In MARC, we are usually quick to add a ham radio to our motorcycle, which is soon followed or accompanied by a radar detector.  Many riders have also added GPS units and high power driving lights.  If we travel much distance, then electrical clothes become a significant barrier against freezing and a receptacle for the clothes usually shows up.  If we like to ride two up, we also need a connector for the passenger’s electrical clothes.  As our readiness grows it isn’t long before we are stretching the electrons thin.  If we aren’t careful, we soon find running lights growing dim.  When this happens our hopeful mantra to deliver us someplace safe before it all goes dark is well rehearsed.  If you find yourself in this situation, you’ll find yourself asking why your luck isn’t better. 

As electrical load increases beyond the bike’s charging system, the voltage level in the battery will drop below 12 volts while riding.  This is the time when it is important to read the electrical signs and this is where experience and volt/amp meters come in handy.  If the voltage level drops below 12 volts at speed, then something must get turned off before the voltage level drops below 11 volts.  Usually, experienced riders develop habits to combat most of these scenarios by learning how to read an amp meter or watching the battery’s voltage meter display. 

However, what if you don’t have a way to see your current draw or voltage reading or if you’ve installed some items that can remain hot when the bike isn’t running.  If the bike drains its battery voltage too low, the battery will be disappointing on return unless it is hooked up to a charger.  Not possible you say, well many GPS units, ham radios and cell phones are installed so they stay hot all the time.  In the case of many ham radios sitting on the bike connected directly to the battery, the radio will consume 100 ma of current in the turned off, bike not running state.  A GPS unit running without the backlight will also eat around 100 ma of current when on, and it jumps to 300 mas if the backlight is on bright.  A radio operating in an event without the engine running can eat as much as 10 amps of power during transmit and this doesn’t include the power it takes to run the radio’s cooling fan afterwards.

My point in all this is to say, if you are going to add items to a motorcycle, run them through their own auxiliary fused Buss panel (Kragen and other after market car parts houses have them for less than $10) so you turn them off when you turn off the bike.   When you run a separate fuse panel, it is easy to power that panel through a simple relay (Radio Shack ~ $6 RS# 275-226) and use a low current line to control the operation of the relay.  This way when the bike is off, the power consumption is off. 

It is also a good way keeping the high load of a ham radio off of the bike’s frail wiring harness.  To power a remote relay for a separate fuse pane, a good place to pick up this ignition signal is off the bike’s fuse panel.  Doing it this way, the bike’s fuse panel will turn on the power to the accessories through a low current line to the separate control relay.  This line will only be active when the bike is running and will turn off when it isn’t running.  In addition, consider adding a simple volt or amp meter to the bike so you can watch what is happening when you are riding or operating with the ignition turned off.  This extra information should keep you from getting surprised.

Another device that can help is a gadget called a Battery Guard.  These are voltage monitoring devices that vary in complexity and capability and can cost anywhere from inexpensive to outrageous depending on your needs.  On the inexpensive side, Radio Shack has a 12-volt battery guard that will monitor your bike’s voltage level and turn off any device operated through it when the battery voltage drops below 11.2 volts.  If a battery guard is installed on a bike that uses a relay to power the added accessories, it can turn off those accessories by automatically disabling the power to the relay until the voltage in the battery returns to normal. 

Usually Battery Guards from Radio Shack sell for $19.99, but I stumbled across them at Radio Shack online store and found them selling for $4.95 if bought online.  That price has now risen to $9.99, which is still a good deal.  When I saw the sale it was too good a value to leave sitting and ordered one for the bike and one for the car.  If you are interested in adding a battery guard, the Radio Shack part# 98-696 can be found at https://radioshack.com.  When you get to the site, enter the part number in the search field at the top of the page and the item will appear.

What comes is a device that measures 4.25” x 1.5” x 1.5” and has two power leads.  One lead has a cigarette adapter plug that will insert into any cigarette adapter and the second lead has a cigarette adapter receptacle that will accept any standard cigarette adapter.  Neither of these line terminators is really needed on most motorcycles unless you wanted to add a separate line using the device.  Installed in the device is a standard 10-amp bayonet style fuse to protect the line from short circuits. 

After getting my adapter, it looked like a great way to power my laptop from a connection in the trunk and I may need to order a third unit so I can use the supplied cigarette lighter receptacle.  For my primary battery guard, I’m going to cut of the ends and put it in line with the control line for the auxiliary fuse panel and not worry about watching the battery so much.

A more expensive and capable battery charge guard unit is sold by the ChargeGuard Corporation https://www.chargeguard.com/.  Their CG12D unit has a programmable turnoff delay, over-voltage protection, emergency bypass and 30 amp current capacity.  This is a great device for an important mobile installation where you need to power down later than when the ignition is turned off or after the low voltage alarm has been triggered.

A story talking about how one amateur used voltage protection for their radio installation is available at: https://www.tbo.net/4Tweb/4Runner.htm.  This site shows the installation in a SUV, but the ideas are the same for a motorcycle.

More cost for more flexible protection.

ChargeGuard®
(12V)............................. $74.95 

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