Speaking of alternators

[Trevethan]

Mine needs replacing. Its a Lucas, about 30 amps, quite puny really and its now charging 400 amps of battery (orginally 200 when I got the boat) and I am thinking of connecting another dedicated starter battery.

I have already fitted a 60 amp mains charger.

The engine is 50 hp, 4.5 litre lister and the boat is 12 volt.

The qausetion is do I buy a 90 amp auto alternator for £90 and then spend some money on a sterling regulator, or is it worth spending three times as much or more and buy a "marine" product.

Ideally I'd like to get a slightly bigger alt -- maybe 110 amp plus, but these seem tough to source according to a couple of place I have called.

In terms of wiring should I connect the output direct to the batteries or should I run it via starter motor?

The cable runs are about the same length.

If running to the starter, do I just connect it to the same stud as the battery connection?

Finally cable. would 1 cm sq be sufficient to carry the load over about 2.5 metres?

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[andyball]

Depending on battery type, there are simpler/cheaper regulators out there (lucas make external reg's with a choice for high med & low charger voltages, all battery sensed. Some types will gas furiously with 14.5V on them though.

Connecting to starter terminal is ok, but if you're planning a dedicated starter battery....you'll have to change it later.

Sounds like you've a single wire (earth via engine block) system now? so advantages of "marine" version are:ignition protection (but if your starter hasn't got that, then why worry?, all shd have higher power fans, better bearings/diodes/windings; hopefully built for continuous use at high load, unlike an average auto one....also some come with a separate regulator included in the price(but what a price).

A 2.5m run of 100 sq mm cable will drop about 0.04V @100 Amps: (don't know if you mean 1cm sq of copper or copper & sleeve)......16mm sq cable is commonly suggested as OK for 100A (0.25V drop over 2.5m @ 100A)....you may find that the alternator connections limit your choice of cable size anyway.

Have seen a lot of 100A+ alternators, but none close to £90 ...if you need a non-marine priced one , look at motorhome & 4wd sources, I remember some on the net.



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[Trevethan]

Thanks for the reply. The batteries are truck type, non-sealed. The sort that run the sli system on a lorry but will also power the tail lift.





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[pvb]

90A would be fine...

Upgrading your standard alternator will probably mean retaining a single V-belt drive, and this effectively limits the alternator size to about 90A max (much more than this will cause belt slippage, noise and rapid belt wear). It helps to use a top quality belt such as Gates Super HC (you can buy these online at rswww.com if local suppliers can’t help). If you can rig a twin V-belt drive, you could use a 110A or 130A alternator, but you won’t benefit from the additional output unless you upgrade your battery bank considerably.

There’s a lot of confusion about alternators - people assume that a 100A alternator will push 100A into the battery bank. In the vast majority of cases, it won’t. The problem is the ability of batteries to accept a charge. A typical 110Ah boat battery might only accept around 15A of charging current if it’s deeply discharged, and this current will progressively reduce as the battery recharges.

With the battery bank size you presently have, you’d be unlikely to overload a 90A alternator, and an ordinary auto version should be OK. If you want a better quality unit without paying “marine” prices, look for a Prestolite Leece-Neville alternator - these are very tough units, with excellent output at lower revs (Adverc sell these). You should certainly consider fitting a “smart” regulator (Adverc, Sterling, etc) which will increase the alternator’s output voltage to optimise the charging current. Most smart regulators also adjust the charging voltage to compensate for temperature changes at the battery.

Increasing your domestic battery bank will also help. The bigger the better, because with more batteries you can benefit from the capability of the alternator. For example, if you just had a single 110Ah battery, you might be able to push 15A into it; but if you had 4 x 110Ah batteries in a bank, you’d be able to push 60A into the bank, thus replacing consumed Ah more rapidly. An additional benefit of bigger battery banks is increased battery life, because for a given consumption the depth of discharge of each individual battery is less, and it’s the depth of discharge which is the real factor in reducing battery life.

As you’ll need to do a bit of rewiring, remember it’s well worth adding a high-capacity fuse right next to the domestic battery bank.


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[timevans2000]

60 amp from breakers

I agree with all the above. but if you want to keep costs down, auto breakers are full of 60 amp alternators. For £10 you can probably yourself a couple of 60 amp units. Get them tested at your local auto electricians for free and you should have more than enough output with a spare unit as well.


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[TonyBrooks]

Re: 60 amp from breakers

But they will not fully charge your batteries. The "normal" regulator will only charge to about 80% of maximum, even if you do have zero voltdrop between alternator and battery - if you do have voltdrop it will be worse.

The "add on" alternator controllers should improve that to well over 90% and convert the alternator to battery sensed (possibly at a small extra cost if you can not modify you existing regulator).

This not only overcomes voltdrop, but also gives more ahs per battery and helps minimise sulphation.

If you can run to it, get an advanced controller - I prefer Adverc, being a reactionary old git who is supiciouse of the long term life of digital systems.

hey do not just boost the charging currant (well the good ones do not), but use a complicated series of charging voltage changes to m,aximise charge whilst minimising gasing.

Tony Brooks

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[timevans2000]

Re: 60 amp from breakers

I dont disagree at all. I personally thought long and hard about fitting a smart charger and in the end decided not to bother. I am fortunate that I have lots of deck space so have 2 very large solar panels. The smart charger on the solar array does all this for me during the week when I am at work!

Also, large input charger seem to cause gasing. I would rather charge gently and reduce gasing. This is where the solar panels come in. In 2 years I have only needed to put a very small amount of distilled water into my 330 amp hour battery bank.

I dont like running the engine for battery charging. If they happen to be doing a bit whilst I am moving in/out of harbour, fine

The best thing I have fitted recently is a battery monitor. It is suprising what various energy user actually use and also suprising what the solar panels can put back in a very short time. With alarms set for high and low voltage, amps remaining, you should never be in a situation where you have a battery problem.

I only have a 30 amp alternator but have rarely had my battery bank discharged below 70%

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[seaesta]

110 amps at 12v = 1.3kW!! - are you running a showboat?

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[Trevethan]

Ummm niot quite, but we do have a fair bit of lighting. (Ran garden stick lights on the stanchions to help inebriated crew onto boat at night....looks festive too!)

The thinking behind the higher output alternator was to speed charging times (I was going to use a smart reguator as well) to limit engine running to recharge batteries.



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[mldpt]

I have had charging problems for years, possible all the gagits . But I am now going to sort it, I have decided on Adverc 105amp alternator with their regulator. very expensive I know but I have looked at a load of alternatives and this is it for me. I have been in touch with Prestolite and they do a replacement 60amp for my V/P 2003 for about £60.
but as I have a possible 400AH of batteries to charge this I understand is not big enough to do the job, I have always been under the impresion the you need the an alternator with output of a third of the battery bank in my case 400AH therfore I need 130AMP alternator I shall reduce my bank of batteries to 300AH and hopefully will manage to keep them well charged with 105amp alternator rather than never getting them anywhere fully charged.
Mike My boat is a sailing boat with all the electonics fridge, heating etc etc so I am looking forward to not worrying about the anchor light on these long dark nights.
Regards Mike


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[pvb]

Big mistake...

Big mistake, Mike. Don't reduce the size of your battery bank - if anything, increase it. The old advice to have the alternator output equal to a third of the battery capacity is not valid in the real world. I think that a 105A alternator is too big for your 400Ah bank, let alone a reduced bank. If you don't believe me, just fit a Link 10 monitor, and see for yourself how many amps you can push into your bank for any useful time. I guarantee you'll be surprised - it'll be some way short of 105A.

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[mldpt]

Re: Big mistake...

Hi I have a Voltronic i think it is called gives me Digital readout of Volts Amps in and out and can be set to calculate AH and works very well. I think that with 400AH it is likely that I will have an excess of AH when fully charged but doubt if I will ever get them anything like fully charged and gradually they will solphate up and so as most of mine have done after a couple of season die on me Ok I have not spent more then £60 on 120 AH batteries but it woud be nice tobe able to keep them fully topped up with just an hour a day charging. During the summer I live on board and am at sea most of the time under sail.
Mike

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[MainlySteam]

Re: Big mistake...

Agree - general advice seems to be that for good deep cycle batteries 20% of capacity is about what they will accept and we find that to be so. On our own boat with 520 Ah of Trojan deep cycle batteries the maximum they will accept is around 100 amps, apart from perhaps for a very short period at the very start of the charge when the plate surfaces are charged - so, for example, for us it is pointless installing a bigger alternator than that (is actually a 105 amp Leece-Neville).

And PVB, I have to say that your earlier post is one of the very best I have seen on batteries and charging. Faultless, in my opinion.

Regards

John

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[pvb]

Thank you (nm)

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[Trevethan]

Thanks very much for all the information.

It looks to me that the best solution will be to buy a 90 amp auto alternator, a smart regulator, and pick up another 200 amp hour battery for the starter.

In terms of connection, the plan will be to have one 400 amp domestic bank on one position on the battery switch and the starter battery on the other.

I'll wire the alternator to both banks independently (split charge diode to do the job?) Is there a way on ensuring the starter gets recharged first other than playing with the battery switch?

I'll also run the spare output from sterling charger I have to the starter battery.

Fuses to be place in the lines Does 400 amp in the starter circuit and 100 amps in the domestic sound reasonable and new cabling to suit.

(Engine is a big heavy lister 4 cylinder (HRW4) that takes a bit of cranking (a 90 amp battery showing 12.3 volts couldn't spin it)

Does this sound sensible?

Cheers!


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[Chris_Robb]

Try a split charge relay

Instead of a diode splitter, try a split charge relay from Kinder Development in Falmouth - Tel 01326 376938.

I have found them to be very robust and misuded the first one which was a 40 amp max unit for 4 years which survived a 100 amp alternator before it finally packed up this year. I have now fitted the correct unit.

Put your main charge to the engine battery and connect this unit accross your battery switches. When the engine battrey reaches 13.8 (you can adjust it) the switch closes and charges both batteries. I have not detected any voltage loss across the splitter. The installation is very simple.

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[TonyBrooks]

Yes, but I would use a split chrge realy with its coil fed from the alternator Warning lamp connection, or better still a phase tap. You do not need to do anything to it.

MY starter battery is always fully charged, so I would not worry about getting it charged first, just let the abtteries themselves charge as they need (which they will do when fed with a common supply).

FWIW My 2x110 ah domestics are use to feed an electric fridge, water & shower pumps, all lighets, a TV & radio. I know I do not have to display lights all night.

My 60amp alternator recharges the batteries within two to three hours.

Tony Brooks

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[TonyBrooks]

Yes, but I would use a split chrge realy with its coil fed from the alternator Warning lamp connection, or better still a phase tap. You do not need to do anything to it.

MY starter battery is always fully charged, so I would not worry about getting it charged first, just let the abtteries themselves charge as they need (which they will do when fed with a common supply).

FWIW My 2x110 ah domestics are use to feed an electric fridge, water & shower pumps, all lighets, a TV & radio. I know I do not have to display lights all night.

My 60amp alternator recharges the batteries within two to three hours.

Tony Brooks

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[DMGibson]

What I did was to get hold of a second-hand truck alternator and run it off the crankshaft extension with its own drive pulley and belt. I left the original one onthe engine together with all the connections to starter and battery. You can then use the second alternator to charge the second battery independantly from the other one without all that split charge malarky. You also have a second source of generation capacity if one or other should fail.

You can get a new pulley and hub from Fenner - their taper-lock hubs are a dream to fit. You will need a set of brackets to hang it from, so you need to get whatever mounting brackets you can find when you get the alternator.

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