How much engine time

[Tiny]

I know it is an old chesnut but, having changed engines and got a new alternator I find running the engine to charge the batteries if moored for a day means leaving it on for a lot longer.

 

My new engine is a Beta38 with a 100amp alternator which I run at 1200 revs to charge (when 800 is tick over and 2,600 is full power). I have 3 110 amp leisure batteries.

 

My current electric usage is for a lec fridge running 24 hours, a mikuni heater running for 30minutes a day and for the lights (one double flouescent for an hour) and the water pump - pumping 10 gallons a day.

 

To charge for this a couple of hours used to be enough but not its more than 3 and the engine fitter maintains it should be nearer 8!

 

I suspect the batteries (4years old) might be going or the alternator is not giving the 10amps per battery per hour that it should but that 8 hours charging has got me wondering. So what do you think. How many hours should keeping the batteries topped take?

Edited July 6, 2011 by Tiny

[ditchcrawler]

I know it is an old chesnut but, having changed engines and got a new alternator I find running the engine to charge the batteries if moored for a day means leaving it on for a lot longer.

 

My new engine is a Beta38 with a 100amp alternator which I run at 1200 revs to charge (when 800 is tick over and 2,600 is full power). I have 3 110 amp leisure batteries.

 

My current electric usage is for a lec fridge running 24 hours, a mikuni heater running for 30minutes a day and for the lights (one double flouescent for an hour) and the water pump - pumping 10 gallons a day.

 

To charge for this a couple of hours used to be enough but not its more than 3 and the engine fitter maintains it should be nearer 8!

 

I suspect the batteries (4years old) might be going or the alternator is not giving the 10amps per battery per hour that it should but that 8 hours charging has got me wondering. So what do you think. How many hours should keeping the batteries topped take?

I am glad you asked that here, I think you will get more response.

[Proper Job]

It might be that the fridge is working harder due to a warmer ambient temperature.

 

But I'd stop guessing as to the state of your batteries and get a monitor. The SmartGauge is generally regarded as good one that is easy to fit.

[Ex- Member]

It's worth checking the pulley ratios, if your drive pulley is 4 inch and your alternator pulley 2 inch then you;re only getting 2 to 1 so at 1200 rpm your alternator is doing 2400 generally most Alternators are at their most efficient at between 5000 and 7000 RPM there are exceptions though.

[Sir Nibble]

It's worth checking the pulley ratios, if your drive pulley is 4 inch and your alternator pulley 2 inch then you;re only getting 2 to 1 so at 1200 rpm your alternator is doing 2400 generally most Alternators are at their most efficient at between 5000 and 7000 RPM there are exceptions though.

I would expect most alternators to be well into the top range of their output by around 3000-3500 rpm.

[alan_fincher]

What engine / alternator did the Beta replace ?

 

somewhat curiously some older engines seem to have more sensible pulley ratios than the more modern ones, meaning they could spin the alternator faster for any given engine revs.

[Ex- Member]

I would expect most alternators to be well into the top range of their output by around 3000-3500 rpm.

 

Lower amperage alternators possibly, most alternators over 70 amps the optimum output is as i stated. My 70amp happens to be 5500

 

In the link the graph shows the 65A alternator this comes into it's prime around 4500

 

The 85 amp at 5 to 6000

 

My alternator is pulley'd up to around 5 to 1 so running the engine at 1100 rpm is producing the best available from the alternator ie 5500rpm

You have to be careful doing this if the alternator has a max rev limit though most alternators can cope easily with around 16000 rpm

 

 

http://www.checkthatcar.com/carfaq5.asp

 

 

[alan_fincher]

On the other hand, a graph like this from the Sterling site.....

 

 

shows it is perfectly possible for the right high power alternator to be producing most of it's amps by the time it is spinning in the range Sir Nibble quoted.

 

EDITED TO ADD:

 

It also adequately demonstrates the point about pulley ratios being so important....

 

That alternator driven by a modern engine with a 3:1 pulley ratio, only at fast tick-over, would be producing perhaps twice as much output, as if the pulley ratio were only 2:1.

 

One wonders why some marinisations of modern diesels go for a relatively small ratio ?

Edited July 6, 2011 by alan_fincher

[Grace and Favour]

Tiny . . A couple of tips to save 'fridge power consumption':

 

Install a small 12v PC fan between the bilge and the back of your fridge (mount it in a 4'' hole in the floor)

and

Turn the fridge off throughout the night, and only turn it back on when you've the engine running - turn fridge back off again last thing at night (and don't open the door, of course - - no post-midnight raids on the l*ger supplies!)

[sebrof]

Neither of these graphs has been produced by an alternator maker to show the characteristics of a particular model.

 

So I am not sure they prove anything.

[Gibbo]

One wonders why some marinisations of modern diesels go for a relatively small ratio ?

 

Myself and Adverc have been slagging them off over this for the last decade.

 

Neither of these graphs has been produced by an alternator maker to show the characteristics of a particular model.

 

So I am not sure they prove anything.

 

All the graphs I have seen that were]/b] produced by alternator manufacturers show the alternator producing at least 80% rated output by 3500 RPM.

[Nev]

I fitted a SmartGauge - perfect way to monitor your batteries IMHO. It also gave me confidence to know when to replace my three aging batteries as I was running my engine longer to get them back up to a reasonable % charge. New batteries and I only need an hour or so. My unscientific observation is 1 hour for every 10% of charge at about 1300 rpm....

 

Works for me and that is what is important.

 

Take care

 

Nev

 

NB Waterlily blog

 

 

 

 

It might be that the fridge is working harder due to a warmer ambient temperature.

 

But I'd stop guessing as to the state of your batteries and get a monitor. The SmartGauge is generally regarded as good one that is easy to fit.

[Ex- Member]

Neither of these graphs has been produced by an alternator maker to show the characteristics of a particular model.

 

So I am not sure they prove anything.

 

I did get the info for my alternator from Lucas well be brother did LOL

 

The reason most alternators put out their optimum charge at between 5 and 7 thousand revs is most vehicles pulley @ 2 to 1 your average car at 70 mph is at around 3000 rpm generating 6000 rpm to the alternator.

 

Simples

 

ETA

Here bosch use 6000 as it's optimum output.

 

http://rb-kwin.bosch...ators/160a.html

 

Performance Output

14V / 100A @ 2000rpm

14V / 160A @ 6000rpm

 

Maximum Alternator Speed

18,000 rpm

 

Temperature Limits

125°C = 257°F

 

Weight

7.2 kg = 15.8 lbs

Edited July 6, 2011 by Julynian

[Ryeland]

I know it is an old chesnut but, having changed engines and got a new alternator I find running the engine to charge the batteries if moored for a day means leaving it on for a lot longer.

 

My new engine is a Beta38 with a 100amp alternator which I run at 1200 revs to charge (when 800 is tick over and 2,600 is full power). I have 3 110 amp leisure batteries.

 

My current electric usage is for a lec fridge running 24 hours, a mikuni heater running for 30minutes a day and for the lights (one double flouescent for an hour) and the water pump - pumping 10 gallons a day.

 

To charge for this a couple of hours used to be enough but not its more than 3 and the engine fitter maintains it should be nearer 8!

 

I suspect the batteries (4years old) might be going or the alternator is not giving the 10amps per battery per hour that it should but that 8 hours charging has got me wondering. So what do you think. How many hours should keeping the batteries topped take?

I can confirm that on my Beta 38, the 100A Iskra domestic alternator reaches it's max output at about 1200 rpm as the pulley ratios are OK.

 

No batteries will charge to 100% on 2-3 hours, so the batteries are probably sulphated unless they have been on a mains charger regularly. To get near 100% 8 hours is more like it, but expensive in diesel!

 

To check whether your alternator is charging measure the voltage at the battery terminals, mine is about 14.4V.

 

Richard

[nb Innisfree]

Batts take 24 hrs or more to reach true full charge, 8 hrs or more to reach nominal full charge, this applies no matter how large your alternator or how many the amps going in. You either have to recharge daily for 8 hrs or more or do a daily charge to replace your daily usage, say 2 hrs, and a long 8+ hr equalising charge weekly. The spacing of these equalising charges will dictate the life of your batts. It's one big sliding scale between battery life and diesel consumption, no definite formula just down to judgement depending on amount of cruising at different times.

[Ex- Member]

One wonders why some marinisations of modern diesels go for a relatively small ratio ?

Has to be money really, most new engines come with a 4 or 5 inch drive pulley and alternators are pretty standard 2 inch so the engine pulley usually needs to be increased, some companies do this (good ones) most don't. It should be part of the marinisation process in my eyes, but your average jo will never realise it's actually ineffective so why bother.

I had ours specially made think it cost 30 quid, you think with a marinised engine costing 5k plus that an extra £30 to get the best out of it would be worth paying for and making a good selling point to the customer into the bargain.

[Tiny]

Thanks for all the responses.

[Proper Job]

All the graphs I have seen that were]/b] produced by alternator manufacturers show the alternator producing at least 80% rated output by 3500 RPM.

After cooking an alternator a while back, I was chatting with the supplier of the replacement unit. He advised that it was best to try to run the alternator a fast as possible (without exceeding it max rpm). Although it's output of 80% @ 3500 rpm (using Gibbo's figure as a for instance) is achievable, the highly inefficient cooling fan on most alternators will not supply sufficient cooling for sustained output at that speed.

[GSer]

If you have a freezer box, freeze some ice packs while the engine is running, then, overnight, just pop the packs into the fridge to keep it cooler longer for less electrical input from the battery pack

 

Paul

[Ex- Member]

If you have a freezer box, freeze some ice packs while the engine is running, then, overnight, just pop the packs into the fridge to keep it cooler longer for less electrical input from the battery pack

 

Paul

 

The most efficient way to run a fridge or freezer is to keep them full. We keep bottles of water at the bottom of the fridge along with what we use like milk and juices, and pack as much in the top as possible, even bread and eggs, when stuff is used replace with something else like bottled/tinned beer soft drinks etc.

 

Same with freezers the fuller they are the less energy needed to run, some people even use screwed up newspaper in shopping bags to fill unused space.

 

If your fridge or freezer is partially full, the moment you open the door all of the cold air is released under suction and replaced with air at room temp, the fridge/freezer then has to work hard to cool this new influx of warm air, the less free space the better the less air can be sucked out, there for less air to re-cool. If you have mass in the fridge already cold this also speeds up the re cooling when door is closed.

 

Another benefit is if you have any power failure your fridge will stay cooler for a lot longer as will a Freezer up to 3 times longer than a half filled fridge or freezer of course that's if you keep the doors closed or use them quickly when you do.

 

 

 

[matty40s]

I have to disagree with the last post, who drinks bottles of water.

I fill the lower half of the fridge with essentials like rose and white along with the cans of brewed items to fill the space. Turn it off in October and turn it back on in march.

 

I have to disagree with the last post, who drinks bottles of water.

I fill the lower half of the fridge with essentials like rose and white along with the cans of brewed items to fill the space. Turn it off in October and turn it back on in march.

[GSer]

I have to disagree with the last post, who drinks bottles of water.

I fill the lower half of the fridge with essentials like rose and white along with the cans of brewed items to fill the space. Turn it off in October and turn it back on in march.

 

I have to disagree with the last post, who drinks bottles of water.

I fill the lower half of the fridge with essentials like rose and white along with the cans of brewed items to fill the space. Turn it off in October and turn it back on in march.

 

 

You seem to drink twice as much as me!

[Theo]

Batts take 24 hrs or more to reach true full charge, 8 hrs or more to reach nominal full charge, this applies no matter how large your alternator or how many the amps going in. You either have to recharge daily for 8 hrs or more or do a daily charge to replace your daily usage, say 2 hrs, and a long 8+ hr equalising charge weekly. The spacing of these equalising charges will dictate the life of your batts. It's one big sliding scale between battery life and diesel consumption, no definite formula just down to judgement depending on amount of cruising at different times.

 

Sounds like a really good reason for having solar panels.

 

Nick

[Ex- Member]

Sounds like a really good reason for having solar panels.

 

Nick

 

Very good point on a sunny day when not using much power decent input from solar panels might manage this full charge state. On a hot day all we'll have running will be a fridge and mini freezer and several computer cooling fans arranged throughout the boat and possibly a dab radio. With the 600 solar watts I'm planning we could quite often reach a state of full charge if we get a few sunny days on the trot.