Dead Starter Battery - 8.5v

[Ayjay]

Doors to the van has been open quite a bit over the last couple of days as I've been slowly loading stuff in preparation for our road trip to Europe road trip starting tomorrow mornings. There haven't been any problems until a short while ago when I pressed the lock button on the remote and nothing happened. Checking the Varta 70Ah EFB, it had dropped down to 8.5V which is probably explains why the lock wasn't working. I've now plugged in my CTEK MX5 charger and hope that it will bring the battery back to life - locking from the remote worked first time after that. I'm now worried that the thing might let me down once we're on the road but I don't want to take the CTEK MX5 as I want to leave my Audi Q5 plugged into it whilst we're away (4-5 weeks might be pushing it's battery a bit).
By coincidence, Lidl seem to have some really cheap chargers in stock from today which I would hope might give the van battery a quick boost if needed but is it likely to be any good at that price (£15) or will it be just good enough to do the job?

Ultimate Speed Car & Motorcycle Battery Charger - |

Ultimate Speed Car & Motorcycle Battery Charger - Intelligent microprocessor control with diagnostics program and fully automatic charging process For all

www.lidl.co.uk

As an emergency back up, I've also got a Noco GBX75 which should also get me out of trouble in extremis.
The obvious solution is to get a new battery but, as I say, we're leaving tomorrow morning for an overnight in Ashford and early train on Tuesday so not a lot of time for that.
Any advice much appreciated as usual.

 

[True Romance]

Interior lights go out after a few minutes. Have you used the van much?

 

[Dave Leaning]

Halfords will do you a new battery, book a fitting slot on line either mobile or at a store and they will code it for you also. Just had to do that in Bristol as I was away from home when it let me down. Great service all sorted on line.

 

[Ayjay]

@Dave Leaning. We're on the road in the morning and haven't really got time (although I guess I could come to regret that statement). Also, whilst I'm glad that you got good service from your Halfords branch, I personally wouldn't trust the spotty faced kids to do that do that sort of thing at my local store - one of them actually lives just down the road from me and he's stoned most of the time (but hopefully not when he's at work!).

@True Romance. It's not moved for almost two weeks but ordinarily that wouldn't be a problem as the solar panel should keep the starter battery topped up via the leisure system but it might just be that with leaving it open for long periods of time doing various odd jobs and loading kit, the solar's not been able to keep up, That said, I always try make a point of having all the interior light switched off - I do however always seem to be inadvertently switching the one over the sliding door on by brushing with my head as I exit the van!

If it all goes pear shaped again, I might wind up picking up a battery in France or Spain while we're away. If the battery shop can't code it, I've always got a Carista dongle on board and can do it myself. Correction: Should be able to do it myself!