is. As an example… a Tv might draw 3amps that means if you had the TV running for 10 hours you would use 30amp hours from your batteries. 3A x10 hours = 30amp hours. your 120ah batteries should only ever be taken down to %50 discharged which = 60ah. Therefore….. based on this example you would get 20 hours usage from the batteries providing nothing else was draining the batteries and you weren’t automatically charging the batteries as well. Hope that helps and wasn’t too confusing.

      PS if you can only find out the wattage of the TV and not amps ( look at the label on back of the TV) then take the wattage figure and divide that by 12volts. EG : 35W / 12 = 2.9amps …. 2.9 amps x 10 hours usage = 29amp hours 🙂

    • Laz
    • April 28, 2019

    another test comment 🙂

    • George
    • July 16, 2019

    What is required to have a setup that shows amperage in each battery (there are 3 AGM 120 ah). Necessary? It’s something that could be advantageous.

      • Sue
      • July 16, 2019

      Hi George, 3 x 120ah batteries is what we have due to free camping often (in fact we now have that in lithiums rather than AGM’s due to our power needs). However depending on your electrical requirements just 2 of those batteries could be sufficient. Some batteries you buy now have built in bluetooth management systems which can show you the amperage of each battery via your phone. otherwise you have options of using a BMS system (battery management system) like the redarc bms1230 to show you all your power and amp consumptions, (along with probably heaps of other products on the market)


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