How do you get the most of of your alternator

[fisherman]

Told wrong I'm afraid, for newer alternators anyway. Mine runs at 14.6v which will get to full charge just the same as a mains charger. Still takes a while with either source.

You may be right, but a friend fitted adverc. Like me, he was seeing full 28 volts on the voltmeters but this dropped rapidly when the inverter kicked in. After Adverc they stayed up much better, and on checking at the engineer's he was told the batteries were much better charged than is normal from an alternator. Rather than fit Adverc I have improved the computer which needed the inverter.

 

[lw395]

Don't forget there will be some voltage drop at 60A.
You need to look at the data for the alternator.
A lot of modern car alternators will put out a high percentage of nominal output at quite low revs.
BUt IMHO, designing around using more than 75% of the rated output is unlikely to be satisfactory.
The alternator on a yacht does not always get the cooling that's available on a road vehicle.
If you run it at 100% with marginal cooling, it may not have a particularly long life.

Also if the inverter is producing 50Hz single phase, the current it is drawing may be anything but steady DC. It might be useful to look at the AC component of alternator and battery voltages.
The alternator might be giving 100% peak but much less averaged over the cycle.

 

[geem]

This raises lots of questions. First, how long were you running the watermaker with the engine running to end up with 25.2v? And was 25.2v the voltage after the engine stopped? Second, 25.2v isn't particularly low, so you may not see 60A charge, even with the Sterling regulator, but will your engine be revving fast enough for the alternator to theoretically be capable of producing 60A?

25.2v is the voltage at the batteries once the inverter and watermaker have been running for maybe an hour. I suspect my revs were not high enough to give me full alternator output. Engine only revs to 2200rpm maximum and I generally run the engine at less than 1400rpm so I guess not enough for full output

 

[pvb]

25.2v is the voltage at the batteries once the inverter and watermaker have been running for maybe an hour.

And was this 25.2v after the engine was turned off?

 

[lw395]

25.2v is the voltage at the batteries once the inverter and watermaker have been running for maybe an hour. I suspect my revs were not high enough to give me full alternator output. Engine only revs to 2200rpm maximum and I generally run the engine at less than 1400rpm so I guess not enough for full output

It sounds like your engine has a pretty narrow rev range, compared to say a petrol car where the engine idles at 800 rpm and revs to 6,000, a range of nearly 8:1.
So your alternator should be 'geared' (with the right pulleys) to be running close to its maximum rpm at your engines max rpm.
At anything around half rated RPM, a modern alternator should reasonably be expected to provide over 80% of its rated output, possibly over 90%.
But if you want 60A continuously for an hour or more, you'd be well advised to have and 80 or 100 Amp alternator.
Or maybe two alternators?

 

[geem]

It sounds like your engine has a pretty narrow rev range, compared to say a petrol car where the engine idles at 800 rpm and revs to 6,000, a range of nearly 8:1.
So your alternator should be 'geared' (with the right pulleys) to be running close to its maximum rpm at your engines max rpm.
At anything around half rated RPM, a modern alternator should reasonably be expected to provide over 80% of its rated output, possibly over 90%.
But if you want 60A continuously for an hour or more, you'd be well advised to have and 80 or 100 Amp alternator.
Or maybe two alternators?

so my 60 amp alternator could reasonably be providing circa 40 amps whilst I am discharging 1500 w from the batteries? if this is the case I am losing out about 500w for an hour of watermaking. At the same time I have my 460w of solar and possibly the wind turbine, so not necessarily a big problem then. if I am engining for two hours and a run the watermaker for the first hour the second hour would bring the batteries back up along with the solar. Once I get the ammeter installed I should be able to see what the alternator is really doing

 

[sailor211]

If i was starting again i would look at a alternator with high output at low revs such as the Balmar. My current setup seldom gets the alternator to its max output of 90 Amps. most hard running it will be only 60 is amps and gentle potter may only be 40 A. so a good sailing day mooring to anchor with less than 1/2 hour motoring will do little for charging.

 

[Dockhead]

Lots of good advice, especially the Adverc. Good regulation is the place to start. Besides Adverc (my own favourite), there are other good external regulators, like Balmar.

Be realistic, however, about how much power you can get out of a car-type alternator. These are not designed or built for bulk power production. You will burn them up if you pull too much power out of them. They are designed and built for topping off starter batteries after the tiny amount of power drawn for starting the engine.

Will cost you a bit, but an extremely worthwhile modification is to fit a large-frame, so-called "hot rated", school bus type alternator, which is a completely different animal. This is on the contrary designed to produce bulk power and will happily do it 24/7.

Best of all if you have room to fit BOTH the standard alternator and a school bus type. Then you can completely separate house and start battery banks, each with its own alternator, a very good thing.

 

[GHA]

By

Lots of good advice, especially the Adverc. Good regulation is the place to start. Besides Adverc (my own favourite), there are other good external regulators, like Balmar.

How can it help? Unless you've an old alternator with a built in regulator set to too low a voltage, an external one can't "throttle back" to go to float, can it? So you're no different to an alternator with a regulator set to 14.5ish, are you?
Assuming a piggy back one, where the external regulator connects on top of the inbuilt one, like adverc I think balmar, dunno.

 

[RobbieW]

If i was starting again i would look at a alternator with high output at low revs such as the Balmar. My current setup seldom gets the alternator to its max output of 90 Amps. most hard running it will be only 60 is amps and gentle potter may only be 40 A. so a good sailing day mooring to anchor with less than 1/2 hour motoring will do little for charging.

Quite so; I've recently swapped out my Balmar for the Iskra it replaced whilst doing some PD. The difference is substantial; the Balmar develops high output at not much over idle whereas the Iskra has to be pushed to mid range revs to get it up near its limits. They both use the same external regulator, the Iskra has been modded to bypass the internal one.

By
How can it help? Unless you've an old alternator with a built in regulator set to too low a voltage, an external one can't "throttle back" to go to float, can it? So you're no different to an alternator with a regulator set to 14.5ish, are you?
Assuming a piggy back one, where the external regulator connects on top of the inbuilt one, like adverc I think balmar, dunno.

Basically I agree, one reason I changed my setup last year. The only Balmar regs I know of are 'external', you either bypass the internal one or buy an alternator that has no internal reg. The only other way I can think of, which entirely disassociates the alternator output with the load, is to use an A2B charger like the Sterling one

Edit: clearly the alternator output is not disassociated with the load; I couldnt quickly think of another way of expressing the concept though

 

[pvb]

Lots of good advice, especially the Adverc. Good regulation is the place to start. Besides Adverc (my own favourite), there are other good external regulators, like Balmar.

If you read the first line of the original post, you'll see that the system already has a Sterling regulator fitted.

 

[geem]

My alternator is a high output alternator specifically adapted for marine application. It is designed to run in a hot engine room. Bear in mind it is equivalent to 120 amps at 12V so is already quite high output. All I am am trying to do is get some advice on what sort of output I can expect when it has a large load on the system which will drag the battery voltage down to something like 25.2v with 400 amp hour (at24v) of domestic bank connected. Can I reasonably expect to get anywhere near the 60amps @24v it is rated at with its sterling regulator. I don't want to change for an Adverc or swap it for another alternator. It's not a car alternator. It is an insulated earth high quality piece of kit that can run at high temperature. It is designed to run hotter than the temperature cut out of the sterling alternator reg so this function of the sterling is not used

 

[pvb]

Can I reasonably expect to get anywhere near the 60amps @24v it is rated at with its sterling regulator.

I'll have one last try at getting this point across. The Sterling regulator is largely irrelevant if you're driving a big load through an inverter. The capability of the alternator to produce current varies according to how quickly the alternator is rotating. The potential output increases with increased revs. You haven't said what make/model your alternator is, but you will be able to get an output curve for it. The output curve will show you the revs at which it can produce 60A. By looking at the ratio of the sizes of the engine and alternator pulleys, you will be able to convert alternator revs to engine revs. If you then motor at that rev level, you should get 60A out of the alternator. We don't know what that rev level is, so can't say with any certainty whether you can reasonably expect to get anywhere near 60A.

 

[lw395]

My alternator is a high output alternator specifically adapted for marine application. It is designed to run in a hot engine room. Bear in mind it is equivalent to 120 amps at 12V so is already quite high output. All I am am trying to do is get some advice on what sort of output I can expect when it has a large load on the system which will drag the battery voltage down to something like 25.2v with 400 amp hour (at24v) of domestic bank connected. Can I reasonably expect to get anywhere near the 60amps @24v it is rated at with its sterling regulator. I don't want to change for an Adverc or swap it for another alternator. It's not a car alternator. It is an insulated earth high quality piece of kit that can run at high temperature. It is designed to run hotter than the temperature cut out of the sterling alternator reg so this function of the sterling is not used

Either you're not giving it enough RPM, your cable losses are too high or it's not actually powerful enough...

As PVb says, make sure it's got the right pulleys to give it the best chance.

The batteries are largely irreleant if you don't want to be discharging them.

I think it's normal to have at least 50% margin on the nominal rating of an alternator.
I'm sure it's a fine quality bit of kit, but you are asking a big job of it.
I don't specify alternators for a living, but sometimes power supplies I do. I don't think many of the manufacturers would recommend running most of those at their nominal rating for an hour at full temperature.
They'd sell me the next size up and I'd buy it.
Electrical stuff is like that.

For one thing, de-rating the power by 20% or so is likely to improve the reliability significantly.

 

[geem]

Either you're not giving it enough RPM, your cable losses are too high or it's not actually powerful enough...

As PVb says, make sure it's got the right pulleys to give it the best chance.

My generator dropped an injector last year two days out from the Canaries on route to Caribbean, we ran the engine to support the inverter running the watermaker. We made 1000 litres of water on route helped by having very light winds towards the end of the trip where we engined for many hours. I fitted the Sterling alternator regulator in the Caribbean to give me more alternator output in case something similar happens in the future. The alternator has not had a problem operating without the Sterling but the alternator may run hotter with the additional load the Sterling can impose. It is only an emergency backup to run the watermaker through the inverter. I have a spare alternator so not overly worried.
We make 130 litres an hour on the watermaker so it wouldn't be a problem to run the watermaker for 1/2 hr to reduce operating temperature. I would just run the watermaker more often for less time until I could get my generator fixed.
The batteries are largely irreleant if you don't want to be discharging them.

I think it's normal to have at least 50% margin on the nominal rating of an alternator.
I'm sure it's a fine quality bit of kit, but you are asking a big job of it.
I don't specify alternators for a living, but sometimes power supplies I do. I don't think many of the manufacturers would recommend running most of those at their nominal rating for an hour at full temperature.
They'd sell me the next size up and I'd buy it.
Electrical stuff is like that.

For one thing, de-rating the power by 20% or so is likely to improve the reliability significantly.

 

[lw395]

If it's really a backup, maybe the nicety of not discharging the batteries at all is not crucial?

Different people have different wants and expectations from their systems.
A few 12 packs of spring water are probably a cost effective backup?

 

[geem]

If it's really a backup, maybe the nicety of not discharging the batteries at all is not crucial?

Different people have different wants and expectations from their systems.
A few 12 packs of spring water are probably a cost effective backup?

The environmentally sensitives types might take exception. Caribbean islands are not great at dealing with plastic waste. Most seem to dump it in the island tip then set light to it once a month. Burning plastic is not great

My main consideration is if my elderly generator goes bad can I make do for a few months until I ship out my spare generator from the UK. I think I probably can, but what I thought was a simple question got a little complicated! I will install CT meters to check accurately what is happening but I suspect if I can get 40 amps out of my 60 amp alternator whilst using the inverter/watermaker I shouldn't have too great an impact on my batteries. I regularly see 13 amps at 24v when charging with my solar so they should charge up again fairly fast, thanks for all the valued input

 

[halcyon]

The environmentally sensitives types might take exception. Caribbean islands are not great at dealing with plastic waste. Most seem to dump it in the island tip then set light to it once a month. Burning plastic is not great

My main consideration is if my elderly generator goes bad can I make do for a few months until I ship out my spare generator from the UK. I think I probably can, but what I thought was a simple question got a little complicated! I will install CT meters to check accurately what is happening but I suspect if I can get 40 amps out of my 60 amp alternator whilst using the inverter/watermaker I shouldn't have too great an impact on my batteries. I regularly see 13 amps at 24v when charging with my solar so they should charge up again fairly fast, thanks for all the valued input

You need a clamp meter, jaws open and close round cable, gives you amps and direction, get one £20/ £30 over here. Check amps out of alternator, amps into battery bank and amps feeding inverter, gives you a idea what goes were.

Check voltage neg to center tap and center tap to positive terminal on each battery, ideally they should be the same, but can be a distance apart, limiting charge and load. Your 24 volt @ 13 amp worries me a little as well.

Brian

Before

 

[geem]

You need a clamp meter, jaws open and close round cable, gives you amps and direction, get one £20/ £30 over here. Check amps out of alternator, amps into battery bank and amps feeding inverter, gives you a idea what goes were.

Check voltage neg to center tap and center tap to positive terminal on each battery, ideally they should be the same, but can be a distance apart, limiting charge and load. Your 24 volt @ 13 amp worries me a little as well.

Brian

Before

Brian, I have already purchased several CT meters to install as you say. I should be able to get lots of real information
What worries you about my 13amps? This is measured by the solar regulator. My panels are all adjustable so in the Caribbean sun this is our peak input to the batteries. In addition we have a large wind generator as well.

 

[sailinglegend420]

......So you're no different to an alternator with a regulator set to 14.5ish, are you? ....

The problem with modern high voltage alternators is they have built in temperature compensation to protect the battery, so as the engine heats up they very quickly reduce their voltage to below the battery gassing voltage. In a boat with less cooling than a car this can go below 14v very quickly. So an external regulator is essential to maintain the voltage at the battery bank until it is nearly full, and then drop the output voltage to float mode.

The Adverc is not a multi-stage regulator so it will NOT provide the best charging regime for boat batteries.

The solution is a hot-rated alternator, like the Balmar, with an external smart regulator that has temperature sensors to measure both the batteries AND the alternator voltage, especially if you try to get the maximum out of it all of the time.

A 'hot rated Marine Alternator', like the Balmar, is 'engineered' to provide its rated output current even at a temperature of over 100 degrees C, so it will maintain that output and charge the bank much quicker. Faster charging is what we all want.

This 'hot rated engineering' may mean:

- High temperature diodes mounted on big heat sinks
- Heavier gauge stator windings
- precision balanced rotor
- Copper composite brushes
- Heavy duty bearings with high temperature grease
- Corrosion resistant materials & coatings
- Dual cooling fans
- access to field windings
- tachometer output
- maybe an isolated ground terminal

All this comes at a much higher price.