Sounds a bit daft, but rather than running the engine for ages while doing electrical stuff and ibus diagnosis, can I somehow plug the car into the mains so that when in position 1 on the ignition I don't run the battery down? Have googled but not come up with anything viable? .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

Yes. just connect up a cheap 12v car charger. I would often do this whilst detailing the interior so I could listen to music for hours without worrying about the battery. 

If you have towing electrics you can run a charger feed via the trailer feed pin and earth. Graham

____
Gone: 10MY L320 RR Sport HSE, Ipanema Sand
Gone: 20MY Jaguar iPace HSE, Silicon Silver
Gone: 17MY RR Evoque SE Tech, Loire Blue
Gone: 08MY Discovery 3 XS, Stornoway Grey
Gone: 07MY FFRR TDV8 Vogue, Stornoway Grey

Is it really that simple? The FFRR is quite happy having charger connected across the terminals with battery connected? I have a cheap 12v charger, so will give it a go.

Thanks guys  .
Experience is the only genuine knowledge, but as time passes, I have forgotten more than I can remember
Volvo V70 P2 2006 2.4 Petrol 170bhp Estate SE
MG Midget Mk1 1962

Previous: L322 Range Rover TDV8 3.6 2008; L322 Range Rover TD6 3.0 2002; P38A Range Rover V8 1999

Only the same as a Solar or Trickle Charger connected but with more ummmph

I was always told you had to disconnect the battery when charging, to avoid damaging the alternator. Is this not true any more, can modern electrics cope with it ?

I wouln't connect a "cheap" charger to the car whilst the battery was connected if you value the future reliable operation of your ecu's in future.
Even the handbook recommends you don't do it.
I have a Cteck charger which I use for that purpose and to date no problems.
You could of course just connect another battery to the car, via jump leads, the tow socket or the cigarette socket to increase the capacity of the battery.

Ordinary chargers can cause 'spikes' in the power supply which can damage ECUs if left

Not something I would do Joe...

I would avoid using an ordinary car charger. The purpose of these chargers are to charge the battery up as soon as possible for convenience – this can often damage the battery if used regularly.

I would instead opt for a battery conditioner, these are designed to stay on the car for prolonged periods causing no damage and keeping your battery in full health. They (CTEK) can be had for very little money too; and they can come with a Cigarette adaptor so no need to have the bonnet open, the wire just slips through the door shut.

Spare battery and set of jump leads. Connect spare battery to FFRR battery, switch on ignition and do what you have to. When finished disconnect spare battery from FFRR and recharge it separately.

With regards to the spikes when connected, I don't see how using a conventional charger is any different to clipping on jump leads. In fact, a charger that only starts when a current is detected is going to do less harm than clipping on some jump leads that can spark when clipping onto the battery.

Back to the original question though, my Mini is left connected to a battery conditioner that's on a timer plug which comes on for an hour in the morning and an hour at night, the battery has been spot on for 3 years as the car has very little use, but when I'm working on the electrics, the charger is on permanent like Dan says, so I have no worries about a flat battery. 2006 Mercedes CLS
1991 Retro-style Mini
But really finding it hard to fight the urge for a S/C...

if you have a 'regulated' battery charger ,then you shouldn't have any problems..

As I understand it the problem is not just the spikes, it's also the ac leakage that can occur due to lower quality rectifiers used in cheaper battery chargers.

So basically, buy a decent one and avoid the £1 shop/Lidl specials  2006 Mercedes CLS
1991 Retro-style Mini
But really finding it hard to fight the urge for a S/C...

The cars electrical system has to deal with voltages ranging from 10V-15V+ due to changing loads, changing charge rates from the alternator and issues caused by different temperatures, as well as massive ampage changes.

Coupled with the range of accessories you can plug into the 12v system, ranging from winches to caravans the loads can be quite comprehensive.

So really, plugging in a 6Amp charger will not damage the car. No one mentioned a "fast charger" though, tat would be a different thing I would have thought. But still no more of a kick in the pants than a jump start!