alarm goes off when disconnecting negative lead

[Stangfan333]

hi,when I go away for a few months I disconnect the negative battery lead,but the alarm goes off for about 5 minutes then stops.
Any tips how to avoid this.I can't use a trickle charger as carport is too far away.
Thank you for any help

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[Skye]

Just to confirm, we're talking about the car's security alarm, yes?

Are you saying the car's security alarm goes off, after disconnecting the battery cables? Or the car alarm goes off, when the cables are later re-connected?

Is the alarm system an aftermarket unit? Or is it a factory unit?

 

[ice445]

Is the car locked when you remove the lead?

 

[Cobra Jet]

I would not be using a trickle charger to begin with, what you really want is a “battery maintainer”. Chargers or trickle chargers in general are bad for batteries and aren’t to be used for long term use.

These (2) companies below are the best in the business and have been around for years with the best reputation and quality products.

https://www.batteryminders.com/industrial-battery-charger.php


https://www.batterytender.com/battery-chargers

—-

As others have asked is your S550 equipped with an aftermarket alarm? I’ve never heard of anyone on here that has disconnected (or reconnected) their battery or when replacing a battery for the factory S550 alarm to sound.

If you don’t have an aftermarket alarm, do you have other aftermarket electronic equipment integrated into the fuse label or other wiring?

 

[Stangfan333]

Just to confirm, we're talking about the car's security alarm, yes?

Are you saying the car's security alarm goes off, after disconnecting the battery cables? Or the car alarm goes off, when the cables are later re-connected?

Is the alarm system an aftermarket unit? Or is it a factory unit?

It is factory alarm & goes off when disconnecting battery

 

[Stangfan333]

I would not be using a trickle charger to begin with, what you really want is a “battery maintainer”. Chargers or trickle chargers in general are bad for batteries and aren’t to be used for long term use.

These (2) companies below are the best in the business and have been around for years with the best reputation and quality products.

https://www.batteryminders.com/industrial-battery-charger.php


https://www.batterytender.com/battery-chargers

—-

As others have asked is your S550 equipped with an aftermarket alarm? I’ve never heard of anyone on here that has disconnected (or reconnected) their battery or when replacing a battery for the factory S550 alarm to sound.

If you don’t have an aftermarket alarm, do you have other aftermarket electronic equipment integrated into the fuse label or other wiring?

Thank you for reply,car is totally original

 

[Stangfan333]

hi,when I go away for a few months I disconnect the negative battery lead,but the alarm goes off for about 5 minutes then stops.
Any tips how to avoid this.I can't use a trickle charger as carport is too far away.
Thank you for any help

I would not be using a trickle charger to begin with, what you really want is a “battery maintainer”. Chargers or trickle chargers in general are bad for batteries and aren’t to be used for long term use.

These (2) companies below are the best in the business and have been around for years with the best reputation and quality products.

https://www.batteryminders.com/industrial-battery-charger.php


https://www.batterytender.com/battery-chargers

—-

As others have asked is your S550 equipped with an aftermarket alarm? I’ve never heard of anyone on here that has disconnected (or reconnected) their battery or when replacing a battery for the factory S550 alarm to sound.

If you don’t have an aftermarket alarm, do you have other aftermarket electronic equipment integrated into the fuse label or other wiring?

Car is totally original

 

[Stangfan333]

I would not be using a trickle charger to begin with, what you really want is a “battery maintainer”. Chargers or trickle chargers in general are bad for batteries and aren’t to be used for long term use.

These (2) companies below are the best in the business and have been around for years with the best reputation and quality products.

https://www.batteryminders.com/industrial-battery-charger.php


https://www.batterytender.com/battery-chargers

—-

As others have asked is your S550 equipped with an aftermarket alarm? I’ve never heard of anyone on here that has disconnected (or reconnected) their battery or when replacing a battery for the factory S550 alarm to sound.

If you don’t have an aftermarket alarm, do you have other aftermarket electronic equipment integrated into the fuse label or other wiring?

Thank you,car is totally original

 

[Stangfan333]

Is the car locked when you remove the lead?

 

[Stangfan333]

Yes car is locked

 

[Stangfan333]

I would not be using a trickle charger to begin with, what you really want is a “battery maintainer”. Chargers or trickle chargers in general are bad for batteries and aren’t to be used for long term use.

These (2) companies below are the best in the business and have been around for years with the best reputation and quality products.

https://www.batteryminders.com/industrial-battery-charger.php


https://www.batterytender.com/battery-chargers

—-

As others have asked is your S550 equipped with an aftermarket alarm? I’ve never heard of anyone on here that has disconnected (or reconnected) their battery or when replacing a battery for the factory S550 alarm to sound.

If you don’t have an aftermarket alarm, do you have other aftermarket electronic equipment integrated into the fuse label or other wiring?

Thank you,car istotally original

 

[Skye]

The Ford Passive Anti-Theft System (PATS) appears to have a backup (battery or capacitor) of a temporary type. You proved that. I can see the use of one by Ford, for all kinds of reasons.

https://forums.mbclub.co.uk/threads/alarm-sounds-when-battery-disconnected.234117/

The thread above highlights one car, a MB, that alarmed during a battery disconnect, while being unlocked. I understand yours was locked. But it speaks to one related topic: low and weak main batteries.

The MB Owner confirmed his battery was low at the time of disconnecting. He had enough power for some accessories, but not enough to start the car.

From various postings, using a weak main battery or letting the battery slowly run down to nothing can create problems with Ford PATS. It's best to disconnect the battery while the car is unlocked.

You have what is now a four-plus year-old car that might have been through this in the past (long disconnects, drains, rapid charges, etc.). With that, it might be time to install a new battery when you return.

If you do replace the battery, perform a BMS reset: (its easy)

https://www.mustang6g.com/forums/threads/bms-reset-no-tools-required.151602/

Long answer, short, disconnect the battery when the car is unlocked. You can always lock it using the physical key in the fob. The instructions are in the Owners Manual and here:

https://stevemarshallfordnanaimo.com/blog/how-to-unlock-the-mustang-with-a-dead-battery/#:~:text=Underneath the key handle, find,twist and unlock the car.

As @Cobra Jet pointed out, a battery tender is a preferred method of keeping the battery at its best. It wasn't clear to me where or if you're charging the battery before re-installing. If you are topping off before re-installation, consider replacing the existing charger with a tender.

Good Luck.

 

[ORRadtech]

What model year is the car? Did you buy it new or used?
Quite a few cars have more than one battery, especially cars with auto start/stop. Although I'm unaware of the Mustang having one.

 

[Stangfan333]

The Ford Passive Anti-Theft System (PATS) appears to have a backup (battery or capacitor) of a temporary type. You proved that. I can see the use of one by Ford, for all kinds of reasons.

https://forums.mbclub.co.uk/threads/alarm-sounds-when-battery-disconnected.234117/

The thread above highlights one car, a MB, that alarmed during a battery disconnect, while being unlocked. I understand yours was locked. But it speaks to one related topic: low and weak main batteries.

The MB Owner confirmed his battery was low at the time of disconnecting. He had enough power for some accessories, but not enough to start the car.

From various postings, using a weak main battery or letting the battery slowly run down to nothing can create problems with Ford PATS. It's best to disconnect the battery while the car is unlocked.

You have what is now a four-plus year-old car that might have been through this in the past (long disconnects, drains, rapid charges, etc.). With that, it might be time to install a new battery when you return.

If you do replace the battery, perform a BMS reset: (its easy)

https://www.mustang6g.com/forums/threads/bms-reset-no-tools-required.151602/

Long answer, short, disconnect the battery when the car is unlocked. You can always lock it using the physical key on the fob. The instructions are in the Owners Manual and here:

https://stevemarshallfordnanaimo.com/blog/how-to-unlock-the-mustang-with-a-dead-battery/#:~:text=Underneath the key handle, find,twist and unlock the car.

As @Cobra Jet pointed out, a battery tender is a preferred method of keeping the battery at its best. It wasn't clear to me where or if you're charging the battery before re-installing. If you are topping off before re-installation, consider replacing the existing charger with a tender.

Good Luck.

 

[Stangfan333]

Thank you for your reply

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