Flat battery
in [Car Maintenance]
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From: Dave Baker on 23 Dec 2008 11:57 Dave Plowman (News) wrote: > In article <gir2fv$6pl$1(a)news.datemas.de>, > Dave Baker <Null(a)null.com> wrote: >> I think your neighbour's experience isn't really that unusual. He >> started the car just to move it a few feet which took some load out >> of the knackered battery but didn't replace it which a longer trip >> would have done and it's showed its true colours. Your charger gave >> it enough for one more start and the overnight charge might have >> given it enough for a few more starts but next time he leaves it for >> a day or two it'll be dead again. > > Yup. He didn't buy the car new - but the battery is a BMW one so in > all probability original. So at 7 years old has done well enough. > Eurocarparts charge 60 quid inc. for one so not the end of the world. I nipped out and had another check on my Focus's Motorcraft battery today in the light of all this battery talk. The car is 8 years old in June so about 7.5 years now and the battery is no doubt older than that dependant on how long the car sat before it was first sold and how long before the car was assembled the battery was actually made. There's probably a code on it I could tell the actual date from. Call it close to eight years though. As I've said previously the battery has a hard life because the car gets very little mileage and usually only 1/2 mile trips to the shops so it sits partially discharged for most of the time which must sulphate it up like crazy. It was well flat last week and struggled to start the car so I charged it somewhat for an afternoon on my shagged little 30 year old Halfords charger which has a broken ammeter now anyway but never went above 3 amps at the best of times. I doubt if that brought it anywhere near full charge though. I was quite surprised to see 12.37 volts a week later and after a couple of days of non use and in such cold weather. It ain't good but it's not as bad as I was expecting. I thought it would be closer to 12 volts. I might treat it to more frequent charges to try and keep it from sulphating further but I reckon it still has a year or two left in it. It certainly won't owe me anything when it croaks. It still starts the car fine even when it's below freezing and in the summer isn't an issue at all. I have a general aversion to buying anything from a main dealer but I'll be well tempted to get another one from Ford when it dies if they don't charge an extortionate amount. I've had cheap batteries in the past and they are definitely not a good idea. -- Dave Baker
From: steve robinson on 23 Dec 2008 12:11 Dave Baker wrote: > Dave Plowman (News) wrote: > > In article <gir2fv$6pl$1(a)news.datemas.de>, > > Dave Baker <Null(a)null.com> wrote: > > > I think your neighbour's experience isn't really that unusual. He > > > started the car just to move it a few feet which took some load out > > > of the knackered battery but didn't replace it which a longer trip > > > would have done and it's showed its true colours. Your charger gave > > > it enough for one more start and the overnight charge might have > > > given it enough for a few more starts but next time he leaves it for > > > a day or two it'll be dead again. > > > > Yup. He didn't buy the car new - but the battery is a BMW one so in > > all probability original. So at 7 years old has done well enough. > > Eurocarparts charge 60 quid inc. for one so not the end of the world. > > I nipped out and had another check on my Focus's Motorcraft battery today in > the light of all this battery talk. The car is 8 years old in June so about > 7.5 years now and the battery is no doubt older than that dependant on how > long the car sat before it was first sold and how long before the car was > assembled the battery was actually made. There's probably a code on it I > could tell the actual date from. Call it close to eight years though. As I've > said previously the battery has a hard life because the car gets very little > mileage and usually only 1/2 mile trips to the shops so it sits partially > discharged for most of the time which must sulphate it up like crazy. It was > well flat last week and struggled to start the car so I charged it somewhat > for an afternoon on my shagged little 30 year old Halfords charger which has > a broken ammeter now anyway but never went above 3 amps at the best of times. > I doubt if that brought it anywhere near full charge though. > > I was quite surprised to see 12.37 volts a week later and after a couple of > days of non use and in such cold weather. It ain't good but it's not as bad > as I was expecting. I thought it would be closer to 12 volts. I might treat > it to more frequent charges to try and keep it from sulphating further but I > reckon it still has a year or two left in it. It certainly won't owe me > anything when it croaks. It still starts the car fine even when it's below > freezing and in the summer isn't an issue at all. > > I have a general aversion to buying anything from a main dealer but I'll be > well tempted to get another one from Ford when it dies if they don't charge > an extortionate amount. I've had cheap batteries in the past and they are > definitely not a good idea. Must admit my motorcraft battery on my focus lasted over eight years and the car used to sit idle for weeks at a time , in the end sitting idle for two months over january seen it off
From: Redwood on 23 Dec 2008 12:12 "Dave Plowman (News)" <dave(a)davenoise.co.uk> wrote in message news:50123ded03dave(a)davenoise.co.uk... > 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. ;-) Do you know which charging mode he had it on? I have the same Lidl charger and when charging a very old battery that's on its last legs, it will charge and go into float mode if left on the slow or medium charge setting - but if on the high setting it will never go into float mode as it never reaches the required 15 or so volts.
From: Chris Street on 23 Dec 2008 12:24 Ian wrote: > On 23 Dec, 01:03, Chris Street <n...(a)chris-street.demon.co.uk> wrote: >> Ian wrote: > >>> Maybe, but it's more likely that sulphated plates will have >>> effectively choked off the discharge after just a few hours. >> The surface area of a battery plate will only fill up with sulphate when >> you have managed to discharge the cell more or less completely until >> then the softer sulphate will permit migration of electrolyte and the >> cell will conduct - it does not "choke off" the plate. A battery goes >> flat when the electrolyte is almost depelted > > Yeah, yeah. But the OPs battery appears to have recoverd fine after > half an hour of driving. That is characteristic of the effects of a > small drain and NOT of a complete flattening. No. A half hour of charging will allow to start the car - a decent SLI battery will enable you to start when it is nearly flat as I said above. Just because it starts and runs ok and maintans voltage doesn't mean that it cannot be nearly flat.
From: Chris Street on 23 Dec 2008 12:27
Dave Plowman (News) wrote: > 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. > 9.5v is flat of course but if you stuck 5 amps into such a battery for an hour that should be enough to start it. If it wasnt a diesel, hence no glow plugs clobbering it then I'd expect a petrol to get a few seconds cranking time and if the alternator can energise and start charing then it should be fine. |