Low battery voltage and spurious messages

[culzean]

Just looked at average hours of sunshine in UK during December

South of England - 60 hours per month
Manchester - 50 per month
Orkney - 25 hours per month

So less than 1 hour per day in Orkney,  I know the solar maintainers can work in overcast conditions, but their output is reduced.

[jazzaro]

The bottom line is that car manufacturers should be building a solar panel into their vehicles to automatially do some trickle charging. The cost would be minimal.

1) this would be useful only for car parked outside, not in a box.
2) A big european manufacturer fits rear parking camera in some its cars, hardware and software are provided by Continental. The manufacturer preferred the low cost version with fixed lines because the  cost is about 0,15€ less than the standard version, WITH curving lines like our Hondas. This to say that our idea of minimal cost is deeply different from what manufacturers think about the same word..

[culzean]

Jazzaro you are right on the priorities of car maker accountants.  we see a cost of £1 per car,  they see the cost as £1,000,000 per million cars made - and the car market is very competitive with the cost of making cars to obey new laws and regulations always going upwards and the customer wanting cheaper cars and always pushing for discounts - add to that the massive cost of potential recalls these days.  The present situation with lockdown is very unusual,  and car makers will simply not fit special equipment to allow for cars standing for weeks.

[Jocko]

In Arthur Hailey's book, "Wheels", written in 1971, they talk about removing a strengthening crease in a panel because that would save them $0.01 per vehicle. Over the cost of a long model run, using that panel on a number of different variants, that alone saved them $100,000.

Bit long in the tooth now, but it is a book worth reading if you are into cars and how they are manufactured. A ripping yarn which I believe ended up as a TV series.

[John Ratsey]

To be fair to car manufacturers, they do build generators into their cars, and they probably expect that anyone who buys a car will actually drive it (why else would you buy one?). The pandemic lockdown is a bit of an unusual situation, so is it reasonable to expect specific design features to cater for that?

The underlying problem is that some of the electronics are insufficiently tolerant of the voltage range that the 12V battery can provide over the whole range of the usage conditions. If there's enough power in the battery to get the engine started without any hesitation then the electronics should be happy. It seems not. The trend to shrink 12V batteries to reduce weight (and cost) can't help.

[plasma]

You can get this one for Scotland in the winter.

!0/10.

Plasma.

[Jocko]

The underlying problem is that some of the electronics are insufficiently tolerant of the voltage range that the 12V battery can provide over the whole range of the usage conditions. If there's enough power in the battery to get the engine started without any hesitation, then the electronics should be happy. It seems not. The trend to shrink 12V batteries to reduce weight (and cost) can't help.

The sophisticated electronics in a modern motor vehicle run on a regulated low voltage, easily achievable with even a battery on a low state of charge. There is obviously software that looks at the battery voltage and tells the ECU that the battery is low and so inhibits devices from working. You can understand this with Stop/Start where the last thing you want is the engine to switch off at a busy junction, then not have enough left in the battery to restart!

[orcadian]

The underlying problem is that some of the electronics are insufficiently tolerant of the voltage range that the 12V battery can provide over the whole range of the usage conditions. If there's enough power in the battery to get the engine started without any hesitation then the electronics should be happy. It seems not. The trend to shrink 12V batteries to reduce weight (and cost) can't help.
[/quote]


Well done John!
Almost all of the other replies are missing the point entirely and merely offering home grown solutions to a problem created (perhaps unintentionally) by the manufacturers.

I don't have a 'flat' battery on the Jazz - it starts the car every time I need it to. I just don't want misleading information - there is enough of that from Westminster!

If the battery on my 4 litre supercharged quad cam V8 Daimler is man enough to start the car, then please don't bother me with spurious messages telling me I have a (transient) traction control fault.

Ian

[John Ratsey]

There is obviously software that looks at the battery voltage and tells the ECU that the battery is low and so inhibits devices from working. You can understand this with Stop/Start where the last thing you want is the engine to switch off at a busy junction, then not have enough left in the battery to restart!

I've had enough of the temperamental stop-start (that's one reason I'm getting a vehicle with a big battery under the boot floor) but there's a big difference between the battery charge being insufficiently charged for the stop-start to be happy and being low enough that it should affect the other electronics. It's not as if the engine is struggling to start.

[culzean]

As a battery ages the internal resistance gets higher,  it is an inevitable part of the battery chemistry aging process,  this means that a new battery may drop say 3 volts 'inside the battery' when supplying the 200+ amps to start engine,  so 9.5 volts at terminals - move on a few years and the battery may drop 4 or 5 volts 'inside' to supply same current, now there is only 8.5 or 7.5 volts available at terminals ( which is what the rest of electrical system 'sees' ) - there will be extra voltage drops before that current gets to starter motor due to resistance of cable connections and the moving contacts in the starter solenoid.  The increase in internal resistance also limits the rate that a battery can absorb power from alternator.

The battery can still supply enough current to start the car,  but the terminal voltage gets lower while it is doing it.

This is the reason that a battery never stays on one of our cars or motorbikes for over 5 years...

[Stanski]

As a battery ages the internal resistance gets higher,  it is an inevitable part of the battery chemistry aging process,  this means that a new battery may drop say 3 volts 'inside the battery' when supplying the 200+ amps to start engine,  so 9.5 volts at terminals - move on a few years and the battery may drop 4 or 5 volts 'inside' to supply same current, now there is only 8.5 or 7.5 volts available at terminals ( which is what the rest of electrical system 'sees' ) - there will be extra voltage drops before that current gets to starter motor due to resistance of cable connections and the moving contacts in the starter solenoid.  The increase in internal resistance also limits the rate that a battery can absorb power from alternator.

The battery can still supply enough current to start the car,  but the terminal voltage gets lower while it is doing it.

This is the reason that a battery never stays on one of our cars or motorbikes for over 5 years...

A very good comment that many "Experts" should note before chipping in with foolish suggestions.  I use the technique of measuring load voltage when battery is stressed, as well as terminal voltage after charging to assess battery condition.
have just helped a local farmer with his tractor and found two batteries showing good voltage levels but cannot take a  sensible charge and not offer adequate starting current - both are over 7 yrs old, so had to replace with new.