In view of recent discussions here, as I drove my motorhome back from a
short trip today I thought it might be worth reporting the behaviour of
the batteries and chargers, so I made notes.

There are five electrical circuits.
1. The vehicle electrics (V), which are 24V. The only connection with
the other circuits is that when the engine has been running for 45
seconds Aux A is connected and is charged, and the same thing after 75
seconds for Aux B.
2. Aux A is a 24V circuit. It has a 110Ah pair of batteries and can
supply anything in the van except vehicle stuff. It is charged by the
alternator when travelling or from the mains via a 20A 'intelligent'
charger.
3. Aux B is a 24V circuit. It has a 110Ah pair of batteries and can
supply anything in the van except vehicle stuff.
4. Aux C is a 12V circuit. It has an 80Ah battery and supplies all the
12V items. Charging is from a 24/12 converter that can run from Aux A or B.
5. Mains. Powered from an inverter, or automatically from external mains
if available. Heavy loads (heaters) can only be powered from external mains.

When parked the van is normally on mains. After a few days the ammeters
and voltmeters will read roughly as follows:
V: 24.4V, -0.01A
A: 27.8V, +0.15A
B: 28.1V, +0.30A
C: 14.6V, +0.03A

Travelling from home following the above state, after five minutes running:
V: 26.4V, +5.00A
A: 26.6V, +0.00A
B: 26.3V, +0.00A
C: 14.6V, +0.03A

Travelling from two nights' non-mains camping, after five minutes running:
V: 26.4V, +3.00A
A: 26.6V, +13.00A
B: 26.3V, +18.00A
C: 14.6V, +8.00A

Travelling from two nights' non-mains camping, arriving home after an
hour's running:
V: 26.4V, +2.00A
A: 26.6V, +4.00A
B: 26.3V, +4.00A
C: 14.6V, +3.00A

Back home and on mains, after two or three minutes.
V: 25.8V, -0.01A
A: 28.2V, +13.00A
B: 28.3V, +18.00A
C: 14.6V, +8.00A

Back home and on mains, after a week.
V: 25.0V, -0.01A
A: 28.2V, +0.20A
B: 28.3V, +0.15A
C: 14.6V, +0.01A

So this shows that the vehicle is set up to charge the batteries quite
slowly, and up to a certain state of charge. This seems to me to be
normal for alternator charging. Charging from the chargers, even after a
period charging from the alternator, is faster and to a higher voltage.
What appears to be leakage from the vehicle battery is just meter error
I think.

Bill

Surely though there is always some drain from the vehicle battery due to all
its electronics running. So that small drain may not be an error.
It must have quite a complex switching set up, probably with some logic
built in in any case and it would be interesting to know which circuit it
uses to keep this running.

Brian

--

This newsgroup posting comes to you directly from...
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Note this Signature is meaningless.!
"williamwright" wrote in message
...
In view of recent discussions here, as I drove my motorhome back from a
short trip today I thought it might be worth reporting the behaviour of
the batteries and chargers, so I made notes.

There are five electrical circuits.
1. The vehicle electrics (V), which are 24V. The only connection with the
other circuits is that when the engine has been running for 45 seconds Aux
A is connected and is charged, and the same thing after 75 seconds for Aux
B.
2. Aux A is a 24V circuit. It has a 110Ah pair of batteries and can supply
anything in the van except vehicle stuff. It is charged by the alternator
when travelling or from the mains via a 20A 'intelligent' charger.
3. Aux B is a 24V circuit. It has a 110Ah pair of batteries and can supply
anything in the van except vehicle stuff.
4. Aux C is a 12V circuit. It has an 80Ah battery and supplies all the 12V
items. Charging is from a 24/12 converter that can run from Aux A or B.
5. Mains. Powered from an inverter, or automatically from external mains
if available. Heavy loads (heaters) can only be powered from external
mains.

When parked the van is normally on mains. After a few days the ammeters
and voltmeters will read roughly as follows:
V: 24.4V, -0.01A
A: 27.8V, +0.15A
B: 28.1V, +0.30A
C: 14.6V, +0.03A

Travelling from home following the above state, after five minutes
running:
V: 26.4V, +5.00A
A: 26.6V, +0.00A
B: 26.3V, +0.00A
C: 14.6V, +0.03A

Travelling from two nights' non-mains camping, after five minutes running:
V: 26.4V, +3.00A
A: 26.6V, +13.00A
B: 26.3V, +18.00A
C: 14.6V, +8.00A

Travelling from two nights' non-mains camping, arriving home after an
hour's running:
V: 26.4V, +2.00A
A: 26.6V, +4.00A
B: 26.3V, +4.00A
C: 14.6V, +3.00A

Back home and on mains, after two or three minutes.
V: 25.8V, -0.01A
A: 28.2V, +13.00A
B: 28.3V, +18.00A
C: 14.6V, +8.00A

Back home and on mains, after a week.
V: 25.0V, -0.01A
A: 28.2V, +0.20A
B: 28.3V, +0.15A
C: 14.6V, +0.01A

So this shows that the vehicle is set up to charge the batteries quite
slowly, and up to a certain state of charge. This seems to me to be normal
for alternator charging. Charging from the chargers, even after a period
charging from the alternator, is faster and to a higher voltage. What
appears to be leakage from the vehicle battery is just meter error I
think.

Bill

williamwright formulated on Sunday :
What appears to be leakage from the vehicle battery is just meter error I
think.

If it is a modern vehicle, it will have various circuits which need
some small amount of power to maintain its systems. My cars various
computer systems, once fully into sleep mode, draw around 20mA. Even
that 20mA pulse higher, when the alarm system has a 'quick look
around'. Only older cars had no discharge at all, when parked, unless
they had alarm systems.

On 26/04/2021 08:59, Harry Bloomfield wrote:
williamwright formulated on Sunday :
What appears to be leakage from the vehicle battery is just meter
error I think.

If it is a modern vehicle, it will have various circuits which need some
small amount of power to maintain its systems. My cars various computer
systems, once fully into sleep mode, draw around 20mA. Even that 20mA
pulse higher, when the alarm system has a 'quick look around'. Only
older cars had no discharge at all, when parked, unless they had alarm
systems.

I could leave my 1998 Astra F estate (petrol), with a factory
immobiliser (that shoed a slow blinking red led on the dash)
for 7 weeks and it would start without an issue.

My current Astra H (59 reg) handbook says disconnect battery
if vehicle is to be lft for more than 3 weeks unused. Seems
a bit OTT to me.

On 26/04/2021 08:34, Brian Gaff (Sofa) wrote:
Surely though there is always some drain from the vehicle battery due to all
its electronics running.

It's thirty years old! Electronics wasn't invented!

So that small drain may not be an error.
It must have quite a complex switching set up, probably with some logic
built in in any case and it would be interesting to know which circuit it
uses to keep this running.

The only thing is, the 12V circuit powers the LEDs that light the
ammeters and voltmeters.

Bill

In article ,
williamwright wrote:
When parked the van is normally on mains. After a few days the ammeters
and voltmeters will read roughly as follows:
V: 24.4V, -0.01A
A: 27.8V, +0.15A
B: 28.1V, +0.30A
C: 14.6V, +0.03A

IMHO. 14.6v is far too high a voltage to float a 12v battery at. But if
this was accurate, I'd expect more than 30mA to be flowing.

I have a checked and accurate volt meter sitting across the battery on the
old Rover. After a cold start the modern 100 amp alternator will read
14.6v, but quite quickly reduces that voltage. It stabilises at 13.8v
after some time.

FWIW, I found connecting that voltmeter to a more convenient part of the
wiring harness gave a very different reading to that across the battery.
So ran new and separate cabling (positive and ground) just to it direct
from the battery. With a relay to isolate it when the engine is stopped.

--
*When you've seen one shopping centre you've seen a mall*

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote:
In article ,
williamwright wrote:
When parked the van is normally on mains. After a few days the ammeters
and voltmeters will read roughly as follows:
V: 24.4V, -0.01A
A: 27.8V, +0.15A
B: 28.1V, +0.30A
C: 14.6V, +0.03A

IMHO. 14.6v is far too high a voltage to float a 12v battery at. But if
this was accurate, I'd expect more than 30mA to be flowing.

I have a checked and accurate volt meter sitting across the battery on the
old Rover. After a cold start the modern 100 amp alternator will read
14.6v, but quite quickly reduces that voltage. It stabilises at 13.8v
after some time.

I agree, somewhere around 14.5v is the terminal (as in final) voltage
to fully charge a nominal 12v lead acid battery. The charger should
then drop back to something like 13.5v, 'float' voltage, to maintain
the battery.

The exact voltages will vary with temperature and the exact type of
battery.

--
Chris Green
·

In article , williamwright
wrote:
On 26/04/2021 08:34, Brian Gaff (Sofa) wrote:
Surely though there is always some drain from the vehicle battery due
to all its electronics running.

It's thirty years old! Electronics wasn't invented!

some was - otherwise you wouldn't have been able to watch the telly

So that small drain may not be an error. It must have quite a complex
switching set up, probably with some logic built in in any case and it
would be interesting to know which circuit it uses to keep this running.

The only thing is, the 12V circuit powers the LEDs that light the
ammeters and voltmeters.

Bill

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On 26/04/2021 17:47, charles wrote:
It's thirty years old! Electronics wasn't invented!
some was - otherwise you wouldn't have been able to watch the telly

It was a joke!

Bill

On 26/04/2021 15:43, Dave Plowman (News) wrote:
IMHO. 14.6v is far too high a voltage to float a 12v battery at. But if
this was accurate, I'd expect more than 30mA to be flowing.

The voltage readings come direct from the battery, rather than from a
point on the general circuit. I think that voltmeter might be reading a
bit high actually. They all read very high in winter when the van isn't
in use. I put this down to damp across the the very high value resistors
in the PD networks. So that might still be a factor.

Incidentally a late addition was a relay that links the two 24V supplies
when the 24V microwave oven is in use. This was to reduce the discharge
rate from the circuit A pair of batteries. The micro is connected
directly to Battery A because its current draw far exceeds what the
ammeters could cope with. So when the micro is in use Battery A shows a
charge of about 10A and Battery B shows a corresponding discharge. It's
interesting that the wiring and relay resistance of the link means that
Battery B only contributes 10A whilst Battery A (very thick short wires
direct to the micro) contributes 30A. I didn't think it was worthwhile
to improve this because it would mean moving Batteries B from the back
of the van to the middle.

Bill

On 26/04/2021 16:33, Chris Green wrote:
I agree, somewhere around 14.5v is the terminal (as in final) voltage
to fully charge a nominal 12v lead acid battery. The charger should
then drop back to something like 13.5v, 'float' voltage, to maintain
the battery.

The exact voltages will vary with temperature and the exact type of
battery.

Yes, I think I'll check the voltage with an accurate meter tomorrow. It
does seem high. Of course it's the output from a 24/12V converter. Oddly
it takes a long time to charge the battery, always has done, and does
now with a new battery.

Andrew was thinking very hard :
I could leave my 1998 Astra F estate (petrol), with a factory
immobiliser (that shoed a slow blinking red led on the dash)
for 7 weeks and it would start without an issue.

My current Astra H (59 reg) handbook says disconnect battery
if vehicle is to be lft for more than 3 weeks unused. Seems
a bit OTT to me.

Modern cars have much more electronics systems which all draw some
current when off, much more regular use is made of cars these days, so
not usually a problem.

I don't make such use of my car, so it sits in my garage whilst unused
and I have it plugged into a charger. The charger comes on for 20
minute each day, timed by a Smart Plug, just to keep it near a full
charge.

On Tue, 27 Apr 2021 05:12:15 +0100, Harry Bloomfield, Esq.
wrote:

snip

I don't make such use of my car, so it sits in my garage whilst unused
and I have it plugged into a charger. The charger comes on for 20
minute each day, timed by a Smart Plug, just to keep it near a full
charge.

I'm not sure that's the best plan, especially if it's a reasonable
current / smart charger.

Like many battery chemistries, lead acid batteries don't like being
stored at full charge (the acid is at it's strongest and so most
corrosive) and if the battery isn't losing much charge between
charges, you may be constantly 'topping off' the charge, again, not a
good idea.

So, if the battery can still easily start the car after being idle for
say 4 weeks, maybe either:

Leave the charger (if 'smart') on 24/7. 'It' will get the battery to
full charge and then just sit in 'maintenance mode', monitoring the
voltage and only applying a small charge current in pulses when
required.

or

If not a smart charger, only have it come on for say 1 day in 10,
giving it a chance to fully charge the battery but not keep doing so
daily.

The bottom line, you really only want to protect the battery from
going flat (damaging the battery) but whilst being able to start the
car when required, even at short notice.

When you dis/re-connect a smart charger it *may* go though a full
charging cycle, including some time on the bulk phase.

I am about to make an 8 way charger multiplexor (managed by my home
automation system) that allows me to switch a relatively expensive
smart charger between up to 8 LA batteries, once a month, spending a
day on each.

Cheers, T i m

In article ,
williamwright wrote:
On 26/04/2021 08:34, Brian Gaff (Sofa) wrote:
Surely though there is always some drain from the vehicle battery due to all
its electronics running.

It's thirty years old! Electronics wasn't invented!

Didn't realise you were that young, Bill. What did you put up aerials for
then? ;-)

--
*If PROGRESS is for advancement, what does that make CONGRESS mean?

Dave Plowman London SW
To e-mail, change noise into sound.

On 26/04/2021 23:11, williamwright wrote:
On 26/04/2021 17:47, charles wrote:

It's thirty years old! Electronics wasn't invented!
some was - otherwise you wouldn't have been able to watch the telly

It was a joke!

Actually, before about 1980, it might as well have been true as the only
electronics that most cars had was the radio. I suppose manufacturers
were worried about vibration, damp and temperature changes. I think
electronic ignition was about the first to come in.

--
Max Demian

On Tue, 27 Apr 2021 12:08:59 +0100, Max Demian wrote:

On 26/04/2021 23:11, williamwright wrote:
On 26/04/2021 17:47, charles wrote:

It's thirty years old! Electronics wasn't invented!
some was - otherwise you wouldn't have been able to watch the telly

It was a joke!

Actually, before about 1980, it might as well have been true as the only
electronics that most cars had was the radio. I suppose manufacturers
were worried about vibration, damp and temperature changes. I think
electronic ignition was about the first to come in.

I remember the good old Lucas [1] 'cutout' device for controlling the
charging 'system'.

[1] Lucas, Prince of Darkness.



--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

In article ,
Max Demian wrote:
On 26/04/2021 23:11, williamwright wrote:
On 26/04/2021 17:47, charles wrote:

It's thirty years old! Electronics wasn't invented!
some was - otherwise you wouldn't have been able to watch the telly

It was a joke!

Actually, before about 1980, it might as well have been true as the only
electronics that most cars had was the radio. I suppose manufacturers
were worried about vibration, damp and temperature changes. I think
electronic ignition was about the first to come in.

Not really. Alternators became the norm when power transistors became
affordable. Over a decade earlier than 1980. And electronic ignition. Of
course such things started first on more expensive cars and spread
downwards.

Car mechanics have had many many years to come to terms with things going
electronic rather than mechanical, but most have chosen not to learn about
them.

--
*He who laughs last has just realised the joke.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
williamwright wrote:
On 26/04/2021 16:33, Chris Green wrote:
I agree, somewhere around 14.5v is the terminal (as in final) voltage
to fully charge a nominal 12v lead acid battery. The charger should
then drop back to something like 13.5v, 'float' voltage, to maintain
the battery.

The exact voltages will vary with temperature and the exact type of
battery.

Yes, I think I'll check the voltage with an accurate meter tomorrow. It
does seem high. Of course it's the output from a 24/12V converter. Oddly
it takes a long time to charge the battery, always has done, and does
now with a new battery.

I've just had the old Rover battery on charge using the Lidl charger I
built into it. It's the smart one which will pulse charge a very low
battery, then charge at a constant current, and change to float when full.
So took the opportunity to remind me of that float voltage. Said to be OK
to leave on indefinitely. Near exactly 13v.

--
*I didn't say it was your fault, I said I was blaming you.

Dave Plowman London SW
To e-mail, change noise into sound.

In article , Roger Hayter
wrote:
On 27 Apr 2021 at 10:51:14 BST, ""Dave Plowman" News)"
wrote:

In article , Roger Hayter
wrote:
On 26 Apr 2021 at 11:11:29 BST, ""Dave Plowman" News)"
wrote:

In article , alan_m
wrote:
I once had disks and pads replaced by a local garage and years
later when replacing the pads myself found that the low pad wires
had not been connected - they had been neatly coiled up and cable
tied safely out of the way.

Most brake pad warning systems show an error if the sensors aren't
connected.

That may be true of more sophisticated cars but the two Fords I had
about 10 and fifteen years ago simply had a single wire that was
open circuit until the pad contact wore down to short it to earth.
So they had no idea whether they were connected.

The connector between the sensor and the loom usually has a link in
it. No sensor connected, no circuit. It's like that on my ancient
Rover. Most modern ones have a loop as a sensor.

The Ford ones didn't. It was a one pin connector. And the pads were
normally o/c. No resistor or anything, apart from the pads not having a
reliable earth path anyway.

OK. Poor design if it doesn't give you a warning things ain't right,
though.

--
*The average person falls asleep in seven minutes *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Dave Plowman (News) wrote:
In article ,
Max Demian wrote:
On 26/04/2021 23:11, williamwright wrote:
On 26/04/2021 17:47, charles wrote:

It's thirty years old! Electronics wasn't invented!
some was - otherwise you wouldn't have been able to watch the telly

It was a joke!

Actually, before about 1980, it might as well have been true as the only
electronics that most cars had was the radio. I suppose manufacturers
were worried about vibration, damp and temperature changes. I think
electronic ignition was about the first to come in.

Not really. Alternators became the norm when power transistors became
affordable. Over a decade earlier than 1980. And electronic ignition. Of
course such things started first on more expensive cars and spread
downwards.

I added an alternator to my Anglia in latish 60s. the load broke the take
off pulley on the crankshaft. I managed to get a solid one, for the Lotus
Cortina - I think

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On 27/04/2021 11:00, Dave Plowman (News) wrote:
In article ,
williamwright wrote:
On 26/04/2021 08:34, Brian Gaff (Sofa) wrote:
Surely though there is always some drain from the vehicle battery due to all
its electronics running.

It's thirty years old! Electronics wasn't invented!

Didn't realise you were that young, Bill. What did you put up aerials for
then? ;-)

Do you mean prices?
An Antiference X15/9K BBC and ITV aerial £9 10s. If they had a BBC2
aerial at the same time it added £4.10s.

Bill