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Hello it's Nobby here, and today I've been thinking about DC Battery-to-Battery Chargers and Split Charge Relays. Here are my thoughts...
DC Battery-to Battery Chargers
The DC battery-to-battery charger draws power from DC sources such as alternators, solar panels, or wind power. It optimises this power to meet the charging requirements of different battery banks. Suitable for modern vehicles with "Smart" alternators (regenerative braking) and older engines with conventional alternators.
DC Battery Split Chargers are suitable for the latest vehicles with smart alternators regenerative braking systems.
DC Battery Charger or Split Charge Relay?
DC-to-DC battery split chargers are simple to fit, as they only need wiring from the starter battery to the leisure battery. No alternator connection is required.
The difference between DC battery chargers and other split charge systems is that a split charge relay is ruled by how the vehicle alternator senses the leisure battery charge; the DC battery charger uses its own microprocessor system to determine the actual level of charge in the leisure battery and tricks the alternator into providing extra charge for long periods so that the leisure battery reaches full charge. Confused? Let me explain further...
As I said earlier, a split charge relay is controlled by the vehicle alternator. When the leisure battery voltage rises to a certain level (surface charge), the alternator will cut down its charge rate to minimal amps because it thinks the battery is now charged; in most cases (i.e. light caravan and camping uses) where the leisure battery is not deeply discharged, this would be acceptable. However, if the battery is deeply discharged, the alternator will cut back too early because it can't distinguish between surface charge (i.e., the voltage has reached a level, but the battery still needs much more charging) and a full charge. This is where the DC battery charger comes in...
Basically, the DC battery-to-battery charger behaves like a good-quality mains battery charger, but instead of using mains electricity, it uses power from the alternator. It will keep demanding that power until the leisure battery reaches its actual full charge.
So, to summarise, if you use a lot of leisure battery power and regularly deep-discharge the battery/batteries, then the DC battery charger should be your preferred option. This is especially relevant on vans from, say, 2010 onwards that may have smart alternators/regenerative braking that a relay will not work with.
That's it from me. I'm off for my afternoon nap. I've listed some of my top buys below. Regards, Nobby.