Voltage regulation - bulb or resistor?

Charging

My first suggestion is that you try another battery. There is every indication the battery is bad if the voltage goes up to 16v with 1 to 1.5 amps going in to it.
A car battery or similar should be able to absorb that current without raising the voltage so much. Not necessarily for a long time and a small battery of course.
Indeed a cheap solution might be to fit another battery in parallel or a bigger battery.

However if what you say is correct and the battery is small what you need is a shunt regulator.
A power transistor is turned on to bypass some of the current to ground. It is turned on by a zener diode which begins to conduct when the voltage exceeds 14v. (you can buy them in a range of voltages. The zener when connected to the base of the transistor will cause the transistor to conduct to the degree necessary to pull the input voltage down to what you want. (14v).
You can fit a power resistor or even a light bulb in series with the transistor to share some of the power and reduce heating although for lower powers a transistor alone will do the job.

If that seems too hard how about a VSR which instead of connecting the charged battery to another battery simply connects in a lamp to waste power when voltage rises.
PM me if you want more details as I have built a few shunt regulators for a friend's solar installation.
good luck olewill
 
William_H said:
My first suggestion is that you try another battery...
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Cheers Olewill - lots of good advice, as always!

I think what I'm going to do first is to take up your suggestion and temporarily wire my two batteries in parallel; this will give a total of 145AH. If this solves the problem, then I shall investigate the possibility that my starter battery is faulty and borrow some other batteries to try. If then there still appears to be an issue, I shall contact the engine manufacturers and insist on a fix. After all, you would assume that a brand new engine should be pretty much "plug and play".

Cheers,

Ron.
 
Ronald_M said:
Cheers Olewill - lots of good advice, as always!

I think what I'm going to do first is to take up your suggestion and temporarily wire my two batteries in parallel; this will give a total of 145AH. If this solves the problem, then I shall investigate the possibility that my starter battery is faulty and borrow some other batteries to try. If then there still appears to be an issue, I shall contact the engine manufacturers and insist on a fix. After all, you would assume that a brand new engine should be pretty much "plug and play".

Cheers,

Ron.
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It is common for small outboards with relatively low output charging coils to have a non regulated output!
(Large ones with power tilt and trim etc do tend to have more powerful charging coils and then they are likely to have a regulated output. )

There is no reason to suppose that the engine is anything other than "plug and play " as you call it. You'll get nowhere trying to persuade the manufacturers that any sort of "fix" is required!.... Thousands of other users will demonstrate that it isn't.

Exactly what problems is this non regulated output causing? You don't seem to have said other than that you have measured 16 volts!

My own experience with an outboard with non regulated charging is that there is no problem. On the contrary i have found that in order to keep the battery properly charged I have had to also fit a small solar panel.
 
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VicS said:
There is no reason to suppose that the engine is anything other than "plug and play " as you call it. You'll get nowhere trying to persuade the manufacturers that any sort of "fix" is required!.... Thousands of other users will demonstrate that it isn't..
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That's not what I found. In #6 I described what heppened with my Mariner. Granted, it was about 10 years ago, but I had exactly the same problem that OP has. I explained the problem to Mariner (well, Barrus) and they sorted it out for me. I was impressed with their willingness to support their customers but it may have been that it was not the first time they had had this problem.

On another issue, OP tells us that he has two batteries, presumably a starter battery and a domestic, on his boat. I can't help but think that that is a little OTT when he has an outboard (presumably fitted with a recoil starter as well as the starter moter) and that the coil is producing only 6 amps.....hardly enough to keep 145 amp/hrs of battery charged up.

Personally, I would dump one battery and get a regulator.
 
VicS said:
It is common for small outboards with relatively low output charging coils to have a non regulated output...............Exactly what problems is this non regulated output causing? You don't seem to have said other than that you have measured 16 volts!
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Hi again VicS.

My main battery is a 100AH AGM. This I regularly charge up with a mains-powered smart charger. When I'm away from the boat I leave it connected to a 7W solar panel which seems to help the battery to hold a decent charge. This simple arrangement has proved adequate to run my LED nav and cabin lights and VHF transceiver.

However, I recently replaced my old manual-start engine with an electric-start model. Initially, I connected this new engine to my trusty AGM battery. When running the engine the voltage across the battery terminals would almost invariably read 17 or 18 volts; For very short periods, this might not do any harm, but as I quite often find myself needing to use the engine for extended periods, I became concerned that damage to the battery might result.

I'm very far from being an expert in these matters, but it's my understanding that different battery types (AGM, Gel, conventional wet cell, etc) will have different internal resistance characteristics, will present different loads to a charging source and will therefore provide different levels of "self regulation", ie will limit the charging input voltage with different degrees of success.

So, as an experiment, I have tried connecting the engine to a smaller 40AH "non-AGM" battery (as recommended by the engine manufacturers). Charging-voltage slightly better - about 16v - but still enough to cause damage if sustained for long periods. I usually use my mains charger to bring this battery up to "full" prior to using the engine. If the battery were partially discharged, I would expect the the charge-voltage to be high at first, then to settle down as the charge began to be absorbed. My problem is that the charge voltage always remains high.

As explained in a previous post, I have found that if I connect a 10w load whilst the engine is running, the voltage across the battery terminals comes down to a more palatable 13.5 volts or so. I imagine that most batteries would be happy with this.

Of course, the normal thing is to incorporate a voltage regulator. The manufacturers do not supply one for my engine, and I wouldn't be happy fiddling around with the engine's internal wiring attempting to fit a third-party unit. There are only two wires coming out of the engine casing; one to battery positive, the other to battery negative - obviously this pair of wires is used for both starting and for charging. So if I am to attempt to regulate the charge voltage without interfering with the engine, I can only do so by raising the load present at the battery terminals.

Bedouin has suggested what might prove to be an answer - a solar-panel regulator. He points out that some of these will be simple on/off types, but others always present a load to the solar panel (or in my case, the starter battery). This is worthy of investigation (thanks, Bedouin). If a suitable model can be sourced, this would load my starter battery sufficiently to keep the charge voltage down and offer a small, yet useful, charge to the domestic battery. Although this arrangement would mean having to retain two batteries on board - perhaps a bit "overkill" on a small boat - it would avoid having to modify the engine's internal wiring.

Thanks again, VicS.

Boating is never boring!!

Ron
 
I think you would have to look very carefully at the way a solar panel regulator operates. One that simply disconnects could put the outboards diodes at risk.

Even a PWM type might endanger the diodes.

What you really need is a shunt type regulator... which as far as I know outboard regulators are although often, if not always, combined into one unit with the rectifier

The trouble is of course that a shunt type simply dumps all the surplus as heat which is why some outboard regulators ( OMC ones anyway) are water cooled.

A motor cycle regulator has been suggested... I guess they are cooled by a good flow of air over them .. but I cannot find one to suggest although I am sure they are out there somewhere.

Other thought perhaps is a wind charger regulator. Older ones are shunt type but I dont know how the more modern ones work.

I dont think you have said what make the outboard is. I was wondering if a regulator from a more powerful model is a possibility.

Another thought is to ask for ideas on the iBoats forums http://forums.iboats.com/forum.php or the MarineEngine forums http://www.marineengine.com/boat-forum/forum.php
 
VicS said:
I think you would have to look very carefully at the way a solar panel regulator operates.......I dont think you have said what make the outboard is.
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You're absolutely right about the solar regulator; one that simply disconnects the source when the battery is fully charged might be OK for a solar panel, but would just leave me back with my 16 volts again - just the situation I'm trying to avoid!

The engine is a Selva 9.9 Piranha - chosen because it is one of the lightest 9Hp electric-start models on the market (and, incidentally, proving to be a superb little engine thus far). The agents have assured me that a regulator is not available for this model (maybe because regulator cooling would be difficult on an engine this small??)

A wind turbine regulator might be a possibility - I shall investigate.

But I still keep coming back to the bulb/power resistor idea!

A DC to DC (battery to battery) charger taking its power from the starter battery and supplying a charge to my domestic battery would, I dare say, soak up some of my excess volts when operating. A VSR also connected to the starter battery would divert excess volts to a 10w bulb if the DC charger, having done its job, were to cut out. The whole arrangement is hardly elegant, but it ought to work and should be completely automatic.

The crux of the problem is that nearly all of the more logical solutions involve modifications to the engine wiring to accomodate regulation to control the charge voltage. The engine, as supplied, allows no means to do so, be it after-market or DIY. Therefore, short of dismantling the engine wiring, the only possible means of decreasing the charge voltage is to increase the load presented to the engine - different battery, running equipment concurrent with engine use, connecting a load, whatever.

My assumption is that Selva have calculated that most users may from time to time wish to run equipment (nav lights? instruments? beer cooler??) at the same time as running the engine, and have designed the engine's electrics to provide a reasonable all-round compromise. Bigger engines will be more sophisticated, but this 9HP jobbie is only a tiddler after all.

Thanks for all the help, and I will investigate the forums you mention - cheers.

Ron.
 
Put your 10W bulb on top of your boat facing forwards and call it an automatic steaming light :)
 
Ronald_M said:
Of course, the normal thing is to incorporate a voltage regulator. The manufacturers do not supply one for my engine, and I wouldn't be happy fiddling around with the engine's internal wiring attempting to fit a third-party unit. There are only two wires coming out of the engine casing; one to battery positive, the other to battery negative - obviously this pair of wires is used for both starting and for charging. So if I am to attempt to regulate the charge voltage without interfering with the engine, I can only do so by raising the load present at the battery terminals.
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I think that this will make fitting any conventional regulator problematic. Just to be clear, am I right in thinking that the starter button is mounted on the motor rather than in the boat? Do you know what sort of starting current is drawn?

I can imagine a set up involving steering diodes: a big one to take starting current from the battery to the +ve wire and a smaller one to take charging current from the +ve wire to the battery via a voltage dropper (far better IMHO than trying to reduce the voltage by applying load to the battery).

While arranging for automatic control of the voltage dropped is not too difficult, a simple manual arrangement might consist of a series of say 6 diodes in series with a wire from each joint to a multi way switch which would allow the charging voltage to be set at roughly 0.7 V increments.

Providing the motor's internal circuitry doesn't need the battery for anything other than starting, the big diode for starting could be replaced by a switch; better electrically, but would require remembering to use it: "start" / "charge" labelling might help.
 
DaveS said:
I can imagine a set up involving steering diodes: a big one to take starting current from the battery to the +ve wire and a smaller one to take charging current from the +ve wire to the battery via a voltage dropper..........Providing the motor's internal circuitry doesn't need the battery for anything other than starting, the big diode for starting could be replaced by a switch; better electrically, but would require remembering to use it: "start" / "charge" labelling might help.
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Perhaps interrrupting the feed to the starter button and inserting a simple mechanical relay circuit.

The wiring diagram is attached.

Ron.
 
DaveS said:
But I thought you didn't want to disturb the internal connections?
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Well, my main fear is that I might end up placing an unsuitable load -too little or too much - to the engine's alternator or diodes, etc and thereby risk burning something out. If it is possible to acheive my voltage-regulation objective without endangering the engine's circuitry, then the engine will come to no harm, and, hopefully, I shall not be invalidating my guarantee.

Ron.
 
Ronald_M said:
Well, my main fear is that I might end up placing an unsuitable load -too little or too much - to the engine's alternator or diodes, etc and thereby risk burning something out. If it is possible to acheive my voltage-regulation objective without endangering the engine's circuitry, then the engine will come to no harm, and, hopefully, I shall not be invalidating my guarantee.

Ron.
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OK, sorry about delayed reply, I've been away for a few days.

Looking at the circuit, I don't think you need a relay. A voltage dropper could be inserted between the + terminal of the bridge rectifier and the main + terminal of the solenoid without affecting availability of full battery voltage for starting. The advantage of a series dropper is that, provided it's suitably insulated and nothing can come into electrical contact with earth, it's virtually fail safe: even if it goes short circuit no more load will be applied to the rectifier / coil than under your current arrangement.

An automatic voltage dropper arrangement (though less intrinsically safe) involving a power transistor could be designed fairly easily, but I would be tempted to start off with the simple variable diode dropper chain as described in my earlier post (well wrapped up in tape or otherwise protected from touching anything). If you include a link to the multi way switch before the first diode this will allow you to reduce the voltage drop - and the power wasted - to zero if, or IMHO more likely when, you find yourself wanting to charge the battery after it is more than slightly discharged.

The obvious down side is that (unless you can find a suitable existing hole in the power head or cowl through which to take the (extended?) switch shaft) adjustment could only be made with the cowl off, and if the switch is sited too close to moving bits this is maybe something better done with the motor stopped. Experience over a range of conditions (1 year?) would indicate whether this is too much of a hassle and replacement by something more sophisticated would be worthwhile.
 
Placing a bulb in series with the charging circuit is a perfectly valid way to drop voltage. I would use a power resistor instead because it is much less likely to break. The problem with the simple voltage dropper, compared to a "proper" regulator, is that it will keep supplying current to the battery even when it is fully charged. It would still be a vast improvement on a direct connection.
If you assume your charging circuit supplies 17V and the battery is flat at 12V then that's a 5V drop across the resistor. The power rating you'd need would be VxV/R, so if you used a 5 ohm resistor it would need to be rated at 5 Watts. There would be 1 amp going into the battery when it's flat and about 0.7A going into it when fully charged. 0.7A is not going to do any harm to a normal sized battery. You might of course try a lower resistance, higher power resistor to get more charging current but I suspect the small outboard charger won't supply any more current anyway, so you would just be wasting money on the more expensive resistor.
 
CreakyDecks said:
Placing a bulb in series with the charging circuit is a perfectly valid way to drop voltage.
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only if (a) you know the source voltage, (b) the voltage is stablised, (c) you know the load current, (d) the load current is fixed.

In other words it's the worst possible way to drop voltage.

And another thing: the resistance of a bulb filament varies according to how hot (bright) it is. If you measure the resistance of a bulb using a multimeter ohm range, it will be nothing like the resistance when the bulb is illuminated.
 
elton said:
only if (a) you know the source voltage, (b) the voltage is stablised, (c) you know the load current, (d) the load current is fixed.

In other words it's the worst possible way to drop voltage.

And another thing: the resistance of a bulb filament varies according to how hot (bright) it is. If you measure the resistance of a bulb using a multimeter ohm range, it will be nothing like the resistance when the bulb is illuminated.
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Totally agree - a bulb has entirely the wrong characteristics - the more power you need the less it lets you have.

The only use I can think of for a bulb is a current limiter
 
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