Re: Ammeter or Voltmeter
The reason people are recommending a voltmeter is that it is wired "across" a 12V line and ground and simply measures battery voltage. An amp meter on the other hand is wired in series with the 12V line and measures current (not voltage). To be effective, it must also be the first device in the +12V buss so you need to run a heavy gauge wire from the alternator, to the gauge, and from the other side of the gauge to the battery. All accessory power comes off the battery side of the gauge. As you can see, wiring must be much larger because the line to and from the gauge carries the entire electrical load. Voltmeters are almost as effective as amp meters in telling you what the electrical system is doing and much simpler for the average person to install. An amp meter can tell you discharge rate as well as charge rate. A voltmeter will tell you only what the system voltage is. Obviously if system voltage is higher than 12.6 the battery is charging (you just don't know at what rate). Using a voltmeter, if the system voltage is below 12.6V the system is not charging which may be due to equipment load higher than alternator output or the charging system is not working.
