# How to disconnect the battery for long term storage?



## Dave 20T (Apr 7, 2013)

Very simple question.

How to disconnect the battery for long term storage?

a. disconnect the positive and negative leads. That's what I would do.

How about...

b. disconnect the positive lead only
c. disconnect the negative lead only

Perhaps there could be some dirt so the battery is slightly grounded. If that is the case, better to disconnect the positive lead only if someone were to disconnect only one of the leads.


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## Zeichen311 (Mar 31, 2011)

Option D: None of the above. Connect it to a battery tender/maintainer ("smart charger"). Otherwise, when the day comes to revive the car from storage, you may be greeted by a dead battery. Batteries do not hold charge indefinitely.

With a late-model BMW, disconnecting or removing the battery carries an additional risk: One needs to take precautions to ensure the trunk cannot be closed accidentally. Without battery power it may be impossible to open the trunk to reconnect the battery....


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## Dave 20T (Apr 7, 2013)

Zeichen311 said:


> Option D: None of the above. Connect it to a battery tender/maintainer ("smart charger"). Otherwise, when the day comes to revive the car from storage, you may be greeted by a dead battery. Batteries do not hold charge indefinitely.
> 
> With a late-model BMW, disconnecting or removing the battery carries an additional risk: One needs to take precautions to ensure the trunk cannot be closed accidentally. Without battery power it may be impossible to open the trunk to reconnect the battery....


Great advice! That's like the advice that I give when changing the oil. Always open the hood first because if you drain the oil and cannot open the hood, it's a lot more trouble than if you find you can't open the hood and then delay the oil change pending hood latch repair.

The car in question is a 2000 model year, not a BMW, and has the battery in the hood. It's parked outside. My suggestion would be to disconnect the battery then occasionally trickle charge it during a time where one is working outside and can supervise the car.


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## Zeichen311 (Mar 31, 2011)

Sounds reasonable; in that circumstance the answer is option C: Negative cable only, securing it in such a way that it cannot accidentally make contact with the battery.

Generally speaking, it's not recommended or necessary to disconnect the positive terminal (unless one is removing the battery from the vehicle altogether). Doing so creates a risk of damage or fire in the event of an accidental short-circuit between the disconnected terminal and the body (_e.g._, a dropped wrench).


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## APLinhares (Oct 25, 2017)

Well pointed!
And when connecting connector after a long time could made a spark/peak voltage and damage something... Again, a messy short-circuit.


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## cezar (Apr 24, 2020)

Battery must be fully charged when it's not used for long time. So you must charge it to tohe max every 2-3 months


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## Haydeny (Apr 27, 2020)

Maybe you have a convertible that you love to drive in the summer, but now winter has arrived. Or perhaps you're going to leave town for a job or an extended vacation. Maybe you are in the military and are being deployed overseas McDVOICE _sl_


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## hottroc (Apr 4, 2020)

Just out of interest are there special measures for PHEVs? I'm more thinking about short term disconnections rather than long term storage (say if you want to retrofit something electrical).


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