A good power management system for a successful big lap around Australia

A good power management system for a successful big lap around Australia

Living on the road requires some sort of power management system to keep the beers cold, shower running and all gadgets charged. This is not much different from the demands of the weekend adventurer. However, living on the road means that you are fully dependent on the power generated through solar and alternator as there is no “home to fill up”. To maximize the time you can stay off the grid, a well-designed power management system containing quality equipment such as a good DC-DC charger is essential. Here, I will give you an overview of my power management system for my trip around Australia.

The power management system I chose for my trip

When I bought the car, it came with a starter and auxiliary battery connected by a battery isolator. A battery isolator is a simple and cheap dual battery system that allows both batteries to be charged from the alternator. However, battery isolators are known to limit the charge to approximately 80% of the battery capacity. In order to get 100% charged batteries, a smart DC-DC charger is such as the REDARC BCDC1225D is needed.


REDARC Dual Battery Isolator
REDARC Dual Battery Isolator: a simple dual battery system


The new REDARC BCDC1225D dual battery smart charger

How does the REDARC BCDC1225D work?

The in Australia made REDARC BCDC1225D is a smart charger which allows charging two batteries from the alternator or a solar panel using MPPT solar charging. MPPT stands for Maximum Power Point Tracking which maximizes the solar current at any voltage, what you can see as a more efficient solar power regulator. In addition, the BCDC1225D has a Green Power Priority built-in, this means that it will select power generated by solar before the alternator.

The reason I replaced the simple isolator dual battery system by this battery charger is because it uses a multi-stage charging algorithm which allows the battery to be charged to the full 100%. This is also important for cases when the auxiliary battery is far away from the alternator, like in a camper trailer or caravan. The charger contains its own isolator to prevent over discharge of the starter battery. This means that the isolator stops further charging of the auxiliary battery from the starter battery when the alternator is turned off.

The reason the BCDC1225D is able to charge the batteries to the full 100% is because of the used 3 stage charging. While the alternator just pumps energy in the batteries, the BCDC1225D uses 3 different charging steps. The first stage is the boost mode which charges the battery at a constant amperage until the battery is charged for 75%. The second stage is absorption, which uses the same high voltage as stage one but now with an adjusted amperage till the battery reaches full capacity (which differs for the type of battery). The third stage is a floating stage in which is a trickle charge to prevent discharging of the battery.

More battery and solar power

To be able to stay longer of the grid, I decided that I wanted an extra battery (making the total 3).However, only so much can be fitted in the bonnet. I decided to place an additional battery in the canopy. My choose fell on a 125Ah AGM battery. I connected this one to a roof solar panel and controller. The great benefit of AGM batteries is that they are safe to use in enclosed spaces. This is important if I decide to sleep in the canopy. In addition to the roof solar panel, I also carry a portable solar panel to charge a 40Ah AGM battery for in the kayak. I use anderson plugs for all batteries, making it easy to switch everything around if needed.

How I designed my power management system

I wanted to keep my power management system simple and flexible enough for future additions. I started out making a list of items I want to charge and run. Next, I divided my car into two compartments: the front and the canopy. I did this because the AGM battery in the canopy has a different maximum voltage compared to the front starter and auxiliary battery. After doing some research, I made a simple diagram of the set-up I wanted.

With this diagram, I went to Greg from 4WD Trekmaster. He gave me valuable input on my diagram based on his experience with 4WD touring. As DIY’er, I do recommend to always get input from an experienced 4WD electrician as you want to make sure nothing vibrates loose and causes a fire. Or as was shown on Facebook not long ago, a fridge cable that came between the fridge slide and caused a fire in the canopy, something that simply could have been prevented.


Diagram of my power management system
Diagram of my power management system

Installation of my power management system

Installation of the system was very simple. Together with Greg, I replaced the old dual battery isolator quickly with the DC-DC charger. The biggest problem we encountered was where to put the unit as my bonnet was pretty full. We decided on a metal plate close to the aux battery. The REDARC unit is made for Australian conditions so installation in the bonnet is fine. We used an REDARC fuse kit to wire up the unit to the Aux battery.


The REDARC charger nicely mounted on a bracket close to the AUX battery. A 40Ah fuse protects the wiring.

Next both batteries were wired up to a dash gauge. The dash gauge shows me the voltage of both batteries at any time. With a built-in Amp meter, I am also ensured to see that the REDARC is charging.


Dual battery voltage gauge
REDARC Dual battery voltage gauge and AMP meter

The solar panel is from the flexible type which is glued to the roof of the canopy. It is connected to the AGM battery in the canopy through a controller unit. The AGM battery itself is connected to a big fuse box to power all attachments. By keeping everything fused, using the correct gauge wire and making sure everything is attached in a corrugation proof manner, ensures a safe to use system.


Solar panel controller and electrical box
Solar panel controller and one of the electrical boxes

I will keep this post up to date with future changes to the power management system. Let me know if you have any questions or like to share your power management system.

See you on the road less travelled!

Disclaimer: the BCDC1225D, fuse kit and gauge kit were kindly provided by REDARC to be used on my trip

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