ammeter vs. voltmeter

[cddetelich]

I would like to install a guage to let me know my alternator is charging properly. Which should I install-ammeter or voltmeter? Proper way to install?

 

[rodbolt]

Re: ammeter vs. voltmeter

my vote is for a voltmeter. its easy and quick to wire in . while it wont show actual amperage draw/charge it will indicate if the chargeing system is working or not. its easy to wire and requires no wiring mods. its normally tapped into the ign circuit in parallel with the hull/engine wiring. an ammeter must be series wired with a wire capeable of handing the load or a rather expensive shunt meter must be used.<br /> for specific installation post what your installing it on.

 

[18rabbit]

Re: ammeter vs. voltmeter

Ammeter (aka amp meter) will show the magnitude (amps) of current flow. Shows how fast energy is whipping out of your battery. Used to manually managed battery resources, especially deep cycle battery banks.<br /><br />Voltmeter (aka voltmeter) will show the quality (volts) of the current flow. Indicates how much of a charge is in your battery, and the voltage output of the alternator/charger. Used when charging and/or discharging the battery.<br /><br />Multimeter (aka multi function meter) can show both volts and amps. Some of these meters get really sophisticated (and expensive - $150+ range) and will compute a battery’s use, time remaining before dead, time left before fully charged, etc. Important for multi-bank battery systems and complex charging routines on larger vessels.<br /><br />When you get into voltage sensing (ammeters also use low-voltage sensing to determine current flow) it starts to become more important to use twisted pairs when installing the meter(s). Twisted pairs are two wires (+ and -) twisted together. This twisting helps to cancel any biasing caused by electromagnetic radiation that is a natural product of all the wiring in the boat. As Rodbolt suggested, when you decide what you want to install, post back here.

 

[JohnRuff]

Re: ammeter vs. voltmeter

Explanation of why I vote for the voltmeter. Your battery at rest should read at 12 volts. Your battery if charging should read 14 - 17.7 volts.

 

[18rabbit]

Re: ammeter vs. voltmeter

I agree with John's explanation. The voltage values, however, may be different, depending on the battery type.

 

[MrBigStuff]

Re: ammeter vs. voltmeter

Originally posted by cddetelich:<br /> I would like to install a guage to let me know my alternator is charging properly. Which should I install-ammeter or voltmeter? Proper way to install?

Technically, you'd want to install a voltmeter for either reading. It's much safer to install a shunt and then read the voltage across the shunt to obtain current magnitude and direction, rather than run high current carrying wires up to a convenient gauge.<br /><br />That method yields the most information but IMO, it's six of one, half dozen of the other. The simple voltmeter showing bus voltage is sufficient for the vast majority of applications and it's much less costly than the alternative.

 

[MrBigStuff]

Re: ammeter vs. voltmeter

*delete duplicate*

 

[levittownnick]

Re: ammeter vs. voltmeter

I too vote for the voltmeter for the above stated reasons and because the ammeter readings to be meaningful has to be interpeted based on all else that is going on at the moment of reading. For example, If the ammeter is only connected to the charging circuit, the reading is a function of all the loads in the circuit. Therefore the current indicated is a composit of the charge going to the battery + current going to lighting + current going to radio etc. The current charging the battery should be a function of the state of charge of the battery (and this function is not linear.) A battery that is near full charge (at the proper charging voltage) draws small ammount of current. The charging system output capacity is also a function of engine RPM. <br />The voltmeter reading is easier to fathom (some pun intended). When the engine is off it shows the terminal voltage of the battery (if nothing is being run from the battery, the voltage should be about 12.5 volts. When the charging system is working, the battery voltage should be greater than 13.2 volts and less than 16 volts.

 

[amirm]

Re: ammeter vs. voltmeter

Actually, it is very useful to have both. My last boat had a smart, three-stage charger with a nice remote. I could instantly tell if the battery was charging by looking at the voltage (12v versus 13+). And the current flow, if negative, showed the system taking in more charge than being used. Positive was the opposite.<br /><br />I could also tell how empty the battery was by the large charge current initially.<br /><br />Unfortunately, the above set up may be rather expensive. And it does require fair amount of wiring with a huge shunt resistor in-line for voltage measurement per above notes.<br /><br />Amir

 

[swist]

Re: ammeter vs. voltmeter

Your battery if charging should read 14 - 17.7 volts.

17.7 volts is an awfully high charge voltage. I would worry about cooking the battery.

 

[DangerDan]

Re: ammeter vs. voltmeter

I have both on my boat. Actually two volt meters, one for each circuit start and house and an ampmeter showing the amount of current going to the batts. These circuits are seperated by an isolator/switch