Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 06-09-2013, 13:26   #46
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Living on dirt waiting for our new yacht to be built.
Boat: Half built Bestevaer.
Posts: 10,618
Re: Battery Bank Size?

Quote:
Originally Posted by Falshator View Post
To clear up the Water maker issue, It is being run off the engine-belt driven so no power off the Batteries, Thanks
In this case the advantages of a larger alternator will be reasonably minor.
I think the money/effort could probably be better spent elsewhere, especially if the change involves re-engineering the belt system.

Do you have any other high powered loads (such as a washing machine) that will be run at the same time?
What sort of batteries will you have?
__________________

__________________
noelex 77 is offline   Reply With Quote
Old 06-09-2013, 14:30   #47
Registered User

Join Date: Aug 2013
Location: somewhere out on the water
Boat: Hanse 445
Posts: 29
Re: Battery Bank Size?

Batteries are 165 ah AGMs x 4, Full electrics include- Auto pilot, 2x chart plotters, Radar,VHF, Stereo, Computer, LED Lights, one galley 130 litre Fridge with small freezer and a portable 50l fridge/freezer, Also have a 12v TV on board.
Surely a bigger Alternator must replace charge quicker?
__________________

__________________
Falshator is offline   Reply With Quote
Old 06-09-2013, 15:00   #48
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,737
Re: Battery Bank Size?

Quote:
Originally Posted by Falshator View Post
Batteries are 165 ah AGMs x 4, Full electrics include- Auto pilot, 2x chart plotters, Radar,VHF, Stereo, Computer, LED Lights, one galley 130 litre Fridge with small freezer and a portable 50l fridge/freezer, Also have a 12v TV on board.
Surely a bigger Alternator must replace charge quicker?
I rarely, almost never disagree with Noelex, but a bigger alternator should be a priority on almost all boats, IMHO. Unlike a generator, your alternator will not be running at its rated capacity all the time. You want usable power at idle because your engine will be idling a certain amount of time, and often just at the time when you would like your batts to be charging. If you are specifically charging with your main engine (if you don't have a diesel generator), then it's positively harmful to run the engine up to the RPM where the alternator will be producing maximum power. You want no more than fast idle, and most alternators will not be producing more than 50% or 60% of their rated power, depending on the pulley sizes and power curve of the alternator. So just because a given alternator is big enough on paper, doesn't mean it's big enough at the fast idle speed you will use when charging with your main engine.

And as another poster above said, your alternator will be supplying other loads besides charging, maybe big ones, so your batts will not be getting the full output of the alternator in any case.

It is really nice to start off with topped-off batts when you arrive into a port, having motored perhaps only a brief period.

Last argument: Car-type small-frame alternators are not designed for sustained heavy loads like charging deep-cycled batteries. Large-frame bus alternators are.

So if you have room and can afford it, put in a large-frame bus type alternator, and invest in good external regulation like Balmar or Adverc. You will be really glad you did. Especially if you don't have a diesel generator and might sometimes have to charge with your main engine.
__________________
Dockhead is online now   Reply With Quote
Old 06-09-2013, 15:04   #49
Registered User

Join Date: Oct 2012
Location: Currently Tasmania after Pacific crossing
Boat: Catalina 42
Posts: 217
Re: Battery Bank Size?

Quote:
Originally Posted by noelex 77 View Post
Sounds like a good plan 435w solar will be a big help. A larger alternator will also help given that your watermaker and other loads will be using a lot of the available power of your 115A unit.
One caution is your current alternator is on the limit for a single belt. If it only has a single belt you will have to modify things to accept a dual belt.
An alternative is second alternator. This requires similar engineering but it helps reduce the sideways load on the crankshaft and gives you some redundancy.

It may be worth starting a new thread on the alternator subject, if you indicate your engine model some members are likely to have done a similar conversion that will help you avoid the pitfalls.

Big alternators require better belting. I researched widely before deciding on an Electromaax 200amp alt + Sepentine belt & pulley kit. I have to say I am very pleased with the set up....I'm still on the first belt too, virtually no belt slip whatsoever!

I would also recomend people interested in learning more about battery banks and charging systems to check out Mainsails very knowledgeable articles.
__________________
Amnesia II is offline   Reply With Quote
Old 06-09-2013, 16:11   #50
Senior Cruiser

Cruisers Forum Supporter

Join Date: Aug 2009
Location: between the devil and the deep blue sea
Boat: a sailing boat
Posts: 17,314
Re: Battery Bank Size?

Loads that can be switched on / off at your discretion are often of less importance to battery bank size. Plan the battery bank size around the loads that cannot be switched off and those that sip energy at their own schedule. Often, on smaller boats these may be the freezer and or the AP.

The point is that if you have choice over when the system will be run, you can sync its use with you charging scheme, and most charging regimes have surplus of energy once the batteries are up to 85% or thereabouts.

b.
__________________
barnakiel is offline   Reply With Quote
Old 06-09-2013, 16:13   #51
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Living on dirt waiting for our new yacht to be built.
Boat: Half built Bestevaer.
Posts: 10,618
Re: Battery Bank Size?

Quote:
Originally Posted by Falshator View Post
Surely a bigger Alternator must replace charge quicker?

The batteries unfortunately place a limit limit on the the charge rate. This limit is dependent on the the size of the battery bank the SOC and the type of battery.
Fitting a larger alternator only helps if the batteries will accept the higher charge.

The batteries control the maximum charge rate.

AGM batteries will accept a higher charge rate and you will get more benefit with this type of battery with a larger alternator than with other lead acid battery types, but you do not have any high load appliances that are likely to be running at the same time.

The effect is not linear fitting an alternator double the size will not halve your engine run time.

Your two hour watermaker run will dominate your engine run time.

A simple test is to monitor your charge rate under motor and see how long it is before the batteries acceptance is less than your real world alternator output. It is only during this time that that a higher output alternator will be of benefit.
__________________
noelex 77 is offline   Reply With Quote
Old 06-09-2013, 22:15   #52
Registered User

Join Date: Aug 2013
Location: somewhere out on the water
Boat: Hanse 445
Posts: 29
Re: Battery Bank Size?

Once again, Thankyou Noelex and others for your input, my wife and I are newbees to Ocean Cruising having done mainly coastal cruising/racing in NZ, have reached the stage in life that we can do it now and are looking forward to the new boat and the challenges that come with it.
No doubt I will be starting another discussion on the Forum at a later date for something else as it is full of experienced good people full of advice
__________________
Falshator is offline   Reply With Quote
Old 07-09-2013, 00:31   #53
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,737
Re: Battery Bank Size?

Quote:
Originally Posted by noelex 77 View Post
The batteries unfortunately place a limit limit on the the charge rate. This limit is dependent on the the size of the battery bank the SOC and the type of battery.
Fitting a larger alternator only helps if the batteries will accept the higher charge.

The batteries control the maximum charge rate.

AGM batteries will accept a higher charge rate and you will get more benefit with this type of battery with a larger alternator than with other lead acid battery types, but you do not have any high load appliances that are likely to be running at the same time.

The effect is not linear fitting an alternator double the size will not halve your engine run time.

Your two hour watermaker run will dominate your engine run time.

A simple test is to monitor your charge rate under motor and see how long it is before the batteries acceptance is less than your real world alternator output. It is only during this time that that a higher output alternator will be of benefit.
All absolutely correct theory. And following the theory, I'm sure there is a cruising boat somewhere on the planet which has an alternator which regularly produces more power than the batteries can accept. I've never seen this boat, however, or heard of it.

Let's do the math in the case of the OP.

Let's say he installed a large frame 200 amp alternator.

At fast idle -- the right speed for charging batts from your main engine -- depending on the gearing and charge curve of the alternator, he might be getting 60% of maximum output. That's probably optimistic. That's 120 amps.

He will be sailing in the tropics. At high ambient temperatures, you lose 20% or more of alternator capacity. Now he's getting 96 amps. At best.

While the motor's running, he'll have other electrical gear running. 20 amps? 30? Will he be running an inverter? Call it 20 -- that leaves 76 amps for charging.

He's installing a 660 amp/hour bank -- that's 11.5% of C, less than half of what his batts could take, so every amp of additional capacity from upgrading his alternator is beneficial to him. In fact, 200 amps may be too small for him -- maybe consider 250. Besides, a large frame alternator is much more robust, being designed to be run continuously at its max output, will run cooler, will last much longer, and can be repaired in case of need rather than just throwing it away.


In my opinion, small frame car-type alternators are really not suitable for cruising boats, with rare exceptions possibly of boats which use almost no power, are completely self-sufficient in solar, have tiny battery banks, etc. These alternators are not made to be run at their maximum output continuously -- they are made to replace a bit of starting power and run a car's onboard electrical gear. They are built as cheap as they possibly can be, do not have much cooling, and are lightly built. They were just never intended for heavy duty applications like charging deeply cycled battery banks. If you didn't guess already -- I don't like 'em.

Rant over!
__________________
Dockhead is online now   Reply With Quote
Old 07-09-2013, 02:14   #54
Registered User
 
Cjwelch's Avatar

Join Date: Jun 2013
Location: currently in greece
Boat: 40 spray
Posts: 55
I have read the thread and not seen mention of anything about not being able to truly "top off" the battery bank without the use of a battery charger on shore power and that it should be done about once a month to preserve battery life.

Am I ill informed or is this true? I am installing new and additional solar panels and a new Trojan battery bank this coming week. I have 100w of panels now, I am installing 2 more mono 80w panels, an mttp, and 6 Trojan t105's. the electrician I hired suggested this set up and routine of topping off.

What say ye?
__________________
If you dont pursue your dream, who will?
Cjwelch is offline   Reply With Quote
Old 07-09-2013, 04:14   #55
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,737
Re: Battery Bank Size?

Quote:
Originally Posted by Cjwelch View Post
I have read the thread and not seen mention of anything about not being able to truly "top off" the battery bank without the use of a battery charger on shore power and that it should be done about once a month to preserve battery life.

Am I ill informed or is this true? I am installing new and additional solar panels and a new Trojan battery bank this coming week. I have 100w of panels now, I am installing 2 more mono 80w panels, an mttp, and 6 Trojan t105's. the electrician I hired suggested this set up and routine of topping off.

What say ye?
This is a good question and a real issue for those of us who are really off grid and almost never on shore power.

Solar is terrific for this, and if your solar panels are big enough in relation to your battery capacity, you should be fine. To be sure to have your batteries really topped up, you just need to be sure to operate well in surplus a day or two a week, which might mean charging from your engine to get to 85% before letting your solar panels do the rest.

On my boat, topping off is done, and I try to do it once or twice a week, by a longer motoring passage or by an extra-long generator run, or by the odd stay at a port with shore power. I bought a Honda EU100i generator specifically for this purpose by the way -- since petrol generator don't mind running at light loads. So when I'm about to leave the boat for a weeks, I leave the little Honda running all day to give the batts a really good absorption charge before I isolate them and leave. Haven't been doing it this year since the carb of the little Honda is clogged and I haven't had time to mess with it, so I have been using extra long generator runs.
__________________
Dockhead is online now   Reply With Quote
Old 07-09-2013, 06:41   #56
Registered User
 
Delancey's Avatar

Join Date: Oct 2011
Location: Miami, FL
Boat: sunk by irma
Posts: 3,462
Re: Battery Bank Size?

Quote:
Originally Posted by Falshator View Post
Hi guys,
Looking at doing a lot of cruising shortly, including Trans Atlantic and Pacific crossings.
I have a 45ft boat with auto helm, galley fridge/freezer and portable fridge, stereo, twin chartplotters etc, so bit of demand on the Electrics.
My question is what size Battery Bank is suitable for long cruising? I have 320ah bank right now but contemplating adding to this for the Trip as dont think thats enough?
Perhaps it would be useful data to see a poll of either battery bank size or typical amp hours consumption? To see what most people are actually working with?

I'm not really sure how to set it up.
__________________
Delancey is offline   Reply With Quote
Old 07-09-2013, 09:56   #57
Registered User

Join Date: Mar 2012
Location: On board in Alanya, Turkey
Boat: Hunter Legend 420 Passage
Posts: 626
Re: Battery Bank Size?

Quote:
Originally Posted by noelex 77 View Post
......The effect is not linear fitting an alternator double the size will not halve your engine run time.....
I think this statement is perhaps misleading!!!!

It will halve the runtime up to the end of the boost stage - and beyond. I have done tests with my 100 amp Balmar alternator that may be charging at 90 amps. I then switch over to my 280 amps DC generator and it charges at 220 amps.

If I know I am motoring the next day for a long passage I will run the genny till it falls below about 70 amps and go back to the alternator when we motor. That leaves the alternator outputting 90 amps - charging the batteries at 70 amps, with the other 20 amps going to boat loads.
__________________
sailinglegend is offline   Reply With Quote
Old 07-09-2013, 12:43   #58
Moderator
 
Dockhead's Avatar

Cruisers Forum Supporter

Join Date: Mar 2009
Location: Cowes (Winter), Baltic (Summer) (the boat!); somewhere in the air (me!)
Boat: Cutter-Rigged Moody 54
Posts: 19,737
Quote:
Originally Posted by sailinglegend

I think this statement is perhaps misleading!!!!

It will halve the runtime up to the end of the boost stage - and beyond. I have done tests with my 100 amp Balmar alternator that may be charging at 90 amps. I then switch over to my 280 amps DC generator and it charges at 220 amps.

If I know I am motoring the next day for a long passage I will run the genny till it falls below about 70 amps and go back to the alternator when we motor. That leaves the alternator outputting 90 amps - charging the batteries at 70 amps, with the other 20 amps going to boat loads.
Originally Posted by noelex 77
......The effect is not linear fitting an alternator double the size will not halve your engine run time.....

Yes, by the way, it can be much better than halving your engine run time. If your car alternator of 80 amps is producing 40 amps at fast idle and in hot weather, and you have a 20 amp load on, only 20 amps is getting into your batts. If you double to 160, you're getting 80, minus the same 20 amp load, your getting 60 into the batts, three times as much, for 1/3 the engine run time. As long as you do not exceed your batts' acceptance rate, but in the hypothetical situation, your bank would have to be less than 240 amp/hours, to even imagine such a problem.

So yes, non-linear - but in the opposite direction!
__________________
"Parce que je suis heureux en mer, et peut-Ítre pour sauver mon ame. . . "
Dockhead is online now   Reply With Quote
Old 07-09-2013, 15:49   #59
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Living on dirt waiting for our new yacht to be built.
Boat: Half built Bestevaer.
Posts: 10,618
Re: Battery Bank Size?

OK I get there is widespread support for significant gains from a larger alternator.

However I do think some posters are responding to their own personal situation rather than considering the specific information the OP has given.

The battery bank size is 660 AHrs not 1050 AHrs as is the case of sailinglegend. The charge acceptance quoted by sailinglegend needs to be reduced by the same ratio to make the information relevant to the OP's situation.

The engine needs to run of two hours a day to run the watermaker. The high initial acceptance which is important for boat using a short run time is less significant for the the longer run time of the OP. There are no high load electrical devices.

We don't know how this is geared, but high pressure watermaker pumps do not tolerate a large variation in RPM's. To avoid problems operating the high pressure pump at cruising revs the minimum engine speed for the watermaker is likely to be such that the alternator will be producing a reasonable proportion of its rated power.

Finally the critical point is the OP will have 435w of solar. This will produce the majority of the required 226 AHrs. The engine still has to run for two hours for the watermaker. The alternators charge rate over this required run time can be quite modest.

Alternators of around 100A as the OP has are very popular because they run on a single belt and do not impart undue side loads on the engines crankshaft.
I agree with Dockhead that a large frame high output alternator is a very nice extra. (I have got a high output large frame alternator on my 12v generator) but fitting such an alternator to the main engine is not a trivial task and not without some concerns about the long term effect on the engine.
__________________
noelex 77 is offline   Reply With Quote
Old 07-09-2013, 16:19   #60
Moderator
 
noelex 77's Avatar

Cruisers Forum Supporter

Join Date: Jul 2007
Location: Living on dirt waiting for our new yacht to be built.
Boat: Half built Bestevaer.
Posts: 10,618
Re: Battery Bank Size?

The whole issue of high output alternators is a very topical one. With the advent of lithium batteries there will be an increasing demand for very large alternators.

Boat engines have not been traditionally fitted with sort of alternators that can be utilised by these new batteries.

Even dual large frame 200A alternators will not be overkill for a large lithium battery bank.
Can we fit 400 A of alternator, without damage, to our boat engines?

If so how do we go about this?

Have a look at the alternator on the 64 foot FPB the equivanlant of 300A@12v is this the future? I hope so. Its a work of engineering art anyway.
Attached Thumbnails
Click image for larger version

Name:	image.jpg
Views:	73
Size:	83.3 KB
ID:	66678  
__________________

__________________
noelex 77 is offline   Reply With Quote
Reply

Tags
paracelle

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Battery & etc opinions... stargazer ltd Electrical: Batteries, Generators & Solar 14 12-09-2013 08:05
Charging Multiple Battery Banks nmit5903 Electrical: Batteries, Generators & Solar 67 10-09-2013 23:32
Size of Battery Charger zboss Electrical: Batteries, Generators & Solar 152 22-08-2013 19:18



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 21:34.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.