Read my post above on voltage under load. Because of this effect, you don’t know what the state of charge actually is from the voltage when the vehicle is running. It could well be that your starter never goes significantly below the designed 80% target, in which case you just don’t have a problem.
Alternator Lack Of Charging Causing Battery Failure.
- Thread starter longtallmartin
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I think only the meaningful measurement of these is #1 the battery voltage after a nights rest, before start up. That gives a relatively good indication what the state of battery is thus if it has been properly charged. The others are as @t0mb0 above mentions voltage measurements under load which really doesn't tell much unless you know what the load is. So actually would be essential to monitor current in/out of the battery to see if it is charged or discharged
If you would keep recording the measurements #2-#5 you would see the alternator having several different charging/voltage regimes, varying from 12.1 - 14.8 V depending on battery's state of charge, outside temperature, etc. A kind of exception seems to be when the engine is doing DPF regeneration - obviously to add load to the engine it starts boost charging the battery at 14.8V.
For example if you would fully charge the battery with external charger, when you would next time drive the vehicke the alternator would go to 12.1V (or 12.3V) mode thus slowly taking the charge level back to about 80%. I have tried this quite a few times and it results a kind of interesting side effects on fuel consumption
during first hour of driving.Some related measurements were done in thread ---> Stop/start...regen...smart Alternator... Dc-dc Charger For Leisure Battery Or Not?
I think the bottom line is that if the battery voltage before start up consistently (over night/week) stays above 12.3 Volts there is no need to worry. If the alternator wouldn't charge the battery would be flat in less than two hours of driving - as the engine alone (ECU, injectors, etc) draws continuosly minimum of approx. 30 Amps.
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I have had my T6 for 12 months now with factory fitted leisure battery. I have read all forum reports about smart alternator and having to fit dc to dc charger to fully charge leisure battery. As i have written before, I have had no problem at all with standard factory fit set up.I can camp with fridge on and only need to run motor 15 to 30 mins to recharge leisure battery to 12.8 volts. (Starter on 12.5v)
I have a plug in voltmeter that I have been using to see how charging works, and from my observations , it appears that when running my fridge and driving, alternator is charging at between 14.3 and 14.9v most of the time.Sometimes it will slowly go back to regen mode if a longish trip.
So as far as I am concerned , factory set up does exactly what I need it to do. Cheers.
I have a plug in voltmeter that I have been using to see how charging works, and from my observations , it appears that when running my fridge and driving, alternator is charging at between 14.3 and 14.9v most of the time.Sometimes it will slowly go back to regen mode if a longish trip.
So as far as I am concerned , factory set up does exactly what I need it to do. Cheers.
Sometimes it will slowly go back to regen mode if a longish trip.
If thats the case, why is a smart alternator necessary, Ford give the option to code it off (or they did), you can do it yourself by disconnecting the sensor on the negative rail of the starter battery, try it, if no like re connect it.
Thanks for that but I'll leave it just the way it is.....as for why is a smart alternator necessary. .....I think Vw set it up so it is only "smart" when the batteries are fully charged..or at least, that's the way it works on mine in practice. Cheers.
GJ
How do the batteries get fully charged in the first place, are you saying that the alternator will continuously charge the batteries under engine power until said batteries become fully charged, then at that point the alternator becomes smart and turns itself off, are you aware that to enable energy generation there needs to be space within the battery ( no space no regeneration). How do you suppose you get that space, could it be that once the battery is fully charged the system will stop any further charging via engine power until there is room in the battery ( normally 25% ) to enable a fast high voltage regeneration charge. It would be really useful if someone here could post exactly how this system works instead of guessing, below is a link to Hyundai, I can`t find any other solid information for other manufactures, personally I believe there is very little gain by having this system but substantial financial pain down the line, bit like selling small Diesel engine cars to folks that do short journeys, save a bit on fuel but balance that with the cost of a new DPF.
Attached is A PDF from Hyundai UK explaining about the AMS system. The text from this pasted below.
This model has an engine ECU controlled alternator and this is designed only to operate in a way that reduces fuel consumption and emissions. So effectively it will actually do very little unless it really needs to, which means that until it detects an electrical load from things such as headlamps, HRW etc it will do the bare minimum to charge the battery up. If the customer is only doing those sorts of short journeys and not using any electrical items then the starting of the engine has taken charge out of the battery, but without any electrical items being used it won’t put that much back into the battery again. The Alternator Management System (smart charge) works in a very different way to a conventional alternator. The conventional alternator is charging at all times whenever the engine is running, and will increase its output back to the battery depending upon electrical load and the speed it is being rotated at. In the AMS system the charging function of the alternator is controlled electronically by the engine control ECU based upon various sensor inputs and how the vehicle is being driven, so it can be that the alternator will not be charging the battery at all dependent upon the circumstances at that time. Effectively as the alternator is controlled via the ECU it will only charge the battery when necessary, this is to reduce emissions and improve fuel economy. In certain conditions the system will only charge the battery in small amounts.
So if the vehicle is only used for short journeys, and as the system often does not charge at all after a cold start, if you are only doing low mileage the starting of the engine can take more charge out of the battery than the system will put back in again.
Start stop (ISG) and AGM brattery
How do the batteries get fully charged in the first place, are you saying that the alternator will continuously charge the batteries under engine power until said batteries become fully charged, then at that point the alternator becomes smart and turns itself off, are you aware that to enable energy generation there needs to be space within the battery ( no space no regeneration). How do you suppose you get that space, could it be that once the battery is fully charged the system will stop any further charging via engine power until there is room in the battery ( normally 25% ) to enable a fast high voltage regeneration charge. It would be really useful if someone here could post exactly how this system works instead of guessing, below is a link to Hyundai, I can`t find any other solid information for other manufactures, personally I believe there is very little gain by having this system but substantial financial pain down the line, bit like selling small Diesel engine cars to folks that do short journeys, save a bit on fuel but balance that with the cost of a new DPF.
Attached is A PDF from Hyundai UK explaining about the AMS system. The text from this pasted below.
This model has an engine ECU controlled alternator and this is designed only to operate in a way that reduces fuel consumption and emissions. So effectively it will actually do very little unless it really needs to, which means that until it detects an electrical load from things such as headlamps, HRW etc it will do the bare minimum to charge the battery up. If the customer is only doing those sorts of short journeys and not using any electrical items then the starting of the engine has taken charge out of the battery, but without any electrical items being used it won’t put that much back into the battery again. The Alternator Management System (smart charge) works in a very different way to a conventional alternator. The conventional alternator is charging at all times whenever the engine is running, and will increase its output back to the battery depending upon electrical load and the speed it is being rotated at. In the AMS system the charging function of the alternator is controlled electronically by the engine control ECU based upon various sensor inputs and how the vehicle is being driven, so it can be that the alternator will not be charging the battery at all dependent upon the circumstances at that time. Effectively as the alternator is controlled via the ECU it will only charge the battery when necessary, this is to reduce emissions and improve fuel economy. In certain conditions the system will only charge the battery in small amounts.
So if the vehicle is only used for short journeys, and as the system often does not charge at all after a cold start, if you are only doing low mileage the starting of the engine can take more charge out of the battery than the system will put back in again.
Start stop (ISG) and AGM brattery
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Sorry...I can't tell you how it works...but I can tell you that the factory fitted VW second battery set up works as I described.
It charges both batteries, but at rest, starter battery is 12.5v, 2nd battery (agm) 12.8v. How VW do that? .....I don't know, but I'm glad that they do. Cheers.
It charges both batteries, but at rest, starter battery is 12.5v, 2nd battery (agm) 12.8v. How VW do that? .....I don't know, but I'm glad that they do. Cheers.
