overcharging battery

[Johnboy2004]

hello
i am buying a new yacht, it is coming with 5hp outboard. i requested that the engine be able to charge the battery, is it just a simple task of connecting a cable from the engine alternator output directly to the battery? or would this damage the electornics , radio, navtex, that are connected to the battery ,etc on the boat and over charge the battery?

the engine i am talking about is the honda bf5 with charging alternator..



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[andyball]

I suggest a search here, since the topic's been covered a few times before & in some detail.

Ask the dealer..." does the honda bf5 have a rectifier fitted for battery charging ?"

If the answer's no, you'll need to buy/fit one & unless it's a regulating type keep an eye on battery voltage during extended high-speed engine use to make sure you don't exceed 16V.

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[jerryat]

Hi Johnbuoy!

I'd be very surprised if output from such a small engine got anywhere near overcharging a reasonably sized 12v battery. Many moons ago I used to use a 9.9 Honda with charging facilites and never got anywhere near even fully charging the battery let alone over-charging it! This was even where several hours (X channel trips) of motoring was involved. I used to take the battery home periodically through the season and give it a boost from a 240v charger to avoid unduly shortening its life. As you are clearly going to use the power supplied by your motor to run instruments etc, you'll be quite safe in my view using it connected directly to the battery and unregulated.

Good sailing!

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[andyball]

an 80W alternator on a yam 8hp was more than able to exceed 16V into 150AH ( when the bank was well charged of course). I used to switch lights on to reduce the voltage if motoring at speed for any length of time.

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[Johnboy2004]

attached the spec of the engine honda 5hp that i intend to use,.
would it take long to charge the battery from it.......or could it over charge the battery?



Type of 4-Stroke
OHV-1 Cylinder


Displacement (cm³)
127


Bore x Stroke (mm)
60 X 45


Full Throttle rpm Range
4000 - 5000


Rated Power hp (kW)
5 (3.7)


Cooling System
Water cooled


Carburation
1 Carburettor


Ignition System
Transistorized pointless


Exhaust
Underwater


Gear Ratio
2,1


Gear Shift
Forward-Neutral-Reverse


Alternator (W/Voltage Regulator)
3 amp


Propeller 4 Blades (inch)
7.88 X 7.50 inches


Dimensions (l,w - mm)
525, 340


Transom Height (mm)
445


Dry Weight (kg)
27


Oil Pressure Alert
Indicator lamp


Emergency Stop Switch



Revolution Limiter
-


Controls
Tiller Handle


Starting System
Recoil


Shaft
Short


Counter Rotation (for twin rig)
-


Engine Tilt
Manual


Engine Trim
Manual 5 stages


Power Thrust
-







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