Help needed with Renault Megane Urgently

[M-Ster]

Hi All

My Partner has a Renault Migrain Cariolet the battery has died so i took the old one off and put the one off my car on hers however the one from my car was flat but is new so i conntected the battery back up andput it on charge but cant get the alarm to stop going off is it because the bonnet is open or that the charger keeps changing the readings to the alarm and its that thats setting it off

Its the standard renault factory fit alarm

[Sammyturbo]

I think the alarm will sound until a fully charged battery is put back on the car

[GingerRob]

I don't know with that megane if you have a seperate horn but have you tried locating the alarm sounder and unplugging it or filling the trumpet up with cloth to muffle the sound

[brakedust]

Just disconnect the +ve terminal from the car and them put on charge, that will stop the alarm going off

[M-Ster]

Ok i fully charged the battery as soon as i connected the positive the alarm sounded (alarm is a seperate unit located right next to the battery not through the horn)
Tried blipping the fob doors locked and unlocked on fob but alarm just keeps sounding left alarm sounding got in the car locked and unlocked the doors via fob tried starting car alarm still sounding car starts, after bout 10 seconds alarm goes off but immoboliser light stays lit switch car off lock unlock alarm goes off straight away.
Do i need to let the alarm sound until it goes off and this is its resetting process??
Is there any kinda reset that maybe needed?!?

Happy to stand there and try different things but think neighbours are not enjoying listeneing to it keep going off