If you have a caravan, Camper Trailer or RV you might often want to take it off the beaten track and get down and dirty with nature.I'm talking about the wilderness experience; selecting a campsite that offers little in the way of services - especially electrical power.In these cases you will have to rely on your battery power, and if you plan on staying a few days and still want the convenience of light, fans, radio and maybe DVD player, etc, you will need to boost your power reserves somehow.In this article I will discuss how you can accomplish that.It may not suit everyone's needs or pocketbook, but if it gives you food for thought it will be a good start.First off let's have a look at some battery facts.There are three main types of battery, conventional wet cell, deep cycle, and AGM, and left to right reads from least to most expensive.The conventional type battery is usually found under your vehicle hood and has to provide a heavy current surge to start your engine.These batteries are not intended to be deep cycled and will have a very limited lifetime if exposed to that.Deep Cycle batteries are not meant for heavy current drains but can be discharged to lower levels.These are usually found as auxiliary batteries in a vehicle or caravan.Both of these battery types need to be vented to the open air because they can generate explosive gases during the charge/discharge cycles.Also bear in mind that batteries do not like being discharged and will rapidly deteriorate if repeatedly discharged below about 50% of their capacity.So, if you have either of these batteries with a 100 Ampere Hour rating, you only really have 50 Ampere Hours of capacity.That is the rule of thumb you should use.Now add to this the fact that if you are charging from a vehicle alternator, the electrics in the charging system will only charge the battery to around 80% of its capacity.This means that potentially you may only have a usable 40 Ampere Hours.AGM (Absorbed Glass Mat) batteries on the other hand are in my opinion the battery of choice.They last longer than the other types.They are sealed and so can be stored just about anywhere, even on their side if you want.All they require is venting to atmosphere.Because of their construction these batteries charge faster and at a lower voltage so will charge closer to that magic 100% of capacity when using conventional chargers.They can also be occasionally discharged below the 50% threshold without long term damage.Consequently an AGM battery will last longer if treated well (typically 8 to 10 years).Now the bad news.They are more expensive than conventional batteries.In my pop-top camper trailer I use two 110 Ampere Hour AGM batteries wired in parallel.This gives me at full charge, a usable 110 Ampere Hours (220 AH / 2).This preserves the life of my batteries and provides me plenty of power, plus a small margin if I need it in emergencies.The camper is fitted with a "smart charger" so that when I am connected to mains power the batteries will charge close to 100% capacity.I also charge the batteries from the vehicle alternator when traveling and this requires some safeguards - you do not want to discharge your starter battery below its operational level, so a battery isolator to protect it is essential.I have used this system on several occasions for extended stay camps and had plenty of power for lighting, water pump, radio/CD player, TV/DVD player and so on.You can work out your battery drain by identifying all the appliances you want to run, what their current draw is multiplied by the use time.For full details including schematic see my resource box below.
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