Engine battery maintenance whilst in storage

[goneoff]

Any one know and can recommend the largest wattage solar to maintain an engine battery which can sit in the windscreen and plug directly into cigarette lighter socket when the motorhome is in storage.
Thank you

 

[pappajohn]

30w to 50w should be adequate, pointing towards the mid-day sun of course

 

[Figaro]

Your cigarette socket may be isolated with the ignition off ?
Worth checking

 

[tonka]

As Figaro says, first check that the socket you plan to use will be live with the ignition off. Many are not.

 

[goneoff]

Our MH is on a Merc Chassis and the socket I will be using is live with the ignition off.
Thanks for your comment

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[Figaro]

Do you have solar on the roof ?
Will this not do the job

 

[gilbaro]

20w Voltset panel in skylight maintained my battery through last winter.

 

[oldiesontour]

I just fitted a cheap (£3.50) 20 amp solar controller and change over switch so the starter battery is charged by the roof solar and lithium hab batteries and all associated can be shut down completely

 

[goneoff]

Do you have solar on the roof ?
Will this not do the job

I do have solar on the leisure batteries but I am looking at the simplest option of maintaining the engine battery. In fact I wired up a couple of Anderson sockets on my previous Burstner and toggled the solar between the hab and engine battery.
Thanks again for your help