Hi it's Reggie: I'm beginning my self-build camper essentials guide with 12 VOLT POWER. Whether you add an electric hook-up or not, you'll definitely need a decent-quality leisure battery with enough amps to run all your chosen appliances for a reasonable time. Before purchasing, check that the battery fits your allocated space (dimensions), the seller's feedback, and the delivery time/options.
For more info on how to determine what size and type of leisure battery you need scroll down the page.
Should I connect my 12-volt batteries in series or parallel?
12-volt or 24-volt camper van/leisure battery systems.
To connect 2 x 12-volt batteries in series, a link lead of a suitable grade must run from the positive (+) terminal of one battery to the negative (-) terminal of the other, creating a 24-volt battery system. To connect 2 x 12-volt batteries in parallel, run a link lead of a suitable grade between each battery's positive (+) terminal. You can either link the negative terminals the same way or earth both batteries to a suitable spot. Linking 2 batteries in parallel keeps the battery system/bank at 12 volts and doubles the Ah output; i.e., 2 x 110Ah leisure batteries linked in parallel = 220Ah.
Volts
Volts explained.
The electrical pressure between two points. The longer the distance between the two points (i.e. the cable/wire length), the greater the potential for voltage drop.
Amps
Amps explained.
The unit used to measure electrical current as it flows past a specified point.
Watts
Watts explained.
The rate at which electrical energy is used. Watts combine voltage and current (volts and amps).
Amp hours
12-volt battery amp-hours explained.
The amp-hour rating denotes the amount of energy that can be taken from a 12v battery before the terminal voltage falls below 10.8 volts. This test is usually carried out over 20 hours (20-hour rate). Thus, a 50 amp-hour car/leisure battery can be discharged at 2.5 amps for 20 hours before the voltage drops below 10.8 volts (i.e. 20 x 2.5 = 50). With leisure batteries, amp-hours are often abbreviated to amps (e.g. 85 amp leisure battery). How much 12 volt power (amp hours) do I need? The simplest way to calculate your leisure battery power consumption is: watts divided by volts = current in amps. Thus, on a 12-volt electrical system, a 120 W pump will take 10 amps (i.e., 120 watts/12 volts = 10 amps). In theory, using the above equation, you might think that an 80 amp leisure battery would be adequate to run the pump for 8 hours, but in practise by the pump will fail to run properly as the 12v leisure battery becomes completely discharged, so a safety margin of around 25% should be applied to the leisure battery amp hours required. See the equation below: i.e., a 10 amp pump running for 8 hours = 80 Ah + 25% safety margin (20 Ah) = a leisure battery of at least 100 Ah is required to run the pump efficiently. You can also do the equation the other way round by multiplying the leisure/car battery volts by the amps, e.g., 12 volts x 10 amps = 120 watts. Ok, let's show off. Here's another way: 120 watts divided by 10 amps = 12 volts.
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