Is it charging

[Neil]

Is there a way I can make absolutley sure that my outboard motor is charging the battery that starts it whilst it's running. Would an amp-meter show me for example ? I seem to recall that on my old Morris Minor (first car), an amp-meter did just that and that if the revs dropped the ignition light would flicker (rightly or wrongly), indicating charging had stopped (I think). Is there an equivalent I could install ?

Thanks in advance for any helpful replies.

 

[bedouin]

Either an ammeter or a voltmeter could help.

If you just want to know that everything is working properly, then measuring the voltage across the battery terminals will tell you. If the alternator is working it should be about 13.6V, if not it will be about 12.6V or even lower. That is probably the most useful instrument for monitoring battery/alternator condition and is easy to install - you can even buy a cheap multi-meter and use that.

An ammeter is somewhat more complicated to install (as it requires a shunt in series with the battery lead, and tells you how much current is flowing into the battery - however if you only ever use the battery for starting the engine that is likely to read 0 most of the time anyway as there isn't much charge to replenish.

As a simpler installation, you could probably wire an ammeter between the alternator and the battery (rather than in the main battery lead) than would measure current flow from the alternator - that would be easier since the ammeter/shunt wouldn't need to carry the current for the starter motor

 

[steve_cronin]

I agree with bedouin but offer the following extra info:-

digital multimeters can now be had with a built-in shunt which allows them to measure up to 10amperes. Since it is only a permanent magnet dynamo and struggles to output more than about 4 amps no harm would be done by disconnecting the charge lead from the battery after you had started the motor. Connecting the meter in series would show wether it was charging or not.

Steve Cronin