I have a Pearson 26 with an 8 hp pull start OMC Yachtwin outboard. It has 2 wires coming from the alternator that are long enough to reach one battery. I have had the boat for 4 years and never connected the wires and the deep cell batteries last all summer. I only use them for running lights in the evenings. They do show a little dimming around September though and I take them home and recharge them overnight. If I connect the wires to one battery will the engine recharge the battery enough to make any difference even though I only run it for 15 min leaving the dock and maybe 30 min in the evening coming back? I'v heard some say that leaving it connected can actually drain the battery some. Any truth to that? David
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Yes...and then No
Yes, delivering alternator output to your battery will make some difference. If only outputting several amps, that's enough to float your nav lights...which by the time fall arrives, should eliminate carrying a battery home to recharge it. No, leaving the wires connected should create no leakage from the battery (unless your wiring is incorrect). Many of us have the alternator output line connected directly (via breaker or fuse) to house banks and our battery selector switches left in an 'On' position. Jack
Yes, delivering alternator output to your battery will make some difference. If only outputting several amps, that's enough to float your nav lights...which by the time fall arrives, should eliminate carrying a battery home to recharge it. No, leaving the wires connected should create no leakage from the battery (unless your wiring is incorrect). Many of us have the alternator output line connected directly (via breaker or fuse) to house banks and our battery selector switches left in an 'On' position. Jack
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Warren M.
Battery Connection
I had the same OB on a previous boat. Yes, connect the alternator wires to the battery. I think that the alternator output is a pretty meager 4 amps or so. That means that only using your engine for a few minutes as you indicated will only provide some small amount of charging for your battery, but you certainly will not hurt it. In my experience, if your battery is in good shape, i.e. 12.6v-12.8v, the OB alternator should keep it up ok. If the battery is gettting old and not holding a full charge for very long, the use of the alternator won't make much difference one way or the other. A new battery will be in your future....
I had the same OB on a previous boat. Yes, connect the alternator wires to the battery. I think that the alternator output is a pretty meager 4 amps or so. That means that only using your engine for a few minutes as you indicated will only provide some small amount of charging for your battery, but you certainly will not hurt it. In my experience, if your battery is in good shape, i.e. 12.6v-12.8v, the OB alternator should keep it up ok. If the battery is gettting old and not holding a full charge for very long, the use of the alternator won't make much difference one way or the other. A new battery will be in your future....
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Dan McGuire
Bothered a Little
I am fairly sure you are not connecting the alternator leads to the battery, but I thought I would make sure. An alternator puts out AC voltage which would not charge the battery. I assume that you are actually thinking about connecting the leads from the rectifier which converts the AC voltage to DC voltage.
I am fairly sure you are not connecting the alternator leads to the battery, but I thought I would make sure. An alternator puts out AC voltage which would not charge the battery. I assume that you are actually thinking about connecting the leads from the rectifier which converts the AC voltage to DC voltage.
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Ted
Trickle Charger
I have an 88 HP Johson on a runabout and it only puts out 7 amps so others are correct you probably can get 3 or 4 amps from yours, sounds like more than you need to get thru the year.
I have an 88 HP Johson on a runabout and it only puts out 7 amps so others are correct you probably can get 3 or 4 amps from yours, sounds like more than you need to get thru the year.
Running the numbers...
I have a 9.9 hp Yachtwin on my Mac 26D, and if I remember right, it puts out about 6 amps at full power. So, if you figure you're running the motor for a total of 45 minutes (15 out and 30 back in) you'll theoretically get 75% of that 6 amps, or about 4.5 amps returned to the battery. Your running lights probably pull a bit under 2 amps, so the 4.5 amps will give you about 2 1/4 hours of running light time. I'd say that's worth hooking up two wires! Use some fairly heavy guage wire (#10 or # 8) to minimize voltage drop (when we're playing with such small amounts of energy, it's extra important to minimize losses) and be sure to fuse the wire (preferrably at both ends) and you'll be good to go.
I have a 9.9 hp Yachtwin on my Mac 26D, and if I remember right, it puts out about 6 amps at full power. So, if you figure you're running the motor for a total of 45 minutes (15 out and 30 back in) you'll theoretically get 75% of that 6 amps, or about 4.5 amps returned to the battery. Your running lights probably pull a bit under 2 amps, so the 4.5 amps will give you about 2 1/4 hours of running light time. I'd say that's worth hooking up two wires! Use some fairly heavy guage wire (#10 or # 8) to minimize voltage drop (when we're playing with such small amounts of energy, it's extra important to minimize losses) and be sure to fuse the wire (preferrably at both ends) and you'll be good to go.
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David
Any danger of overcharging?
I have also been debating this situation; I have an 8hp Honda outboard on my Pearson 26. The outboard puts out 5A (from the datasheet), but does not have any charge regulation that I can determine. I don't use it much (maybe 30 min to 1 hour max), but with a new battery, I don't want to overcharge. I also have a 5W solar panel that seems to do a good job of keeping the battery topped off; and I have access to shore power if I really need to do a deep recharge. When I was re-wiring the battery this winter (previous owner had just run all the wires to the battery - I added a bus-bar and new battery meter), I found that the wires from the outboard were broken at one of the connections - no wonder the battery died on me last season. Anyway, I think that the guage of the wire is only 16, so I will have to upgrade that (the run is about 6 ft). So, back to my question - given the small amount of AH that the outboard will supply, should I worry about overcharging? I have an Optima Blue-Top, 55AH single bank (the outboard is not electric start). The datasheet on the battery allows only 1A max for continuous charging. For solar panels, I think that the rule of thumb is if the amps output are less than 1.5% of the battery's AH rating, then you don't need a regulator. At 55AH, this is .825A, much less than 5A from the outboard. The options that I have considered are: 1. Get another solar panel, 11W, for a total of 16W (theory) with a regulator. This would give about 5AH per day (if the sun would ever shine here), almost as much as one hour at max RPM (which I almost never use). 2. Wire the outboard rectifier through a switch so that I can choose to use it or not. We've only had the boat for about 6 months; the solar panel has been enough for our once a week usage - if we were to overnight sometime, I might have to use the outboard charger. Thanks! David Jones S/V Wild Goose
I have also been debating this situation; I have an 8hp Honda outboard on my Pearson 26. The outboard puts out 5A (from the datasheet), but does not have any charge regulation that I can determine. I don't use it much (maybe 30 min to 1 hour max), but with a new battery, I don't want to overcharge. I also have a 5W solar panel that seems to do a good job of keeping the battery topped off; and I have access to shore power if I really need to do a deep recharge. When I was re-wiring the battery this winter (previous owner had just run all the wires to the battery - I added a bus-bar and new battery meter), I found that the wires from the outboard were broken at one of the connections - no wonder the battery died on me last season. Anyway, I think that the guage of the wire is only 16, so I will have to upgrade that (the run is about 6 ft). So, back to my question - given the small amount of AH that the outboard will supply, should I worry about overcharging? I have an Optima Blue-Top, 55AH single bank (the outboard is not electric start). The datasheet on the battery allows only 1A max for continuous charging. For solar panels, I think that the rule of thumb is if the amps output are less than 1.5% of the battery's AH rating, then you don't need a regulator. At 55AH, this is .825A, much less than 5A from the outboard. The options that I have considered are: 1. Get another solar panel, 11W, for a total of 16W (theory) with a regulator. This would give about 5AH per day (if the sun would ever shine here), almost as much as one hour at max RPM (which I almost never use). 2. Wire the outboard rectifier through a switch so that I can choose to use it or not. We've only had the boat for about 6 months; the solar panel has been enough for our once a week usage - if we were to overnight sometime, I might have to use the outboard charger. Thanks! David Jones S/V Wild Goose
Yea, overcharging can be a problem....
generally speaking, the voltage regulation on small outboard alternators is pretty poor, if there at all. Especially with AGM batteries, which are quite intolerant of too-high a charging voltage, you might be wise to put a voltmeter on the system to see what your getting from the alternator. If the voltage is getting too high, I can't see why you couldn't install an external regulator on the output, although you'd have to rig some sort of a bypass switch if you also want to start the motor with the electric starter. (not a problem on pull-start only motors) And I'll beg pardon for hopping up on the soapbox again on the subject, but why can't the outboard manufacturers give us a small outboard with a decent sized alternator with good regulation? Give me a 9 hp long shaft with a 30 amp alternator and tack a few hundred extra on the price. I'll gladly pay the difference!
generally speaking, the voltage regulation on small outboard alternators is pretty poor, if there at all. Especially with AGM batteries, which are quite intolerant of too-high a charging voltage, you might be wise to put a voltmeter on the system to see what your getting from the alternator. If the voltage is getting too high, I can't see why you couldn't install an external regulator on the output, although you'd have to rig some sort of a bypass switch if you also want to start the motor with the electric starter. (not a problem on pull-start only motors) And I'll beg pardon for hopping up on the soapbox again on the subject, but why can't the outboard manufacturers give us a small outboard with a decent sized alternator with good regulation? Give me a 9 hp long shaft with a 30 amp alternator and tack a few hundred extra on the price. I'll gladly pay the difference!
D
David Guthridge
Thanks!
Thanks guys! Think I will connect the wires to the battery. There is a fuse in the wire. Have a great summer!! David
Thanks guys! Think I will connect the wires to the battery. There is a fuse in the wire. Have a great summer!! David
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