Battery voltage query - Page 2

Bolin · 6th May 2013, 19:39

Yes, the 0.32v drop due to the door open/interior lamp/BCU/satnav/ignition aux/use of OBD does seem to be a bit much.

I am in the habit of just starting the engine just to check the fan each week as I usually do my weekly checks on a saturday morning when fluids and pressures are cold - I should check it when getting back home at the same time I check the oil level. This would be better and I'll try to do this from now on.

The one mile trip is weekly, unless the wheather is very nice - this is not something that I can change sadly.

Quote:

Originally Posted by SD1too

Iyou're original complaint is that your engine "takes a moment" to start. Can you define this in terms of seconds of cranking? And has this battery been on the car throughout the winter months? If so, did it fail to turn over the engine when the ambient temperature was close to freezing?

The car does take a few seconds, perhaps up to three? (which doesn't sound long, but try it on a stopwatch and think of cranking time) rather than an 'instant' start. However, I read a thread where other V6 owners were saying similar things so I don't think that's really a problem. My complaint is really the fact that T4 was complaining, si something didn't seem right.

The battery was on the car all winter and never gave any trouble so I'm not expecting imminent failure

bl52krz · 18th May 2013, 20:39

Either your battery is duff,or your alternator has given up the ghost. If it is only charging at the low figure, if it is charging,then i would suggest alternator.

Bolin · 18th May 2013, 23:12

So you think that 14.22v across the terminals when idling from cold isn't good enough?

smudger252 · 20th May 2013, 19:01

Quote:

Originally Posted by Bolin

So you think that 14.22v across the terminals when idling from cold isn't good enough?

Id be looking at a tired battery first, Do you know anyone with a discharge tester so you can get an idea of amps as low amps not volts will make your car difficult to start

Bolin · 6th May 2014, 16:30

OK, an update.

Old battery died last October, so I fitted a Varta silver dynamic, 5 years guarantee model. Car has had no problems starting since replacing (the old one died such that I needed to charge the battery just to get the car started. It even went to MOT less than half a mile away, and after being parked following the test I couldn't start it to drive home!).

However, I have noticed that the message centre dims during cranking (the large display).

I thought I'd try taking some measurements. This is with a freshly fully-charged battery.

Everything off (inc satnav comp. off), bonnet, driver's door and boot open - 12.55 measured by multimeter, going up 0.01 every 15 seconds.

Everything off, bonnet, driver's door and boot open, ignition pos. I - 11.9 occasionally flickering to 12.0 measured by OBD & 12.30 measured by multimeter.

Everything off, bonnet, driver's door and boot open, ignition pos. II - 11.8 constantly flickering to 11.9 measured by OBD & 12.17 measured by multimeter.

Everything off, bonnet, driver's door and boot open, engine cranking - lowest recorded voltage 10.1 measured by OBD.

Everything off, bonnet, driver's door and boot open, engine idling - 13.9 constantly flickering to 14.0, occasionally flickering to 13.8 measured by OBD & 14.37 slowly flickering up to 14.39 and back measured by multimeter.

Lots and lots of electrical equipment on, engine idling - lowest recorded voltage 11.3 but constantly flickering, generally mid-high 11 volts, measured by OBD & without windows or blind in use but otherwise same electrical equipment on, 11.94 average, flickering in the low-mid 11.9 volts (same when checked 2-3 minutes later too).

This may be too low according to Haynes, but they suggest using higher revs until the multimeter reading is stable. I found the reading became stable at 14.41v, but that was under the bonnet pulling the throttle cable so I don't know what the revs were.

So, is there a better way of checking the alternator output? Haynes says not to flash the alternator output lead to earth.

Also, the flickering of the OBD figures compared to the figures of the multimeter looks odd, as the OBD is a lower resolution and yet the multimeter doesn't fluctuate as much

Any thoughts on my figures or things to check next greatly appreciated

Thanks, Bolin

klarzy · 6th May 2014, 16:37

Quote:

Originally Posted by Bolin

OK, an update.

Old battery died last October, so I fitted a Varta silver dynamic, 5 years guarantee model. Car has had no problems starting since replacing (the old one died such that I needed to charge the battery just to get the car started. It even went to MOT less than half a mile away, and after being parked following the test I couldn't start it to drive home!).

However, I have noticed that the message centre dims during cranking (the large display).

I thought I'd try taking some measurements. This is with a freshly fully-charged battery.

Everything off (inc satnav comp. off), bonnet, driver's door and boot open - 12.55 measured by multimeter, going up 0.01 every 15 seconds.

Everything off, bonnet, driver's door and boot open, ignition pos. I - 11.9 occasionally flickering to 12.0 measured by OBD & 12.30 measured by multimeter.

Everything off, bonnet, driver's door and boot open, ignition pos. II - 11.8 constantly flickering to 11.9 measured by OBD & 12.17 measured by multimeter.

Everything off, bonnet, driver's door and boot open, engine cranking - lowest recorded voltage 10.1 measured by OBD.

Everything off, bonnet, driver's door and boot open, engine idling - 13.9 constantly flickering to 14.0, occasionally flickering to 13.8 measured by OBD & 14.37 slowly flickering up to 14.39 and back measured by multimeter.

Lots and lots of electrical equipment on, engine idling - lowest recorded voltage 11.3 but constantly flickering, generally mid-high 11 volts, measured by OBD & without windows or blind in use but otherwise same electrical equipment on, 11.94 average, flickering in the low-mid 11.9 volts (same when checked 2-3 minutes later too).

This is too low according to Haynes.

So, is there a better way of checking the alternator output? Haynes says not to flash the alternator output lead to earth.

Also, the flickering of the OBD figures compared to the figures of the multimeter looks odd, as the OBD is a lower resolution and yet the multimeter doesn't fluctuate as much

Any thoughts on my figures or things to check next greatly appreciated

Thanks, Bolin

and the output with everything on at 2000 rpm?

Bolin · 6th May 2014, 16:49

I'll have to wait until I have an assistant available who is able to hold it at 2,000rpm

klarzy · 6th May 2014, 16:49

Quote:

Originally Posted by Bolin

I'll have to wait until I have an assistant available who is able to hold it at 2,000rpm

I have such an assistant.... his name is "brick"

Polly · 6th May 2014, 20:01

When measuring voltages to decimal point, the internal resistance of the measuring device may be affecting your readings, also the quality of the connection may be affecting your readings.
Put simply, with engine running at a little more than a fast tickover, if you have more than about 13.5v with lights, hazard lights, heater etc on, then your alternator is working. Looking for voltages above that might be affected by the quality of the instrument you are using, or even the temperature.

chrissyboy · 7th May 2014, 06:57

your readings are spot on ,theres nothing wrong with them.heres something to put your mind at rest ,also dont forget when a car is hooked up to any reader it will take some juice from battery ,your slow starting is proberly as with my focus ,a lazy starter

http://www.aa1car.com/library/2003/us20310.htm

http://www.aa1car.com/library/charging_checks.htm

18th May 2013, 20:39	#12
bl52krz This is my second home Rover 75 cdt club + Rover 2.5 KV6 Conni SE Join Date: May 2008 Location: Birmingham Posts: 11,396 Thanks: 6,587 Thanked 2,262 Times in 1,729 Posts	Either your battery is duff,or your alternator has given up the ghost. If it is only charging at the low figure, if it is charging,then i would suggest alternator. __________________ Great Barr, Birmingham.

6th May 2014, 16:30	#15
Bolin This is my second home Rover 75 2.5 V6 Connoisseur SE 4dr manual Wedgewood Blue 2 04-05/06/2001 Join Date: Nov 2006 Location: N.E. Hampshire Posts: 4,617 Thanks: 289 Thanked 308 Times in 243 Posts	OK, an update. Old battery died last October, so I fitted a Varta silver dynamic, 5 years guarantee model. Car has had no problems starting since replacing (the old one died such that I needed to charge the battery just to get the car started. It even went to MOT less than half a mile away, and after being parked following the test I couldn't start it to drive home!). However, I have noticed that the message centre dims during cranking (the large display). I thought I'd try taking some measurements. This is with a freshly fully-charged battery. Everything off (inc satnav comp. off), bonnet, driver's door and boot open - 12.55 measured by multimeter, going up 0.01 every 15 seconds. Everything off, bonnet, driver's door and boot open, ignition pos. I - 11.9 occasionally flickering to 12.0 measured by OBD & 12.30 measured by multimeter. Everything off, bonnet, driver's door and boot open, ignition pos. II - 11.8 constantly flickering to 11.9 measured by OBD & 12.17 measured by multimeter. Everything off, bonnet, driver's door and boot open, engine cranking - lowest recorded voltage 10.1 measured by OBD. Everything off, bonnet, driver's door and boot open, engine idling - 13.9 constantly flickering to 14.0, occasionally flickering to 13.8 measured by OBD & 14.37 slowly flickering up to 14.39 and back measured by multimeter. Lots and lots of electrical equipment on, engine idling - lowest recorded voltage 11.3 but constantly flickering, generally mid-high 11 volts, measured by OBD & without windows or blind in use but otherwise same electrical equipment on, 11.94 average, flickering in the low-mid 11.9 volts (same when checked 2-3 minutes later too). This may be too low according to Haynes, but they suggest using higher revs until the multimeter reading is stable. I found the reading became stable at 14.41v, but that was under the bonnet pulling the throttle cable so I don't know what the revs were. So, is there a better way of checking the alternator output? Haynes says not to flash the alternator output lead to earth. Also, the flickering of the OBD figures compared to the figures of the multimeter looks odd, as the OBD is a lower resolution and yet the multimeter doesn't fluctuate as much Any thoughts on my figures or things to check next greatly appreciated Thanks, Bolin __________________ "...the new Rover 75, which is a fabulous car......I think it looks fabulous....It's like sitting in a Rolls Royce......For me, this is the star of the show.....it looks so good" - J. Clarkson, motoring journalist on the launch of the Rover 75 in 1998. Last edited by Bolin; 6th May 2014 at 16:42..

6th May 2014, 16:49	#17
Bolin This is my second home Rover 75 2.5 V6 Connoisseur SE 4dr manual Wedgewood Blue 2 04-05/06/2001 Join Date: Nov 2006 Location: N.E. Hampshire Posts: 4,617 Thanks: 289 Thanked 308 Times in 243 Posts	I'll have to wait until I have an assistant available who is able to hold it at 2,000rpm __________________ "...the new Rover 75, which is a fabulous car......I think it looks fabulous....It's like sitting in a Rolls Royce......For me, this is the star of the show.....it looks so good" - J. Clarkson, motoring journalist on the launch of the Rover 75 in 1998.

7th May 2014, 06:57	#20
chrissyboy This is my second home lovely little ford focus. Join Date: Jul 2009 Location: East Dulwich Posts: 7,877 Thanks: 2 Thanked 82 Times in 68 Posts	your readings are spot on ,theres nothing wrong with them.heres something to put your mind at rest ,also dont forget when a car is hooked up to any reader it will take some juice from battery ,your slow starting is proberly as with my focus ,a lazy starter http://www.aa1car.com/library/2003/us20310.htm http://www.aa1car.com/library/charging_checks.htm __________________ [ I'm really confused. -I keep dreaming I'm an insomniac Last edited by chrissyboy; 7th May 2014 at 07:14..

18th May 2013, 23:12	#13
Bolin This is my second home Rover 75 2.5 V6 Connoisseur SE 4dr manual Wedgewood Blue 2 04-05/06/2001 Join Date: Nov 2006 Location: N.E. Hampshire Posts: 4,617 Thanks: 289 Thanked 308 Times in 243 Posts	So you think that 14.22v across the terminals when idling from cold isn't good enough?

6th May 2014, 20:01	#19
Polly Posted a thing or two MG ZT 260 SE, ZS120, ZR105 Join Date: Mar 2014 Location: Peterhead Posts: 1,375 Thanks: 203 Thanked 350 Times in 241 Posts	When measuring voltages to decimal point, the internal resistance of the measuring device may be affecting your readings, also the quality of the connection may be affecting your readings. Put simply, with engine running at a little more than a fast tickover, if you have more than about 13.5v with lights, hazard lights, heater etc on, then your alternator is working. Looking for voltages above that might be affected by the quality of the instrument you are using, or even the temperature.