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over the past 2 mondays(30 october and 06november), i have had a flat battery after leaving the car idle from the previous saturday afternoon.

i have no problems driving to and from work 7.5 miles  each journey monday thru friday 0800-0825 and 1700-1730

the aa have come out and they have confirmed that my battery is fine(they supplied it in december 2016 and it s under a 4 year warranty).

it has been looked at by a local garage and they can find nothing that  is draining the battery when the car is idle.

has anyone experienced a similar situation and has anyone any theories?

i am about to replace the battery and if that does not resolve the problem take the car to lexus(arm and a leg springs to mind)

 

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Once the engine is running the alternator supplies all of the car's electrical needs and then, IF there's any power left over so to speak, it'll charge the battery. Your journey is only half an hour each way so if it's cold you may have heated seats on, heated rear window, for the evening journey you'll also have the headlights on etc., etc., so the alternator may not have enough time to get enough charge back into the battery and leaving the car standing at weekend may be the final straw for it.

Make sure your alternator is working alright for a start - I'll add more later but got to go for now.

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many thanks.

silly questions time(please get accustomed to this) -

1. even though the interior lights are not visibly on when i lock the car, is there anyway that they could still be on and if so how do i ensure that they are definitely off?

2. how do i ensure that the light in the  boot is off?

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If the car/battery has been out in the frosty nights then this will take its toll on a battery that is not in 100% good condition and it is only going to get worst if exposed to more frosty nights.

 

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51 minutes ago, juniorhashim said:

many thanks.

silly questions time(please get accustomed to this) -

1. even though the interior lights are not visibly on when i lock the car, is there anyway that they could still be on and if so how do i ensure that they are definitely off?

2. how do i ensure that the light in the  boot is off?

Both lights have switches close by.Make sure that they are switched off at all times. Look in your Handbook for more information.

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What capacity battery do you have and have you measured it when parking up sat pm and then again on monday morning to see how much juice your losing over 36hrs?

Seems odd to lose so much you can't start on Monday, after a day and half, but are ok to start each morning. Assuming this is the issue your having? Must be a heck of a current draw.

Do you have a meter that can show current draw? If so, get it hooked up, somewhere you can see it when car locked, ie so cables coming out boot. Lock car and leave it to go into sleep mode, then check what draw you have.

You can also check draw with car off and then start isolating circuits to see which is drawing what current.

You sure the battery ok though? I'd get it tested elsewhere as aa may have just wanted to save the claim etc.

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  • unfortunately i have no way of doing any tests on current draw etc. etc.
  • i have had the battery tested elsewhere and the conclusion is the same(there is nothing wrong with the battery).
  • i have spoken to lexus and a reputable garage and they have quoted as follows for a diagnostic test :-
  • lexus - £117.60(will be deducted from any work that needs doing by them as a result of the diagnostic)
  • garage - £100.80 - non deductable.
  • i plan to check all the lights again(heaven knows how i check the boot(wish it was a hatchback)) but i may remove the bulb(i assume that no bulb no current) -
  • and probably wait until next monday(to replicate the last 2 mondays)) and if the battery goes dead, call the aa out to get me going and take it to lexus or the reputable garage.
  • sounds logical? 

 

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3 minutes ago, juniorhashim said:
  • unfortunately i have no way of doing any tests on current draw etc. etc.
  • i have had the battery tested elsewhere and the conclusion is the same(there is nothing wrong with the battery).
  • i have spoken to lexus and a reputable garage and they have quoted as follows for a diagnostic test :-
  • lexus - £117.60(will be deducted from any work that needs doing by them as a result of the diagnostic)
  • garage - £100.80 - non deductable.
  • i plan to check all the lights again(heaven knows how i check the boot(wish it was a hatchback)) but i may remove the bulb(i assume that no bulb no current) -
  • and probably wait until next monday(to replicate the last 2 mondays)) and if the battery goes dead, call the aa out to get me going and take it to lexus or the reputable garage.
  • sounds logical? 

 

Taking the bulb(s) out will mean no current being consumed and see LED trunk light - ClubLexus - Lexus Forum Discussion

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I got similar problem few year good years ago with Honda Accord. All the tests were fine but then after night it can go flat. 

I've done some tests by disconnecting it for the night and measuring the current when car is in standby mode - as far I remember I've seen like 150mA which was reasonably OK.

After all I've bought new. battery and are problems have disappeared.

 

Lesson from that story - you can really reliable test battery with the load test. Buy the meter and check the current if low just buy new battery.

Additionally don't forget it is getting colder now. My battery was fine up until it dropped below 5C at night.

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What type of testing did these places do to battery? Simple voltage check, or proper load drop test?

You've not said what capacity the battery is, perhaps it's too small? I've no idea how big they should be, I'd guess rather small given the setup, vs other large saloons, so I'm using fictitious figures here on in.

Assuming a 100 amp hour battery, then to be a non starter, you'll need to drop it to say 50, so given it won't be fully charged, 100% by time you park up let's assume a healthy 90%, means your losing circa 40 amph between sat pm and Mon am, so assuming you park up at 6pm sat until 8am Mon, that's a loss of 40 amp hours during the 38hrs, so your dropping over an amp an hour, thats a lot. 

A 5w bulb in boot will draw 5/12 of an amp, or 0.42amp, so unless you've got 2 x 5w bulbs in the boot, this isn't the only source of drain, unless your battery lacks the juice at 75% charge, which would be a poor show.

You can try removing bulb, but easier and faster method is to stick your video recorder on your phone, lie it in boot, camera up of course and shut boot. When retrieved, play video back and see if the lights on, confirmed result in minutes.

Paying £100 plus at this stage, I say hold off, likely the fix, even if a new battery, would be cheaper than that.

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Ended up changing my battery this weekend. The frost finally killed it. Looks like it was still on the original battery (Panasonic) so not bad for 9 years old. Managed to get a Bosch S4 from Eurocarparts for £94 in the weekend 35% sale.

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update -

car parked on saturday around 1200 -

not used until 0800 this(monday) morning - started first time -

it maybe that when i left it with the garage last monday, any tests/rundowns etc. that they did recharged the battery fully.

one swallow does not make a summer, so i will monitor and see what happens next monday morning(i hope the weather is very cold between now and then so that it will be really tested)

fingers crossed and thanks for your(S) support -

knowing my luck, i parked it at 0815 this morning and will be starting it in 20 minutes time hope is is not GRrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr

 

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I was just wondering when its time to replace the battery do you go for aftermarket or OE over the years I have replaced many battery's on different cars with so called top quality one's and have yet to find one that lasts any where close to original fitment

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my last one was supplied by the aa(after a callout in december2016) - prior to that i had a genuine lexus one(i was surprised how cheap it was at the time)

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