Choosing the right charger for your dual battery system

Choosing the right charging solution can be confusing. With so many different options available, it’s hard to know exactly what solution is right for your setup and how you’re wanting to travel. We’ve broken down the three most popular charging solutions to give you a better idea of which charger would best fit with your setup.


Battery Isolator

A battery isolator is the simplest solution for ensuring your start battery doesn’t get drained while you’re using your auxiliary battery to run accessories. They’re fairly cost effective and perfect for those looking for a set and forget option to running all your gear on the road.

Battery isolators works by sensing battery voltage to know when your vehicle’s engine is running, and charge is going to the starting battery via the alternator. When a certain voltage is reached, the isolator will connect and start charging the secondary battery.

When the alternator stops running and the engine is turned off, the isolator will disengage the auxiliary battery from your start battery. This isolates the start battery, hence the name. This stops any loads connected to the auxiliary battery from also draining your start battery.

REDARC’s SBI or Smart Start Dual Battery Isolators, are generally recommended for vehicles with a fixed voltage alternator. They’re great if you’re looking for a setup on a budget or want a simple set and forget under bonnet solution.

Perfect for: vehicles with fixed voltage alternators, budget builds & under-bonnet installation


DC to DC Battery Charger

If you’ve got a variable voltage alternator, are looking for more flexibility or want to charge from solar, a DC to DC battery charger is the solution for you. DC-DC chargers work similarly to a battery isolator at their core though with a bit more smarts.

With more technology built in, DC-DC battery chargers can detect what type of auxiliary battery you’re wanting to charge and supply the optimal charge voltage. This means that they can effectively charge your secondary battery to 100%, while ensuring its prolonged health and life. If you’re wanting to install your charger away from your alternator, a DC-DC battery charger is better at overcoming voltage drop from these long distances.

If you’re wanting a 12V dual battery setup that can charge via solar, you’ll need a DC to DC charger. These battery chargers can take power from solar or your vehicle’s alternator, and with in-built Green Power Priority in the REDARC BCDC range, they will always choose to use incoming solar power before putting excess strain on your alternator.


BCDC Classic
BCDC ClassicBCDC Classic

Depending on where you’re wanting to install your BCDC charger, there are two models available – the Classic and the Core. If you’re wanting a charger that can be mounted under your bonnet, the BCDC Classic is the way to go. Being fully potted, the electrics are sealed and protected against dust, dirt, water and vibrations. It’s a charger that can handle anything your trip can throw at it and not miss a beat.

Perfect for: Under-bonnet installation or installation anywhere with exposure to dirt, dust, water or harsh vibrations & set and forget charging



If you’re planning to install your charger into a canopy or the cabin of your vehicle, the BCDC Core could be a great option. It’s perfect for tucking away in a side panel, hiding behind seats or mounting on the power wall of your canopy where it won’t be subjected to extreme heat, water or dust.

Perfect for: Canopy or in-cabin installations, budget builds & set and forget charging


Battery Management System
Manager 30Manager 30

A battery management system is the next step up from a DC-to-DC charger. While working in a similar way, it allows you to have more visibility into what your system is doing. Battery management systems combines the functionality of a battery isolator and dual battery charger into a single unit. REDARC’s Manager30 Battery Management System includes DC to DC battery charging, 240V charging (from mains power), battery isolation, a load disconnect controller, solar regulator and remote monitoring all in a single unit.  

Battery management systems are a great option if you’re wanting full visibility of your system. With the remote monitoring screen, you can always see exactly how much power is going in out and out of your battery, as well as how many days’ worth of power you’ve got left.

Similar to the BCDC, the Manager30 also features Green Power Priority. With many chargers on the market only being able to take charge from either your alternator or solar, the Manager30 can take both and will always choose solar first whenever it’s available.


Having a load disconnect control has the benefit of allowing you to make sure your batteries are not over-discharged by your loads, The Manager30 will warn you when the battery is nearly flat. If you miss this warning, the Manager30 will disconnect your loads to keep your batteries at a safe level of charge.

The built-in AC charging input means that whether you’re parked at home or at a powered campsite, you can plug your battery management system into mains power and keep your batteries topped up. This allows you to make sure your batteries don’t die while your vehicle is in storage waiting for your next trip.

Perfect for: Canopy, in-cabin, camper trailer & caravan installations, those who want increased monitoring & an all in one solution

Choosing a charging solution definitely depends on your setup and what you’re wanting to get out of it but we’re hoping your options are a little clearer now. For more information on choosing and designing the best power system for how you want to travel check out our build your dual battery system tool and designing the perfect power system blog