A battery charger is an apparatus that deposits electrical energy back into a rechargeable battery.
Basically, a solar panel is a battery charger. Some stand alone solar systems may occasionally require additional battery charging (e.g. during periods of prolonged cloudy weather). Other situations require daily backup because the solar, wind or hydro system has not been designed to completely meet all the electrical loads.
Larger systems often incorporate a diesel generator set with an interactive inverter charger. These are sometimes referred to as diesel hybrid systems as they can also include charging from renewable sources such as solar, wind and hydro.
Choosing a Battery Charger
To suggest a battery charger to meet your needs, could you advise:
- Type of batteries (e.g. wet/flooded, AGM, gel)
- Capacity at 20 and 100 hour rates
- Automatic or manual charging desired
- Frequency and duration of each charge cycle
- Voltage of the battery bank
- Generator rating
Battery Chargers for Mobile Homes
There are several options for keeping your auxiliary battery in your motor home charged. Which option is the best for you depends on your driving patterns, your electrical loads and where you will be staying. Some folks only want a few lights and a small radio. Others require a fridge, television, fan and maybe even a microwave oven and an air conditioner!
Battery Isolators and Charge Equalisers
Battery Isolators and Charge Equalisers are ideal for dual battery systems in mobile homes and boats. A typical situation where either an Isolator or a Charge Equaliser is used is where one battery is used for starting the vehicle and the other battery is used for lights and appliances.
The loads may either be direct DC or via a DC to 240V AC inverter. Battery isolators and equalisers may also have an application in stationary solar power systems for emergency lights, refrigeration for medical supplies etc.
A Battery Isolator is used when connecting two batteries of the same voltage to a common charging source such that the lights and appliances cannot discharge the engine starting battery or vice versa. Battery isolators are available in either 12V or 24V.
When you have a dual battery system where the battery voltages are not the same, particularly when the starting battery is 24 volts and the appliance and lighting battery is 12 volts, a Battery Charge Equaliser will then allow you to charge the 12 volt battery from the 24 volt supply when you are driving or when you want to provide both voltages stored in separate batteries from a single solar array.
If you plan on staying in powered caravan sites most nights, you could get a fairly small automatic battery charger which will charge your battery while you are connected to the mains power (grid).
If you are going to be camped away from the grid and stationary for more than a few days, you will probably need either a generator set or solar panels to keep your battery charged. If you have large electrical loads like an air conditioner, you will probably require a 240V AC generator set. You can then connect a mains powered battery charger to this. On the other hand, if you don't have any large 240V electrical loads, then a smaller petrol powered 12/ 24 volt battery charger would be more efficient. However, generators have a lot of disadvantages. You need to carry fuel and they make noise and fumes. Your neighbours in the park or campground may not appreciate your noise! You also need to remember that you can only charge a battery at something like ten to twenty percent of its capacity. So if you have a completely discharged battery it will take at least several hours to charge it up which is a long time for a generator to be on for.
Solar photovoltaic (PV) modules are an ideal way to charge your batteries. While they have a high capital cost, they are maintenance free and should add to the resale value of your motor home. You should have your loads assessed by an accredited solar installer so that the system will meet your needs. Don't buy a fridge until you've discussed it with your solar supplier! Solar panels need to be in full sun to operate to their full capacity. Most people prefer to mount their panels on the roof - 'Out of sight, Out of mind' so to speak. The only disadvantage is that it means that this portion of the vehicle must be parked in the sun. This can be somewhat annoying on a hot summer's day. The other alternative is to have your solar panel on say a ten metre lead which allows you to park under a tree and place the panel out in the sun. Depending on where you are parked, theft may be a worry with this method if you aren't nearby.
All the methods of keeping your batteries charged have their good points and their limitations. Many people will need to select at least two methods to meet their requirements.