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Another Alternator Thread


davidb
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I am sure one of our favourite topics is batteries and alternator, so I shall start another.

 

When my setup is running normally I start up the engine in the morning when the voltage gets down to around 12.0 across the batteries - 4  Trojan T - 6620s wired in series/parallel. A clamp meter on the return cable to the bank soon starts reading about 25 amps, and an hour's charging at about 14.4 volts at that rate gets it up nicely before the day which often involves another a few hours cruising, so they are always well above 20 and have never been low on water.

.trojan.jpg.3eb1e4148bc1e0e64764fa88411047ff.jpg

 

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I think the Alternator is a Lucas and it is wired through a split charge diode, below

 

Isol.jpg.5785922d4d29d46cf924d8e78d5b0c5f.jpgIsolator.jpg.71bc9b07d6425e80d61a41fc85465eb4.jpg

 

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Yesterday the alternator failed so I took it out and replaced it with a spare I keep on board, but this has not got the tapping for an Adverc booster, but I thought it might keep us going for a while till the original was repaired. But it isn't getting the battery over about 13.7 volts. When I tested the voltages on the Surepower Isolator, the input is at 14.3 or 14.4, but it is losing about 0.7 volts.  So I assume these isolators are not a lot of use for with a standard alternator? I shall report back when I get the new one fitted, firstly as standard, then with the Adverc attached.

Edited by davidb
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20 minutes ago, davidb said:

When It tested the voltages on the Surepower Isolator, the input is at 14.3 or 14.4, but it is losing about .7 volts.  So assume these isolators are not a lot of use for a sandart alternator?

 

I have a pair of exactly the same "Shore Power Isolators' my measured voltage difference between the input and output is 0.8 volts.

I am using standard 14.6 volt regulated HC-Cargo Alternators

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All diodes "lose" 0.7 to 0.8 of a volt.  Better to have a Voltage Sensitive Relay or even just a split charge relay.

 

Its "easy" to put the extra connection in a Lucas or just about any make of alternator if you have any mechanical/electrical ability.

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On 12/10/2021 at 20:32, Tracy D'arth said:

All diodes "lose" 0.7 to 0.8 of a volt.  Better to have a Voltage Sensitive Relay or even just a split charge relay.

 

Its "easy" to put the extra connection in a Lucas or just about any make of alternator if you have any mechanical/electrical ability.

or even a SmartBank!

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Well above 20 - what?

 

Starting charging at 12v is probably a bit on the low side.

 

I would suggest you get the alternator to an  auto or marine electrician to have the extra cable fitted. I think the Adverc website has instructions for DIY fitting the wire on the more common alternators. You will never get the batteries properly charged until you:

 

get the wire fitted,

 

get a battery sensing alternator or maybe a battery sensing regulator is available for your alternator,

 

or get rid of the split charge diode and either fit a "zero volt drop" electronic version or a decent VSR and rewire.

 

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16 hours ago, Tony Brooks said:

Well above 20 - what?

 

Starting charging at 12v is probably a bit on the low side.

 

above 20 Amps on the clamp meter.

 

I appreciate starting at 12v is low, but since my last post I have contacted the previous owner of the boat and it looks like the batteries could be 13 years old!  So next spring will probably see me looking for new Trojans or similar.

 

I have got a new alternator to fit now with the extra cable fitted, might be a week before I get it replaced, but I shall report back here.

 

Thanks for your replies.

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If you are stopping charging at 20 amps charge or higher, then you are destroying the batteries by sulphation. You need to go on charging until the current has stopped dropping over about an hour at 14.2volts plus or when the current has dropped to 1 to 2% of batery capacity, again at a voltage of 14.2V or higher

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8 hours ago, Tony Brooks said:

If you are stopping charging at 20 amps charge or higher, then you are destroying the batteries by sulphation. You need to go on charging until the current has stopped dropping over about an hour at 14.2volts plus or when the current has dropped to 1 to 2% of batery capacity, again at a voltage of 14.2V or higher

I'm getting confused, Do you mean that the charging current is 20A?  I think you must mean that and I would agree that it would be at far too low a soc...

 

I am no longer confused. I see exactly what you mean.  I just needed to allow my aging brain to catch up and finish processing. 🙂

 

N

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Fitted the new alternator today after testing all the battery cells with a hydrometer and found two batteries with a bad cell each. I gave the engine  a run and it didn't get above 13.7 volts on the domestic battery even with the Advec in circuit. I shorted out the split chage diode and there was soon 14.3 volts showing, but after running the engine for half an hour stopped it and the voltage nearly immediately dropped to below 11 volts.

 

So I pulled out the two bad batteries and now have a bank of two that seems, after a short trial, to have more capacity than all four had when acting "normally" two weeks ago.

 

Not spent a night on board for a while now, but fingers crossed..........

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4 minutes ago, PineappleGuy said:

Out of interest, what model of alternator was it, did you replace like-for-like and where did you get it from?

 

 

I am not sure how that would relate to anything other than the OP's boat. In his case the passive split charge diodes means it is all but vital that he has a battery sensed alternator or an add on to make his standard alternator battery sensing. If you have another form of charge spitting or a two alternator boat you would not need either, a "standard" alternator would do the job. Most major towns have an alternator and starter specialists who can supply a suitable one for your boat. Do not try to drive one of much over 90 amps on a single V belt or it is likely to end in constant belt failures.

 

 

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Just now, Tony Brooks said:

 

and most major towns have similar companies.

 

True, but LRE are only a few miles from David's boat.  I know this because he's sharing a mooring ring with me!

 

And we've been moored on the 2 day mooring since last Monday ... :icecream:

 

 

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I have just come home from the boat and was pleased to see that the reduced size battery had held its charge well and the new alternator could keep the invertor running at full load pushing out just over 50A ( and the belt was starting to complain!). The Alternator is a Lucas127 type with a brush pack looking like this:

712573966_ScreenShot2021-10-20at20_58_16.png.ba67a4e367d5e97e8945b66758c730f6.png

 

 

It was quite expensive, being fully insulated for use on a steel boat, probably twice as much as a standard one. I got it from LRE near Leyland as Peter said, they got it in next day for me and soldered the extra wire on the brush holder for the Adverc. A very obliging firm, I thought.

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Personally I would not bother with an insulated return alternator on a narrowboat with a decent engine block and hull negative. I know the theory but have seen so many with earth return alternators and the negative bolted to a mounting that did not seem to suffer excess hull corrosion.

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13 hours ago, Tony Brooks said:

Personally I would not bother with an insulated return alternator on a narrowboat with a decent engine block and hull negative. I know the theory but have seen so many with earth return alternators and the negative bolted to a mounting that did not seem to suffer excess hull corrosion.

Especially as the starter negative is connected to engine. But some advice given is bad. If you install a negative wire from battery negative to hull (next to the ac mains earth, like a good boy!) , and hull is connected to engine by means of exhaust, cables etc. there is a circuit path from battery negative to alternator negative both directly via the wiring, and also indirectly via the engine and hull.

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GSNC 

10 minutes ago, nicknorman said:

Especially as the starter negative is connected to engine. But some advice given is bad. If you install a negative wire from battery negative to hull (next to the ac mains earth, like a good boy!) , and hull is connected to engine by means of exhaust, cables etc. there is a circuit path from battery negative to alternator negative both directly via the wiring, and also indirectly via the engine and hull.

 

Thanks Nick, that needed saying, a misunderstanding I think, I meant to say (and I have no idea why I did not), I have seen insulated return alternators with their negative bolted to a (n alternator) mount. There is no way i would intentionally suggest you can put an negative on an engine mount. However many apparently insulated return alternators are no such thing. The B- is just fixed to the case and also the negative diode plate so they will operate as earth return without a B- cable but one needs to inspect the alternator to see if this is the case. Because of the dangers to control cables etc. i would always use a negative bond to both the hull (engine bed) and the engine itself, probably the starter negative if one is fitted or a mounting bolt. This goes against the "only one negatve hull bond" mantra but it's no different from unitentionally using the cables etc. as an negative path.

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3 minutes ago, Tony Brooks said:

GSNC 

 

Thanks Nick, that needed saying, a misunderstanding I think, I meant to say (and I have no idea why I did not), I have seen insulated return alternators with their negative bolted to a (n alternator) mount. There is no way i would intentionally suggest you can put an negative on an engine mount. However many apparently insulated return alternators are no such thing. The B- is just fixed to the case and also the negative diode plate so they will operate as earth return without a B- cable but one needs to inspect the alternator to see if this is the case. Because of the dangers to control cables etc. i would always use a negative bond to both the hull (engine bed) and the engine itself, probably the starter negative if one is fitted or a mounting bolt. This goes against the "only one negatve hull bond" mantra but it's no different from unitentionally using the cables etc. as an negative path.

On our boat and Beta engines generally (not sure about others) there are studs on the engine frame for positives and negatives - domestic alternator/battery on one side and engine alternator/battery on the other side. The negatives are not insulated from the frame, thus the whole engine including the starter and alternator casing is firmly connected to battery negative. Which is fine, unless someone decides to add a wire battery negative post to hull somewhere. The correct way to do it would be to add a wire from the negative stud on the engine, to hull. That way, no significant alternative current paths through the hull are created.

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6 hours ago, nicknorman said:

Especially as the starter negative is connected to engine. But some advice given is bad. If you install a negative wire from battery negative to hull (next to the ac mains earth, like a good boy!) , and hull is connected to engine by means of exhaust, cables etc. there is a circuit path from battery negative to alternator negative both directly via the wiring, and also indirectly via the engine and hull.

Seen a Ford throttle cable burned out from that. 

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