[RedDevil]

On my Insight pack I saw residual voltage on the terminals for some time after switch off.
The battery cells are cut off all right but the control electronics have capacitors etc. that hold some charge.
Always test the contacts with a volt meter before you do anything on a full pack.

Also, though the main contacts are cut off some parts deeper in the Insight pack do hold the full voltage. That may be so with the Prius pack too? When the pack is open make sure nothing drops inside.

When I was assembling my additional booster batteries I wrapped a plastic strip over each cell terminal connection, feeling silly about it but just in case.
Almost done, I let a wrench slip and it dropped right on top of my cell array.
Nothing happened because of the strips.

I could not imagine the mere possibility of losing control over the wrench while assembling the battery, being concentrated and well prepared on the build and all, but it happened nonetheless.
When I thought about covering the terminals I told myself that now I had to do it.
I would regret it if I thought about it, skipped it and had an accident because of it.
You'll never regret extra safety measures. You will regret being short on them.