Nige . . .have got used to it being almost flat by Friday . . so put it on the charger for about 4 hours Friday night or Sat morning. It is then fine all over the weekend .
But thinking about it . . .a few weeks ago I did do an overnight charge & it started ok on the following Friday . But then back to being almost flat at the end of that week .If that makes sense
Battery is just over a year old.
Question . . .is it usual for the battery to drain over a 2 week period with the car not being used at all ?
That makes good sense to me ...
take a 70 odd Ah battery ... standard battery charger will run at around 6-8 amps (average over time .. starts at 10 and drops off as battery charges up), so if it is "flat" it needs 12 hours .. 12 * 6 = 72 to charge up .. so your overnight charge sorted it.
If it has a current drain of 0.5 amp the over a day that's 12 a/hr, after 5 days thats 60 a/hr and you battery is flat.
If it has a current drain of 0.1 amp then over a day that's 2.4 a/hr, over 5 days its 12 A/hr .. or a quarter of your battery
anything else you can do the maths !!
so, back to the overnight charge and lets say your current drain is 0.1 amp .. at the end of the week your battery had lost 12 a/hour... you then started the engine from cold, you used power .. call it 30 amp .. so down to 28 ,.. drive it for an hour put about 8 back in .. you have 36 ... leave it for another 5 days .. its down to 24 ... quarter of a battery .. but you need 30 to start and you are a few short .... get out the jump leads !!
All figures are guesses but, hopefully, you'll see what i'm trying to get at ... leaving a half charged battery standing doesn't do it any good !!