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Current mystery


Cottonlung

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Hello.. I wonder if someone could shed some light on a mystery. ( yup tried google ) Over the weekend I installed a Durite vsr to which works as it should, however, i was thinking once the leisure battery is fully charged ( if it ever will be) but for arguments sake say it does get fully charged, where does the extra juice it's taking in go? Common sense says it just keeps trying to go in, but rarely do common sense and science go together. 

I'm just curious to know if anyone has ever wondered. Cheers 🙂

 

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2 hours ago, Cottonlung said:

Hello.. I wonder if someone could shed some light on a mystery. ( yup tried google ) Over the weekend I installed a Durite vsr to which works as it should, however, i was thinking once the leisure battery is fully charged ( if it ever will be) but for arguments sake say it does get fully charged, where does the extra juice it's taking in go? Common sense says it just keeps trying to go in, but rarely do common sense and science go together. 

I'm just curious to know if anyone has ever wondered. Cheers 🙂

 

The alternator is fitted with a regulator. The theory is that once the capacity of both starter and leisure battery are full the regulator switches off power at the alternator. The alternator is still producing power but it doesn't go anywhere.

However there is much more to it than this as the vehicle is constantly using power in one degree or another, ie radio, instruments, spark for a petrol engine etc.

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Simplistically: 

Traditional alternators will produce power when they are given a field current. The 'voltage regulator' is designed to convert 3 phase ac electricity (produced by the alternator) into DC electricity at a suitable voltage (13.8v to 14.1v) to charge a lead acid battery. The starter battery will pull current to try and get a full charge from the alternator. Once the starter battery is above a certain voltage your split charger will connect the leisure battery to the starter battery and thus the leisure battery will pull current from the alternator. When both are full the current draw will decrease but there will always be some current draw. When ever the alternator is producing power it saps engine power, they are only about 50% efficient! So say 13.8 v at 50 Amps = 690 watts so about 1380 watts pulled from engine!

On most EU5 and all EU6 the alternator is 'smart' so that they can be switched off as often as possible while maintaining starter battery charge level. Some are even controlled to the extent that when you brake they pull as much current as possible to charge the battery, that way they save fuel and thus meet their emission targets. That allows the battery voltage to fluctuate more and some 'smart' alternators will put out 16V to charge faster. The batteries in EU5 & EU6 are usually bigger to cope with stop start but also to allow more margin to not be fully charged.

The smart alternators (not really smart just ecu controlled) are complicating things, hence why some vehicles need Battery 2 Battery chargers like the Sergeants.

The above is a simplistic overview of how an alternator works, it's not a perfect description by any means but should give you an idea?

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37 minutes ago, spruce said:

The alternator is fitted with a regulator. The theory is that once the capacity of both starter and leisure battery are full the regulator switches off power at the alternator. The alternator is still producing power but it doesn't go anywhere.

However there is much more to it than this as the vehicle is constantly using power in one degree or another, ie radio, instruments, spark for a petrol engine etc.

Brilliant thank you 👌

3 minutes ago, ched999uk said:

Simplistically: 

Traditional alternators will produce power when they are given a field current. The 'voltage regulator' is designed to convert 3 phase ac electricity (produced by the alternator) into DC electricity at a suitable voltage (13.8v to 14.1v) to charge a lead acid battery. The starter battery will pull current to try and get a full charge from the alternator. Once the starter battery is above a certain voltage your split charger will connect the leisure battery to the starter battery and thus the leisure battery will pull current from the alternator. When both are full the current draw will decrease but there will always be some current draw. When ever the alternator is producing power it saps engine power, they are only about 50% efficient! So say 13.8 v at 50 Amps = 690 watts so about 1380 watts pulled from engine!

On most EU5 and all EU6 the alternator is 'smart' so that they can be switched off as often as possible while maintaining starter battery charge level. Some are even controlled to the extent that when you brake they pull as much current as possible to charge the battery, that way they save fuel and thus meet their emission targets. That allows the battery voltage to fluctuate more and some 'smart' alternators will put out 16V to charge faster. The batteries in EU5 & EU6 are usually bigger to cope with stop start but also to allow more margin to not be fully charged.

The smart alternators (not really smart just ecu controlled) are complicating things, hence why some vehicles need Battery 2 Battery chargers like the Sergeants.

The above is a simplistic overview of how an alternator works, it's not a perfect description by any means but should give you an idea?

That's very helpful thanks! 

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