Duration Resmed battery Power Station II

[Asjb]

7 years ago my wonderful technician gave me a Resmed Power Station II battery as there were then lots of local power cuts. But, good luck, none happened overnight so I never needed to use it. I charge the battery every month but that seems always a little unnecessary as it retains 4/5 charge over a month anyway. 
So, last night - a power cut overnight. To my surprise the fully-charged battery was flat after just 2 hours. I do have high pressures & I need warmed hose & humidifier as I have Sjögren's auto-immune disease which dries out my respiratory tubes.
Resmed info says Power Station lasts "12-14 hours".
Has the Power Station run its life out at 7 years (despite seeming to retain it's charge well) & I should replace it with a new one or are my demands on it so high that its one-sixth stated duration last night is to be expected? And if the latter, which other marque (for home/hotel use only, no off-grid) would you recommend (available in Europe) please? 
France runs on 220. I am not at all electro savvy so complex DIY battery set-ups with transformers/clips etc etc probably won't suit me!
Thanks for any advice.

[enjoysleep59]

It doesn't sound like you use the battery backup much, and if you don't travel much, I would consider something like one of these as a UPS backup for your bedside. Since you use humidity and a heated tube you are most likely pulling about 145 Watts of power or so. One of these models should power your CPAP for about 7 or 8 hours and they have replaceable batteries.

Do an Internet search for a UPS (Uninterruptable Power Supply) similar to the Tripp Lite SMART1500PSGLCD.

[Asjb]

Thank you for the advice