Is my alternator ok?

[Northern Boy]

Having just been away for nearly two weeks in the Hobby, with a mixture of EHU and off grid I have some questions about my electrics that someone may be able to shed some light on.

I have the original 2007 electrics, no B2B, no solar. 200AH domestic bank. My electric usage is very low, led lights, charging mobile phone and tablet. No TV, no anything else.

Driving for say 12 hours with the fridge on 12v I see a 10 amp draw on the display panel. When I stopped for the night and had EHU I noticed a six hour charge at about 10 amps, despite have been driving all the hours, is my alternator charging properly?

First thing in the morning with Engine off the engine battery voltage was about 12.5 v. After starting engine and at tick over the voltage on the engine battery was about 13.5 v. Not enough?

I don't know what other information may be helpful but I have a feeling all is not quite how it should be.

 

[paddymcc]

I think that the 13.5v suggests that the alternator is working but because the starter battery is fully charged it is on float charge only. Are those figures from the panel or measuring at the battery terminals? You could rev the engine and see if the starter battery goes up to about 14.4v but you need to be in two places at onceto do that...

 

[cmcardle75]

Having just been away for nearly two weeks in the Hobby, with a mixture of EHU and off grid I have some questions about my electrics that someone may be able to shed some light on.

I have the original 2007 electrics, no B2B, no solar. 200AH domestic bank. My electric usage is very low, led lights, charging mobile phone and tablet. No TV, no anything else.

Driving for say 12 hours with the fridge on 12v I see a 10 amp draw on the display panel. When I stopped for the night and had EHU I noticed a six hour charge at about 10 amps, despite have been driving all the hours, is my alternator charging properly?

First thing in the morning with Engine off the engine battery voltage was about 12.5 v. After starting engine and at tick over the voltage on the engine battery was about 13.5 v. Not enough?

I don't know what other information may be helpful but I have a feeling all is not quite how it should be.

Sounds like you might have a smart alternator. If you have a split charge relay, it will only charge your leisure battery when the engine battery needs charging, which is rare.

You may need to replace your split charge relay with a B2B charger which will operate whenever the engine is running, not just when the alternator decides to charge the engine battery.

Of course, you might also just have a knackered dumb alternator not producing enough voltage, or a knackered starter battery bringing the voltage down as it internally boils.

 

[SandraL]

Our 2005 van had 2 relays that energised when engine was running.
One connected engine to leisure battery, the 2nd connected the engine to fridge.
Cant remember how the step was powered.
Possibly the relay or associated fuse to charge leisure battery is faulty?

Of course yours may not be anything like this.........

Perhaps put meter on leisure battery, then start engine to see it any increase in leisure battery voltage.

 

[Lenny HB]

Sounds like you might have a smart alternator. If you have a split charge relay, it will only charge your leisure battery when the engine battery needs charging, which is rare.

Not on a 2007 van.

Alternator output seems a bit low I would expect 14.4 to 14.7v, the fridge will be putting enough load on the alternator for the volts to stay up.
Where are you measuring the voltage? You need to measure at the alternator, if you are measuring at the leisure battery the volt drop across the cables could easily take it down to 13.5v.
Also if the battery is not taking a charge properly it could be the battery on its way out.

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[autorouter]

With 2007 original electrics it's unlikely to be a smart alternator. Can you get a voltage reading on the leisure battery, and the amps going into the leisure battery? When the engine is stopped, and when it's running.

If the leisure battery is very flat, it might keep the alternator down at 13.5V until it's charged up a bit. If there's lots of amps going into the leisure battery, that will be the reason. If the amps is low, you might have a problem - unless both batteries are fully charged.

 

[gus-lopez]

You could rev the engine and see if the starter battery goes up to about 14.4v but you need to be in two places at onceto do that...

or you could buy a plug in 12v voltage reader & see what that says.
like this

<Broken link removed>

I have one in cab plugged in permanently. & one in the rear just to check. On passenger side under top storage I changed the 12v socket for a usb /'C' charging point for wife's phone which also has a built in voltage display
I'd check the 13,5v with engine rnning by turning off fridge & seeing whether it rises to 14+.

 

[Spriddler]

or you could buy a plug in 12v voltage reader & see what that says.
like this

<Broken link removed>

I have one in cab plugged in permanently. & one in the rear just to check.

I have the same readers; one permanently plugged into the cab battery cig lighter for the starter battery and the other one in a cig lighter socket in the back for the leisure battery. Checked against my multimeter they were accurate as well. Great peace of mind at very little cost.

 

[Northern Boy]

Where are you measuring the voltage

On the terminals of the engine battery.

 

[Northern Boy]

I think that the 13.5v suggests that the alternator is working but because the starter battery is fully charged it is on float charge only. Are those figures from the panel or measuring at the battery terminals?

Engine battery terminals,

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[Lenny HB]

Sounds a bit low then, assuming the starter battery is OK and not dragging it down.

 

[Wagoneer]

My 2009 Fiat 3 litre with CBE system didn't charge the leisure batteries very effectively from the alternator, less than 14v (13.5 to 13.7).

Installed a 30 amp B2B and now get a solid 14.4v at the leisure batteries (bypassing the CBE split charge relay) although the charge rate never exceeds 10 amps.

The Fiat engine wiring diagram shows that the wiring from the alternator, first goes to the starter motor solenoid and then onto the starter battery via the ECU box.

The starter motor solenoid is at the front of the engine and subject to the elements with the potential of creating a bad electrical connection for the transfer of power from the alternator to the starter battery and leisure batteries.

Maybe, a direct connection from the alternator to the starter battery (with connection from alternator to starter motor solenoid removed) could possibly resolve the OP's problems.

Hopefully, our electrical experts may be able to comment on my obsevations.

 

[Northern Boy]

Thank you all for your input and words of wisdom, I will do some more thinking and investigating with the knowledge gained.

 

[autorouter]

The starter motor solenoid is at the front of the engine and subject to the elements with the potential of creating a bad electrical connection for the transfer of power from the alternator to the starter battery and leisure batteries.

Maybe, a direct connection from the alternator to the starter battery (with connection from alternator to starter motor solenoid removed) could possibly resolve the OP's problems.

The connection from starter battery to starter motor solenoid is supposed to be the thickest wire with the highest current capacity in the whole vehicle. If the contacts at each end are solid, the voltage drop across it from normal alternator amps will be minimal. The connection from alternator to starter battery is critical to maintaining the voltage regulation characteristics of the alternator. If there's a bad connection, the voltage can go too high, possibly blowing bulbs and causing other problems with electrics. If there's any possibility of a bad connection in the alternator/solenoid/starter motor pathway, best get it seen to asap. I might be wrong, but I have the impression the problem is not that wiring.