alternator output

[stephen_warby]

Hi,

Is there a way to get an increased output from an alternator apart from buying an expensive three stage regulator?

Cheers
Stephen

 

[Guest]

I'm alittle confused...... doesn't your current regulator deliver the maximum possible output from the alternator? If not, I would think replacing it might be the trick..... but if not, I would think replacing the alternator with one with a higher output would be the best way to go.

 

[stephen_warby]

Sorry, my question is probably a little light on detail.

What I am concerned with is the terminal voltage at the battery. Automotive alternators reduce the voltage too early making the charge period much longer to get a full charge. You can buy mutistep charge regulators to get over this but they are a bit expensive for me at this time and I wondered if anyone knew of a cheap shortcut.

Cheers
Stephen

 

[andyball]

I'll get around to trying this one day (it can wait until I have a boat with a car type alternator).

One possibility is buying an "old" style regulator ,that allows nearer to 14.8V. I used to sell regulators to replace the old "mechanical" ones on bmw motorcycles -the "no-moving-parts" replacement used to cost £5 in the late 80's, and produced a lower charging voltage than the mechanical ones. (14.4 instead of 14.8)

You can buy "external" types that would be easier to wire up -pattern ones are made by durite & others & they may well make ones to suit obsolete applications where a small alternator cannot charge a battery quickly enough if set to 14V or less.

DON'T do it if you've got sealed/gel/fancy batteries, & do check fluid levels more often.

I can only speak from personal experience, but most, if not all motorcycles ( and many cars) that I've ever looked at regulated to 14.8V,sometimes more( yes, even according to the manufacturers data). With "modern" batteries, that would be a problem, but with ones you can top-up, you just had to do it more often.

People often say that you need a special muti-stage regulator, so it reduces the voltage after a while, to reduce gassing....well these car/bike ones didn't do that, and afaik, increased topping-up was the only "problem", although bulbs used to blow more often, but that may well be due to other factors.

If they still make it, the 14.4V external reg. was a Durite 0848-10.

 

[stephen_warby]

Ah thank you, I'll look into this. There must be simple ways of doing it. My alternator almost always only runs for 1,2 or 3 hours and I can see the votage is too low (14.1). I used to have a battery sensing alternator but I have had to replace it (new mount and all for a Bosch which is easier to get parts for.

Thanks Stephen

 

[andyball]

Another thought.....even machine sensed alternators can be sensitive to voltage drop : my Renault regulates to 14.2V, until even a small load(like the brake lights-42W) is applied, then it drops to 13.8V -quite a difference.

I have previously found,on some,not all cars/bikes that by wiring the charge warning lamp almost directly to the battery (naturally use a fuse & switch), that 0.5V increase is seen at the battery terminals. It's easy to try, and very cheap indeed if it helps.

It's also worth bearing in mind that some (all?) regulators just work as a switch: they reach 14.x volts, and shut off the power to the field coil, the voltage immediately drops, and it switches back on again- this works OK on (at least some)commercially available regulators, and makes designing/building a suitable 14.8V regulator look fairly easy.

 

[boatone]

In many marine installations there is a significant voltage drop between the alternator and the battery posts caused by inadequate cabling and possibly other things like blocking diodes.
Get hold of a digital meter, select the 20v range and put the positive probe on the alternator positive and the negative probe on the battery positive terminal. The reading will be the voltage drop in your circuit and should be no more than 0.1 or 0.2 volts.
On my motor cruiser (a Princess 32) I have 3 x 110Ah domestic batteries and work on the assumption that I should not discharge the batteries below around 50% and I am unlikely to recharge them to more than around 85%. This gives me 35% 'sweet' capacity ie around 110 Ah of useable power. Seems to work fine with no major traumas and no special charging arrangements. The voltage drop between alternator and battery post is only around 0.2 volts so machine sensed regulator still gives 14.2volts or so at the posts.

<A target="_blank" HREF=http://www.boatsontheweb.com/galleryframes.html> My P32, BoatersGallery, VolpenUsersGroup</A>

 

[david_bagshaw]

If you need a short term answer, theoutput & hence the voltage can be controlled manually with a rheoststat, & wiring up to the brushes. (or even just an on off switch) would not recommend as a long term answer, but a great get you home when the nearest agent is shut/ on holiday/ wanting the earth for a regulator.


David
<A target="_blank" HREF=http://www.euroboating.net>http://www.euroboating.net</A>

 

[stephen_warby]

Thank you very much. I'll look into all of this particularly voltage drop from alt to battery. I just want to get it to 14.4.

Cheers

Stephen