Leisure Battery not reaching full charge on Alternator

Molly 3

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827
My understanding of a smart alternator the output is controlled by the engine ecu .on an old type the output is controlled by the alternator regulator .
 

wayne townsend

Free Member

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9
xsilvergs graphs are clearly those of a smart alternator vehicle . That confirms something a dealer told me recently about ducato's fitting a smart alternator on recent new builds . I fitted an Ablemail AMC12-12-30 on Vw t6 with smart alternator and it worked really well .
 

in h

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747
The other factor to consider is the 12v power of a three-way fridge. Of course you have to stop the SCR connecting the batteries together when the alternator kicks in if you have a B2B, but normally it will still switch the fridge power on (though my fridge has a separate D+ wire, which makes the change different)
I power the fridge from the starter battery, not the habitation ones, so the B2B charger is basically just charging, and the fridge runs off the alternator. The amount of 12v power the fridge takes when the engine is off is minimal.
 

in h

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747
Here is charging from a 2017 Fiat Ducato alternator. This was a drive down a motorway, a bit stop - start and slow progress due to an accident. I will be fitting a B2B charger

View attachment 52793
That's as good as it gets without a B2B charger.
You fit 100Ah of leisure battery. You can only charge it to 85% full and only safely discharge it to about 50% full.
So your battery has a total usable capacity of around 35Ah. That's 438 watt hours: the equivalent of 31 grammes of LPG, costing 3.4p
 
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in h

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747
A standard alternator regulator will not drop back to 13.7v, voltage will remain above 14, depending on the load and revs.
That's simply not true in my experience.
I have two meters visible when driving. One shows the starter battery voltage. After a few minutes running it's up to 14+ and after about 45 to 90 minutes it drops back to around 13.7v.
The state of the hab batteries doesn't affect that: they're connected via a B2B charger. And it's not a smart alternator: just a fairly hefty standard one.
 

chas142

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198
That's simply not true in my experience.
I have two meters visible when driving. One shows the starter battery voltage. After a few minutes running it's up to 14+ and after about 45 to 90 minutes it drops back to around 13.7v.
The state of the hab batteries doesn't affect that: they're connected via a B2B charger. And it's not a smart alternator: just a fairly hefty standard one.
I have not seen that with a conventional alternator system, that's working correctly, that's in my 25 years of being an Auto Electrician. I used to change a lot of alternator regulators that from new charged at 13.8v. But if yours shows it and your system is ok perhaps they now manufacture with that facility, I don't think it would be of an advantage, as many special systems would do the opposite and charge at slightly high voltage, 14.5volts for 30-45 mins, then drop back to say 14.3volts, like boat systems.
 

in h

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747
This alternator is about five or six years old. If it was doing what you describe, I'd be worried about its design.
I had expected it to simply put out about 14v regardless (it's rated at 215A, significantly more than it is called on to supply). It was a pleasant surprise to find that it has multi-stage charging built in.
The one it replaced never really managed to be on top of its job, but it was only a 90A one. Allow 15A for the fridge, 40A for the b2b, 10A for lights, 5A for other electric loads, that leaves very little left over for a decent rate of starter battery charging.
 

chas142

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198
This alternator is about five or six years old. If it was doing what you describe, I'd be worried about its design.
I had expected it to simply put out about 14v regardless (it's rated at 215A, significantly more than it is called on to supply). It was a pleasant surprise to find that it has multi-stage charging built in.
The one it replaced never really managed to be on top of its job, but it was only a 90A one. Allow 15A for the fridge, 40A for the b2b, 10A for lights, 5A for other electric loads, that leaves very little left over for a decent rate of starter battery charging.
post you are replying to
Not sure what post you are replying to but it would seems that you probably have a none conventional alternator fitted, as you say was a 90A original and now 215A.
 

in h

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747
post you are replying to
Not sure what post you are replying to but it would seems that you probably have a none conventional alternator fitted, as you say was a 90A original and now 215A.
I was replying to your comment that an alternator ought to drop back to 14.3v after 15 minutes at 14.5v. That's a fault, in my opinion.
The person who I bought it off didn't seem to think that my alternator had any special "smarts" in it.
The price suggested it was a very basic one. Perhaps I just got a bargain.
 

Okta

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505
I was replying to your comment that an alternator ought to drop back to 14.3v after 15 minutes at 14.5v. That's a fault, in my opinion.
The person who I bought it off didn't seem to think that my alternator had any special "smarts" in it.
The price suggested it was a very basic one. Perhaps I just got a bargain.
Does the ECU have a role to play in voltage control?
 

wildebus

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2,869
I was replying to your comment that an alternator ought to drop back to 14.3v after 15 minutes at 14.5v. That's a fault, in my opinion.
The person who I bought it off didn't seem to think that my alternator had any special "smarts" in it.
The price suggested it was a very basic one. Perhaps I just got a bargain.
I think you did! Has he got any more? (I think I need a new alternator anyway).
 

in h

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747
I think you did! Has he got any more? (I think I need a new alternator anyway).
It was a few years ago, but I expect they're still in business. I'll need to look the details up, though.
Oh, and it wasn't an exchange, so it left me with a spare.
 

chas142

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198
I was replying to your comment that an alternator ought to drop back to 14.3v after 15 minutes at 14.5v. That's a fault, in my opinion.
The person who I bought it off didn't seem to think that my alternator had any special "smarts" in it.
The price suggested it was a very basic one. Perhaps I just got a bargain.
I am not going to respond to this post anymore as it would appear that you have not read or understood the points that I made, and you are miss quoting what I have said, there is no point in going round & round.
 

in h

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747
I am not going to respond to this post anymore as it would appear that you have not read or understood the points that I made, and you are miss quoting what I have said, there is no point in going round & round.
I did not misquote you at all.
You're just taking your bat home because I challenged something you know to be incorrect. You are quite right on one thing: there's no point in continuing this discussion with you.
 

in h

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747
A 12 v battery con not be charged to 14 volts .check after a cooling of period about 6 hours 12.7 is fully charged .
You are correct that a battery cannot be charged TO 14v, but it can be charged AT 14v. Then it needs time for the charge to sink in.
You have to let a battery rest for at least an hour or two before assessing its state of charge from its terminal voltage. Six hours is good, but a bit less time will probably be nearly as good.
Yes, I know you know that: I'm just clarifying it for others who might misread what you meant.
 

Wildstar

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12
Bear in mind that if a blocking diode pack is in use the forward drop on a diode can be as much as 1.4 volts thus reducing the applied voltage by that ammount. If split charge relay is used then the applied voltage should be the same as the starter battery up around 13 to 14 volts depending on the regulator settings.
 

Okta

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505
i dont think your aloud to run with gas on. please correct me if i am wrong .p.s. dont light my firer. ok pj
You are allowed but ONLY if you have a crash protected regulator (e.g. SecuMotion) and burst protection on the gas cylinder. You need both, one protects the low pressure supply from the regulator and the other the high pressure hose from cylinder to to regulator. Without these the bottle must be turned off when travelling.
 

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