WIP: how to replace your alarm siren box back up battery

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Franciswat
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WIP: how to replace your alarm siren box back up battery

Post by Franciswat » Thu Nov 01, 2018 4:30 pm

Hi guys, since alarm's battery recently has gone leaving me with error on vcds I was looking to replace siren.
Considering a new part will cost a lof of money I started to check If could be possibile to replace the nimh battery only with a smaller amount of money. As far as I learned on forums problems with those siren's battery are not so uncommon on VW, Audi, Skoda. Is there anyone here who replaced battery by himself successfully?

Pictures from the web.

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Last edited by Franciswat on Wed Nov 07, 2018 8:51 am, edited 1 time in total.

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Re: Alarm's battery fault

Post by RUM4MO » Thu Nov 01, 2018 4:51 pm

Have you Googled Varta 2X3V150H batteries?

I did and there are a few pictures of VW Group siren boxes open, I've read about on either VW Passat forums or Audi forums, and yes people have been replacing their failed alarm batteries, depending on where the siren box is located, some people have just bought a battery of the correct voltage and same or capacity and if it was the wrong size, bought a plastic box to seal it into and wired it to the original siren box.

I'd think if you Googled this topic you would find many hits and help, I've owned 2 VWs in the past and kept them until they were 13 years old, but never had any alarm box battery problems. Edit, sorry you have done this and found these pictures!

Edit:- https://www.a2oc.net/community/index.ph ... ent.35824/

Another Edit:- I have done what the poster on the A2OC forum did - not on a car, but with other electrical equipment, ie bought as close as I could and maybe taped or glued them together and used suitable tinned copper wire to connect them to the PCB.

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Franciswat
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Re: Alarm's battery fault

Post by Franciswat » Thu Nov 01, 2018 8:39 pm

RUM4MO wrote:
Thu Nov 01, 2018 4:51 pm
Have you Googled Varta 2X3V150H batteries?
Well yes I did it... I know that you said I just asked if anyone did It on this forum.

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Re: Alarm's battery fault

Post by RUM4MO » Thu Nov 01, 2018 10:15 pm

Personally I'd doubt if anyone has done this, so this is your chance to make up a "this is how to replace your alarm siren box back up battery"?

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Re: Alarm's battery fault

Post by Franciswat » Wed Nov 07, 2018 8:49 am

Finally i disassembled the alam using a cutter to separate the 2 sides being careful to not damage the interior components.

Even if battery exterior conditions are good voltmeter confirms that It has no charge.

I've ordered a new battery and will keep you updated.

Image

Image

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Last edited by Franciswat on Thu Nov 08, 2018 11:41 pm, edited 1 time in total.

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Re: WIP: how to replace your alarm siren box back up battery

Post by RUM4MO » Wed Nov 07, 2018 2:28 pm

Where did you find this alarm siren box located in your car, and maybe try soldering a couple of long leads onto the terminals to see if that battery is being charged when the engine is running, ie is the voltage getting increased when the engine is running.

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Re: WIP: how to replace your alarm siren box back up battery

Post by Franciswat » Thu Nov 08, 2018 1:12 am

RUM4MO wrote:
Wed Nov 07, 2018 2:28 pm
Where did you find this alarm siren box located in your car, and maybe try soldering a couple of long leads onto the terminals to see if that battery is being charged when the engine is running, ie is the voltage getting increased when the engine is running.
That's a good suggestion. :wink:

May be possible to power on the unit using an external 12v source to execute this test?

I'm not an electrician so this is probably wrong but I post it anyway so maybe someone can correct me!

Image

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Re: WIP: how to replace your alarm siren box back up battery

Post by RUM4MO » Thu Nov 08, 2018 10:24 am

Well there are 3 pins on the connector for this box, logically it needs +12V, 0V and a trigger input to switch the siren on to sound, so maybe that circuit diagram is okay.

Where in the car did you locate this box?

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Re: WIP: how to replace your alarm siren box back up battery

Post by Franciswat » Thu Nov 08, 2018 11:29 pm

Where in the car did you locate this box?
I post an image to show you. Alarm position is much uncomfortable to reach (wipers have to be removed).

Image

After original batteries check I noticed they are not linked in series themselves (you can separate them) but through the circuit board to reach 7,2v.

Image

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Re: WIP: how to replace your alarm siren box back up battery

Post by RUM4MO » Fri Nov 09, 2018 9:05 am

Very good, thanks for that information, I suppose that there are only 2 positions that the alarm siren box could be, either where you found it or behind the trim in the boot/hatch area at the other end of the car.

Removing that water deflector shield, did you use an online guide which I think suggested starting at each side of the car and ease it out - or what else did you need to do, and was it quite difficult to remove? I'll add these picture to a folder I have just in case I need to carry out this repair in the future!

On the topic of these batteries not being connected together, it must be due to the fact that that specific "2X" battery pack is only used in situations like this. I think if you were doing this again, it might be better/easier to cut the long leads as high up as you can and leave them soldered into the PCB, then hold the 2 batteries down and maybe glue them to the PCB after cutting their contact leads a bit shorter, then solder the original leads onto the ends of these batteries - that was just a though after seeing what you have done.

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