Upgrading an Alternator

[Stemar]

In another thread, that I don't want to hijack, there was a link to Smartgauge.co.uk, which is full of interesting stuff. Wandering around the site, I found this way to improve charging rate. It's rather tempting to do as I have an older type alternator.

Any comments from any of the resident experts?

My alternator has a connection which allows me to unplug a wire from the B+ terminal and connect it to the battery + to make the alternator battery sensed. There's no advantage to doing that, because I use a split charge relay and have negligible voltage drop, but it seems that that's going to be the rotor supply, so putting the diodes between D+ and the wire would be a good thing to do. Is this correct?

For a 65amp alternator, are the 10amp diodes suggested likely to be OK? SOmething like this?

Finally, why, as suggested in the artilce, should I consider Shottky diodes - wouldn't I need 2 in series to get the same voltage drop?

Thanks in advance.

 

[halcyon]

Is this correct?

For a 65amp alternator, are the 10amp diodes suggested likely to be OK? SOmething like
QUOTE]

If it's a machine sensed alternator the sense feed will be internal, so you may well have to take the alternator apart. It can be a link from the positive output diodes.

The rotor feed comes from an internal diode feed, the warning light feed is only for initial excitation.

The big danger can be what voltage are you regulating at? 13.6 volt fitting a diode may be advantageous, but regulating at 14.3 volt will be a big danger.

First job is to find out how your alternator is wired internally for sensing, and what regulation voltage you have.

Brian

 

[TrueBlue]

I would only attempt what you suggest

If you are comfortable with working with electrics; not only in the mechanics of setting it up, but are prepared to monitor the system constantly, and tweak it from time.

Been there, done it. My modified system is so powerful that I have to switch it down to "slow" mode while the engine warms up (MoBo) otherwise the twin row belts will shred.

A less painful way of getting what you want is to fit a slightly smaller alternator pulley - cost about £15 from Bearing Boys. That will make the alternator run faster, and charge your batteries quicker.

Alternatively get yourself one of those "charge your batteries in a trice" gizmos:-
That awfully nice Mr. Sterling has a slightly older model on sale (currently £60) here

There is also another one currently on eBay at £20.

or, this adjustable unit might be pressed into service, but you'd need advice as it's suitability

The two Sterling units are fit and forget (as is the pulley) as the former have circuitry to limit the time that the charge is at a higher voltage, and I'm not happy to have the voltage high for any length of time. Advanced regulators also attempt to condition the batteries as well.

I wouldn't denigrate you alternator as being "old", these units were designed to give their output at lower rpm (engines didn't spin as fast in those days, so a more modern unit is not a solution, either.

OK that's enough for starters
except for - why did you want to fiddle in the first place; has your alternator ceased to hack it (worth giving it and your wiring a checkover in case brushes or cables have poor connections), or have your requirements changed?

 

[mitiempo]

Steve
Your better solution would be to convert your alternator to an external 3 stage regulator. Most standard alternators with internal regulators are designed to replenish a starting battery only (as in a car) and will slow output fairly quickly. A good 3 stage will keep the alternator output at max until the batteries are about 75% charged and then slow output as the battery acceptance rate drops.

 

[Chris_Robb]

In another thread, that I don't want to hijack, there was a link to Smartgauge.co.uk, which is full of interesting stuff. Wandering around the site, I found this way to improve charging rate. It's rather tempting to do as I have an older type alternator.

Any comments from any of the resident experts?

My alternator has a connection which allows me to unplug a wire from the B+ terminal and connect it to the battery + to make the alternator battery sensed. There's no advantage to doing that, because I use a split charge relay and have negligible voltage drop, but it seems that that's going to be the rotor supply, so putting the diodes between D+ and the wire would be a good thing to do. Is this correct?

For a 65amp alternator, are the 10amp diodes suggested likely to be OK? SOmething like this?

Finally, why, as suggested in the artilce, should I consider Shottky diodes - wouldn't I need 2 in series to get the same voltage drop?

Thanks in advance.

In the article you refer to, the author says that you, with an older alternator, will be the beneficiary of a alternator controller such as Sterling. There is probably no substitute for sensing the voltage on the battery, so I would go with that solution.

I am not entirely convinced with the arguements for them being unnecessary on a new alternator. I have just put a new 110 ah one in replacing an old 13.8V 50 ah one, and connecting the sterling up, considerably increased the ampage going into the battery than without. I have not done extensive tests yet, with and without, but I will do so when I next get to the boat and have used some juice from the batteries.

This articel refers to 14.4 being the top limit for charging ( and yes it is, I understand for sealed batteries,) but sterling uses 14.8V - again a significant % difference for charging. I don't necessarily agree with these articles, as I am the original sceptic, and wonder what his angle is - especially as my initial observations don't agree.

An important consideration is what charge splitting methid you use as well. If the older diode systems, then a controller IS the way to go.