How long should a battery last?

As per the title I just wondered how long you should reasonably expect a car battery to last for?
Cheers
John

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Decent quality starter battery (not deep cycle) should last 5 to 7 years if:
Its never discharged deeply Its always charged right back up asgain with a sensible length drive Its never discharged even slightly (left lights on for 30 mins etc) and left Your alternator charges at the correct level for your battery (modern stuff 14.4 when running)
Or days to weeks if...
If you let it go flat ever (even once) especially if you leaver it that way or if you do it more than a few times. You do short winter trips. Your leave a modern car without a maintainance charger for a week or more often you drive an old car (13.8v) with a modern battery Your acessories outdo your alternator... You use a crappy cheap non logic controlled 3 or 4 stage charger.
And everything in between.
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I've left my 197 for a couple of weeks a couple of times. It's fine?
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Dan
Clio R27 F1 #65
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Nope you damaged it.
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Nah.
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Dan
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Yep! Only a bit! But all the "bits" are what kills them in the end!
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Luckily the battery for my Sierra only costs 23. At that price I could afford a new one every winter. Mine does sit regularly for a week at a time unused. Forgot about it recently and time just zoomed by and realised today it had been sitting there since June 28th. Turned over, but hardly and not enough to fire, so didn't try it once I realised. To be honest it was this thread that made me think how long it had been since I last started it. I checked the terminal voltage half an hour after cranking it and was spot on 12 volts.
I didn't realise modern cars had slightly higher voltage batteries. My car is designed for 13.8V not 14.4V and presume the battery is still the 13.8V type? My charger is modern though, but guess it doesn't make much difference in charging, even if it is designed for 14.4V batteries. Lidl charger BTW and very good it is too.
Graham
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State of Charge Voltage (measure after standing 12 hours or so) 12.7+ = 100% 12.45 = 75% - And as low as you want to go ever with a starter battery! 12.25 = 50% - Deep Cycle batteries only or damage! 12.10 = 25% damage... 11.95 = less than 5% remaining - Discharged and not well.
You get thousands of cycles at 10 percent. You get hundreds from deep cycle and tens from starter batteries at 50 percent You get 300 from GOOD deep cycle batteries at 80 percent discharge but 20 or so from starter batteries. You get tens of cycles at 95 percent discharged from good deep cycles. You get one or two if you are lucky with starter batteries.
Modern maintaintainance free batteries use slightly different chemistry so require a slightly higher charge voltage. Otherwise if you charged at say 13.8v it would take forever to recharge them fully as this is only .3 of a volt over the standard float / maintainance level.
Onthe other hand you are slightly overcharging them if on a very long trip. Swings and roundabouts.
Trucks are usually set a bit lower like 14v because of this.
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That is a very useful list of voltages. Especially on my campervan that has two batteries, one for leisure use (deep cycle) and huge one for the engine. Thanks for that. Very good info and saved it for future reference.
Graham
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No worries. The exact voltages vary with battery type and make and temperature. And are only accurate if said battery has been disconnected from any car/system/charger for 12 hours or preferably a day.
12.7V plus = full charge refers only to a battery thats been stood 12 hours or more after charging. Otherwise you are only measuring a "surface charge". Some batteries have more or less of this. So just because a quickl test with a digital volt meter shows 13. something volts under the bonnet that doesent mean its actually fully charged.
If you start your car and it reads 14.4v (or very close) then you have no alternator worries. If you then stop it and measure battery voltage it wont tell you anything, you need to wait a long time.
I sell Optimas so have to know this stuff... Funny how almost all the ones returned as faulty are from leisure or race vehicles that only get used very occasionally. Or boats, leisure equipment, or similar... Almost never get a return on a standard regular driver.
Makes you wonder why manufacturers dont fit a 5 watt solar panel with 13.6v regulator chip (float/charge level) in the roof of all cars doesent it...
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Open circuit voltage tells you pretty well nothing about the state of a battery. There's too much spread between samples - unless you're talking brand new. A proper tester measures the voltage while applying a heavy load. Modern ones do this using a pulse system.
The battery on my SD1 was reading 11.8 this morning - it hasn't been used for some time. But it started ok. According to that list it was completely flat.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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London SW

If it read 11.8 it was flat or almost so. Its voltage was pulled down artificially due to the slight evelectrical load on the car.
It inly needs a few percent left to start after all. And you would need to actually disconnect it from its loads and leave it 12 hours to see the true state af charge voltage or disconnect a battery cable the night before. Then it would climb to a stable figure and settle there. You cant measure it with a load even if its only milliamps.
Voltage DOES accurately tell you the state of charge if you do the measurement properly!. Load or pulse testing tells you its internal resistance which is a guide to its condition. Although a knakered optima will still have lower internal resistance than a new cheapy so that pulse tester isnt accurate. Plus most deep cycle batteries would fail that test from new.
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Which just goes to show that an unloaded voltage test is meaningless.

Not so - mine takes quite a bit of churning due to an injector leak and the fuel rail being depressurized when cold. The pump only runs when turning over.

Like I said a useless test.

That plus the current it can supply are the important things.

Optima is a con.

We're talking car batteries here.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

Its still not much in terms of a percentage discharge.

No the test is and always has been valid if you know how to perform it. You failed...

You still dont seem able to get it... Voltage test = state of charge. Pulse load test = test of internal resistance (which should tell you the battery state. as in knackered or not) It has nothing to do with state of charge other than it must have enough remaining just.

Err how? They do everything claimed. They have lower internal resistance and therefore greater starting current capability than other similar weight/capacity batteries. The Deep Cycle ones also have better Current capabilities than almost any similar sized pure starter battery.
They can be fast charged in an hour with no damage at hundreds of amps provided 14.7v isnt exeeded.
Etc etc.
A con "how" ??? Because you dont understand batteries?
Sorry but they are good well made non spillable and even work upside down happily.
A small one will easily start a truck so excellent for motorsports where weight and big high compression engines are used.
Tell me mr expert, why do YOU think they are crap?

Yes but an optima deep cycle IS a car battery. It can do BOTH! They are capable of 300+ 80 percent discharges while at the same time being able to supply MORE current than a "normal" starter only battery... Even though in your expert opinion they are a con!!! After 1/5 th of that your already less capable starter battery would have shed its lead sponge coating and be nothing more than a paperweight. Which is why I will ignore your opinion since you dont have much clue about batteries.
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Poor value - and claiming to have a very long life while only actually warranting it for the same time as any other decent make.
Just how useful it is for competition is irrelevant for road cars.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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London SW

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Do you sell them or something?
Watch my lips.
They're an expensive and unnecessary luxury for a road car.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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London SW

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How about "they're an expensive and unnecessary luxury for the majority of road cars"?
Coz let's face it, cheap and nasty batteries work well enough for most people.
cheers, clive
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Yep I never said otherwise. But he claims that optimas are a "con" his words. Simply because he doesent care about the advantages. Nobody is forcing him to buy one! If he wants a cheap "works well enough" battery thats his choice. Its not mine. But just because he doesent undertand the difference it seems they are a "con"! Not everybody wants the cheapest solution do they. Or we would all drive korean built cars. They "work well enough" too. but we choose not to. Well most of us do.
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