Is my battery charging?

How do I know if my battery is being charged by the charging system of the motor? I tested the charging system and everything checked out ok. I got 9.11 amps output from the rectifier/stator setup. My question is how do I know if my battery is receiving that 9.11 amps?

Re: Is my battery charging?

Forget the amps. With the motor shut off measure and record the Voltage on both batteries.

Start your motor and run at fast idel around 1000 RPMs. Now again measure and record the Voltage on each battery. For the battery to be correctly charged it needs from 13.8 to 14.8 Volts. If the battery is discharged and needs a lot of charge the voltage may not come right up to the 13.8 to 14.8 range but if the battery is good and the alternator is working then the voltage should rise until it reaches that voltage. With big batteries and small outputs like 9 amps it can take some time to charge both batteries. Each battery will only get 4.5 amps if it is a 9 amp alternator on an older motor or small Motor. 4.5 amps charging a group 27 discharged battery would take more than 24 hours.

Today I/O engines have 60 amps or more and Large outboatds are 30 amps. Still the alternator will regulate the voltage to around 14.4 volts on average then it is up to the battery to take a charge.

With discharged batterys and a small or older outboard outputing 9 amps the voltage will rise slowly as the battery charges still it will be higher than before you started the engine.

If wired thru a battery isolator then both batteries will charge. If wired thru a battery switch then switch postion will determine which battery will charge. Battery 1 or Battery 2 or Both. Do not turn the battery switch with the engine running unless you know it a good "Make before Break Switch". Never turn thru off with the engine running.

Re: Is my battery charging?

On the older outboards the charging output was unregulated. I have seen batteries with a terminal voltage as high as 17 volts, which is why you should only use marine batteries. They are designed to be able to handle the high voltage with no ill effects.