Charging Caravan Battery from Tow Vehicle
Should my car battery charge my caravan battery while driving?
Ultimately yes, your caravan house battery should be charging while driving. The caravan fridge, as well as potentially your electric hot water system, and even electronic devices will be drawing down the battery while in transit. Therefore, it is necessary, particularly to power the fridge, to have a solution to charge your caravan batteries while in transit.
Which DC to DC Battery Charger to use?
The answer to this depends on many factors, such as current load dependency - ie portable fridges, compressor fridge or 3 Way Fridge, water heaters, camping equipment, lights, solar panels and solar setup, type of batteries, ie lithium batteries or AGM batteries, the type of tow vehicle, type of trailer and the list can go on as wiring in caravans and power load demand varies from caravan manufacture to caravan manufacture.
There is countless manufactures and versions of DC to DC chargers available to the 4WD, caravan and recreational vehicle market.
There are DCDC Chargers that charge from either solar or the vehicle alternator system (car battery) but will choose the car as priority. Therefore, even in full sun and when connected to the car, charge will only be generated from the car. Conversely, there are DC to DC chargers with solar input that feature an inbuilt MPPT solar regulator to incorporate ‘Green Priority’. These battery chargers charge from either the vehicle alternator system (car battery) or from solar panels, but will choose the ‘green power priority’, which is priority given to solar power over the alternator battery.
Additionally, with the adequate components and wiring some DC to DC battery chargers can charge the start battery when charging from solar. HOWEVER, we do not recommend this.
Key Considerations when choosing a DC to DC Battery Charger.
You should choose a charger that has a current rating within the battery manufacturer’s recommended maximum charging current. A higher current charger should not be used because excessive current flow into a battery can impact it in several ways, the worst of which can be the degradation of battery service life and capacity; likely to void warranties and is an expensive mistake if running lithium batteries.
Benefits of using a DC to DC Charger:
Charging direct from an alternator or through an isolator does not limit the charging current and it is possible for the aux battery to be damaged by being charged above the manufacturer’s recommended maximum current. To prevent this, choosing the correct DC to DC charger limits the charging current to a safe level suitable to the battery manufacturer’s recommended maximum charging current.
A fixed voltage alternator can charge the aux battery at 14V or more all the time you are driving, but most battery manufacturers recommend a lower “float” voltage. A correctly matched DC to DC charger recognises the battery aux is fully charged and will drop to lower float voltage.
DCDC, BCDC, Combined DC-DC/MPPT, Enerdrive, Redarc Victron; with so many options and applications it can be difficult to determine the most suitable and cost effective solution for your caravan and tow vehicle.
NOTE: Not all battery chargers are lithium compatible, so when upgrading from deep cycle batteries, lead type batteries (flooded, AGM, Gell, Calcium Lead Crystal) to lithium (LifEdPO4) batteries consideration to a compatible DC to DC charger is necessary.
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