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Discussion Starter #1 (Edited)
Dumb question of the day. Just bought a float charger since I'm headed overseas for 3 weeks soon. Do you connect this directly to the battery or the connector points under the hood???????

Thanks,
Jason
 

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On the E39 either location is appropriate. I have mine hard-wired in the trunk.

As an aside, on the newer BMWs (2006+ ... depending on series) you have to use the connections under the hood as a direct connection to the battery bypasses the IBS (Intelligent Battery Sensor) and that will result in the car later roasting the battery.
 
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Without battery drain, you shouldn't need a float charger for a mere 3 week trip.... Is there something else indicating a battery drain problem?
 

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Without battery drain, you shouldn't need a float charger for a mere 3 week trip.... Is there something else indicating a battery drain problem?
These cars are well known for parasitic draw. Don't know the age or health of his battery but a battery tender is a good precaution to ensure the battery is not dead in 3 weeks. I've also heard that using a tender will prolong the long term life of a battery.
 

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These cars are well known for parasitic draw. Don't know the age or health of his battery but a battery tender is a good precaution to ensure the battery is not dead in 3 weeks. I've also heard that using a tender will prolong the long term life of a battery.
Can't be any worse then my 'airport beater' E38 w/Electrical issues, which regularly sits for 1+ months at a time. Parasitic draw is one thing, but any car with a decently fresh battery that can't last at least a month without being started has other concerns.

(Now that I've said that, I'll be sure to return to a dead battery from this trip)
 

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Discussion Starter #8
Without battery drain, you shouldn't need a float charger for a mere 3 week trip.... Is there something else indicating a battery drain problem?
Just bought a new battery. Just trying to prolong the life as I have 4 of these trips a year. My other E39 tends to suffer after only 6-7 days, so will probably use it on that vehicle or buy two.
 

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The original owner of my M5 was OCD about the battery and put it on the battery tender anytime the car went more than 24 hours without being driven or if he went away and left it in the garage during vacation. His battery tender came with my car when I bought it, but I have since bought a new Battery Tender Plus (one made in the last 5 years that has the new circuit board logic). I connect mine under the hood. My M5 rarely goes more than 24 hours without being driven, but when it does, I clip the leads on under the hood. How well does it work? I'm still on the original factory battery! I also put dielectric grease on the battery terminals in the trunk every 6 months to keep corrosion away.
 
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