For the last 3 months, once or twice a month i get the battery low message when starting the car

maybe due to a 4 mile drive to work.

i see a few solar panel 12v kits to top up the car when parked.

Does anyone know if the cig lighter on S1 can be used with one of them small panels ( charge in and not a only a out ), or do i need to connect to boot battery and somehow get some wires longer and put on the front console 

Hello James, 

The fundamental issue here is whether the battery is as serviceable as it needs to be. 
How old is it?

Its condition is likely to be aggravated by short journey use - possible barely recharging the capacity necessary to start it in the morning. Does it have stop/start and is it working/ do you isolate it? 
Solar chargers? Probably well worth doing a search on their efficiency before diving into buying one.

If it were mine:- I would be charging the battery overnight with an ‘intelligent’ charger, or take it for a 30 mile run, before getting  it efficiency checked. Halfords stores will usually do this while you wait. This would be my first elimination check - unless the battery is near-new. 

If it is deemed to be below par, just come back to us before committing to buy. 
Perhaps you could come back to us with the question answers anyway. 
Kind regards,

Gareth. 

all good now, since coming back on from holiday, no warnings, so must of been cold weather

Thanks James, but if it were mine, I would still be getting the battery efficiency checked, along with the alternator output, to be better equipped to know what is likely to be ahead of you, rather than experience issues in the future. 
Kind regards,

Gareth. 

did a 70 mile run and since the warm weather all ok

 

Glad it's all good 🙂