Re: Low Input Voltage in Mobile

Jim Szalajeski

There are some good diode isolators on the market that are made just for applications like this.  Many are used in the marine area on the larger pleasure boats.  It is a low voltage drop device that you install between the alternator and the two batteries.  Like lift the wire from the alternator that would normally go to the original battery. Put this on one of the battery terminals on the diode isolator.  You will have to add some length of wire.  Don't cut the wire so you can remove this isolator when you go to sell your vehicle.

Run a wire from the output of your alternator where you removed the original wire and go to the common input terminal on the diode isolator.  Then run a wire from the second battery terminal on the diode isolator to your second battery.

A hint here is to use wire ring lugs for your connections.  Then you can use like a 1/4 inch short bolt and some washers to connect together the wire you removed from the alternator.  I always put just a small amount of some anti oxidant compound like Pentrox or Never Seize on the threads and connections.  This way you can get the connections apart later down the road with no problems.  This also goes to the diode connections.  You don't need a whole lot of the paste.  Just enough to get it on the threads.  Don't glob it on and make a mess.  You can use a Q Tip to put the compound where it needs to be.  Just remember a little goes a long way. 

To go to the other question, my memory is lacking me right now, but there is a company that makes a device that I used on many front end loaders to run some big Motorola radios on.  It took the 24 volts and made it into the needed 12 volts.  I am pretty sure that they also made some units that was just 12 to 12 volts.  They provide regulated voltage and come in various current selections.

Hope some of this information is of some help.


On Thursday, February 14, 2019, 6:29:15 AM CST, Mark Brueggemann via Groups.Io <qrq_cw@...> wrote:

From: Bob Rodgers <kc4tvo@...>

> I agree on diodes failing. 

What is the failure mode?  This is the first I've heard of it.  It certainly isn't due to the tepid draw of a mobile radio.

Mark K5LXP
Albuquerque, NM

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