Can't figure out if my engine is charging the Battery

[dszjlane]

I have a 1966 650 Merc. Took it out for the first time this season recently. Battery was low on charge of course. So I boosted it from my truck battery and got the engine running. Ran the boat around the lake for a few hours. Decided to check charging circuit in my yard to find the battery was still too low on carge to turn engine over. Boosted it once again and checked to see what voltage I had at the battery terminals to find it at 10.5 Vdc, I suspected to see it at 14 Vdc (Same as you would expect to see on a car) Thus indicating that it was charging. Am I expecting it to do something it wasn't designed to do. I guess what I'm askingis will the altenator on that engine charge a dead battery or will it only help hold the charge on a fully charged battery. FYI Battery is new Bought near the end of last season.

 

[dajohnson53]

Re: Can't figure out if my engine is charging the Battery

What was the state of the battery all winter? Where was it stored? Are all the terminals and cable connecters nice and clean? Could be your battery, although new late last season, is no good now, depending how it was stored all winter. Or the terminals/connectors are not clean, that can affect charging.<br /><br />I don't know exactly how the alternator on a motor that old works, but with my outboard (early 80s), when the battery is being charged by the engine, the volt meter on the dash (an analogue gauge, which I consider an estimate) shows 13-14 volts. A digital voltmeter on the battery at the same time would give a more accurate reading in that range. I can't tell you off hand what it is, but somewhere between 13 and 14 if I recall. When the engine's off, if the battery is fully charged it's something like 12.6 - closer to 13 than 12.

 

[Lion hunter]

Re: Can't figure out if my engine is charging the Battery

I sure that my '68 merc 1000 charging is similar to yours. Mine probably charges at .5-1 volt. depending on the state of the battery. With a full charge on the battery mine will charge at 13.5 volts. If the battery is is below 12.5 volts it will only charge at 12.75. So it seems that these systems are to maintiain a fully charged battery, not charge a dead one.

 

[achris]

Re: Can't figure out if my engine is charging the Battery

These charging systems only put out about 4-5 amps, so you won't see a huge voltage step from the battery voltage, but, given enough time they will charge a low battery. Also be aware that they are unregulated, which is why the charge current is so low, and will continue to charge an already fully charged battery. I have seen some batteries reach 17 volts. Not good for a standard auto battery. Which is why you MUST use a MARINE battery on these older, unregulated, outboards.<br /><br />The way to check if the engine is charging the battery is to measure the voltage with the engine running, then stop the engine and measure again. No difference, dead rectifier (most likely).<br /><br />Chris...............

 

[briannh1234]

Re: Can't figure out if my engine is charging the Battery

10.5 volts could indicate a shorted cell, or it could be that it's just low on charge. Boosting it from your truck should get it into the 12volt range within about 15 to 20 minutes (with your truck running of course.) Try charging it up with a conventional charger overnite and see if that fixes it up right. Once charged, most auto parts stores will test the battery for free.

 

[dszjlane]

Re: Can't figure out if my engine is charging the Battery

Thanks Guys.Some good Info Here. The Battery was stored in the boat under cover for 3 months.The temperatures here rearely drop below 34 f. I have charged the batery with a charger for 24hours. I've checked all wiring connections for tightness and corrision all good. we'll see what happens on the next sea trial. It is by the way a deep cyclemarine battery. I'll let you know what happens.

 

[dszjlane]

Re: Can't figure out if my engine is charging the Battery

Well took theBoat out this after noon. Batteryseems to have held charge. Motor cranks fine, and fires fine. Still have to test the charge rate of the altenator. Had a great afternoon boating and fishing with my kids and wife.Life is good!!!!!!

 

[briannh1234]

Re: Can't figure out if my engine is charging the Battery

Excelent -<br /><br />To test that the motor is charging the battery, connect a volt meter to it. Before you start the motor it should read around 12.6 volts. Then start the motor - While cranking the volts will drop - but once the engine is started the volts should return to 12.6 volts and then go higher. Anything above 13 volts is charging the battery.<br /><br />Have fun.<br /><br />P.S. for the off season you may want to check out one of those small cheap solar panels.