Heated Grips - how to avoid the flat battery blues

The most common (and generally reliable) heated grip on the Australian market is Oxford HotGrips.  Over the last 10 years these have progressed through a number of models, with each (in the eyes of some) being an improvement on the earlier versions.  The latest model (at October 2010) which is computer controlled is available in 2 variants, OF693 or OF 696, and the only difference between the two seems to be the pattern embossed on the rubber grip.

More info on the Oxford range of products can be found here:

www.oxprod.com

 This latest model consists of 4 main components:  Left Grip; Right Grip; Controller Box and the Heat Controller.  Both grips connect to the controller box, as does the heat controller.  Additionally the connection to the bikes battery also goes to the controller box.  What this means is that the user is "encouraged" by the Oxford supplied instructions to connect BOTH the positive (red) and negative (black) power leads from the controller box directly to the battery.  The problem is that even when the heat Controller is switched off the controller box continues to draw between 8 and 10 milliampere/hour from the battery - and if left alone, this will definitely, over a period of 1 to 2 weeks, drain the bike battery to the point where the bike will be hard to start.  If your bike has fuel injection it is even more dire - if there is insufficient power left in the battery to operate the fuel injection electronics and/or bring the fuel pump up to operating pressure your bike will not be just hard to start - it simply will not start at all.

Reproduced below is the Wiring diagram supplied by Oxford.

The key to how to overcome this problem is actually hidden away in the Oxford Wiring harness Installation instructions at item 11 which in part states: " If the (control box) must be connected to a switched ignition supply feed, please ensure that the wiring harness is connected (with) cabling that can take the extra load of up to 4 Amps."  What this is saying is (to avoid having a flat battery) DO NOT connect the controller box direct to the battery, rather connect it to a switched circuit that can provide at least 4 amps.

What is needed is some enhancements that will;   1. Ensure that when the bikes ignition is OFF that there is no power being consumed by any part of the heated grips and;   2.  That the wires that do connect to the heated grips can supply at least 4 amps.

The solution is to insert an automotive grade relay into the positive (red) power lead of the hot grips between the supplied 5 amp fuse and the control box.  I would suggest an automotive horn relay rated at 20 Amps to 30 Amps.   Shown below is such a unit, that can be obtained from any automotive parts  or electronics supplier

The relay which in itself uses less current than your number plate light, can be operated by any switched positive lead on your bike - such as the number plate light or you instrument lights.  With this enhancement there is no way the HotGrips can flatten your battery when the ignition is NOT on.

 Here is my enhancement of the wiring diagram for the connection from the battery to the Controller Box that I believe Oxford should have supplied.  Note there is only one additional component that you need to obtain - a Automotive relay.

 Now for some caveats, based on experience.

1.  Never use the frame of your bike for the earth return.  To do so will cause corrosion and resistance at all dissimilar metal interfaces on your bike - in the long term this can be very expensive to fix.

2.  Never "tap" into any of the cabling associated with Fuel injection or electronic ignition.

3.  Carefully check all Oxford supplied connectors before you use them to ensure nothing is bent, damaged or miss-aligned within them. 

Finally.

If you have any questions, drop me a line