Strange battery charge problems

[Zebster]

I believe that for the purpose of fuel efficiency the alternator only produces charge output whilst the engine is on the overrun.

[Tannaton]

Originally Posted by Zebster

I believe that for the purpose of fuel efficiency the alternator only produces charge output whilst the engine is on the overrun.

^^^^^ That (or something of that ilk)

With the battery at 100% charge, the system will likely not apply a normal charging output until the SOC drops to say 80% or something.

[Zebster]

Originally Posted by Tannaton

^^^^^ That (or something of that ilk)

With the battery at 100% charge, the system will likely not apply a normal charging output until the SOC drops to say 80% or something.

Good point, the alternator will not provide charge if the battery is already over 80/85% charged. VIDA or even cheap diagnostics (ELM327 with Car Scanner app) will show this percentage.

[cheshired5]

Originally Posted by Zebster

I believe that for the purpose of fuel efficiency the alternator only produces charge output whilst the engine is on the overrun.

Originally Posted by Tannaton

^^^^^ That (or something of that ilk)

With the battery at 100% charge, the system will likely not apply a normal charging output until the SOC drops to say 80% or something.

Originally Posted by Zebster

Good point, the alternator will not provide charge if the battery is already over 80/85% charged. VIDA or even cheap diagnostics (ELM327 with Car Scanner app) will show this percentage.

Got round to checking Vida and there is nothing relating to a high battery state of charge stopping alternator output so where exactly is this information coming from?

A depleted battery or cold conditions would result in a higher alternator output voltage once out and about but that's standard on pretty much every car charging system.

From the Design and Function section which I recommended should be checked, there can be little to no alternator output following starting of the engine and on occasions where the engine is idling but at higher RPM, there's nothing to suggest that alternator output will be anything other than what you'd expect to see on any charging system i.e. above 13.5v
Nothing about no alternator output if the battery is charged above any percentage let alone the very specific percentages you've mentioned.
Nothing about only charging on the overrun.

Maybe on the occasions where OP was receiving battery voltage only, it was because the engine was idling in which case this is in line with how the system is designed to work.

The battery's condition is irrelevant as far as I can see but I'm always happy to be corrected and learn more.

Perhaps the OP could observe voltages at various engine speeds and electrical loads and on a drive to fully describe the system voltage behaviour.

[Zebster]

Originally Posted by cheshired5

Got round to checking Vida and there is nothing relating to a high battery state of charge stopping alternator output so where exactly is this information coming from?...

If it was easy to do so I'd find the relevant forum thread and post a link to the specific post where a former Volvo technician gave this information. So for now it's from my memory.

[cheshired5]

Originally Posted by Zebster

a former Volvo technician gave this information.

Regardless of source, I have to say that it made no sense hence why I looked a little deeper into the system design.
Fortunately OP has a good battery at effectively full SOC so hopefully he can report back live voltage data particularly out on the road.

If system voltage is regularly >13.5 whilst driving (as Vida suggests it should), the no alternator output theory would only appear to exist in the ether.

[Tannaton]

Originally Posted by cheshired5

Got round to checking Vida and there is nothing relating to a high battery state of charge stopping alternator output so where exactly is this information coming from?

A depleted battery or cold conditions would result in a higher alternator output voltage once out and about but that's standard on pretty much every car charging system.

From the Design and Function section which I recommended should be checked, there can be little to no alternator output following starting of the engine and on occasions where the engine is idling but at higher RPM, there's nothing to suggest that alternator output will be anything other than what you'd expect to see on any charging system i.e. above 13.5v
Nothing about no alternator output if the battery is charged above any percentage let alone the very specific percentages you've mentioned.
Nothing about only charging on the overrun.

Maybe on the occasions where OP was receiving battery voltage only, it was because the engine was idling in which case this is in line with how the system is designed to work.

The battery's condition is irrelevant as far as I can see but I'm always happy to be corrected and learn more.

Perhaps the OP could observe voltages at various engine speeds and electrical loads and on a drive to fully describe the system voltage behaviour.

I get VIDA is a good source (the best source) but which car, model, year are you looking this up on?

Power management systems have developed significantly in the past 10-15 years. With the suggestion of the alternator increasing its output when the engine is on overrun this may not be documented in VIDA but it is a key part of Volvo's Driv-E technology and VW's Bluemotion system. Logic says therefore that there is a threshold above which the battery will only be charged when the engine is on overrun, but below which the battery will be charged normally to prevent it becoming too discharged to operate start/stop etc. I can't recall where I read 80% as the SOC threshold (which is why I caveat'd it) but the general principle is documented in this Volvo press release:

https://www.media.volvocars.com/glob...releases/18752

It's the sort of thing that could easily change as a result of a software update during a service.

Its for the reasons above that whenever I buy a new battery for a modern car now, I always trickle charge it on the bench for circa 24 hours before fitting it as it is never likely to reach a 100% SOC in the car - and then a few weeks later (if I remember) I do the same with it connected in the car.

[cheshired5]

Originally Posted by Tannaton

I get VIDA is a good source (the best source) but which car, model, year are you looking this up on?

Well we're in the V60 section so I viewed the V60 charging system across 5 years from 2011-2015.
D5244Txx variants.

It wouldn't make sense for me to research any other.

Can you please quote the section of the press release you linked to which is relevant to this discussion?
I can't see anything relevant.

[Tannaton]

Originally Posted by cheshired5

Can you please quote the section of the press release you linked to which is relevant to this discussion?
I can't see anything relevant.

If you search the page for "alternator" or "regenerative braking" you will find it.