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There is a small current drawn by leakage in the alternator diode pack, the radio tuner memory and the like. This usually does not exceed 1ma. However a car alarm can pull from between 10 and 90 ma the latter being the ultrasonic or doppler RF, and volumetric types. The 10 ma example will not kill you battery in 6 weeks. However the 70 to 90 ma load will cause a 3 year old battery to loose substantial capacity in 6 weeks. If you have no alarm then a battery sitting for 6 weeks will not loose significant charge. Unfortunately you started the car then turned it off without going for a run and there you have a flat battery. You mention you left it running for 20 mins, not particularly good thing to do to the engine, and this is far from a fully charge battery and ideally you should use a charger for 24 hours at a couple of amps. If you are concerned as to the battery or the load presented by your car use your meter on the current range 10ma is you have no alarm , 100ma if you do, then lock the car and set any alarm that you use, wait a couple on mins then with the meter attached directly to the battery terminal and the other to the lead itself disconnect the terminal and take a reading. This is sometimes more easily done by two people. Regards Peter
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Must be to do with saving space and weight, probably not as substantial inside, and vibration makes a contact break - effectively turning the battery off forever.
Well, your battery was 6 years old, so you can't really complain.....why do people replace batteries when they fail, best to consider them a 4 year service item, or it's it's a cheapo one, 2 or 3 years....After twice being stranded at the least convenient moment for the sake of a £60 battery, I now replace them every 4 years with ones witha 3-4 year guarantee.
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dont forget the effectdifferent temps have on the modern batteries if a car never does more than 10 miles then it is unlikly to get hot however a journey of 100plus miles will get it quite hot and if its not used to it then the battery may well suffer premature failure i know its happened to me several times especially when travelling overseas during the winter.
cheap and expensive alike and a warenty isnt much good in a forign country.
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A battery should never overheat even on a long journey if it does happen voltage reg on alternator is up the wall.?
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sorry not very clear.
ididnt meen the battery overheat just that the physical enviroment around it gets much hotter and thus the electrolite will take on a different chemical property, especially when you come to a stop at the other end as the whole engine compartment will take that much longer to cool down.
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Peter D
Whilst I agree leaving it running is not the best way to charge it, I had little alternative. The battery charger was out on loan, and I was not prepared to stall somewhere in rural France and find the battery was genuinely knackered and incapable of a restart.
I would suggest that anybody trying your method of monitoring should take care leaving it on a 10mA range and operating central locking is NOT to be recommended. Whilst you probably get away with it with a DVM the current taken by central locking could be terminal for a mc meter movement.
Whilst I accept your figures for 'standby' currents, I am afraid I dont buy your suggestion of sufficient capacity to operate starter motor 'very vigorously' once and then losing almost all charge overnight.
pmh (was peter)
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You have misunderstood me !! the car is all locked up and nothing should be operated whilst you take the measurement. "You don't buy my suggestion " well it just happened to you and I've come across that a lot particularly with batteries 3 years old plus. You asked, you get. Regards Peter
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PD
1 Sorry.. reread your post! (But someone else could misread it....)
2 Your suggestion....whilst it may fit in with your experiences (and mine) I still do not think that the figures can hang together to form a conclusive case. I can only surmise that possibly some complex chemistry takes place following the high current discharge of operating the starter motor (heating of the plates?) and that this can cause the battery to self discharge???.
pmh (was peter)
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Sorry to interupt.from previous posts on the subject I would think it possible for a battery failure due to method/construction of battery ie if a cell fails battery is dead.whether a new battery or old if this happens you have a dead battery.
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I recently tested a 5 year old 095 type Exide battery 60 amp hr new. Battery was charged for 36 hrs terminal on charge voltage 14.84, rested for 24 hrs then, using a pulse discharge battery tester I could only get 210 amps cold cranking ( should be over 460 ) put battery on a 5 amp discharge and at 3 hrs 35 mins later the voltage dropped to 10.5 volts and it was all over. That is less that 18 amp hrs. Due to the modern design of batteries the internal resistance stays fairly low even when the capacity ( effective chemical surface area ) has depleted. This is one of the major reasons why a battery holds on to the last then just quits. Now lead acid batteries do not particularly like low current discharge as it does not encourage the electrolyte to circulate thus is becomes chemically stale and micro bubbles are formed in the mesh of the plate design. If, as in your case an old battery has stood for six weeks, its amp hr capacity has fallen probably to around 12 or 13 amp hrs but can still provide a one off cold cranking current of may be 150 amps. This shock, no pun intended, causes the cells to gas i.e. all the accumulated micro bubbles that were trapped in the mesh of the plate construction now form larger bubbles that obstruct the surface area thus considerable reducing the cold cranking figure and next time you turn the key, “click” and nothing else.
If your car does not have an alarm so the quiescent current is below 1ma then you need to purchase a new battery as the one you have is about to let you down. You have had six years out of it so I’d change it. Happy Motoring my Friend. Regards Peter
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Peter D
Good explanation, this is the sort of thing that I hoped somebody would come up with. It explains the chemistry ( or should I say physics?) of why a short high current discharge can then cause the battery to suddenly appear to be very flat. I would suggest that the bubbles forming large bubbles contribute to the very high internal resistance experienced. As this is a physical form of failure presumably the underlying chemistry will remain capable of providing some AH capacity if the bubbles disperse.
Now the interesting thing is whether the battery would then recover over a period of time if the bubbles can be tempted to disperse? This is presumably what happens as a result of recharging it but can the bubbles be dispersed by standing or vibration?
I will watch the battery very carefully ( probably carry a spare in the boot) and see whether I can monitor it carefully next time it fails. As I have a variety of vehicles, see profile, tending to the bangernomics model, and swap batteries around sometimes. I have often said that I go outside and find which one will start!
This would model would account for the many sudden failures and the 'willingness' of the trade to instantly replace the apparently flat battery. For most people this is the correct course of action as they cannot afford to be caught out again.
pmh (was peter)
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I wonder if in such a situation if banging the battery would shake the bubbles loose to get you going?
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On the older style this was the case but the designs today have much finer cause and the casing requires quite a rattling to get the bubbles to come up. Regards Peter
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My warm thanks to all of you who have responded to my originating posting on this thread, and especially to Peter D for his authoritative contribution.
That really answers the "why?" aspect of my query.
However, what about the other part: Can manufacturers of batteries incorporate a warning device to indicate when the battery is about to expire?
On my car the battery has a colour indicator viewer (as described by one respondent to the thread above) though I don't know how reliable that will be. Anyone had any experience or got any knowledge of such indicators?
They seem better than merely changing the battery every 3 or 4 years, becuase that seems an arbitrary interval not related to the battery's condition.
Anyway, thanks again to all who took the trouble to answer. What an excellent forum this is!
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The little light is an indication of the specific gravity of the electrolyte not the surface area and chemical condition of the plates. If the battery has been charged it can have the correct PS but cann, due to plate degradation, hardly light a bulb. Light works for 2 to 3 years but then is is somewhat false. If you know your battery is well charge you can always pop in to your local independant car accessory shop and they will do a pulse discharge test to establish the cold cranking current for you. Do it once a year and keep a note of it. When it is 30 % to 40% of the original then a new battery would be wise. Regards Peter
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Again, very many thanks. That's most helpful - have printed and shall apply!
That said, I remain somewhat surprised that consumers haven't complained that we seem to have taken a step backwards: it must be possible (admittedly, at a price) for manufacturers of batteries to devise and incorporate a reliable indicator of imminent death of the battery, so that motorists are not stranded as a result of the propensity of their modern batteries to die wihour warning.
But we meekly accept the status quo! I'd wondered whether my originating post would have generated such a campaign, but seems not!
Nevertheless particular thanks to Peter D, and to the others who took the trouble to respond.
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I think my second post comes into play here.?
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They have an indicator that tells you when the battery is about to die. It is called a Warrantee !! Ha Ha
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A long time ago (1989) we went for a week to France in our Citroen GS. Great car apart from the rust. Anyway car was perfect for the 1000 miles we did (were looking for property at the time) but when we got back to Portsmouth, the battery was COMPLETELY dead. No warning at all. So even old technology batteries can suddenly die.
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All the battery deaths I have experienced did go suddenly with no warning. Fine one minute then go to start car and nothing, so dead that even a jump start won't work. Having lived in a rather hot Ft. Lauderdale, the deaths occured about every two years, so I have been through at least 6 batteries while living there and they all went the same way.
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I have rejuvenated a lazy, tired, left on the shelf, C10 Varta battery 3 years ago using ethylenediaminetetra-acetic acid (which I purchased from Boots)and it is still the best battery I own. I got this product information from Bugantics magazine. It is no use using this product on a dead battery.
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Modern batteries are far more compact and light for a given output and last much longer than older types. However the thinner plates are less able to recover after being fully discharged/jump started compared with old technology batteries.
No such thing as a free lunch
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Modern batteries are far more compact and light for a given output and last much longer than older types.
Longer than the 20 year life of a battery I used to start a marine diesel in the 1960s? It held its charge during the winter and always started the engine in the spring with no difficulty. When it finally gave up it was relegated to service as a subsidiary lighting battery.
I knew someone who ran an old milk float as a second car. It still had its original batteries, about 30 years old.
Big and heavy, yes, but they lasted longer.
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Big and heavy, yes, but they lasted longer.
Have to disagree. Battery's like almost everything else on a modern car last longer. Powertrains , fuel and ignition systems, paint systems and oils are just a few examples I can think of. Battery technology like everything else has needed to keep up. Battery's also have to work harder than before driving additional electrical equipment.
Most modern batterys have a 3 year guarantee as standard - I don't think this was the case in the 1960's.
Partly I think this is attributed to improved battery technology and also better charging systems giving a smoother output, which partially explains the longevity of a milk float battery. It just won't experience the rapid discharge/charge cycling that a car battery does.
The battery on my Peugeot diesel lasted 5 years, which i think is pretty good for a relatively light battery starting an often reluctant to start diesel engine.
It does seem though that the modern battery's do suffer more of a sudden death compared to the older types that would soldier on for a few more months given the occasional jump start or trickle charge before failing completely.
Recovery from sulphation maybe the controling factor, but it must surely be that battery design over the years has become optimised for low weight, volume and higher specific power, resulting in the various chemical proceses and materials operating more towards the outer edges of their performance capability. When one or more of these capabilities is eroded by wear and tear, rapid failure occurs.
So although the size, weight and life is better, the downside is that the failure process will tend to occur abruptly, rather than by a slow degradation of performance as happened with older battery technology.
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Well, there are pluses and minuses, I agree.
Paint doesn't last so well - look at all the bird poo threads!
Brake disks are now expendable.
I agree engines last forever.
But only 5 years for a battery is pretty poor in my experience. I haven't bought one for 10 years - the old ones on my three vehicles are still going strong. My recipe is DO keep them clean and corrosion-free, DO check the acid level regularly and keep topped up, DON'T trickle-charge them unnecessarily, just let the generator/alternator do its job.
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Paint doesn't last so well because they insist on putting metallic paint on. Metallic has always been prone to fading & damage - stunning when new, but a liability when old.
Brake discs are only expendable because technology means that brake pads don't kill you (or whatever the tiny quantities of asbestos dust might or might not have done to you!). Pads last longer though - they just wear out the discs.
Cars don't rot these days, though. ND's tractor will still be ploughing fields many years hence (provided the electrics are up to it).
Why should trickle charging damage a battery? Is it that different to how an alternator charges it?
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I was once told by someone in the battery industry that the main cause of damage to batteries, apart from obvious neglect or abuse, was persistent over-charging. In his view most batteries that failed to cope with the strains of winter use had been ruined by prolonged over-charging in hot weather in the summer.
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Agree I think there is an issue with the durability of modern water based paint systems used for environmental reasons. It's a step backwards in my view but the environmental brigade wield an increasingly big stick over the motor industry.
Overall the paints/sealants etc. applied today keep rust at bay for far longer than materials used even 20 years ago. Most paint finish problems are caused by poor maintenance by vehicle owners rather than any particular problem with paint technology.
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