What if the display batteries give out

[ShinySideUp]

Can't find the answer to this anywhere. You're out riding around and you didn't notice that your display batteries were on their last legs and they give out leaving you with no display. Probably not really a problem display-wise, but will the control buttons still work or are you stuck in Turbo/tour/whatever mode? Worse, does the display packing up cause the main battery to stop outputting energy as there may be no control?

I have bought a spare pair of batteries for my Purion display just in case but was still wondering.

 

[ShinySideUp]

Further to my above post. I have realised that if the batteries do give out in the Purion then since it can't be turned on then one can't turn on the main battery power and as such, for the sake of two tiny batteries, one's bike turns into a very heavy lump indeed; not good if you happen to be twenty miles from home.

Since realising this I have purchased an extra pair as I would not like to be almost stranded for the sake of £2.50's worth of batteries.