I'm looking at using some of those portable power banks that I can buy for £2.00GBP as they charge the battery rather just than a boost converter. Plus the fact I can buy them complete for strip down and reuse the parts rather than buy them separate which costs more.

As I can't get my scope back until towards the end of the week, so in the mean time I thought I'd ask your thoughts, Means they are cheap I don't think the output is very clean so my thoughts where to add some extra smoothing caps ?

I've added an auto turn off circuit which I control with an Arduino, External button press turns it on(for 2 seconds) then the Arduino holds the hold pin high to keep it running then after a time it will sends this pin low and turns it off. Where I've also added some extra caps to help it smoother and hopefully clean output.

Would the values be correct and any improvements that could be made?