Alternators - again

[johnneale]

I seem never to get my batteries fully charged despite running for 4 or 5 hours. I get 30/40 amps for about a 1/2 a minute after starting before dropping down to 2/3 amps. I get 13.8volts when charging which drops to 12.3v for about an hour with the engine stopped then stays at 12v (no current drain occuring). Also I have to rev up the engine to get it charging in the first place (then can drop the revs and its OK)

I experimented with a diode in series with the field which raised the charging voltage to 14v - is this acceptable or should I put another diode in series to raise this to 14.2. - All terminals are tight and run cool, though the alternator itself gets quite hot. I havent been able to check the spg of the batts, and they never need topping up.

The voltage and current measurements are in the cockpit with the batteries 4 metres away (Very thick cables). 1 battery new this year, the other 1 year old
I am reluctant to get another alternator here in UK as the boat is in Greece, it would be heavy to take out there, and the wife might object with it wrapped inside her knickers

On another matter - If I wish to use a small battery charger when connected to shore power, is there any likely problem when charging through a cigar lighter socket in the cockpit (assuming it doesnt get too hot)

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[halcyon]

!3.8 is low, you can go to 14.4 / 14.6 volt, but if running for extended periods gassing could be a danger.
Diodes normally have a 0.7 volt drop, 0.2 is probably due to a very low current flowing.
If you are likely to need the engine for long periods fit a switch to bye-pass one or two diodes, thus lowing the charge rate.
A 12 volt battery at 12.3 volt is around 50% charged, 12 volt nearly flat, you need to be around 12.6 / 12,7 volt off load after 5 hours.

Regards

Brian

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[AOWYN]

Go to www.adverc.co.uk

The product is excellent, the service is very good, it solves problems.

Good luck.



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[Chris_Robb]

Go and talk to adverc - you will probably end up buying an adverc controller - which I think everyone on this forum will aprove of. They will tell you what you need to do. Sounds like you have enough knowlede to fit it - basic understaning of plus and minus and using a digital multimeter!

WWW.adverc.co.uk

When battery charging, connect direct to the batteries - should be just as easy. If you have the funds get a proper marine charger with 3 stage charging eg Sterling. A small 6 - 10 amp charger from Halfords is almost a waste of time - and you cannot leave it alone for several days, and you cannot draw a decent charge off it whlist charging and running your fridge for example, ie they are not designed to basic charging and supply demaond to applicances at the same time..

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[stevebirch2002]

Try Sterling for chargers and alternator controller. Excellent product and excellent service. Looks as though you need one of the advanced alternator controllers, makes all the difference.

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[Gunfleet]

John, I have had success with an adverc and would thoroughly recommend them. By the way I once knew an airline hostess who imported small objects in her knickers (Walkmen when they were £150 each, for example) but I think she would have drawn the line at an alternator, owing to it spoiling the line of her skirt. My sympathies are with Mrs John.

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[pampas]

Always start with full throttle, some alt. always require more revs to allow the field to gain iron saturation, or fit a smaller pulley if problem persists. I would not advise playing with the regulator but fit a Sterling type booster,I did and it has enhanced the capacity beyond belief.very useful for fridge battery hope you find this useful.

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[mainshiptom]

A good Battery should be at around 13.4 when not concated to anything !

Therefore disconnact the battries ! charge over night and measure voltage in the morning !

Any battery that does not show 13.4 after a night charge , Replace !

I have a bank of four battries and had lots of problems but there was no probs with chatrging but one battray was draing the other three, 50 pounds , one new battary and bingo no problems !

Tom


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[VicS]

You say you've experimented with a diode in series with the field. To achieve the result you were looking for the diode should be in the voltage sensing connection. Easy to do if the alternator is of the battery sensing type but not so easy, if practicable at all, with a machine sensing type although it depends on whether your regulator is separate or integral with the alternator. From what you say it sounds as though you connected it in the field supply from the regulator to the alternator. This would not give the result you were looking for.

When checking battery condition by voltage reading you must use a high impedance voltmeter, preferably a digital multimeter. Take the reading directly from the battery terminals under absolutely no load conditions (disconnected if there is any doubt) after the battery has rested for 12 hours after charging. While the battery condition meter you have fitted may give you some useful indications of what's going on you cannot rely on its accuracy unless you have compared it's readings with an accurate meter. You will find some variation in quoted readings to expect but the rule of thumb I use is 12.7 fully charged, 11.7 flat. (Source: PBO several years ago.) If the state of charge is as low as your readings suggest you would expect to have engine starting problems, certainly below 12.5v.

Your observed current readings sound reasonble for a well charged battery in good condition but a good battery in a semi discharged state will take a high current for much longer than 1/2 minute before slowly falling to 2-3 amps after an hour or more.

13.8 is a lowish voltage to be getting but is OK (the spec for my car is 13.5 - 14.1 when warm ie after 10 minutes operation)

I would have suspected your batteries as being on their last legs but they are nearly new. I would try charging them for a good long period with a good mains charger. Then check the no load volts as outlined above. Or get them professionally checked. If they really have been sitting for long periods in a semi discharged state they will not have benefitted to say the least.


I wouln't rush to change the alternator they can usually be repaired if at fault. Bring it home (wrap it in on oily rag then in the knickers) and get it checked if at the end of the day you really do suspect it.

I have reservations about using the cigar lighter socket for connecting a battery chager, although ideal for say a small solar panel. Most accessory plugs just push in and do not make reliable contact on the centre connection, also sockets supplied for accessories do not have the spring clips to hold the plug in positively. They incidentally come in two sizes which is why mobile phone chargers (at least mine does) have two interchangable end pieces. A word of warning here my phone charger damaged the inside of the cigar lighter socket in one car, eventually shorted it out, blew a fuse and put several circuits in the car out of action. So all in all it would be safer to connect the battery charger directcly to the battery. It is usually recommended that the battery is disconnected while charging any way (failure to do so on one of our cars which is only lightly used and therefore periodically charged from the mains may explain why it's on its 3rd alternator).

Finally while re-reading your question I realised it was 2 batteries not one. Do you have a simple blocking diode type split charging system. If so that could be the cause of your problems, or do you really have problems other than unexpected voltage readings, as it would drop the voltage between alternator and battery by 0.7 volts. There should be a connection on the split charging unit (incorporating a extra diode) to which the votage sensing connection is made. This will do what you were trying to do with your diode in the field connection, ie increase the output voltage by 0.7 thus overcoming the 0.7v drop acroos the main diodes.

I hope you can make some sense out of all of this and that at least one little bit is of help. Distance diagnosis is not always easy. Best of luck anyway

<hr width=100% size=1><font color=purple>Ne te confundant illegitimi.</font color=purple>

 

[johnneale]

Thanks - This is all good stuff & I will look at adverc -

I run 2 batts independently and charge them up separatly. i.e controlled on the 'off 1 2 both' big red switch (no blocking diodes). When the charge rate drops to about 1 amp on each, I run the rest of the day with them parallelled up and still see 1 - 2 amp charge.

When cranking the engine on both batts, voltage drops to 8 volts.

I dont have a voltage sensing connection on the alternator. Only an output and a field (which goes through the warning light to positive switch)



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[VicS]

Ah you are calling the warning light connection the field connection. The field connection is inside the alternator between the regulator and the slip ring brushes.

The warning light connection has two functions however. One is obviously to operate the waning light the other is to provide a small current to the field via the regulator to energise the alternator initially. Once it starts to generate it provides its own field current and the light goes out.

<hr width=100% size=1><font color=purple>Ne te confundant illegitimi.</font color=purple><P ID="edit"><FONT SIZE=-1>Edited by VicS on 21/07/2003 20:42 (server time).</FONT></P>

 

[charles_reed]

Sounds as tho' something is wrong with your in-alternator voltage regulator.

I'd suggest you don't consider a new alternator - as it's charging it's probably OK.

In your position I'd fit a permanaent pulse charger (one that senses battery voltage and turns onto a float charge when fully charged). A 10 amp one is about the smallest that is available and barely sufficient to be of real value.
I'd also fit an Adverc smart regulator - I've had mine for 11 years (from when they first came out and Adverc have very supportively upgraded it every time there has been a change).

A standard automotive trickle charger is not a serious answer to the challenge of boat electrics - to start with the output is derisory when you need a good boost charge and, if used for any time it will soon degrade the batteries.

Both these two can be fitted yourself, tho' you may have to amend the alternator so the field brush wire can connect direct to the external regulator.

I've found the pulse-chargers to be considerably less expensive in France than in the UK, but you'll be hard-pressed to source any supplier who offers better value for money and such outstanding pre- and post- sales service as Adverc.

If you'd like any further info e-mail me via the BB link.

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[Chris_Robb]

Re: Adverc

Charles - I have had my Adverc now since 1997 - you say that Adverc has upgraded yours? Is this a chip change internally or what? so far I have had faultless performance with the odd unexplained flash of the warning light. I would like the max charging voltage to be slightly higher - I achieve about 14.2 but other than that - it was money well spent. I added one of their Prestolite 100 amp alternators about 4 years ago - so far its brilliant.

Great people to deal with!

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[charles_reed]

Re: Adverc

Mainly new software.

Talk to Trevor or Brian about it.

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