ASK THE EXPERT – DC to DC IN VEHICLE BATTERY CHARGERS
Just after some help/ info regarding all the hype about these DCDC in-car chargers.
I’ve been camping and 4WDing for about 20 years now, and I run a heap of 12V stuff. Ovens, compressors, lights, big inverters etc. Over the last five or so years, I’ve been doing this with the added bonus of a solar panel (great things).
Now I’ve never had any issues, as the alternator charges both batteries and the solar is now doing my third and also helping with the other two.
So my question is, how does a DCDC charger make this better?
This is a serious question as I’m always learning and want to understand.
So please educate me.
Kim John Hardy
It’s a good question. It actually comes down to the type of battery you have fitted in your 4WD set up, as well as the alternator type fitted to the vehicle. There are many different types of batteries – lead acid, calcium, AGM, lithium etc, and each battery type has a different chemical make up, with their own limitations both for charging and discharging.
The use of a DCDC charger will allow you to select the correct battery make up, and will then charge the battery using the correct profiles.
A DCDC charger is also capable of charging and maintaining a battery, rather than just providing a bulk charge direct from the alternator.
It is also capable of lifting the charge voltage to the auxiliary battery in order to provide the correct conditions for the battery to accept proper charge. What I mean by this is that most modern alternators are now either smart alternators, or with Toyotas, they are temperature compensation alternators.
As the engine gets hot, it reduces its voltage. An AGM battery requires about 14.6V to charge correctly, but the Toyota alternators can drop voltage down to 13.5V when hot. The DCDC will lift the charge voltage to the AGM battery and supply the correct charge voltage.
DCDC chargers usually have a three-stage charging profile. When the battery is fully charged, they will go into a float mode or they will otherwise enter an absorption mode. This will charge and maintain the battery correctly and not only give you a 100% fully charged battery, but it will also maintain the battery correctly giving you 100% maximum battery life.
The other bonus is that if you run a solar panel to the DCDC charger, most chargers will use the solar first and then add power from the vehicle making it a bit more green friendly.
Hope that helps