Camper Trailers Tech Tips

cheap LED dual battery monitor




cheap LED dual battery monitor

convert a hand held battery monitor


  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 camper trailer.

   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 Charger/Alternator output.

    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 vehicle's chassis.



    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 switch Cat. HP-0390  $0.90

Other parts include wire & two in-line fuse holders to suit.



from the shop


LED lights







Thanks to Kevin Davis for supplying the information for this article

 may 2007