Monitoring the condition of your
battery as well as the charge coming from your alternator is very
handy to know, whether on the batteries of your vehicle or in your
Kevin has made up an inexpensive
monitor located underneath the hand brake lever in his Prado fixed
with double sided Scotch tape. He is able to check both his main &
auxiliary battery in his vehicle via a switch.
The 'battery, charger &
alternator tester' he used can be bought from Jaycar
Cat. QP-2258 at a cost of $9.95 & for the DIYer can easily be
converted into an onboard battery monitor.
The battery monitor has
six LED lights to quickly indicate the condition of your 12 volt
battery, charger or alternator. It uses 3 LEDs (12.6V Full, 12.0V
50% and 11.5V Low, to indicate battery condition), and 3 LEDs
(15.5V Over voltage / Regulator failure, 14.5V Max. Charger
Voltage, 13.2V Charger and Alternator Charging) to indicate
Kevin fitted the monitor
with a miniature two position slide switch to easily switch
between batteries. He then wired each end of the slide switch to
the positive of each battery (via a fuse) & rewired the common on
the slide switch to the monitor, wiring the neutral to the
To fit the switch into the
monitor unit undo the rear two screws and use your drill & a
small square file to carefully cut out the rectangle for the
slide. Use two small screws to fix the switch. Cut off both
crocodile clips & solder your wires to the switch tags.
You will see in the photo the switch is located just under the
"12V DC ONLY" label.
All parts were purchased from Jaycar
A Battery, Charger & Alternator Tester
Cat. QP-2258 at $9.95
DPDT Panel Mount Sub Miniature slide
Cat. HP-0390 $0.90
Other parts include wire & two in-line
fuse holders to suit.