Nissan Australia

12 Volt System


One thing I have found with most 12 volt systems, both on vehicles and campers, is that there is a lot of confusion about the design and operation of installed configurations and in knowing how to properly maintain the setups for optimum performance and maximum life.

When picked up from the factory, the Aussie Swag had a basic 12 volt system that was only capable of running a few lights, water pump and a fridge for a couple of hours. Although simple, it did its job as was intended however it was far from meeting the requirements that we had in mind.

Our camper has now been setup to provide long term power whilst away from civilisation. This is accomplished using alternator, solar and generator charging. The current setup consists of 4 x Concord PVX-1040T 120AHr AGM batteries for a total capacity of 480AHr (existing setup was 4 x 100Ahr Dynasty AGM batteries), Manson 20A 3 stage solar charger, 2 x BP380 80W solar panels setup as a briefcase arrangement, Durst 30A 3 stage smart charger, Honda EU10i invertor generator and various other components such as an isolator, NASA BM-1 battery monitor, current shunt, 12V outlets and fuse box.

The heart of the system are the chargers and battery monitor. From here I can view the charging status of either the solar regulator or 240v charger and what stage in the charge cycle they are up to. Both chargers utilise LED's to indicate whether in Boost, Absorption, or Float charge. The Solar regulator also has an LCD readout that cycles every few seconds to indicate batt volts, PV volts, PV current, total AH today, total AH day 2, total AH day 3 and charge status. Each of the chargers are set to the GEL battery profile and are connected to the batteries via heavy 16 mm˛ starter cable. I had to put a small dob of silicon on the 240V charger's profile switch as it had a habit of being accidentally switched over to Flooded. I purchased the chargers on eBay with the solar regulator costing $130 and the 240V charger $370. Compare this to other similar products and is around a third the cost but for exactly the same performance.

Needing accurate Amp and Volt readouts is a must with any DC system but unfortunately there are not many displays around that can do this without costing an arm and a leg. I was not interested in the voltage displays with clocks and thermometers as they are both inaccurate and tacky so for the same amount of money I made my own. All up cost was around $37 and little bit of time to assemble.

The setup consists of 2 LCD displays from Dick Smith (part no. Q2220 cost $9.98 ea), a 50A current shunt from Jaycar (part no. QP5412 cost $9.95 ea), a switch, resistors (to setup the displays), wire, terminals, a box and a 9V battery. The shunt is located in the battery compartment and is secured with a dob of silicon to reduce holes in the tub. The negative leads of all accessories go to one side and the batteries negative lead is connected to the other side. All accessories have their negative lead terminated at the shunt with nothing being grounded to the chassis. The LCD is then connected to the shunt to display Amps. You can then see current going into and out of the batteries (displays a negative sign when current going out). Both readouts are powered by a 9V battery and I put a switch in to turn them on and off as a battery was only lasting a couple of weeks when they were always powered on. I am extremely happy with the setup and can see what current each accessory is drawing and what the chargers are putting in.

I have now replaced the individual readouts with a NASA BM-1 battery monitor. This is a marvellous bit of gear that shows Volts, Amps (in and out), Capacity, time remaining to discharge, time remaining to charge and is illuminated. It comes with a 100Amp shunt and is great in that it is very accurate, self learning and has a large readout so is easily viewed from a distance. The price of these units is $295.00 which is well priced considering other battery monitors cost $400 +.

The batteries were purchased second-hand from eBay for $100 each shipped and were from a mainframe UPS system. The batteries are replaced every 2 years (they have a life of several years if looked after) so it was with caution that I bought one to check to see how good they were. After thoroughly testing and confirming that all was good I bought another 4 and proceeded to fit one to our Patrol and the other 4 to the camper. A wood frame in the bottom of the compartment stops the batteries from moving around and a metal strap on each one holds it securely to the bottom. Again 16 mm˛ cable was used to connect them all in parallel. As they are AGM batteries, a different charging profile is needed to keep them well charged and maximise life. I went to the Dynasty website and checked what the manufacturers recommend and then proceeded to program the solar regulator to these specifications.

An isolator located behind the water level indicator switches the charge from the alternator to the batteries however I very rarely use this due to the very basic and primitive method of alternator charging. The isolator can be switched on or off via a switch next to the 2 DC outlets inside the camper. A third DC outlet is located outside and powers the fridge when camp is setup. The fuse box that all the accessories draw power from sits next to the isolator.

A Bifacial solar panel is also used to charge the batteries via the solar regulator. It is a 2 sided panel with the main side consisting of a 90W panel and the reverse side a 60W panel. Bifacial modules can produce between 10% and 40% more energy in comparison with monofacial modules with the same dimensions. Maximum gain is achieved with using a reflective or white colour object behind the modules. I use the white side of a real estate sign but hope to get some polished stainless sheet to try and see if I can get a higher reading. The panel is currently stored under the bed but future plans will see it moved to the top of the pantry/stove box in a quick release frame. The panel is connected to the regulator via 10 meters of 6 mm˛ cable and an Anderson plug. The regulator side Anderson plug is mounted on the right side of the camper just behind the gas bottles. Tests carried out so far have seen the panel produce around 30 amps over a moderately cloudy day in summer.

During times of heavy cloud or the need to quickly recharge the batteries, we use a Honda EU10i Digital Invertor generator to supply 240V to the Durst 30A charger. With only a couple of hours of run time, I can put back all the current taken from around 2 days of use.

The next thing I want to do is to fit a 1000W invertor to the isolator so it can be switched to either the vehicle alternator or the campers batteries. That way when I am driving around, the invertor will be on and powering the 240V smart charger so that the campers batteries can be optimally charged and then when camped, the invertor can be switched to the campers batteries if 240V is required. This will only be done when we cannot use the Honda generator for our 240V power such as in National Parks.