Battery charging from outboards

[snowleopard]

20 or so years ago I had a Sonata with a 5hp outboard. It was manual start so no electrics but it needed battery charging to run cabin and nav lights etc. I acquired a lighting coil that sat inside the flywheel and produced 12v AC, plus a rectifier/regulator to give a DC charging current. Before I could fit the rectifier the motor was nicked.

Clearing out the shed yesterday I came across the rectifier and wondered if modern outboards still used that type of electrical system - obviously not electric start types but in the smaller sizes suitable for small yachts. Oddly, the one I have was designed for a Mariner 55 but it could be fitted to any engine, internally or externally.

If the committee thinks it could still have a use I'll put it on For Sale, otherwise I'll bin it.

 

[2nd_apprentice]

I've been wondering about that myself, actually just thought of it yesterday. Never bothered to connect my Tohatsu MFS6 but why not make use of it? Some sources seem to indicate it throws out unregulated AC (in which case I'd gladly take your regulator!) whereas others claim it's DC. How to test?

Edit:
From the Tohatsu website:

These Alternator Kits are used to provide 12V power for manual start models. Supplies AC current which requires either a regulator for lighting or charging rectifier kit for DC battery charging. Kit includes an alternator, screws and clamp for mounting under flywheel assembly. This alternator kit is standard equipment on 6hp "Sail Pro" models.

AND:

Charge Rectifier Kit
For use with alternator coils, these provide DC current for recharging a 12 volt battery. Kit includes a rectifier, wiring, mounting, bolt, washer and clamp.

 

[VicS]

Some small outboards have no electrical output. An "alternator" coil may be available as an accessory, often called the "stator" coil

Some are fitted with a coil with an AC output for powering lighting. A battery charging kit, basically a rectifier, may be available as an accessory.

If the AC output coil is fitted it should be possible to use a suitable rectifier from an electronics component supplier ( eg Maplin or RS), but some stator coils have two output wires while others have three. An ordinary bridge rectifier can be used with a two wire stator but a three phase rectifier is needed for a three wire stator.

Some outboards are fitted with a stator and a rectifier for battery charging.


Small outboards tend to have a very meagre electrical output although more modern ones tend to be a little larger.
Higher output stators, especially on larger outboards, are likely to also have a regulator in addition to the rectifier or to have a combined rectifier/regulator.

Essential therefore if opting for any DIY approach to converting an AC output to DC for battery charging to be sure what is fitted and what is required.

 

[Bru]

Certainly when I bought the new 6hp Suzuki for Brigantia three years ago I needed to specify the optional regulator to convert the default "lighting" (ie AC) alternator output to DC for battery charging. IIRC it cost an additional hundred and twenty quid or so, fitted (steep but fitting an after market product myself would have compromised the 6 year warranty)

 

[VicS]

Certainly when I bought the new 6hp Suzuki for Brigantia three years ago I needed to specify the optional regulator to convert the default "lighting" (ie AC) alternator output to DC for battery charging. IIRC it cost an additional hundred and twenty quid or so, fitted (steep but fitting an after market product myself would have compromised the 6 year warranty)

Just to clarify its a rectifier you need to convert AC to DC. Low output stators in small outboards do not need this to be regulated, higher output stators do to avoid over charging.

It should be possible to avoid any warranty issues by feeding the AC to a remotely sited rectifier rather than trying to emulate the genuine accessory by fitting one into the motor.
I did this with my first outboard. The current one has a rectifier fitted as standard.

On the whole though the output from a small outboard's charging circuit is so small as to be of limited value, esp on a sailing boat where the length of time the outboard is used is usually quite small.

My main charging source is a solar panel and Id suggest solar would be more cost effective than any OEM charging system added to an outboard.

 

[Bru]

Just to clarify its a rectifier you need to convert AC to DC. Low output stators in small outboards do not need this to be regulated, higher output stators do to avoid over charging. .

My bad, as the youngsters say! I MEANT to type rectifier, why I typed regulator I really can't imagine. I think I need to put more water in it in future

 

[Bru]

On the whole though the output from a small outboard's charging circuit is so small as to be of limited value, esp on a sailing boat where the length of time the outboard is used is usually quite small..

Pt.2 ... that however I'd be inclined to gently disagree with to some extent

The Suzi on Brigantia, rated at a 6A output, delivered in excess of 5A continously at normal motoring speeds (about half throttle plus a bit) and in the course of a normal days sailing (for us) was sufficient, along with (as a general rule) roughly alternate nights on shore power, to keep our batteriens topped up

I grant that not so many small boats with outboards routinely make coastal passages and (due to the vagaries of time, tide and weather) generally end up being motored for at least a couple of hours a day so in the case of day sailors / weekenders where the outboard is getting very little use I'd agree the money would be better spent on solar (hence the only gentle disagreement)

 

[snowleopard]

Some small outboards have no electrical output. An "alternator" coil may be available as an accessory, often called the "stator" coil

Some are fitted with a coil with an AC output for powering lighting. A battery charging kit, basically a rectifier, may be available as an accessory.

If the AC output coil is fitted it should be possible to use a suitable rectifier from an electronics component supplier ( eg Maplin or RS), but some stator coils have two output wires while others have three. An ordinary bridge rectifier can be used with a two wire stator but a three phase rectifier is needed for a three wire stator.

Some outboards are fitted with a stator and a rectifier for battery charging.


Small outboards tend to have a very meagre electrical output although more modern ones tend to be a little larger.
Higher output stators, especially on larger outboards, are likely to also have a regulator in addition to the rectifier or to have a combined rectifier/regulator.

Essential therefore if opting for any DIY approach to converting an AC output to DC for battery charging to be sure what is fitted and what is required.

A simple rectifier isn't really going to do the job as it will let the voltage go outside the 13-14.5 volt safe range. In particular if it goes up to say 16v at high revs it will cook the battery. I had the internal rectifier on an alternator fail and that was the end of a 3-battery bank.

 

[viago]

i recently acquired an old evinrude 6hp which has the facility to charge batteries, i haven't used the outboard yet so dont know what it'll do in terms of charging. it would be nice if it was reasonable. anyone used one?