LPG Report
The importance of good design for your 12volt house battery system.
"What has this got to do with LPG?" you will no doubt mutter. Well a lot with the new generation
of appliances on the market now.
Most automatic LPG fired water heaters, fridges and air heaters, now use electronic flame
detection to keep them burning safely, in place of the old thermocouple system of flame detection.
Electronic flame detection, uses a small voltage that is past through the flame, this voltage
is then monitored to determine whether the flame is burning correctly or not. The control system,
which controls the gas flow, then determines if the gas supply should be allowed to continue or not.
The reason we use 12vdc house battery system, is that most modern appliances require 12vdc to operate.
Ensure that the 12vdc negative terminal is securely connected to the chassis of the vehicle
earth). Failure to do this will cause small voltages to be superimposed on the 12v negative
wire which will cause major problems with appliances. These small voltages will cause the
appliance control system to become confused and shut the gas flow off.
The design of your house 12volt DC house battery system is very important. In fact this is
the cause of many "warranty" failures of new appliances. Very embarrassing when your 12v system
is causing the operational failure of the appliance, as the cost of the diagnosis of the problem
will become your problem and not the appliance suppliers. There have been cases, where to prove
this fact, the Engineer tasked to diagnose why the appliance is not operating correctly, spent
quite a few hours of his time to locate the fault within your house battery system. His time
doesn't come cheap.
Do not simply take the 12v supply for the house, off one of the batteries of the 24v start battery
system, as this will definitely cause major problems with both the start battery life and the 12v
house system operation.
It is best to have a 12v alternator fitted to the engine to charge separate 12v house battery, if
your motor home is 24v start. This will give your house battery system the best charging performance,
much superior than the electronic switched mode 24v to 12v converter method. However if you do choose
to go down this path, make sure you add a battery to the house system to help smooth the voltage
supplied to the appliances by the converter. Don't just connect appliances to the output of the
converter.
It is also good design to try and make your house battery system as efficient as possible.
Start with lighting, as that could be the biggest single draw on the house battery, consider u
sing LED lighting, as these devises will save huge amounts of power consumption. Don't leave TVs
and radios in the standby mode, switch them off at the supply as small current draws add up to large
draw downs when multiplied by 24 hours and 7days.
Good quality 230v automatic battery chargers are very important as well.
Don't forget to plug your motor home into mains as soon as you arrive home after a rally or use,
to charge the battery right up to the top, as a fully charged battery will last for many years,
half charged ones will last months.
When disconnecting batteries always disconnect the negative terminal that goes chassis earth first
and when reconnecting batteries always connect the earth terminal last. If you spanner happens to
accidently contact the chassis of the vehicle when you are tightening the positive terminal of the
battery all should be ok.
But if you have connected the earth to the negative terminal and your spanner brushes against the
chassis while tightening the positive terminal of the battery, you will have a big problem. The
spanner will most like spot weld itself to the chassis and become red hot within seconds with the
current passing through it causing serious burns to your hand unless you let it go very quickly.
The high current flow through the spanner could even cause the battery to explode.
One final word of warning, ensure that you protect the whole house battery system by using circuit
breakers and fuses to protect all wiring that is connected to the battery. Batteries store very large
amounts of electrical energy, if a short circuit should accidently happen any where within that house
battery system a very serious situation could quickly develop if the circuit is not broken by either
a circuit breaker or a fuse. The end result could be a fire that is be very hard to get at with your
fire extinguisher as the wiring will most likely be hidden behind cabinetry or wall linings or even
the floor of the motor home.
It is much easier to locate why a fuse blew, fix the problem and then replace a fuse than rebuild
a burnt out motor home.
I hope this article helps you enjoy hassle free use of your motor caravan.
Lex Ward 12673
NZMCA LPG Advisor