Information from a car battery with multimeter?

[carl_w]

The battery on our competition Saxo cranked the car OK but would go flat between events. I managed to find a replacement for £26 from this place, so it was a no-brainer https://www.tayna.co.uk

There may be better batteries available, but a £26 shiny new one is better than one that goes flat when you need it.

[E65Ross]

Had a look online and whilst Bosch do a battery for £75 it's rated at 610cca and 63Ah

http://carbatteries-online.co.uk/product/bosch-s50...

but there's another from a brand I haven't heard of who make one rated at 630cca and the same Ah

http://carbatteries-online.co.uk/product/027-type-...

and for £20 less! Why would I go for the Bosch!?

Have saved that link for the future. £55 for a decent battery is a revelation from replacing the 7 series' battery

They also do one for £45 which also has 63Ah but only 590cca....would that be sufficient?

http://carbatteries-online.co.uk/product/heavy-dut...

Mine is only a 1.6 litre and they also suggest the same batteries for the 1.8 makes me think the cheaper (£45) one would be fine for the 1.6....??

Edited by E65Ross on Monday 26th September 21:09

[Huff]

Cars in the last 10years(say) tend to draw a lot more 'off' than they used to, thanks to all the ECUs. Body ecus, audio gizmos, wireless unlock/start thingummies that keep the body ecu watchdog awake, all that kind of thing.

If you want certainty and the car will often stand for weeks on end, fit an FIA_alike cutoff switch - except for many modern cars that causes other annoyances (from losing your radio station preferences to custom button assignment) - but with one, my BEC (for example) can stand 6months and restart on the button (on a wee 10Ah lump!)

In the last ten years I've simply bought a new battery each time I bought a car s/h (which is all 4 of them) and as a result, never had a problem; it just struck me once that paying £50-80 to simply know it's good was cheap insurance in the scheme of things - comparable with a single fill of fuel, and less than a call-out.



PS. Slight correction, if I may, to post 3 - a standing SLA battery, once the surface charge is depleted (5mins of sidelights) should read 12.7-12.8V unloaded at 100% charge, not 13-13.5. Gel/absorbed-mat batteries - up to 0.3v higher (13.0 - 13.2 say)

Edited by Huff on Monday 26th September 20:56

[E65Ross]

Hmmm, checked voltage this morning (unlocked car, opened bonnet, locked car to shut everything off) and then checked.....was only 12.48V. Would having opened/unlocked the car and locked it again caused a small drop? I'm beginning to think it may be worth just getting another one anyway, for the sake of £45....! I'll be keeping the car for at least 2-3 years I'm sure so it'll need changing at some point during my ownership anyway.

[battered]

What did I say about reckoning you'll swap it out anyway regardless of what the test said?

Leave it, sausage. 12.5ish probably just indicates it wasn't fully charged when you parked it. The difference between 12.5 and 12.7 isn't a big deal. The acid test is the cranking capability.

Yes, sometimes a battery won't hold a charge but you know this when it's under 12V having been tested at between 12.5 and 13 the day before.

[lostkiwi]

E65Ross said:

Had a look online and whilst Bosch do a battery for £75 it's rated at 610cca and 63Ah

http://carbatteries-online.co.uk/product/bosch-s50...

but there's another from a brand I haven't heard of who make one rated at 630cca and the same Ah

http://carbatteries-online.co.uk/product/027-type-...

and for £20 less! Why would I go for the Bosch!?

Have saved that link for the future. £55 for a decent battery is a revelation from replacing the 7 series' battery

They also do one for £45 which also has 63Ah but only 590cca....would that be sufficient?

http://carbatteries-online.co.uk/product/heavy-dut...

Mine is only a 1.6 litre and they also suggest the same batteries for the 1.8 makes me think the cheaper (£45) one would be fine for the 1.6....??

Edited by E65Ross on Monday 26th September 21:09

Try looking here:
https://www.tayna.co.uk/027-Car-Batteries-G12.html

[Dr Doofenshmirtz]

You're worrying over nothing.
~12.5v after sitting for a while is absolutely fine.

[E65Ross]

Well for the sake of £45 it makes sense when I consider I'll be having the car for a few years at least, and that the battery will almost certainly need changing in that time anyway....

[Dr Doofenshmirtz]

The battery in my Saab is 11 years old (it'll be 12 years in March) - as long as they're kept fully charged (so the don't start to sulfate) they easily last 8-10 years.

[SHutchinson]

E65Ross said:

Well for the sake of £45 it makes sense when I consider I'll be having the car for a few years at least, and that the battery will almost certainly need changing in that time anyway....

Just change it, you clearly want to, despite everyone telling you that you don't need to. That way you can move on to fussing over something else that doesn't need changing, like erm, have you checked your diff oil? I bet it's all sludgey and brown. ;-)

[E65Ross]

SHutchinson said:

E65Ross said:

Well for the sake of £45 it makes sense when I consider I'll be having the car for a few years at least, and that the battery will almost certainly need changing in that time anyway....

Just change it, you clearly want to, despite everyone telling you that you don't need to. That way you can move on to fussing over something else that doesn't need changing, like erm, have you checked your diff oil? I bet it's all sludgey and brown. ;-)

Changed at the last service

[JuniorD]

I noticed the original 12 year old Moll battery in my car was dying so I replaced with a Bosch which rapidly went downhill. I connected up a multimeter to see what was up and noticed that after everything had went to sleep, a cyclic 8mA was being drawn from the battery like a slow pulse. After doing the whole fuse removal checks, it turns out the radio has been silently doing something in the background without actually switching on. Well it’s £350 for a replacement OEM radio so sod that, I just slide it out when I park and disconnect the power cable from the back. How very council.

[Classy6]

Pay no attention to voltage, it means absolutely nothing on it's own. It's amps that are the main concern and you can't measure those unless you've got the kit. I've replaced hundreds of batteries showing 12v+ for them to be dead as a door nail with a couple of amps in them.

Keep using it until it dies, if you're lucky you may get some sluggish starts that'll indicate it's dying or one day you'll get in it and nothing will happen.

[Ozzie Osmond]

battered said:

That' the most reliable test and it takes 2 minutes. Watch them doing it, it's good fun. The device is just 2 prongs with insulated handles, a voltmeter and a bloody great resistor coil between the two prongs. God knows what current it pulls, it's several tens of amps, possibly 100. The test is to monitor the battery under heavy load and see how well it stands up.

Yes, that's the best way to check a battery.

However, if all you've got is a decent home multimeter remove the battery from the car, charge it, disconnect charger and then allow the battery to stand indoors overnight (to stabilise and ensure correct temperature). In the morning check the voltage at the terminals. Ideal voltage is around 12.7v. Anything 12.4 volts or less is a knackered battery.

[beko1987]

We had a battery die in the Meriva. Symptoms were slower to crank but was fine, until the day it wasn't!

Multimeter showed 4v iirc when I took it off, £37 from euro car parts and we were back in the game, the starter cranked over faster than it had done for ages before too, we just hadn't noticed!

[carl_w]

lostkiwi said:

Try looking here:
https://www.tayna.co.uk/027-Car-Batteries-G12.html

It's the cheap Powerline one that I bought. Even if it only lasts a year it'll be OK.

[E65Ross]

carl_w said:

lostkiwi said:

Try looking here:
https://www.tayna.co.uk/027-Car-Batteries-G12.html

It's the cheap Powerline one that I bought. Even if it only lasts a year it'll be OK.

Had a look there and due to the £8 postage unfortunately they were more expensive than the other site for a similarly specced battery. Can't argue with £45 for a battery with almost identical specs as the Bosch one (which is £75!!) and also has a 4 year warranty. Due to the driving I do (20 miles each way to work) I'm sure it'll last longer than that!

[Ozzie Osmond]

I've just changed two car batteries, both at 10 years old and purely as a "precautionary" measure ahead of winter. A decent modern battery can easily last a decade.

[Depthhoar]

Ozzie Osmond said:

A decent modern battery can easily last a decade.

My 2001 M5 has just had its original battery changed (installation date marks visible on the battery). 15yrs old.

Last two owners kept the battery on a smart charger when the car was not in use which may have helped.

Signs of the battery's demise were a bit odd: one or other of the front windows would randomly open just a little when unlocking the car. Also, occasional non-crank on first turn of the key even though all other dash lights came on but would always fire when the key was withdrawn and re-inserted. New battery seems to have sorted those issues.

Cheapest place for a replacement battery was my local BMW dealer at £112.

[E65Ross]

Well, the new battery turned up today and so I'll get it fitted tomorrow or Friday. Any point shoving it on charge overnight to ensure it's fully charged before I use it?