DiY magneto on an outboard to charge the battery !

[Poor fruit cake]

On my little boat I have no means of recharging the battery....but I do have a 5hp outboard engine! I removed the flywheel and inside was the coil providing the spark with a vacant space opposite. With some steel sheet and copper wire from a motor rewinders I made a coil! Someone donated me a gadet which converts the AC to DC. Guess what, at about

75% revs I got 2 amps at 12.5 volts perfect.

The problem is I've started to think this is too easy something must be wrong. As you increase the revs the volts increase, as you decrease the revs the volts decrease what will the battery think about the differrent voltage ? or is the current so small it won't be bothered? Does the battery still get some benifit when the volts are low?

This can't be rocked science our garden grass cutter charges a battery with no problem..... do I have to go out and but a widget or somthing ?

Any thoughts anybody

Regards,

Poorfruitcake

[Guy King]

The message from "Poor fruit cake" contains these words:

Not if it drops below about 13.something.

Still, assuming there's a diode in there somewhere (that donated rectifier, presumeably) it'll not matter - if the voltage is high enough to put some charge into the battery then that's what it'll do. If not - it won't flow backwards.

You could always fit a cheap ammeter. eBay item 8074506026 would do.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Poor fruit cake" saying something like:

What you need is a regulator/rectifier to limit charge and convert the output to DC for the battery.

A small reg/rec from a small Japanese motorcycle will do the job. Offhand, I think the CD175 is 12V and a single charging coil, but I could be wrong. Ask in rec.motorcycles.tech

[meow2222]

It all depends on the capacity of your battery. You may well not need a regulator, depends.

NT

[Fred]

I assume your friend gave you a diode. Was this a 2 legged device, ie a single diode, or a 4 legged one which might be more efficient and better suited to what you're trying to do?

In order to charge a lead acid battery you need a voltage source of a minimum of 13.2V and ideally something towards 14V. If you go much above

15V you'll substantially reduce the life of the battery through overcharging. Whilst it isn't rocket science, the charging requirements of a lead acid battery is quite demanding.

The fact you get 2.5A at 12.5V suggests you will probably get 14V at a lower current.

Some older bikes use a shunt resistor to absorb some of the charging current when the headlamp isn't being used. However on these bikes the battery is really only there to provide ignition for starting the bike and as a float when the engine is off. I don't know much about more recent ones. Any bike with electric start would have a more pucker alternator to ensure the chunk of charge in starting is replaced fairly quickly.

[meow2222]

if you want to charge one as quick as possible, yes. If youre wiling to charge it slowly, theyre very undemanding, hence it depends on the capacity of the battery.

NT

[Harry Bloomfield]

Fred has brought this to us :

The modern larger bikes use a 3ph alternator feeding a rectififier/regulator block. The regulation is by means of shorting out the surplus alternator output.

[Nick]

use for the function of an alternator, it suggests the thing is dumping the balance of its output capability into a dummy load, which I am sure it is not. Nick

[Guy King]

The message from "Nick" contains these words:

You're right, it's not. The feed to the field coils is varied to control the output. The power is not generated in the first place, rather than being dumped. Apart from considerations of economy it's also better not to run the alternator at full power/full heat all the time.

[Sylvain VAN DER WALDE]

Using a Zener diode? Just curious.

BTW, I used to be a (fairly) keen short wave listener. I first became interested when I tuned in an A.M. station on Top Band (160 metres) whilst aligning a medium wave radio receiver kit. The callsign of G3 RIW (Beatrice) comes to mind: Unusually, a young _female_ medical student who had an article about her in the local newspaper. Your signature prompted this info, of course. P.S. I still have a Lowe HF150 receiver, not used for some time unfortunately. P.P.S. I used to listen keenly to the 2 metre FM amateur repeater stations; but gave up when they eventually dwindled in numbers due to the increased use of computer related hardware/software for amateur radio use.

Sylvain (now 70 years "young").

[Sylvain VAN DER WALDE]

I think that he means "shorting to earth". A Zener diode (the most basic voltage regulating device) shorts the excess voltage to earth. Having listened to radio "hams" for many years, I've generally found their statements/observations to be reliable. Please don't jump to any conclusions: my own knowledge on electronics is _strictly_ limited. What I did know, I've probably forgotten.

Sylvain.

[Mark]

LOL not with the Prince of Darkness (Lucas, bikes and Zener diode) way of doing things

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[Sylvain VAN DER WALDE]

You're describing a car alternator's regulator, here. I don't know about modern motorcycles, but I'm reasonably sure that my Norton Navigator (_not_ Dominator) had a very basic regulator (the Zener diode, mentioned in my previous message/s, probably).

Sylvain.

[Guy King]

The message from "Sylvain VAN DER WALDE" contains these words:

My W-reg CX500 certainly had a proper regulator pack - that was years ago.

[Neil J. Harris]

As has been said it depends on whether the battery can tolerate an overcharge. Old bikes used zener diodes to absorb the excess power. But this method was rather crude but OK when you could top up the battery every week and expected to have flat batteries every now and then, and to have to replace the battery every couple of years (and they you grew up, got married and bought a car) You can get shunt regulators for solar panels and small wind powered generators. These would work with your set-up. You could add either wind or solar power or both to you existing set-up to your boat, one shunt regulator would cope with all three! The battery won't charge with much less than 14.5 volts from any source. Modern 'inverter' generators take whatever voltage and frequency comes out of the alternator and electronically convert it into the standard voltages that people use, but that's not really a DIY project.

In message , Poor fruit cake writes

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Guy King saying something like:

Your Honda had a field-coil alternator. My ShiteOldGSs have permanent magnet alternators, hence the reg/rec dumping excess.

The amazing thing is it works well, once the factory windings have done obligatory hari-kiri act and taken out the factory reg/rec too (or vice-versa). The reg/rec can be replaced with a Superdream one and the alternator stator rewound with decent wire. After that, no problems.

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Guy King saying something like:

That's exactly what happens on a PM alternator, as fitted to many Jap bikes of the 70s/80s. Crude, but effective.

[Mark]

Is the Superdream regulator 3 phase, neg or pos earth, cost ? Reason for asking is Lucas 12v zeners are becoming RHS.

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[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Mark" saying something like:

3ph, neg earth.. they're getting rare in breakers now, so if you find one grab it quick. They're almost bulletproof - the two I've got are at least 20 years old. As for cost, I don't know these days; I only paid a fiver each for mine.

As for wiring up... the 3 phase wires are obvious (black or white afair), there's a red ignition-fed sensing wire and a green earth.

Hold that thought; I'll check and make sure tomorrow...

[Mark]

Grimly Curmudgeon >

Ok thanks, its 3ph so im technically buggererd I think. Converting to a later Lucas 3ph stator seems counter-productive, as you say the superdream regulators are also becoming scarce. I'll have to start stashing Lucas 12v zeners ;(

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