Additional power sources fall into two main categories. Permanently mounted auxiliary battery systems and portable power packs. The latter becoming increasingly more popular now that newer vehicles on the market have limited under bonnet space.
In some cases, these auxiliary batteries may be mounted in the tool box of a caravan or camper trailer, or even on the rear tray of a ute. These auxiliary batteries in both fixed and portable systems are available in varying capacities and depending on your needs, will determine which system will best suit you and which battery type you should have fitted. There are also fridge packs available but as they take a longer time to recharge and have a lower capacity than conventional batteries they are not recommended for quick car charging and will not suit most travellers.
Conventional lead acid batteries fitted as auxiliary batteries to vehicles (or power packs), average around 90 to 100 amp hours. Broadly speaking this is the available amps in the battery for use to power accessories.
Device Usage Guide
Some typical amp hour usage values for some devices are listed below:
- 2.5 to 3.0 amp hours for a 12 volt fridge (compressor type)
- 1.0 amp hour for a 12v fluorescent light (twin tube)
- 2.0 amp hours for a 12v portable DVD player
- 5.0 amp hours for an inverter powering a laptop
- 1.5 amp hours for an inverter powering a camera charger
- 4.0 amp hours for an inverter powering a small TV
An ExampleLet's look at a typical real-life situation and make some calculations:
Between 6pm and 8am the vehicle is at camp and not being driven - the fridge is on; the camera and laptop chargers run off a 600 watt inverter for 3 hours; and the 12 volt lead light is used for 5 hours. The total capacity taken from the battery is estimated over this 14 hour period to be 60 ampere hours. With a 90 ampere hour wet cell cranking battery and with 14 hours of usage overnight it's down 60 ampere hours. This will have to be replenished by the vehicle's charging system.