alternator charging?

[noah4009]

When I last started the engine, yesterday I let if run 10 minutes. Then I started it maybe 7,8 times only letting it run a couple of minutes each time during the afternoon. I really did not let it charge, except when it ran for 10 minutes. I know thats not much. but the battery needed to be recharged that evening. It is a brand new marine battery. 875 cranking amps at 32 degrees and it is in the 70's here. I am trying to see if this engine is charging the battery? It does have the coils on the side and was told on this forum it has an alternator. It is electric ignition, not magneto. How do I check to see if this alternator is charging the battery? You mentioned testing the rectifier. How do I do this? Will this tell me if it is charging

 

[DJ]

Re: alternator charging?

Simple.

With the engine off, put voltmeter leads across the battery. Record the voltage.

Start the engine. Does the voltage climb? If so, it's charging.

If not, it's not.

Earlier outboard alternators are pretty weak. 10 amps was a powerful one.

Most are unregulated, so don't be alarmed if you see charging voltage as high as 16 volts.

 

[Frank Acampora]

Re: alternator charging?

Yep! That alternator was designed to do no more than recharge the battery while cruising. Even above 2500 RPM it will ony put out about 7 amps and on some, the cut-out is at 1000 RPM--meaning that below 1000, you will get no meaningful amperage delivered. With the amount of starting and running you did, you did not put back enough amps for starting purposes, AND you were draining battery storage capacity to fire the ignition coils.

Start the engine and like DJ said above test battery voltage. It should be more than 13 volts.

Since each cell of a 12 volt lead acid battery is actually (if I remember correctly) 2.1 or 2.2 volts, even at rest, a new fully charged six cell 12 volt battery should read 12.5 to 13 volts. Regulated charging voltage is usually 13-14 volts. Unregulated can go as high as 18 volts