Car battery

[ericmark]

There is also the so called lazy starter. As the bearing on the starter ware the armature can get closer and closer to the pole shoes, but under starting conditions with a warm engine they don't touch, however with a cold engine the strain means it draws more current, this in turn means a greater attraction between armature and pole shoe, this is enough to bend the armature slightly causing it to touch the pole shoes, it then needs even more current which bend the armature even more. Net result is there is a point where just a little extra strain makes a huge difference in the current required.

Changing the bearings cures this. But a fully charged battery or new battery will also cure it short term. Once spinning the armature and pole shoes don't touch, it is only when nearly at a stall that the armature bends enough to touch. There is many a motorist been sold a new battery when really it's the starter at fault.

 

[JohnW2]

... there was a rash of stories of people leaving upmarket cars with newly acquired levels of sophisticated gizmos but no concomitant levels of sophisticated management in airport car parks for just 2 weeks and coming back to find they had a 1.5 tonne hollow steel brick....

That doesn't surprise me. It happened to me once, a good few years ago, with a car that was 'mid-market', with an almost new battery. Airport (and other long-term) car parks seem to be well equipped for jump starting these days!

Kind Regards, John

 

[JohnW2]

And how long when the battery is, say, 10 years old?

In my experience, they don't last that long these days! ... but, yes, that's partially what all my "in an ideal world" caveats were about (e.g. new battery, fully charged, no self-discharge, full charge recoverable etc. etc.).

Kind Regards, John

 

[EFLImpudence]

New battery and all is well.

I know this thread is a week or so old, but on the subject of the car starting ok after being jump started but not starting the next morning, the current required by the starter to start the engine is likely to be much higher the next morning when then engine has had time to completely cool (plus the extra discharge/ self discharge, etc). If you are using the car in the day, the engine is likely to still be warm the next time you start it and hence much easier to turn over. This is because the oil cools and becomes thicker when cold. The battery itself will also perform better when warm.

Yes, I do know (all) about cars but it just happened so suddenly - all perfect and then one day trouble - it was as if something else was the cause.

Regarding the 150mA current draw, assuming no glove box or boot lamps stuck on as has already been mentioned, aftermarket alarms, radios, amplifiers, dash cams, sat navs, etc are usually the culprit – do you have any of those things fitted?

My original question was just to find out if there was a way to calculate what was the result of such a current draw and then got into general questions and being told off because it was obvious.

I did find (or realise) the cause of the 150mA. It was my wi-fi OBD link. When removed the current reduced to around 35mA.

150mA is also not necessarily out of the normal, many newer large cars like Jan XF, Range Rovers, etc can have high quiescent current draws due to the amount of kit fitted – but these vehicles will typically also have big batteries fitted so they will still start after several weeks of non-use. Some of the Merc models have 2 batteries fitted to help with this situation and make sure settings aren’t lost when 1 battery is changed.

I used to have a BMW which, I think, recommended disconnecting the battery if it was going to be unused for six weeks or more. Its battery did not actually go 'flat' but the brains would switch off and refuse to do anything at less than about 11V.

 

[JohnW2]

New battery and all is well.

Glad to hear that.

My original question was just to find out if there was a way to calculate what was the result of such a current draw and then got into general questions and being told off because it was obvious.

I don't think you were really told off - not the least because it is anything but 'obvious'. Even with a brand new battery, one cannot assume (as per simple/'obvious' arithmetic) that the full Ah capacity will be available to be drawn, at any current and over any period of time, nor can one assume that the voltage will remain constant throughout the period of discharge (which it certainly won't with a lead-acid battery).

As far as voltage during discharge (at various rates) is concerned, one really has no alternative than to look at manufacturers'curves.

However, once the battery ceases to be new, everything can change, and I think it would be very difficult to make any reliable calculations/predictions at all. With an old battery, one can fully charge (charge as much as is possible) and it will be 'flat', with a non-useful voltage output with any load, after sitting around (with no load) for just a short period of time.

I did find (or realise) the cause of the 150mA. It was my wi-fi OBD link. When removed the current reduced to around 35mA.

That ought to help a lot.

Kind Regards, John

 

[ericmark]

As to disconnecting battery it cost me a new radio with my Vauxhall, seems there should have been a number written in the book to put into the radio to get it working again, however it had not been put in the book, £30 to get the number £50 for new radio which did not need number and also had blutooth so could use phone hands free with radio. So new radio it was.

My car now also has a radio and again no number to put in should battery become disconnected, so very wary about disconnecting battery if left for a long time.

 

[John D v2.0]

Older vauxhalls (mine is 2003) do have a radio code, but any newer than that and they sync the radio with the engine management system, so power loss is not an issue.
I just disabled the code on mine as who'd steal the radio cassette from an ancient car?
Incidentally, it's still on the original 14 year old battery and starts first time even after sitting for a couple of weeks (it did 3.5 weeks last winter no issues) but that could have something to do with the fact it's very low tech.

 

[JohnW2]

Older vauxhalls (mine is 2003) do have a radio code, but any newer than that and they sync the radio with the engine management system, so power loss is not an issue. I just disabled the code on mine as who'd steal the radio cassette from an ancient car?

Modern cars My Vauxhall is 1996, and certainly has a radio code.

Incidentally, it's still on the original 14 year old battery and starts first time even after sitting for a couple of weeks (it did 3.5 weeks last winter no issues) but that could have something to do with the fact it's very low tech.

Not as lucky as you there - I think I'm on my third battery, after 21 years.

Kind Regards, John

 

[ban-all-sheds]

Older vauxhalls (mine is 2003) do have a radio code, but any newer than that and they sync the radio with the engine management system, so power loss is not an issue.

Modern cars My Vauxhall is 1996, and certainly has a radio code.

Isn't that what he said? Sometime after 2003 (when "modern" started), manual codes were replaced with a link to the EMS. So a 1996 car would still be using a manual code.

 

[JohnW2]

Isn't that what he said?

Exactly - I was agreeing/confirming that such was apparently the case with Vauxhalls older than 2003 (and probably somewhat younger than that).

What was your point? You seem to be re-stating what has already been said twice.

Kind Regards, John

 

[ban-all-sheds]

You seemed to be disagreeing with him by saying that your car had a code and it dated from 1996.

Otherwise you were re-stating what had already been said. So what was your point?

 

[John D v2.0]

Relax! There's no winner at the end of the thread.

 

[JohnW2]

You seemed to be disagreeing with him by saying that your car had a code and it dated from 1996. Otherwise you were re-stating what had already been said. So what was your point?

As I said, I was agreeing/confirming. What you thought "I seemed to be saying" is not my problem.

You must be having a very boring day!

Kind Regards, John

 

[JohnW2]

Relax! There's no winner at the end of the thread.

Tell BAS that!

Oh, you have

Kind Regards, John

 

[ban-all-sheds]

As I said, I was agreeing/confirming. What you thought "I seemed to be saying" is not my problem.

Indeed.

It's just that I was utterly unable to understand why anybody would bother to say "My Vauxhall is 1996, and certainly has a radio code." in response to "Older vauxhalls (mine is 2003) do have a radio code".

Try these:

JD: "Wednesday was the fourth day in a row of heavy rain."
JW: "It rained heavily on Sunday, Monday & Tuesday as well."

JD: "They don't show children's programmes on TV after 19:00."
JW: "They have children's programmes on TV at 15:00."

JD: "If you go to Europe you need a passport."
JW: " If you go to France you need a passport."