batteries - Maximum charging current

[bedouin]

I've just purchased, but not yet fitted, the OrcaGreen LED combined anchor / tri light. That claims to be USCG approved for vessels up to 20m. Since mine is <12m and so has reduced visibility requirements I'm sure it's good enough.

However in the overall scheme of things the projected usage from your fridge and autohelm is so high that the difference the LED light makes is insignificant

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[zefender]

Will check out the OrcaGreen - thanks.

Pending further work on getting a more accurate figure, my re-worked consumption looks like this (before I have to start slashing things!)

Consumption Hours used total

Fridge 2 16 32
Autohelm 2.25 24 54
Laptop 3 3 9
Interior lights 0.8 (each) 4 9.6
Radio/CD 1 6 6
Nav lights 2 12 24
Radar 2 3 6
water/sh pump 3 1 3
GPS/instruments 1 24 24
VHF 0.08 24 1.92

(sorry about the formatting)
Making a total of 170 amp hours. Taking a 20% contingency, gets me to 203 amp hours and an average hourly charging rate of 8.5 amps.

Presumably then, I'll need about 400 amp hours worth of batteries (leaving the engine battery out of the equation) since its not wise to flatten them down the whole time. Suddenly that oil lamp looks intersting....



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[Talbot]

I dont disagree that 200 is in the right ball park, but that is more to do with the items you have not included in your budget, rather than the numbers that are there! That is why my solar panel is 180w, and plan to add duogen before setting off!
There are LED tricolours that are USCoast Guard approved <A target="_blank" HREF=http://www.orcagreen.com/trianchor.cfm>Here</A>, and they are good, but do not quite have the power economy of the Deepcreek technology - but will still only use 5 amp/hr per night

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[halcyon]

Two things,
How many days are you planning to be at sea for before putting into a port/marina? if you charge before leaving, you only need arrive with 50% capacity left, you can then put them back on charge.
Will the auto pilot be running 24 hours a day under full load, or is it going to sit there make a small correction, then a minute or two later make another ?

Brian

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[Ships_Cat]

A 40 odd foot cruising boat will typically need around 500-550 AHr of batteries if use is not to be uncomfortably frugal and to cover refrigeration (and would cover an efficient freezer as well assuming around 80AHr/day for that).

Even if you make your boat look like an outback forest shack covered in wind generators, solar panels, etc, etc you will never maintain the batteries at a proper charge without an 100 odd Amp alternator and step charging regulator. Also, it is impossible to properly maintain a reasonably sized bank of batteries with the engine's standard 60 Ampish alternator and non stepped regulator (we have tested that - you need inordinantly long engine runs to get them up to full charge). If you do turn your boat into a forest hut going the natural way, your battery replacement costs will be significantly higher because you will frequently discharge them deeply and rarely charge them fully.

We normally bank on 2 hours charging a day (with higher refrig and freezer loads than you) and if we are just coast hopping do that by motoring for 2 hours a day - say 1 hour out to fishing or sightseeing, 1 hour back to anchorage, that is assuming that one is not in a marina for the night (which we hardly ever are when away). In my experience these charge times are typical of self sufficient cruising boats whose crews are not of the uncomfortably energy frugal nature.

We have 60 watts of solar panels which are normally enough to cover the autopilot during sunshine hours (also an Autohelm 6000) but their main purpose is only to maintain the batteries at full charge when the boat is uninhabited in the marina rather than for meeting any daily use. They make no significant difference to the energy budget - perhaps saving about 10 minutes engine run charge time a day.

John

<hr width=100% size=1>I am the cat but I am only 6.

 

[Robin]

John

As always a good answer from down under though I would add a couple of comments:-

1) There are 2 separate power consumption figures, one for underway under sail and one for at anchor. In the first case there is an extra consumption for autopilot, navigation lights, instruments, GPS, plotter, VHF etc. At anchor there is a reduced demand and an opportunity to better align solar panel(s) or add more 'temporary' ones.

2) If running the engine solely for charging then it is not necessary to routinely do this to 100% capacity. With a 500AH bank as your illustration, only 250AH (max) is useable without going below 50% charge which is not recommended, and the last 20% of charge with a smart regulator is still slow in order to avoid battery gassing. Maximum charging efficiency is therefore achieved if the battery is run between 50% and 80%, ie 250AH and 400AH in your example, so really only 150AH is routinely available which would take a 100A alternator 1.5 hours to replace (maybe 2 hours to allow for efficiency losses).

There is no such thing as a free lunch I guess so the first priority is to reduce consumption where possible. We run solar panels ( 75W fixed and 110W moveable) plus a wind generator and can normally anchor 5 days without running the engine to charge and without dropping below 60% charge. Normally after 5 days we are needing to move anyway at which point the alternators (we have 2) get work to do and if we go in a marina for food/water then the shorepower charger comes into play and batteries go back to 100%. We can also charge via a 750W petrol generator and the shorepower charger but haven't needed to do this for several years.

Robin

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[Ships_Cat]

Hi Robin

Yes, I think we are in general agreement.

My comments were on the basis of getting to full charge each day which is important to protect battery life as it limits the opportunity for irreversable suphation of the plates (and is especially important if thick plated batteries have been deeply discharged). If one is prepared to trade off shorter battery lifetime through not charging to close to 100% then the 50-80% usage is certainly agreed.

Also, of course, against the higher battery cost for not full charging is the increased engine running cost to obtain full charge through the absorption charge step so one does not get anything for nothing (unfortunately).

John



<hr width=100% size=1>I am the cat but I am only 6.

 

[zefender]

Re: coming out

OK, I'm planning to go on the ARC 2005, so I'll be at sea for 3 weeks or so. Given that it will be the trade winds route, with broadly following seas, I suspect the autopilot will be working quite hard, most of the time, although obviously it'll need a rest every now and then!

So, with thanks to all posters here for useful info, I need:

1, To look at getting an Adverc or similar
2, Uprating the alternator (and presumably checking implications on belt spares!)
3, Doubling my existing battery banks to reach 450 a/h
4, A Duogen generator and solar bank
5, A battery monitor/amp hours counter
6, An LED tri-light (now on order)
7, Consider use of LED lights for the interior
8, Spend a few months working out an accurate energy budget, particularly with bigger power consumers.

...makes me wonder whether carrying a bit more fuel for charging via the main engine (not for propulsion of course!) might be a sensible compromise on weight/cost. Hmmm..




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[Robin]

Re: coming out

If not going to the expense of a windvane gear then also consider a spare autopilot. We have a 4000 wheel pilot to back up our 6000, the control head is permanently mounted and wired but the wheel unit is stowed below. If needed the wheel needs to be removed (emergency tiller) temporarily for fitting the drive unit, but then it simply plugs in and is ready for use.

Battery capacity definitely needs to be upped. Battery capacity is like water tanks, if you have plenty you can take every opportunity to fill up, nothing worse than motoring with a full battery and all those lovely (free) amps getting wasted!



<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[Anonymous]

Re: coming out

>>Uprating the alternator (and presumably checking implications on belt spares!)<<

When you install your Adverc (or the Sterling equivalent, which is what I bought for my last boat) put a cut-out switch in circuit so that you can always switch back to the conventional charging circuit if all the clever stuff fails. Now, having done that, always make a point of not engaging the smart charger until you are properly under way and the revs are at a decent level - say >1800/2000. This will greatly reduce the wear on you belt because power = torque x revs so if you double the revs you will halve the torque, for a given power.

You see, if you engage the smart charger immediately you will be drawing almost full power from the alternator when the engine is still idling while slipping off, moving away from moorings, etc. In five years of ownership I did not change the belt once on mine despite having been told by so-called experts that I would have no end of trouble.

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[Anonymous]

>>I need to check the fridge rating<<

Just a note on that....I am presently carrying out a discharge test on my batteries using the new BEP monitor and it seems to me that as the volts are falling the fridge current is rising. I haven't broken the fridge circuit or taken accurate measurements but I think that these compressors are supplied from an inverter in which case they probably keep the POWER consumed constant, so as the volts fall so the current rises. W = I x V so if the Watts stay constant and the battery volts fall from, say, 13V to 12V over the battery operating range that is an 8% fall in voltage or an 8% rise in current. If you are measuring the current when the battery is on float charge, say 13.8V, then the error will be nearly 12% and could mess up your calculations. In your case you would be best to use the current at average voltage, i.e. 12.5V.

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[Robin]

Re: coming out

Well intentioned I know, but not entirely accurate I'm afraid.

With an Adverc at least (don't know the Sterling regulator) the alternator regulator is retained and if the Adverc fails it will revert to the original alternator automatically.

There is absolutely no benefit from switching back to the standard regulator until the boat is under way! Even a basic car style alternator regulator will set a maximimum output charge from the alternator initially. The difference with an Adverc or similar in simple terms is that the full output is maintained for longer and not quickly tailed off. For the record we run TWO alternators at 90A each on our Yanmar 44hp and BOTH alternators are controlled by Adverc regulators. We routinely change the belts on the winter service and keep the old ones as spares, they are not expensive so why risk having to do the job at sea? The old belts sre pefectly serviceable and very probably would last much longer if we chose to do so.



<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[Anonymous]

Re: coming out

>>Well intentioned I know, but not entirely accurate I'm afraid.<<

It's perfectly accurate in the case of an integral Lucas regualtor. I've sat there with the switch and flicked between the two watching the ammeter. Have you actually tried switching between Adverc and conventional control with the engine at very low revs (i.e. just fast enough to produce a proper output from the alternator)? My comments were based on actual observations, not theory, and I gave the theory to explain why it happens.

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[pvb]

You\'re both right, in a way...

Robin's right to say there's no point in switching an Adverc off until the boat's under way. It's just an added complication, and something else to forget to do.

Lemain's right to say that switching between an Adverc and the standard alternator at low revs can show a significant difference in current.

But the crucial factor is "when". The Adverc doesn't start to boost the charge voltage until 5 minutes after the engine's started, and only if the battery voltage has risen to around 13.5 (can't remember the precise figure, and it's temperature compensated anyway). This means that the engine has a chance to start warming up, including the belt, before extra load is put on the alternator. So switching the Adverc out of circuit when the engine's first started is a bit of a waste of time.

However, once the Adverc starts to increase the charge voltage, it's quite possible to see (as Lemain said) a significant drop in charge current if you switch the Adverc out of circuit - even at very low revs. But by that time, the engine and belt should be quite capable of handling the load.

I'm assuming of course that the engine is large enough to drive the installed alternator, and that the drive belt is capable of driving the alternator without slipping. I run a 90A alternator on a 43hp Volvo, charging a 660Ah domestic bank, with Adverc control, and don't have belt problems. In the past, I had a 130A alternator which ate belts because I can only fit a single belt. I reckon a 90A alternator is about the biggest you can drive happily on a single belt.

My comments relate only to the Adverc unit; I don't have experience of the Sterling regulator although I believe it may start boosting as soon as the engine is started.

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[Robin]

Re: coming out

I don't have and wouldn't have a switch. But yes I have watched the ammeter on one of our alternators (it happens to be a Lucas/Magnetti Marelli one too) when I unplugged the Adverc cable, it reverted to the built in regulator as it is supposed to do, the amps remained more or less the same. If your alternator output on standard regulator is low enough to make a big difference then maybe switching backwards and forwards has damaged the built in regulator. You are advocating making a tried and trusted 'smart' system into an unnecessarily complicated one. I have used a smart regulator on 3 different boat engines ( Mercedes OM636, Volvo MD22L and current Yanmar 44JHE) over a period of 17 years, starting with the earlier TWC regulator now the Adverc. At no time did I ever have a problem with belt loadings or feel the need for a cut off switch. Did you have a problem that caused you to fit this cut off switch or did you fit the switch then invent the theory to go with it? Believe me, all alternators start up high - ever heard a car one screech as a loose belt slips with headlights on? Certainly the belt load will remain high as at start up for longer, but should be no problem for a properly maintained system, and pulleys that are in line. If you install a double sized alternator that is a different question, to which the correct solution would be double pulleys and stronger double belts, ie solve the problem not cure the symptom.



<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[Anonymous]

Re: You\'re both right, in a way...

>>My comments relate only to the Adverc unit; I don't have experience of the Sterling regulator although I believe it may start boosting as soon as the engine is started.<<

My Sterling (purchased March 2000) does start immediately. You can hear the belt squealing at times if you don't switch out the Sterling on starting out. I don't find it hard to remember to do these things - I always take note of temperatures, pressures, charging current, voltage, etc. after we are well under way and out of close-quarters situations. Being always single or short handed, I have to do things that way and anyway the pressures and temperatures are pretty meaningless immediately after starting.

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[Anonymous]

Re: coming out

>>Did you have a problem that caused you to fit this cut off switch or did you fit the switch then invent the theory to go with it?<<

I don't see why you need to get rude. Sterling make a special point of recommending a switch in series with their output control line - it is just one normally closed switch in series with one wire. The point is that the Sterling does not modify the original controller in any way, it just rides 'piggy back' so switching it out cannot harm the original controller. Of course, my comments are based on the Sterling as installed in accordance with the Sterling instructions. I cannot speak for the Adverc, but I am surprised if anyone would install a piece of sophisticated electronics which could fail without ensuring that if it did then the system could automatically or manually revert to a normal system. Seems daft not to as it costs nothing material in resources. And if you've got the switch in place surely you use it from time to time to see the effect? With a low-powered engine you might want to override the smart charger if you need plenty of power - say fighting a foul tide.

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[pvb]

Sterling...

Strange that Sterling don't include a "soft-start" feature like Adverc (and a number of US smart regulators).

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[Robin]

Re: You\'re both right, in a way...

>>>In five years of ownership I did not change the belt once on mine despite having been told by so-called experts that I would have no end of trouble.<<<

>>>My Sterling (purchased March 2000) does start immediately. You can hear the belt squealing at times if you don't switch out the Sterling on starting out<<<

QED IMHO. If you have screeching belts you have a problem, either the adjustment is wrong or the belt is worn or both. How old is the belt that screeches? It is quite possible for the belt to look OK but not grip in the vee of the pulleys. Once again unless you have a larger than normal alternator (we run up to 90A ones on single belts) there shouldn't be a problem with a well maintained system, ie belts replaced regularly, no oil, diesel or water leaks onto belts or pulleys

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>

 

[Robin]

Re: coming out

I apologise if I seemed 'rude', it wasn't intentional, just my frustration showing. If you read my replies you would see that the Advercs DO revert to the standard regulator if they fail. Unlike Sterling though they do this automatically, they don't need the extra complication of a switch. Neither Zefender nor you have small engines so the maximum HP question doesn't arise, and in any event merely switching off a smart reg wouldn't neccessarily make a difference, only disconnecting the alternator would do that for sure - and don't even think of that!

<hr width=100% size=1><font size=1>Sermons from my pulpit are with tongue firmly in cheek and come with no warranty!</font size=1>