Engine Alternator and Idling Questions

[XAMK]

Hi there, 

 

I’m fairly new to boat building and am in the initial stages of fitting out my boat. 

 

I did have a look but couldn’t find anything on the following questions.  

 

I have a couple questions that I could really use an experienced boaters expertise on: 

 

1. I currently have a 55hp canalline engine onboard with the normal two alternators, the domestic is a 12v 175A alternator. My first question is: does anyone have experience with replacing it with a larger alternator? For example a 24v 400A alternator? If yes, how did it go? How did you mount it?
    
2. I appreciate running your engine is not pleasant for boating neighbours and know about the restrictions in time when running it. In order to prevent the alternator from running at idle and not pulling through that many amps, is there anything stopping me disengaging the gear wire on the engine and throttling a little bit?

 

At the moment the main thing I’m trying to work out is if I should fit a bigger alternator and run the engine for 45mins a day or go with solar and run the risk of it getting stolen in London. 

 

I’m sure I will have loads more questions in the future but to start with thanks for your help with these two. 

[GUMPY]

don't know where you would find a 24v 400amp alternator

 

[frangar]

2 minutes ago, Loddon said:

don't know where you would find a 24v 400amp alternator

 

That would be “interesting” to fit. 

[Ex Brummie]

I would be very surprised if your 175amp alternator was putting anything like that into your battery for very long. As the charge level rises, the input drops. There are alternator controllers that will fudge the voltage feedback so you charge higher, but you will also be topping up your batteries more often.

When you ask about disengaging the gear wire, your controller should give you that facility to increase idling speed without churning up the cut.

Edited December 30, 2019 by Ex Brummie
fast finger

[XAMK]

6 minutes ago, Loddon said:

don't know where you would find a 24v 400amp alternator

 

 

It's certainly not easy! 

 

I found this 370 Amp one in the states. 

https://www.ceniehoff.com/productdetail.asp_Q_catID_E_153_A_subCatID_E_281_A_productID_E_1515_A_skuID_E_1367

 

But admittedly that should belong on a truck, still does the same job, right? ?  

 

I guess maybe my question is more, what is the largest that is possible to fit, or that you know off? 

[frangar]

Are your boat domestics going to be 12 or 24v?? That’s your first choice then fit an alternator to suit...and learn how batteries accept charge etc. It’s not as simple as you think. 

[XAMK]

8 minutes ago, frangar said:

Are your boat domestics going to be 12 or 24v?? That’s your first choice then fit an alternator to suit...and learn how batteries accept charge etc. It’s not as simple as you think. 

 

Definitely don't think this is simple.

 

Would go with 24v if I can get a bigger alternator than the current 12v 175A I have. 

Would stay with the 12v if I can't get anything bigger than 175A and add 12v solar input. 

 

Domestics can be either as am fitting things like nav lights and horn to existing 12v starter engine, and inside lights/plugs/fans/pumps can be either 12v or 24v.

Edited December 30, 2019 by XAMK

[Alan de Enfield]

49 minutes ago, XAMK said:

At the moment the main thing I’m trying to work out is if I should fit a bigger alternator and run the engine for 45mins a day or go with solar and run the risk of it getting stolen in London. 

A straightforward question - no hidden agenda.

 

Do you know that it is not the alternator that controls the current going into the batteries but the batteries themselves that control the current. ?

 

A 400 amp alternator (assuming you have a big enough battery bank to allow it) will probably take 10 minutes running time less than a 175A alternator to get the batteries from 50% SoC to 99% SoC

Edited December 30, 2019 by Alan de Enfield

[WotEver]

1 hour ago, XAMK said:

is there anything stopping me disengaging the gear wire on the engine and throttling a little bit?

That is the normal way of doing it. You raise the revs until the current stops rising. After an hour or so you see how much you can reduce the revs. After another hour you do it again. Repeat until you’re at idle. 

25 minutes ago, Alan de Enfield said:

A 400 amp alternator (assuming you have a big enough battery bank to allow it) will probably take 10 minutes running time less than a 175A alternator to get the batteries from 50% SoC to 99% SoC

Very true. Even a 6 battery, 720Ah bank wouldn’t take 400A even right down at 50% SoC. 

[XAMK]

14 minutes ago, Alan de Enfield said:

A straightforward question - no hidden agenda.

 

Do you know that it is not the alternator that controls the current going into the batteries but the batteries themselves that control the current. ?

 

A 400 amp alternator (assuming you have a big enough battery bank to allow it) will probably take 10 minutes running time less than a 175A alternator to get the batteries from 50% SoC to 99% SoC

No I didn't know this - thanks for clarifying. I assumed the 400A alternator would simply charge the batteries from 50% to 99% SoC about 2 and a bit times faster than the 175A.

 

I guess this answers my question on whether to go larger alternator route or solar panels. 

 

I was told that chargers aren't a necessity and you save a bit of cash by going straight from alternator to battery, I take it this isn't case? 

 

 

[WotEver]

Just now, XAMK said:

I was told that chargers aren't a necessity and you save a bit of cash by going straight from alternator to battery, I take it this isn't case? 

I’m not sure what you mean by ‘charger’. That normally means a mains powered battery charger. Alternators are usually connected directly to the batteries. An Alternator Controller (if that’s what you meant by ‘charger’) is unnecessary if you have a modern regulator in the alternator, outputting 14.4V+ and decent sized cables.  

4 minutes ago, XAMK said:

No I didn't know this - thanks for clarifying. I assumed the 400A alternator would simply charge the batteries from 50% to 99% SoC about 2 and a bit times faster than the 175A.

Did you also know that to fully charge a lead acid battery (of any size) from 50% SoC to 99.9% SoC takes well over 12 hours?

[XAMK]

5 minutes ago, WotEver said:

I’m not sure what you mean by ‘charger’. That normally means a mains powered battery charger. Alternators are usually connected directly to the batteries. An Alternator Controller (if that’s what you meant by ‘charger’) is unnecessary if you have a modern regulator in the alternator, outputting 14.4V+ and decent sized cables.  

Yes that's what I meant, sorry learning a lot of new words. 

 

I've just gone through the manual and didn't find anything regarding a regulator in the alternator. I guess it should have one though as I bought the boat new earlier this year. Its a Canaline 52 on the off chance that you know from memory if it has one? 

[WotEver]

Just now, XAMK said:

Yes that's what I meant, sorry learning a lot of new words. 

 

I've just gone through the manual and didn't find anything regarding a regulator in the alternator. I guess it should have one though as I bought the boat new earlier this year. Its a Canaline 52 on the off chance that you know from memory if it has one? 

It’ll almost certainly have a 14.4V (or higher) regulator fitted. Only way to know the exact voltage is to measure it when it’s connected to a battery. 

[Alan de Enfield]

20 minutes ago, XAMK said:

No I didn't know this - thanks for clarifying. I assumed the 400A alternator would simply charge the batteries from 50% to 99% SoC about 2 and a bit times faster than the 175A.

Ok - these numbers are just for example, every alternator and battery bank will vary.

 

500Ah battery at 50% SoC (so need to replace 250Ah) But because of 'physics' and losses you actually need to replace ~20% more, ie 300Ah

100 Ah alternator.

Assuming you get the alternator running at the optimum speed of 5000 rpm +

 

The 1st half hour the alternator will out put at about 13 volts and 100 amps so 50Ah replaced

The next hour the batteries will limit their input (note it is the batteries that say 'that's all we can take') to 75Amps so another 75Ah replaced

The next 2 hours the batteries will limit their input to 40amps so another 80Ah replaced, by now the voltage is up to 13.5v

The next 2 hours the batteries will limit their input to 20 amps, so another 40 Ah replaced.

The next 4 hours the batteries will limit their input to 10 amps so another 20Ah added, by now the voltage has increased to 14v

The next 5 hours the batteries will limit their input to 5 amps so another 25Ah added, the voltage is now approaching 14.4v and are approaching 'full'

The nest 5 hours the batteries will limit their input to 3 amps so another 15Ah added, the voltage is now 14.4-14.5v and the batteries can be considered to be 'full'

 

You have replaced 300Ah in 20 hours.

 

Batteries need to be charged daily to avoid damage by sulphation (loss of capacity)

You can obviously not achieve such long running times every day so it is 'normal practice' and accepted that you are going to suffer some small amount of sulphation every day by not fully recharging your batteries.

Run the alternator for 2-3 hours every day and get the batteries back to 80% SoC and then run them for 8-10 hours on Saturdays and Sundays.

 

If your daily electrical consumption does not reduce the batteries to 50% SoC then obviously it will take less time to recharge, but the thing to remember is that the last 10-15% will always take probably 10-12 hours.

 

The fact is that Lead Acid battery chemistry is not ideal for boaters requirements and everything is a compromise - you can charge them everyday and they will last 3 years (or so), or you can charge them once a month and they will be dead in 6 months, it is a balancing act between convenience, costs (diesel and battery replacement costs) and battery bank size.

 

The alternator plays a very small part in the system. From the above illustration you can see that after the 1st half-hour of running you only need a 75Ah alternator anyway.

 

[Boater Sam]

2 hours ago, XAMK said:

 

1. I appreciate running your engine is not pleasant for boating neighbours and know about the restrictions in time when running it. In order to prevent the alternator from running at idle and not pulling through that many amps, is there anything stopping me disengaging the gear wire on the engine and throttling a little bit?

 

Put the lever into neutral and open the throttle a bit is the usual way, no messing with the "gear wire". 

[XAMK]

9 minutes ago, Alan de Enfield said:

Ok - these numbers are just for example, every alternator and battery bank will vary.

 

500Ah battery at 50% SoC (so need to replace 250Ah) But because of 'physics' and losses you actually need to replace ~20% more, ie 300Ah

100 Ah alternator.

Assuming you get the alternator running at the optimum speed of 5000 rpm +

 

The 1st half hour the alternator will out put at about 13 volts and 100 amps so 50Ah replaced

The next hour the batteries will limit their input (note it is the batteries that say 'that's all we can take') to 75Amps so another 75Ah replaced

The next 2 hours the batteries will limit their input to 40amps so another 80Ah replaced, by now the voltage is up to 13.5v

The next 2 hours the batteries will limit their input to 20 amps, so another 40 Ah replaced.

The next 4 hours the batteries will limit their input to 10 amps so another 20Ah added, by now the voltage has increased to 14v

The next 5 hours the batteries will limit their input to 5 amps so another 25Ah added, the voltage is now approaching 14.4v and are approaching 'full'

The nest 5 hours the batteries will limit their input to 3 amps so another 15Ah added, the voltage is now 14.4-14.5v and the batteries can be considered to be 'full'

 

You have replaced 300Ah in 20 hours.

 

Batteries need to be charged daily to avoid damage by sulphation (loss of capacity)

You can obviously not achieve such long running times every day so it is 'normal practice' and accepted that you are going to suffer some small amount of sulphation every day by not fully recharging your batteries.

Run the alternator for 2-3 hours every day and get the batteries back to 80% SoC and then run them for 8-10 hours on Saturdays and Sundays.

 

If your daily electrical consumption does not reduce the batteries to 50% SoC then obviously it will take less time to recharge, but the thing to remember is that the last 10-15% will always take probably 10-12 hours.

 

The fact is that Lead Acid battery chemistry is not ideal for boaters requirements and everything is a compromise - you can charge them everyday and they will last 3 years (or so), or you can charge them once a month and they will be dead in 6 months, it is a balancing act between convenience, costs (diesel and battery replacement costs) and battery bank size.

 

The alternator plays a very small part in the system. From the above illustration you can see that after the 1st half-hour of running you only need a 75Ah alternator anyway.

 

Thank you so much for clearing that up in an easy to follow way. 

 

I take it LiFePO4 don't behave in the same way, is this one of the reasons people are switching to them? 

 

 

3 minutes ago, Boater Sam said:

Put the lever into neutral and open the throttle a bit is the usual way, no messing with the "gear wire". 

 

Does it not churn up the bank? There isn't a downside of disengaging the gear wire is there? 

[Boater Sam]

1 minute ago, XAMK said:

Thank you so much for clearing that up in an easy to follow way. 

 

I take it LiFePO4 don't behave in the same way, is this one of the reasons people are switching to them? 

 

 

 

Does it not churn up the bank? There isn't a downside of disengaging the gear wire is there? 

I am having difficulties understanding you and your "gear wire".

How can it churn up the bank if its in neutral? The prop will not be going round.

Do you not know that there is a neutral in the gearbox? Have you ever cruised a boat?

[XAMK]

4 minutes ago, Boater Sam said:

I am having difficulties understanding you and your "gear wire".

How can it churn up the bank if its in neutral? The prop will not be going round.

Do you not know that there is a neutral in the gearbox? Have you ever cruised a boat?

Not sure if you're being sarcastic but yes to your questions. 

 

I have one lever, middle is neutral and has little to no amount of revs, engaging the lever forward puts it in gear and therefore turns the propeller and produces more revs. 

 

Maybe I'm getting the names mixed up but by unhooking the wire I can put the throttle to full power, lever fully extended (increasing the revs) and the propeller won't turn. 

[David Mack]

30 minutes ago, Alan de Enfield said:

The 1st half hour the alternator will out put at about 13 volts and 100 amps so 50Ah replaced

The next hour the batteries will limit their input (note it is the batteries that say 'that's all we can take') to 75Amps so another 75Ah replaced

The next 2 hours the batteries will limit their input to 40amps so another 80Ah replaced, by now the voltage is up to 13.5v

The next 2 hours the batteries will limit their input to 20 amps, so another 40 Ah replaced.

The next 4 hours the batteries will limit their input to 10 amps so another 20Ah added, by now the voltage has increased to 14v

The next 5 hours the batteries will limit their input to 5 amps so another 25Ah added, the voltage is now approaching 14.4v and are approaching 'full'

The nest 5 hours the batteries will limit their input to 3 amps so another 15Ah added, the voltage is now 14.4-14.5v and the batteries can be considered to be 'full'

 

You have replaced 300Ah in 20 hours

Fit solar, then use the alternator fotr a couple of hours in the morning, and then, in summer, the solar will do the lower current charging for the rest of the day, and start again next morning at first light.

[bizzard]

5 minutes ago, XAMK said:

Not sure if you're being sarcastic but yes to your questions. 

 

I have one lever, middle is neutral and has little to no amount of revs, engaging the lever forward puts it in gear and therefore turns the propeller and produces more revs. 

 

Maybe I'm getting the names mixed up but by unhooking the wire I can put the throttle to full power, lever fully extended (increasing the revs) and the propeller won't turn. 

If the lever unit has two cables coming out of it, one throttle and one gear change it would have a either a button on the lever or perhaps pull the lever out which should disconnect the gear change just leaving the throttle adjustments working

Edited December 31, 2019 by bizzard

[David Mack]

4 minutes ago, XAMK said:

 

I have one lever, middle is neutral and has little to no amount of revs, engaging the lever forward puts it in gear and therefore turns the propeller and produces more revs. 

And there's usually a little knob below the lever. Pull that knob out when the lever is in neutral, and then push the lever forward to get more revs and the gearbox won't go into gear.

[Boater Sam]

On some Morse controls the lever pulls out in neutral and then it disconnects the gear cable so that you can rev the engine out of gear. Some have a red tab that clicks out instead.

Every single lever control I have ever seen has this feature.

I thought you did not understand how it worked but was worried in case I was being insulting by assuming such an obvious thing was outside your knowledge.

Hope I have not offended.

Edited December 31, 2019 by Boater Sam
added more

[Alan de Enfield]

7 hours ago, XAMK said:

Does it not churn up the bank? There isn't a downside of disengaging the gear wire is there? 

Your 'lever' will have 3 positions, central is 'neutral' back is reverse and forward is forward.

Your lever also has a 'disengage' button / knob which when used disengages the gears (like a clutch in your car). There are different mechanisms to do this on each manufacturers control level.

 

This is how you start your engine from cold, disengage the gears, move to half throttle (like choke) and turn the key, when engine fires, come back a bit on trhe throttle to a fast tickover, then as the engine warms us, back of the throttle to the 'vertical', click the lever back into its normal position ready to engage gear and you are ready to 'go'.

 

On mine you actually pull the whole 'lever' out 'sideways' about 5mm this allows you to get full throttle (high revs) without engaging gear. I have 2 levers because I have 2 engines. At the bottom of the lever (where it goes into the circular 'boss') are two finger grips, grip here and pull sideways and the whole lever and boss move and disengage the gear selector.

 

Others have a button in the centre (pivot point) of the lever, and others have a small plastic flap/switch.

Some systems are 2-lever, one for the gears and one for the throttle but these are not common.

 

If you post a picture of your control lever / box we can tell you how to get 'neutral' and be able to rev the engine.

 

No one is trying to be insulting, we all started off knowing nothing about boats, but your questions are very basic, hence the question 'have you driven a boat', if you had then you would have already actually done the things you are asking how to do.

 

If you detail your actual boating experiences, hopefully we can tailor the replies to your knowledge level without being insulting or condescending.

Edited December 31, 2019 by Alan de Enfield

[Alan de Enfield]

Here is another type - press the button to disengage the gears.

 

[nicknorman]

8 hours ago, XAMK said:

Not sure if you're being sarcastic but yes to your questions. 

 

I have one lever, middle is neutral and has little to no amount of revs, engaging the lever forward puts it in gear and therefore turns the propeller and produces more revs. 

 

Maybe I'm getting the names mixed up but by unhooking the wire I can put the throttle to full power, lever fully extended (increasing the revs) and the propeller won't turn. 

Just to reinforce, there will be will be a means of increasing the revs without putting it into gear and without disconnecting any cables. You just haven’t discovered it yet! If you post a picture or tell us the make and model of the control, we will be able to tell you. But most likely, if there is no separate button /knob etc, you pull the whole lever sideways, then you can move the lever forwards or backwards to increase the revs without it going into gear.

 

It is bad for both the engine and the alternator to have a high power alternator putting out a lot of charge at idle rpm.

 

However as mentioned by others, just because an alternator is rated at x amps doesn’t mean it can put those amps into a battery - charging a battery is a physical / chemical process and this has a limited speed that depends on various factors. As an example, we have 450Ah of batteries and a 175A alternator. On starting with low batteries, we have an initial surge of perhaps  160A, then very quickly the current drops to 120A or so and for the next several hours the current decreases asymptotically until it falls to 1% of capacity after about 6 hours, at which point the batteries are fully charged.

 

If we had a 400A alternator, that process would be no quicker. You simply cannot force a lead acid battery to charge quickly.

Edited December 31, 2019 by nicknorman