Disconnect battery leaving car for a while?
 

I'm off on holiday soon and this will probably mean not driving my car for an entire calendar month.

If I disconnect the battery either fully, or just one terminal are there any potential issues?

I'm worried about the CEM losing memory and this then causing issues or the alarm system not working or something?

Thanks!

There should be no reason to disconnect if your battery is in good condition and the standby current is within spec as it should start comfortably up to around 10 weeks.

Hmm alright thanks. I ask because it's gone flat twice in the past but ever since I removed the insurance black box which was fitted a few years ago it's been better.. Hopefully that was the source of the problem.

If you disconnect the battery the alarm is unlikely to work anyway on a car that age unless you've renewed the auxiliary alarm battery.

If you are still on original battery prehaps you would be better off renewing it rather than disconnecting it then the month layup will be no problem. Alternatively leave a trickle or smart charger connected to the battery if possible, you don't say where you are leaving it, if at home the charger is possible if airport car park even disconnecting the battery is possibly impractical.

Paul.

It's in a work car park.. I'm just going to leave it and make sure to take my jump starter with me when I come back! The battery is about 2 1/2 years old.

I would take the car for a longish run before parking the car so that the battery is charged.

Pop across to ebay. Loads of solar chargers on there for a reasonable price.

When I had a slightly 'tired' battery, and was only doing short journeys with cold starts, I bought one. (Item... Visua-4-Watt-12V-Solar-Panel-Trickle-Car-Battery-Charger). Used to pop it on the dashboard and run the wires direct to the battery with croc clips (the cigarette lighter socket on my V70 was ignition controlled - so no good for charging through!)

I did this every day for about six months!

Never had a problem for ages until the battery really had had enough of life! Though, for safety's sake, I did put an in-line fuse into the cable!

No good if the car's kept in a garage, though!

Then, one day, I actually afforded a new battery!

The maths prove that a correct standby drain on a healthy battery simply cannot cause a problem in a month so if you can answer yes to both, there's no reason to worry.
If it is flat when you return, you know you have a problem which needs addressing.
Checking the level of the standby drain and condition of the the battery is very simple though so personally, I'd be finding that out before any issue occurs.

It had a fairly long run before parking up so should be good.

No time unfortunately, the S40 is also ignition controlled, car is now parked up.

KwikFit had checked the battery and apparently it's fine, so I suspected the black box was draining power faster than would be natural.

Sounds to me like you don't need to worry.