P38A Alarm, EKA, battery

1997 4.6 HSE. Working fine until I got in and couldn't start it. It had stood for a week. Chattering from bonnet (starter motor solenoid?), "gearbox fault" on display. So I jump started it and all was OK. Ran it for a bit to let the battery recover.
Last night, the alarm went off (at 0230!). Remote button wouldn't stop it. Door locks were rattling at same rate as display was showing EKA message.
Eventually alarm stopped (battery too low?) but I couldn't enter EKA. 4 unlocks didn't register, although occasionally display changed to require code, but as soon as I tried code, the "disabled" message resumed.
I put the battery charger on today, but the alarm began again, so I disconnected the battery (probably incorrectly) and the alarm has stopped.
NOW THE QUESTION
I think the battery's duff; charger is showing high charge rate even after hours of charging.
If I replace the battery (it's currently disconnected), do I have to go through any special sequence to start the damn thing?
Thanks in advance. I've read a lot of threads here which suggest all sorts of things.

You've answered your own questions really.
If the battery has been disconnected then the car will disable itself until you put the EKA in with a decent charged battery installed.
I would bite the bullet and dump the duff battery and go get yourself a decent one if I were you, or you will be inputting the EKA many times over.
Which is OK......until the switches in the doorlock fail and you don't have a Nanocom alternative.

Car should come back online in the state it had the battery taken off. Sp always make sure it is disarmed, unlocked and the driver's door is open when connecting or disconnecting the battery.

DanClarke said:

You've answered your own questions really.
If the battery has been disconnected then the car will disable itself until you put the EKA in with a decent charged battery installed.
I would bite the bullet and dump the duff battery and go get yourself a decent one if I were you, or you will be inputting the EKA many times over.
Which is OK......until the switches in the doorlock fail and you don't have a Nanocom alternative.

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That is not true, I have disconnected batteries on P38's many times and never had to use diagnostics or the EKA code. A battery going flat however may wall cause a problem as the BECM does not cope well with a slowly descending voltage
To the OP, get a 1000CCA battery, the bigger the battery the better on a P38.
With a standard car battery charger, it can take 2 days or more to fully charge a P38 battery. The alternator will also take many hours.

Datatek said:

That is not true, I have disconnected batteries on P38's many times and never had to use diagnostics or the EKA code. A battery going flat however may wall cause a problem as the BECM does not cope well with a slowly descending voltage
To the OP, get a 1000CCA battery, the bigger the battery the better on a P38.
With a standard car battery charger, it can take 2 days or more to fully charge a P38 battery. The alternator will also take many hours.

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@Datatek It may not be true in all cases (I have not encountered all cases so my knowledge is limited to my own observed behaviour) in my experience (admittedly not as vast as yours) it is what I have observed. I was not trying to mislead anyone, so my apologies. Seen the need to re-enable with EKA after battery removal on both of my P38's so far, so I had assumed it was par for the course. In the first vehicle the battery was definitely dying a slow and painful death. Mea-Culpa.

Big battery ordered (1000 CCA) as advised. I'll hitch it up once fully-charged, then let you all know what happens next....!

Well! Battery reconnected (tentatively, waiting for the alarm to go off!) Nothing! Opened door, nothing, jumped in, inserted key and ... Everything normal, started happily. I only had to reset the windows and sunroof. How strange.
I've disconnected the blue antenna wire from the RF receiver, and moved the car to another position to negate the "stray radiation effects"
Here's hoping. I wonder whether to try inputting the EKA to check it. Or should I let sleeping dogs lie...

ibgarrow said:

Well! Battery reconnected (tentatively, waiting for the alarm to go off!) Nothing! Opened door, nothing, jumped in, inserted key and ... Everything normal, started happily. I only had to reset the windows and sunroof. How strange.
I've disconnected the blue antenna wire from the RF receiver, and moved the car to another position to negate the "stray radiation effects"
Here's hoping. I wonder whether to try inputting the EKA to check it. Or should I let sleeping dogs lie...

Click to expand...

If it ain't broke, don't even think of touching it.

ibgarrow said:

Well! Battery reconnected (tentatively, waiting for the alarm to go off!) Nothing! Opened door, nothing, jumped in, inserted key and ... Everything normal, started happily. I only had to reset the windows and sunroof. How strange.
I've disconnected the blue antenna wire from the RF receiver, and moved the car to another position to negate the "stray radiation effects"
Here's hoping. I wonder whether to try inputting the EKA to check it. Or should I let sleeping dogs lie...

Click to expand...

Just goes to show the difference between a good battery and a weak one. Now you need to check that the alternator is putting out the correct voltage, it needs to be around 14.7v at 2K rpm.
Why would you try the EKA code? It's not locked out so the code should have no effect and if the door latch switches are dodgy, it could just cause you a problem.

Having failed to input the EKA properly, I worried that it may not work when it has to. If it'll have no effect, then I'll just cross my fingers for when/if it's needed.
Thanks for the help, folks.
PS I'll check the input voltage soon.