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Old 08-25-2014, 04:34 AM
kuanglee kuanglee is offline
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Location: Australia
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Question Not sure whether safe to charge battery


My car's battery is now completely dead (car won't even take my key in the slot) and I've taken it out thinking I needed to change it; but it's said on the battery that it's rechargeable.

Not sure whether it's safe to charge it with a wall plug battery charger, straight onto the battery, or whether to charge it while it is in the car.

Not very car savvy, any assistance would be appreciated!!!

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Old 08-25-2014, 04:49 AM
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blue boy blue boy is offline
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Mein Auto: 2011 328ix
is the battery old and died from old age or did something being on - bring it down?
sometimes you have to hit it with 25 amps for a few seconds to get the batt to take a charge. and after that normal charging at 10 amps or under for 12 hours or enough to start. keep in mind the alternator is not designed to charge up a a dead battery but to maintain it.
check for charge ports under the hood first- im not familiar with 2005 arrangements. hopefully someone with more 2005 intel will respond to bail me out.

good luck mate
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Old 08-25-2014, 04:55 AM
kuanglee kuanglee is offline
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I believe the battery is dead because the car is/has been used mainly for short trips.

Also, the little spot where there's an indicator that tells you whether or not it's dead, the indicator is on 'Insufficiently Charged'.

Wasn't able to jump start/charge from charge ports because car is stuck in my garage in a tight park.

I've taken the battery out and I am currently trying to charge it with a manual 12 volt 2700 mA charger.

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Old 08-25-2014, 06:17 AM
fdriller9 fdriller9 is offline
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You can't use a normal AC to DC 12v inverter. You need a battery tender or power supply.

If the battery has been dead for more than a day or 2, the plates inside are sulfating and decreasing battery performance.

Special battery tenders can repair a sulfated battery but it will never be the same.

I would just get a new battery and a simple battery tender and keep the tender on the car when it's not in use.

Make sure you use the jump terminals under the hood to connect the tender. Do NOT connect directly to the battery in the back.

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Last edited by fdriller9; 08-25-2014 at 06:56 AM.
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Old 08-25-2014, 08:08 AM
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Location: Fog City, California
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Mein Auto: 09 E93 335i somewhat mod
Originally Posted by fdriller9 View Post
You can't use a normal AC to DC 12v inverter. You need a battery tender or power supply.

It is good to have a charging profile appropriate for your battery - lead acid car batteries for instance have different profiles than lithium. A desulfating alternating current is useful initially - chargers like CTEK do this - 3300 is $52.78 w/2 day delivery on Amazon.

In a pinch can use an inverter, but it's not recommended, especially if you over-charge and start generating hydrogen - a thing that happens over 85% charge - can lead to deleterious effects.
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Old 08-25-2014, 08:14 AM
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DSXMachina DSXMachina is offline
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The OP's charger is 2.7 amps max. He should be OK in making an attempt. A more modern 'smart' charger would be better, but at this point if the battery has any age at all he might as well just replace it. I'll be watching for the "How do I know if I have a parasitic battery draw?" thread.
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Old 08-25-2014, 09:57 AM
hondo402000 hondo402000 is offline
Location: Charlotte, NC
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or take it to you local Autozone and have them put it on their charger, just make sure you dont lock the doors or trunk while the battery is out other wise you might not be able to get back in the car
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