Help with crazy flashing dash display & won't start

Hello, I had to go with my family out of country for 4 months so I left my 2010 prius at a friends house. I was worried of it sitting so long and since it was in the back of their garage, from reading online I asked my friend every two weeks to go out and turn it on and let it run for twenty minutes to keep the batteries charged.

Everything has been working fine for the last few months, but yesterday he went out to start it up and it beeped at him and the lights on the dash board starting freaking out and flashing crazily with a beep in the background and it would no longer start up.

I am heading back home in a few weeks, but wondering if anyone knows what this could possibly be. I am kind of scared of what has gone wrong and how expensive it could be to fix. I live in South Africa and live quite far from the nearest dealer that could look at it.

Any ideas? Here is a video he took of the dash.

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Thanks, that is encouraging, When I get home in a couple weeks I can do that. Didn't realize it flipped out like that when the batter was dead. Hopefully that is all it is. Thanks.