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Battery & alternator help required.


Lucas

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Hi

 

I have a Autotrail 2003 cheyenne, Mercedes 2.8 cdi.

Our starter battery died not long after buying it the other month.

Just fitted a new Varta LFD 90, started straight away.

Been for a half hour drive, just put my meter on the starter battery and it reads 12 volts,

On my Sargent ec200 display it reads fair 11.6v.

I Put a meter on the starter battery whilst the engine was reved and got a reading of 13.47v, when engine

is idal I get 12v.

Before the drive my leisure battery read 12.v on the screen, now it reads 12.5.

I believe everything in the habitation area is switched off.

The PSU 2007 has been permanently switched off.

My questions are,

Should the starter battery be charged to 13v/14v after my drive?

What volts should the starter battery be sitting at when the engine is off?

Does it sound like the alternator has issues?

 

New motorhome so thanks in advanced for your comments :)

:-D

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I have a Autotrail 2003 cheyenne, Mercedes 2.8 cdi.

Our starter battery died not long after buying it the other month.

Just fitted a new Varta LFD 90, started straight away.

Been for a half hour drive, just put my meter on the starter battery and it reads 12 volts,

On my Sargent ec200 display it reads fair 11.6v.

I Put a meter on the starter battery whilst the engine was reved and got a reading of 13.47v, when engine

is idle I get 12v.

Before the drive my leisure battery read 12.v on the screen, now it reads 12.5.

I believe everything in the habitation area is switched off.

The PSU 2007 has been permanently switched off.

 

My questions are,

Should the starter battery be charged to 13v/14v after my drive? -

 

"Yes and No. The Alternator should charge at 14.4v and if you check the battery soon after taking it off charge, i.e. stopping the engine, the battery will be higher than it's normal rest voltage of 12.93v (LFD 90 only, a conventional Starter battery voltage will be nearer 12.6v). So if you stop the engine and then check the battery it should be up near 14.4v with a slow decline to 12.9v.

Note 2 : A new Varta LFD 90, like all batteries, will only reach their full capability after several charge/discharge cycles.

So initially you may only see the Varta at 12.8v but after a few weeks it should 'rest' at 12.9v off load".

 

 

What volts should the starter battery be sitting at when the engine is off? -

 

"See above"

 

 

 

Does it sound like the alternator has issues? -

 

"Maybe, but more likely a poor Earth cable.

Connect a Black Jump Lead from Battery Negative to Alternator body (or semewhere clean and shiny on the Engine) and see if the Voltage at the Starter battery rises.

If it makes a difference run a new decent cable from Battery Negative direct to Engine, even if it isn't the only issue it is a good cheap fix.

We don't usually see such low charging voltages as 13.4v, more like 13.8 to 14.2v so you may have more than one issue?

Make sure the Fridge is not on 12v when you do the tests"

 

 

 

Be wary about your Leisure batteries, 12v is very low for a pair of them, depending on technology that can be totally flat batteries. Modern 12v batteries sit at nearer 13v than 12v, 12v is flat or at least over discharged battery, see the chart below.

Asking an old low power Alternator (90amps?) to bring them up from so low is asking a lot, especially if you have other issues that may be contributing to the loading on the Alternator with low readings.

I would guess the low 12v reading and poorly charging system would mean they are possibly past their best. It is possible they have not been charged properly for some time?

Monitor them carefully if you don't want other Bills, like a new Alternator and mains charger.

 

 

 

234189462_BatterystateofChargeChart.jpg.8a8fec8857c798862b314a1853ce25c6.jpg

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Do try Allan's suggestion of a temporary earth connection, but given the age of the vehicle and the possible mileage, I would consider the possibility of a failing alternator. I have experience of a couple of alternator failures on cars where the mileage has been 60,000+. The common cause of failure is worn brushes, but often in modern vehicles access for replacement is restricted.

 

.ou seem to have to rev the engine to reach charging voltage. Please check thet the alternator warning light illuminates when the ignition is switched ON, and before the engine is started. If this bulb fails the alternator will be reluctant to start generating.

 

Alan

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Thanks for the reply.

I tried the earth test you suggested but this did not increase the volts.

 

The starter battery has been disconnected and I will fully charge it at home.

 

Looks like I may need a new leisure battery and possible a new alternator.

Do you have any recommendations for alternators?

 

Thank again.

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Alanb - 2017-11-19 12:55 PM

 

Do try Allan's suggestion of a temporary earth connection, but given the age of the vehicle and the possible mileage, I would consider the possibility of a failing alternator. I have experience of a couple of alternator failures on cars where the mileage has been 60,000+. The common cause of failure is worn brushes, but often in modern vehicles access for replacement is restricted.

 

.ou seem to have to rev the engine to reach charging voltage. Please check thet the alternator warning light illuminates when the ignition is switched ON, and before the engine is started. If this bulb fails the alternator will be reluctant to start generating.

 

Alan

 

Hi

 

The millage is low for the age, just 14,500.

Looks like the alternator may need replacing.

 

Thanks for your input...

 

 

 

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Hi Lucas,

 

14,500 miles is wery low for a 2003 vehicle. I consider my 2006 2.8jtd Ducato to be low mileage at 29,500.

 

I am not familiar with the Mercedes engine, but if you can see the alternator you may save some cash by giving it a visual inspection. Not easy but look fo any signs of over heating of the stator windings. Also you you could google "relplace alternator brushes" to see what is involved. However do please be aware that the alternator B+ (main output terminal) will be connected to the battery by a high value fuse. Do not disturb this terminal without first disconnecting the battery negative connection.

 

Alan

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Alanb - 2017-11-19 7:06 PM

 

Hi Lucas,

 

14,500 miles is wery low for a 2003 vehicle. I consider my 2006 2.8jtd Ducato to be low mileage at 29,500.

 

I am not familiar with the Mercedes engine, but if you can see the alternator you may save some cash by giving it a visual inspection. Not easy but look fo any signs of over heating of the stator windings. Also you you could google "relplace alternator brushes" to see what is involved. However do please be aware that the alternator B+ (main output terminal) will be connected to the battery by a high value fuse. Do not disturb this terminal without first disconnecting the battery negative connection.

 

Alan

 

I will check out YouTube to see if there is any videos on how to check.

Thanks for the tips :-D

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We would suggest you go to a specialist Auto electricians that also rebuild Alternators.

Rebuilding your one (most likely a Bosch unit), by a specialist, will be much cheaper than new.

 

The problem with the 'affordable' after market Alternators is that they are often made in places like Lithuania and not always the best quality or efficiency.

 

 

The only time that is not so cost effective is when the Alternator has covered high miles.

 

Google Alternator rebuilders in your area.

 

 

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  • 1 month later...

Thought I would give everyone a little update.

Had a new Varta battery fitted and there was still a drain.

Turns out the issue was not the alternator but the relay switch for the glow plugs.

Thanks for all your help and advice.

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