28th January, 2015


Recently my family and I went on an overnight camping trip at one of our local beaches. I have a LandCruiser 100 Series TD 06 model with the dual battery set up as standard. During the night’s festivities I was running the 40L Engel on the second setting (fridge only) with the radio going for about five hours until it was turned off, and the fridge continued running all night as it has done in the past.

The next morning saw us with both batteries flat as a tack. Luckily we had a battery pack which subsequently went flat as we had used it to jump start a boat earlier on, so we resorted to the trusty jump cables to get it going.

Is there any way that I can do a load test using a 100W lamp arrangement or the like to ensure their reliability for the next outing, and do the battery places have a formula that they use to calculate this as mine are sealed ones?

I have heard that lots of people in the Pilbara use the Redarc solenoids as their battery drain solution. Can you tell me what they are like and if there are quality alternatives competitively priced – plus what size would I need for my set up, the 100 amp or 200 amp rated ones?

Are these easy to wire up to my circuitry as it is in standard form and are there any special considerations?

My next question is: can you put a small CTEK charger in to trickle charge the starting battery using the auxiliary battery once the engine has been switched off?

Any help would be appreciated.


Mike Keogh

Dear Mike,

To correctly load test a battery, a battery load tester, which can apply the correct amount of load proportional to the rating of the battery, is required. The battery must be fully charged to carry this test out. Another way of checking the condition of a battery (wet cell batteries only) is with a Hydrometer. This is a tool that measures the specific gravity of the electrolyte, which indicates the battery’s state of charge. Both of these tests can be carried out by your local ARB store to give you confidence in your batteries before heading away on your next trip.

The 100 Series LandCruiser turbo diesels have two large cranking batteries to start the engine. This is due to the large current required to start these engines, especially in cold conditons. To ensure that you maintain this large reserve of cranking power for all starting conditions, we recommend that an auxiliary battery is fitted to the vehicle, leaving the standard starting battery configuration as it is. Adding an auxiliary battery and isolator allows you to run loads when the engine is off, and leave the start batteries fully charged.

You can have the auxiliary battery in the engine bay with the ARB battery tray, or in the cab with an ARB battery box, and use a Century C12-55DA deep cycle 58A/Hr AGM battery.

Ensure you charge your auxiliary battery to 100% state of charge to get the best run time of your loads between charges. To achieve this, and to take care of your auxiliary battery, use the Redarc BCDC1220 in-vehicle battery charger. The BCDC1220 is a multistage charger that will charge your auxiliary battery with the specific profile required for correctly charging your AGM battery. It also has inbuilt battery isolation – this will ensure you don’t end up with flat start batteries and give you peace of mind for a trouble free camp out at the beach!

To answer your last question, when you implement a system that incorporates battery isolation such as the BCDC1220, there is no need to trickle charge your main battery from the auxiliary while the engine is off, as the main battery is left in a fully charged state ready to start the engine.

Stuart Peddle
(Sales & Customer Support Technician – Redarc
Electronics Pty Ltd)