Battery drain when standing

[westcr]

2003, 986 Boxster 2.7

From a fully charged battery (about 13V) if I don't use the car for about 5 days the battery voltage is down to 12.3V. Any longer - say a week, and the remote locking does not work but the car starts OK. The battery is new (last month). Is this normal?

PS I noticed a previous post about sleep mode which may explain the remote locking problem.

 

[spyderman]

Indeed - the central locking shuts down automatically after 5 (?) days to save power - that's not a battery problem.

I use a CTek 3600 battery conditioner on my 2004 550 Anniversary if there's the slightest chance I won't be using it the next day. And I no longer use the Porsche Moll battery!

Chris.

 

[Clewsey]

As Chris says this is normal behaviour after 5 days of non-use.

Whilst I use a CTEK also, I also have an Ultimate Speed conditioner bought from Lidl (yes Lidl) which costs a fraction and is exactly the same. It's TUV certified and I've never had a problem. It's about £20-25.

http://www.lidl-service.com/cps/rde/SID-F86DE9F8-9DB64BB3/lsp/hs.xsl/product.html?id=2844174&rdeLocaleAttr=en&title=BATTERY%20CHARGER%20ULG%203.8%20A1

Cheers,
Simon

 

[westcr]

Thanks Simon & Chris

It would seem the Boxster electrics are very power hungry, even when not driven. Perhaps a design fault? Still very annoying for an otherwise brilliant car.

Ray

 

[Glyn]

The maximum drain on the battery providing you have no accessories (aftermarket fitted) should be under 25miliamps, therefore there shouldn't be an issue with battery going flat or significantly reduced after just 5 days.
There are 1000 miliamps in an amp.
So 40 hrs to use an amp at 25 milliamp drain

Therefore If you have an 80 Amp hour battery you should be able to leave the car for 3200Hrs before the battery would be flat that's 133 days 8 hours, so if you are having a battery going flat in 5 days then there is a problem. OK that's theoretical and things very rarely work to theory.

Battery voltage is typically 12.6 to 13.3 volts but voltage alone is not the be all and end all so you should not be too concerned about it, however, to satisfy yourself that you don't have a current drain you need to borrow an Amp clamp meter and measure the drain, The amp clamp meter is a simple meter that has a "C" shaped claw head, you open the claw just like you would a set of pliers, they are spring loaded to close like an insects pincers over a cable, you don't need to tap into a cable or disconnect anything just place the claw over the positive lead from the battery - yes over the insulation - from that point any current running through the cable will be detected and will give you a reading.

Open the bonnet and let the car stand for at least 15 minutes locked before you measure as the car draws a little more power initially on lock up but shuts down standby components after 15 minutes - at this point take your reading - If its over 25 milliamps then something is drawing the power and you need to investigate what that is.

With the meter in place unlock the car and take note of the higher reading as the standby components will be reactivated and therefore a higher current draw, this now becomes your base measurement. (just the difference between the lowest reading and the now unlocked reading - add the difference to 25 milliamps and that is your target total draw)

Pull one fuse at a time and take note of the reading, keep doing this until you find the circuit that is responsible for drawing the extra power, once you have this its simply a matter of establishing what the fuse supplies.

One other thing to do is to disconnect the alternator connection and see if that reduces the draw, It shouldn't make one iota of difference but the alternator does have an habit of blowing one of the diode packs (there are three).
A diode allows current only in one direction and these are set to provide power away from the alternator, if a diode fails it allows current to drain to the alternator and in turn it tries to work like an electric motor but it cant turn because of the drive belt - so it draws quite a bit of power.

You may be able to get just a diode pack for the alternator but it is difficult, so a recon one off Ebay for £130 ish is perhaps the cheapest and easiest way to fix it

Sorry if this reply seems a bit teckie but I have tried to keep it simple

 

[Robin M]

If the car starts OK what is the issue. The battery is a 12V battery so if standing without charge you wouldnt expect more than what you are seeing. You could always get a garage/auto electrician to check the current drain when the car is standing with everything turned off. This would guide you as per the above post to if there are any current drain issues.

 

[Wollemi]

I have a solar battery charger panel which sits under the windscreen and just plugs into the cigarette lighter socket and supplies enough power to keep the battery topped up.

 

[BartyB]

12.3 V sounds about right after 5 days. At this time of year when you tend to use lights, wipers, rear screen heater, etc a lot more, if you're doing mainly short journeys, then the battery may not be getting fully recharged which is why Chris' and Simon's recommendation of using a battery conditioner when the car is parked up makes sense. As Graham suggests, if you park it outside a PV charger is also a good idea although I have experienced problems with these in the past not generating sufficient output to compensate for current drain over extended periods (> 1 month). I would suggest you check the output of the alternator too. Just measure the voltage across the battery when the engine is running. If the alternator is healthy you should get a reading of about 14.3 V.