The least expensive way to keep track of what’s happening in your boat’s electrical system is with a voltmeter.  It tells you the battery voltage, which gives a general idea of the state of charge (SOC) and charging and discharge.  However, in order for the voltmeter to give you an accurate measure of SOC, the batteries have to sit for at least several hours (some manufactuers recommend 24 hours), before you can read the “at rest voltage”.   This is hard to do when you are living aboard and the battery is constantly being charged or discharged.   Your electrical panel probably includes a voltmeter.  However, if it has a needle and scale (called analog), then it only gives a rough estimate.  A fully charged battery at-rest voltage is about 12.8 volts.  A battery at 50% discharge is about 12 volts.   It is unlikely that you can  see the voltage to an accuracy of 0.1 volts, unless you have a digital voltmeter.  

If your panel has an ammeter, it probably just shows the amperage going out of the battery.  Upgrading to a digital ammeter and sensing the current flowing into or out of the battery will give you a better indication of what is going on. 

The best way to keep track of your boat’s electrical system is with a system monitor.  This has a display will tell you the battery voltage, amps, and battery state of charge (as well as a number of other things that are not as important, like maximum voltage, days since equalization, etc).   We sell the TriMetric system monitor that has proven to be very reliable, as well as being the least expensive monitor. 

TriMetric 2020

We use to recommend the model 2020, which can only monitor one battery (bank), because the house bank is the one that gets cycled up and down.  The engine start battery typically gets completely recharged each time the engine is started, and so closely monitoring it is not as critical.  If you have a system monitor that has failed, you can probably use the shunt that you have, saving $25 on your new TriMetric.  The new TriMetric 2025 will do all the 2020 does, but also gives you the volatge of a second (typically the engine start) battery.  Slightly smaller in size, the 2025 comes with a box for surface mounting.   It also has more resistance to damage from lightning and is easier to program, all for $10 more (I think it looks better too).

We’ve also come up with a couple of tricks that can be used with the TriMetric (or othersystem monitors), where you can monitor the wind and solar output.  Call for more info. 

TriMetric    2020   $175     MORE INFO      BUY NOW

2025

TriMetric    2025   $185      MORE INFO       BUY NOW