Ampmeter

[john-206]

I've just installed a rectifier on my outboard engine and it has a dial that shows it is charging the battery ok.<br /><br />There is also an Ampmeter on the boat that is not connected. Should this just have a positive lead from the battery connected to it and what exactly is its purpose.

 

[Silvertip]

Re: Ampmeter

An ampmeter usually has a scale that reads -30/0/+30, -60/0/+60 or something similar. When the gauge reads in the minus (-) side it means one of two things: 1) either the charging system is not working at all, or 2) the electrical demand is exceeding the charging system output. In other words, if the accessories you have running are drawing 10 amps and the gauge reads minus 5, the drain is exceeding the output by 5 amps. If the gauge reads on the plus side it means the charging system is working and the value being read is the amps going to the battery. Since you don't say what type of engine you have, we don't know what the charging system maximum output is. To connect the gauge, it must be connected in the charging circuit. On an outboard, you would disconnect the charging wire (usually red) and is connected at the starter solenoid terminal on which the large positive battery cable connects to. The wire you remove is connected to one terminal on the amp meter. The other terminal on the ampmeter connects to the terminal on the solenoid from which you disconnected the original wire. The amount of needle movement you see will be dependent on the gauge scale and the max output of the alternator. In other words, if the alternator output is 20 amps and the gauge is calibrated at 30 or 60 amps, you will never see it in the upper ranges. The ampmeter therefore tells you how many amps are going to the battery (Plus reading) or are being taken from the battery (minus reading). Minus readings are bad. Plus readings are good.

 

[john-206]

Re: Ampmeter

Thats great thanks. My boat is a small cruiser with a 9.9 yamaha outboard. I have fitted an external rectifier which converts AC power from the engine to DC power to charge the battery.<br />Therefor I do not have an Alternator.<br />Would the Ampmeter work if i connect it in line with the positive lead from the battery???

 

[john-206]

Re: Ampmeter

For Upinsmoke

 

[Silvertip]

Re: Ampmeter

If you fitted an external rectifier you indeed have an alternator otherwise there would be no need for the rectifier. I think you mean there is no belt driven external alternator. Yes -- although the alternator (rectified) output is relatively small on this engine, the gauge may or may not be of much use. Again -- it depends on the meter scale. In your application the voltmeter may be of more value.

 

[phantoms]

Re: Ampmeter

I would replace the ampmeter with a volt meter. Much easier to hook up and less complicated. Does not show you charging amps, but rather charging volts.

 

[jlinder]

Re: Ampmeter

Something that people fail to think about is that the ammeter has all the charge current going through it.<br /><br />It may not be a big thing on a small outboard, but when you get the bigger engines and all the electrical on a boat, you can 20, 30, and 40 amps flowing (my alternator is rated at 55 amps).<br /><br />For 40 amps you need 8 ga wire minimum. 6 ga. for 55 amps. When you consider voltage drop if the ampmeter is any distance you have to go way up in size. Remember, you are only putting out 1-1.5 volts above the battery voltage. Even a small voltage drop will limit your ability to charge the battery quickly.<br /><br />Voltmeter is the way to go.

 

[john-206]

Re: Ampmeter

Thanks guys a voltmeter it is, I'll sell the ampmeter on ebay to pay for it.

 

[DangerDan]

Re: Ampmeter

I have a three battery system with a switch & VSR. One start battery, two house. I have a 94amp alt. and a 100amp meter. I rarely see my volt meter go above 30A. Would it be over kill to have volt meters for the two seperate battery systems? I use this boat to fish, run a long ways off shore and also use an inverter for coffee and tv from time to time.

 

[swist]

Re: Ampmeter

It's "ammeter", not "ampmeter".<br /><br />Damned if I know why....

 

[DangerDan]

Re: Ampmeter

I rarely see my volt meter go above 30A. Oops I meant ammeter go above 30A.

 

[Silvertip]

Re: Ampmeter

Irregardless is not a word either but people still use it. And because of that it's being added to Websters -- go figure. Do it wrong long enough and sooner or later it beomes OK.