MD2020B - Alternator hot, but not used

Jokani

Jokani

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Over the weekend, I removed my alternator so that I could see behind it.

When I came to put it back it was noticeably hot to touch - A quick check on the engine battery voltage and it was only 12.5v and I would have expected it to be fully charged.

I'm concerned that something could be amiss.

Here is a picture of the alternator, and a wiring diagram.

Any ideas?

Gemini-12v-Charging-System-800.jpg


and

Gemini-Alternator-Rear-View.jpg
 
Some alternators will draw current through the regulator circuit, leading to heating up. The solution is to put a relay in so that power is only connected when the engine panel is switched on.
 
pvb said:
Some alternators will draw current through the regulator circuit, leading to heating up. .
Click to expand...

Thanks for taking the time to help me out, I'm confused with the terminology 'regulator circuit', which wire is that?
 
There was no need for 35mm cable for the alternator charging, 10mm would have been fine unless you have ridiculous wiring runs. That said, it won't hurt so don't change it.

There should not be a 10mm cable from the alternator b+ to the starter motor. Current will be flowing from the starter battery to the starter motor, then through the 10mm cable to the alternator, then to the Pro Split, which will then be trying to charge the engine battery with that current.

That may well be what's causing the heat at the alternator too, but either way it needs to be removed.
 
if it got hot when you were doing what you were, it means you had the batteries on also. Not to teach you to suck eggs, but had you touched the back of the atlernator and the b post or cable to the engine block or another earth when thw alternator was loose, you would have had a major problem as you would be shorting the battery.
 
solent clown said:
if it got hot when you were doing what you were, it means you had the batteries on also. Not to teach you to suck eggs, but had you touched the back of the atlernator and the b post or cable to the engine block or another earth when thw alternator was loose, you would have had a major problem as you would be shorting the battery.
Click to expand...

All the cables were still connected, alternator was resting on the cabin floor, I don’t think I was shorting anything. Starter battery is fused, so I guess that would blow if I shorted it.
 
GaryCottam said:
All the cables were still connected, alternator was resting on the cabin floor, I don’t think I was shorting anything. Starter battery is fused, so I guess that would blow if I shorted it.
Click to expand...

thats coolo, didnt mean to insult, just giving you a heads up it sounds like you did not need :encouragement:
 
solent clown said:
that B+ to starter motor wire is just the main charging cable surely Paul? If he disconnects that he wont have a charge
Click to expand...

I hate trying to interpret semi pictorial substitutes for proper wiring diagrams like Gary has posted in #1 but ITYWF that the alternator output should go to the ProsplitR "Alt In" terminal

This then feeds the charge to the battery banks connected to its "Start Batt" and "Batt 2" terminals . Sterling does not show any battery isolation switches but I guess Gary has his batteries connected by isolation switches

(More feckin pictures instead of proper wiring diagrams to interpret on Sterlings website !!!! )
 
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VicS said:
I hate trying to interpret semi pictorial substitutes for proper wiring diagrams like Gary has posted in #1 but ITYWF that the alternator output should go to the ProsplitR "Alt In" terminal

This then feeds the charge to the battery banks connected to the "Start Batt" and "Batt 2" terminals . Sterling does not show any battery isolation switches but I guess Gary has his batteries connected by isolation switches

(More feckin pictures instead of proper wiring diagrams to interpret on Sterlings website !!!! )
Click to expand...

Aah, I totally ignored the pictorgram and looked at the wiring diagram beneath for the same reason
 
GaryCottam said:
Hi Paul, just double checking, have I misinterpreted the wiring diagram, that seems to show a red 10 between the B+ and the starter?
Click to expand...

For the reason I have explained to Solent Clown , not when you have the Prosplit R. The altrenator output goes to the "Alt In" terminal of that via the 35mm cable
 
It is common practice for the 35mm starter cable to go to the starter motor (where else :)) and then to have a 10mm cable between the alternator B+ and the starter solenoid. This allows the alternator current to go up the starter cable, rather than running a separate cable all the way to the battery. This is how the VP diagram shows it.

With split charging by the likes of VSRs this wire is left in place, but in the case of the ProSplt or the likes of the Victron Argofets, diodes etc the cable is removed and on is connected from the B+ to the split charge device.

Gary has left the cable from the starter to B+, it must be removed.

Also, there was no need for 35mm cables from the alternator to the ProSplit, ProSplit to the batteries/isolators or the alternator negative, all of those could have been 10mm, as i previously posted.

For the inevitable pedant that will turn up to say that his 6 billion amp alternator needs more than 10mm cable, i'm not interested, i'm answering Garys post.
 
VicS and PaulRainbow, sorry for the late reply, just returned from a week away. I really appreciate your advice, I'll remove the cable this weekend.
 
I had a similar problem with my alternator. I traced it to the external regulator trying to excite the alternator even when the engine wasn't running. I solved it by a relay operated by the oil pressure switch with the excitation (in your case blue/red) running through the NC contacts. I can leave the "ignition" switch on more or less indefinitely.
 
I removed the cable, I didn't have time to test much but charging wise, I was seeing 75A at 2000rpm and 14.1 v, which is better than I have been seeing. Does the alternator get hot with just the panel on, I still need to test that fully, but it didn't seem to.
 
GaryCottam said:
I removed the cable, I didn't have time to test much but charging wise, I was seeing 75A at 2000rpm and 14.1 v, which is better than I have been seeing. Does the alternator get hot with just the panel on, I still need to test that fully, but it didn't seem to.
Click to expand...

Generally not.
 
jiris said:
I had a similar problem with my alternator. I traced it to the external regulator trying to excite the alternator even when the engine wasn't running. I solved it by a relay operated by the oil pressure switch with the excitation (in your case blue/red) running through the NC contacts. I can leave the "ignition" switch on more or less indefinitely.
Click to expand...

I removed the red 10mm cable between the Alt B+ and starter motor, but if I inadvertently leave the control panel on the the alternator till gets hot. So I think I need to implement a solution as jiris suggests.

Is this the correct type of relay that I need Standard (Mini) Make & Break Relay - NO Contacts, 12V 40A ?
 
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