Today my battery has failed its on charge but the radio and sat nav screen are powered up why would that be. I will be fitting a new one tomorrow

I would be on my third battery by now as you are on borrowed time after four years. They degrade roughly 20% a year. Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

so far as I can tell as its still a LR branded battery, my Ewok is still on the original battery at 7 years old and the stop/start still works... im actually in shock

It is the hot ambient temperature together with the high engine bay temperature which gives the battery a hammering down under. Our number one road service help is battery related and then you get a sh_t replacement battery. Procrastination, mankind's greatest labour saving device!

Acoustic insulation ARB TPMS 3xARB air compressors After cooler Air tank On-board OCD pressure air/water cleaning Additional 50L fuel Carpet in doors ABE 2x1kg Waeco 28L modified fridge Battery 4x26ah Solar 120w Victron MPPT 100/20 DC-DC 18amps 175amp jumper plug Awning 6x255/60R18

The FL2's battery charging system/algorithm is temperature dependent. So, in a way, it doesn't matter the temps.
Just tested my battery a few weeks ago and it's at 50% of its original capacity, after 5 years. So about 10% per year in my case.

My fl2 my13 is still on the original battery. Stop/start still works. Last September i bought a ctek mxs5 and charged it through a recondition cycle. The battery is a Varta F21.

I fitted a new battery cheaper from car spares that are local than from Internet all good and working