DC Battery-to-Battery Chargers

The DC battery charger/splitter obtains its energy from DC sources such as alternators, solar panels or wind power and optimises this power to meet the charging requirements of different battery banks.

Suitable for the most modern of vehicles with "Smart" alternators (regenerative braking) and older vehicles with conventional alternators too!

Battery to battery (DC to DC) split charge systems.

DC to DC battery split chargers are very simple to fit as these units only needs wiring from the starter battery to the leisure battery. No connection to the alternator is required.

The difference between DC battery chargers and other split charge systems is that the DC battery charger uses it's own micro-processor system to determine the actual level of charge in the leisure battery and tricks the alternator into providing extra charge for long periods in order that the leisure battery reaches full charge.

Confused? Let us explain further...

As stated previously a split charge relay is governed by what the vehicle alternator does. When the leisure battery voltage rises to a certain level (surface charge) the alternator will cut down it's 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 differentiate between what is just surface charge (i.e. the voltage has reached a level, but the battery actually needs much more charging) and what is full charge. This is where the DC battery charger comes in... Basically it reacts the same as a top quality mains battery charger, but instead of using mains electricity is uses power from the alternator and it will keep demanding that power until the leisure battery's actual full charge is reached.

So, to summarise, if you use a lot of leisure battery power and deep discharge the battery/batteries regularly then the DC battery charger should be your preferred option. Popular brands include Ring Automotive, Ctek and Sterling Power.

DC Battery Split Chargers are also suitable for the latest vehicles with regenerative braking systems.

Need to know more? See the examples below.

Ctek D250S DUAL
Ctek D250S Dual battery charger

Ctek D250S Dual battery to battery charger

The D250S DUAL charger obtains its energy from DC sources such as alternators, solar panels or wind power.

Charging automatically starts as soon as DC energy is provided to the charger, such as from alternators when a vehicle is started or from solar panels when connected. The D250S DUAL has a temperature sensor which ensures optimal charging voltages at all temperatures. Ensures that your batteries are always in good condition, quick charging and long battery lifetimes. Very simple to fit.

See it on the CTEK website.



Model #:

D250S Dual

Charge rate: 20 amps
Voltage input: 12v
Voltage output: 12v
Dimensions (mm): 192 x 110 x 65 (LxWxH)
Warranty 2 year
Multi-stage charging:


Instructions included: Yes
Installation difficulty rating: Easy

Ring Automotive DC SmartCharger 30 amp

The Ring DC battery charger takes the energy from a vehicle's main battery (engine running) and converts it into multi-stage output for charging an auxiliary battery. Input voltage (starter battery bank) can be between 12v - 50v and output is 12 volts to charge a 12v leisure / auxiliary battery bank.

Compensates for high voltage or a drop in voltage to maximise charge to auxiliary battery. Programmable for most battery types. 3-Stage smart charge output for optimal battery performance. Suitable for battery banks from 40-500Ah.

Will work with smart alternators to deliver accurate charging voltage. Low battery shut off to protect main battery. Sleep mode to eliminate battery drain.

Solar panel input with MPPT feature for charging at rest. Applications include utility vehicles, vans, motorhomes, caravans and boats.

See it on Ring Automotive.



Ring Automotive

Model #:


Charge rate: 30amps
Voltage input: 12v - 50v
Voltage output: 12v
Dimensions (mm): L 236mm x W 203mm x H 87mm
Warranty 1 year
Multi-stage charging:


Instructions included: Yes
Installation difficulty rating: Easy