any recommendations?
i am asking as my no fault battery gulps power when switched of and fan running during these colder days.
it has gone flat once this week, and its the wifes car....so i thought as a precaution to buy a booster pack.
so the battery will not be totally flat, but will need a little extra power to help it crank ...if the problem arose again.
are the lighter 300-400 amp ones adequate..or the full fat 900amp ones required.
cheers 2011 4.4 TdV8 Nara Bronze

Why not use an overnight charger/conditioner ?

Not sure why the battery would be going flat. Same car as mine, same year. I fitted a new battery last year and even when using the pre-heat function it always starts first pop. Are you sure the battery's good? Been properly tested? Is the car just used for short runs etc? What I'm saying is address the real issue, don't just provide a fix for when it doesn't start. Much easier.

Anyway, a CTEK would sort this for sure. Better solution than a humping great booster pack kicking around. BTW, if you've ever seen what one of those can do in a crash you'd think twice about having one loose in the boot.

the car is used on the school run.....30 mins each way
i have had it drop tested at halfords , and they said it was good.
also been checking alternator output via the 753 funtion on the screen and that gives a figure of 13+amps.
if the car is left for a week at the airport, starts first time...
your right about the bulk issues and more important issue of accidents if i was lugging one of these things around...
as i have asked on an other thread..
would there be a possibility of fitting a bigger battery? 2011 4.4 TdV8 Nara Bronze

I assume the 13+ is volts not amps and if so doesen't sound very reassuring.
I would also seriously question the results a volt drop test carried out a Halfords.
If its the original battery on the car, time for a new one.

I always go for the biggest capacity battery that fits into the space, just to be on the safe side.

I would also suggest to do a current leak test. Switch everything off, leave the car for 15 to 30 minutes so all ECUs should have gone to sleep and then take the ground clamp of the battery and measure current between ground clamp and battery minus. That should be very low, say substantially less than 1 Amp I would expect, with the car unlocked (hood open would set off alarm), all doors and tailgate closed (so interior lights are off). If you do measure a few amps then you have a "leak" and to find it, it means removing one fuse at the time. MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

Largest battery available is a Bosch one - do a search on here. About 1000 cranking amps I recall.

Anyway, from what you describe, 30 minutes sounds like a decent enough run. That's what I do at least 3 days a week without issues. This would point to either a failing battery or a suspect alternator. 13 volts sounds low BTW, these things normally run at over 14 volts. Mine is 14.2. Possibly worth checking with a more accurate meter.

As per the other thread here get the Bosch from Europarts - best £100 you will spend.

Mine struggled to start a few times last year, then one time failed but seemed to recharge, then occasionally struggle - passed all the tests, but I stuck a new Bosch in anyway & never had a problem since.

IMHO well worth the £100 for the peace of mind

Alternator output should be 12.5v MINIMUM 14.2v is desirable. But that can vary if smartcharge is used!(not applicable here!)
Ampage can vary depending on loads used .
Sounds like a duff battery

Having your battery checked by someone who knows what they're doing is very advisable!
Do you have breakdown cover?
The guy's in orange vans do a battery assist thingy: they come n test your battery, charging system, any excess drain and can supply n
Fit u a battery with a 4yr wtty.
They also supply and fit ctek chargers.
It's all on their website thingumy jig.
U don't need to be a mar either!!!
Other breakdown secs are available!!!!!

Hth Why is it, the easier it breaks, the more expensive it is?