Off the radar means unnoticed or not in someone’s thinking.
Recharging your batteries is a figurative expression for becoming reinvigorated through rest, sleep or holidays. Unless someone has a pace-maker for heart problems they are unlikely to be battery-powered.
Ever-ready batteries were often advertised on billboards.
A trunk call is the description of a long-distance telephone call.
Ticker-tape is moving words on a new website for example.
“Get your finger out!” is a way of telling someone to take action. (It is not an expression which appeals to me.) In Psalm 74:11 the psalmist (Asaph) asks God to remove his hand from the folds of his garment and destroy his enemies. This is more like, “Take your hands out of your pockets!”
Galvanised into action is an expression about being impelled to do something. Galvanisation is a process by which iron is coated with zinc to prevent corrosion. However batteries used to be known as galvanic cells, which is how the phrase came into being. People sometimes are charged up, or fired up before a stressful activity.
I’ll have to stir my stumps means the speaker has to get up and get on with some task. I suppose stumps might be legs. (The Concise Oxford Dictionary agrees with me.)
A tree stump is what remains above the ground after a tree has been felled. Nebuchadnezzar had a dream about one, which Daniel interpreted. (Daniel 4)
A stump garden has many tree stumps in it. There is one at Biddulph Grange Garden.
Stump up means pay money (perhaps on behalf of someone else).
There shall a root from Jacob come forth and a shoot from Israel spring up.
The first line of a beautiful choral work by Felix Mendelssohn is based on Isaiah 27:6 which speaks of roots, buds and blossom. There are so many references to trees, roots, pruning and viniculture in the Bible that a whole book could be written about it. Perhaps one has.