Flat battery
in [Car Maintenance]
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From: Dave Plowman (News) on 23 Dec 2008 10:16 In article <6rccqqFj6bsU1(a)mid.individual.net>, Conor <conor_turton(a)hotmail.com> wrote: > In article <5012386bcddave(a)davenoise.co.uk>, Dave Plowman (News) > says... > > This morning he returned the charger and said on a whim - or more > > likely to stop the earhole gbh - he'd tried to start it after an hour > > or so and it did. With a charger who's peak output is less than 5 amps? > > > > He kept the engine running while she shopped then put it back on > > charge overnight. By the morning the charger had gone to float mode so > > had decided the battery was fully charged. > > > > What's the explanation? > > > Starter motor is possibly fucked - maybe brushes. Doubt it. As I said the battery volts were very low. So at the time I measured that it was flat. I can't think of any battery fault that would show that but correct itself. > Just changed the one > on the Capri last week - similar symptoms. Turned over fine if the > voltage was there but once the voltage dropped a bit, i,e when parked > overnight, it didn't want to know. What was really wierd is it'd turn > real quick for a few seconds then if it missed firing and you instantly > tried again, it'd turn over like the battery was flat. All connections > absolutely fine, battery in good nick. > I put a new starter motor on and it's been fine since. I had a starter in a P6 which worked - but must have had some shorted windings. Knackered batteries in short order. Had three replaced in as many weeks under warranty before it dawned on me. ;-) -- *What am I? Flypaper for freaks!? Dave Plowman dave(a)davenoise.co.uk London SW To e-mail, change noise into sound.
From: Dave Plowman (News) on 23 Dec 2008 10:18 In article <giquol$vus$1(a)news.datemas.de>, Dave Baker <Null(a)null.com> wrote: > > What's the explanation? > Assuming there wasn't an unusual parasitic drain or bad connection after > he'd moved the car to wash it then the battery is probably near as > dammit dead with very little reserve capacity left. It may be partially > shorted inside already. However the charger would have put enough > surface charge into the cells after an hour to start the car easily > enough. If the engine and ignition is in good nick you only need a > fraction of an ampere hour to turn the starter over at say 200 amps for > 1 second. The true test will be to check the voltage after the surface > charge has been removed by putting the headlights on for a few minutes > and then letting it sit for a few more - or just wait until next > morning before he starts it next time. If it shows 12.65V then well and > good but if it's really on the way out the voltage will be much lower > than that and it probably won't hold a charge for very long. I'd say it did come up to the correct voltage as the charger switched to float mode. They're off on holiday now - so I'll keep my fingers crossed for them. ;-) -- *Certain frogs can be frozen solid, then thawed, and survive * Dave Plowman dave(a)davenoise.co.uk London SW To e-mail, change noise into sound.
From: Duncan Wood on 23 Dec 2008 10:27 On Tue, 23 Dec 2008 14:18:31 -0000, Dave Plowman (News) <dave(a)davenoise.co.uk> wrote: > Had an interesting one late yesterday afternoon - a neighbour knocked on > the door and asked for some help. His '01 BMW 325T wouldn't start. Flat > battery - just a relay or two clicking when you tried. He'd started it > earlier - normally - and moved it a few yards to wash it. > > Got the meter out and it was certainly flat - 9.5v on the battery posts. > Loaned him my little Lidl charger and agreed if it wouldn't start the > next > day I'd take him to get a new battery. His lady wasn't pleased - she > wanted to go shopping that evening. > > About a couple of hours later I went out and noticed their car wasn't > there. Sort of concluded she'd nagged him into getting the AA or whatever > out. > > This morning he returned the charger and said on a whim - or more likely > to stop the earhole gbh - he'd tried to start it after an hour or so and > it did. With a charger who's peak output is less than 5 amps? > > He kept the engine running while she shopped then put it back on charge > overnight. By the morning the charger had gone to float mode so had > decided the battery was fully charged. > What's the explanation? > If he'd left the lights on then you can quite often get one to recover enouigh voltage to start the car by just leaving it standing for an hour.
From: Harry Bloomfield on 23 Dec 2008 10:30 Conor pretended : > In article <5012386bcddave(a)davenoise.co.uk>, Dave Plowman (News) > says... > >> This morning he returned the charger and said on a whim - or more likely >> to stop the earhole gbh - he'd tried to start it after an hour or so and >> it did. With a charger who's peak output is less than 5 amps? >> >> He kept the engine running while she shopped then put it back on charge >> overnight. By the morning the charger had gone to float mode so had >> decided the battery was fully charged. >> >> What's the explanation? >> > Starter motor is possibly fucked - maybe brushes. You failed to notice the mention of 9.5v measured across the battery in the OP. My own guess would be that the 9.5v was not a true reading of the actual voltage across the battery terminals, that you too the reading from the cable lugs and that there might have been some high resistance between lug and battery. Your disturbing the connections testing and/or putting the charger across them, improved the connection enough to make it start. -- Regards, Harry (M1BYT) (L) http://www.ukradioamateur.co.uk
From: Dave Plowman (News) on 23 Dec 2008 10:59
In article <mn.bba27d8c10ae1ca4.86812(a)NOSPAM.tiscali.co.uk>, Harry Bloomfield <harry.m1byt(a)NOSPAM.tiscali.co.uk> wrote: > You failed to notice the mention of 9.5v measured across the battery in > the OP. > My own guess would be that the 9.5v was not a true reading of the > actual voltage across the battery terminals, that you too the reading > from the cable lugs and that there might have been some high resistance > between lug and battery. Your disturbing the connections testing and/or > putting the charger across them, improved the connection enough to make > it start. Absolutely not so. I was using sharp probes direct to the battery posts. And a recently calibrated Fluke 179. The battery terminals were tight anyway. -- *Why is the word abbreviation so long? Dave Plowman dave(a)davenoise.co.uk London SW To e-mail, change noise into sound. |