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Old 01-19-2016, 07:41 AM   #1
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battery charging question

Hi Forum,

I have a 2000 2.7 Boxster and I'd like to ask if there is a fault in the electrics. It needs charging or running at least once a week. When fully charged the meter only goes down as far as 4 on the scale instead of to 2. It had a charging problem in the past when a previous tracker caused the battery to drain, but I'm beginning to think it wasn't completely cured at that time. The battery is new but the car couldn't be left for a couple of weeks when I was on holiday or the alarm would come on when the battery ran down. Surely the red dash light wouldn't cause the battery to run down too quickly? Thanks, Barry.
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Old 01-19-2016, 08:27 AM   #2
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Mine does run down, I just attribute it to the alarm. I find it runs down quicker if I don't lock the car. If you know you won't be running it for a few weeks I'd recommend a battery tender.
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Old 01-19-2016, 02:24 PM   #3
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You don't say what the meter units are so it is a bit difficult to know much.

This web posting will give you insight into the typical current draw after the car is shut off. Modern cars spend lots of electricity looking for signals via intrusion detectors and looking for key fob signals.
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Old 01-21-2016, 08:38 AM   #4
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battery tender

Thanks for your replies - I don't know if there's a fault or not, but maybe the tender is the answer so the level of charge is always maintained. I've been using a charger for short bursts and a solar charge for long spells of inactivity. This however is not strong enough to prevent the battery from running down. I'll give the tender a go and see if it'll maintain a proper charge so the alarm doesn't go off or the hood won't open.

Regards, Barry.
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Old 01-21-2016, 08:52 AM   #5
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Does anyone knows if the Boxster car goes to sleep after a certain period. I admit I have the same issue, after let's say 4~6weeks the battery becomes so low it barely start. If any longer than 6 weeks then its click-click-click.

Bypassed the battery NEG with an amp meter with all of the lights and system shutdown and still see a 0.3amp draw. Yes I pulled every single fuse that I could find in the car and the thing still reads 0.3. Seem like a lot for a 'sleeping mode'. Do these cars ever goes to sleep mode at all? I'm I inventing this?

Next time I park for a few weeks I'll just unplug the ground from the batt :/
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Old 01-21-2016, 11:45 AM   #6
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I have used a battery tender plugged into the cigarette lighter for over a year now.
Works great, with minimal investment.
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Old 01-21-2016, 11:57 AM   #7
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You must lock the Box with top & windows up to allow it to go to sleep. After a few days it goes into a deeper "sleep" to conserve battery power. I forget how long exactly, it's in the owners manual. Once it's in the deep sleep the remote control won't open the car you must open with the key.
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Old 01-21-2016, 05:51 PM   #8
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Quote:
Originally Posted by BYprodriver View Post
You must lock the Box with top & windows up to allow it to go to sleep. After a few days it goes into a deeper "sleep" to conserve battery power. I forget how long exactly, it's in the owners manual. Once it's in the deep sleep the remote control won't open the car you must open with the key.
Yay! I'm not crazy! (Still debatable I admit).

I knew mine ran down really fast if left unlocked. So I lock it even in the garage.
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Old 01-22-2016, 08:37 AM   #9
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Quote:
Originally Posted by BYprodriver View Post
You must lock the Box with top & windows up to allow it to go to sleep. After a few days it goes into a deeper "sleep" to conserve battery power. I forget how long exactly, it's in the owners manual. Once it's in the deep sleep the remote control won't open the car you must open with the key.
That's very nice of you explaining how things works. Once had a Owners Manual and seriously can't remember reading about this. I'm a speed reader when it comes to these sort of user manual. Its faster pressing on buttons and learning that way... for some weird reasons

So... I have to lock the car. I see. That could explain a lot then

Thx again
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Old 01-22-2016, 09:35 AM   #10
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It may go to sleep, and the remote key may stop working (after 5 days?), but there will still be a drain on the battery. Get an AGM battery and disconnect the negative terminal if you are leaving the car for more than 2 weeks. Or use a trickle charger (I do one or the other, depending on how long I'll be leaving it).
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Old 01-22-2016, 09:53 AM   #11
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Is there anything in the car that is not standard...for example a tracking device or GPS or radar detector? Even some radio or amp? We are looking for something that might stay on long after things are supposed to go dormant.

The link I posted above gives a diagnostic approach for finding out what circuit is creating the current draw. Basically it is a measure the current draw across each fuse and then figure out what is connected to that fuse.

A tender or maintainer is often different than a charger. The chargers will often overcharge the battery. The maintainer will maintain the level of charge but will not really charge a charge depleted battery below a certain level.

My car used to hibernate in winter for months at a time outdoors in freezing weather with many cm of snow on it with a maintainer connected and would start immediately on request.

How is your tender hooked up? Are you sure that connection is connected to the battery when the car if off and key removed? US and UK cars can be different.
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Old 01-22-2016, 10:27 AM   #12
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I was told/taught to put the car in sleep mode as follows. When exiting the drivers side close the door and insert the key into the door lock. Then turn the key three times quickly clockwise. The car will beep once and in theory is in sleep mode.
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Old 01-22-2016, 04:23 PM   #13
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disraeli posted this years ago on Porsche Pete's Boxster Board

The factory technical manual (Section 97-07 page 2) has the following table of total electrical load after the car has been shut off (Model Year 02):

(electrical current is worst case, i.e. car loaded w/all options...)

FROM TO mA

0 min 5 min up to approx. 950

6 min 15 min up to approx. 900

16 min 20 min up to approx. 750

21 min 60 min up to approx. 50

61 min until the battery is empty up to approx. 30

1000mA equals, of course, one amp.

If the car had no options whatsoever, the load after 60 min would be 17mA instead of 30mA.

From this table you should be able to insert an amp-meter between the battery and battery cable and tell if the car is within spec before you begin pulling fuses or removing the battery to get it tested.
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