ELI5: Why do devices with dying batteries sometimes work if you swap the batteries around?

Swapping dying batteries gives a device a brief burst of life because it cleans the metal connections and gives the chemicals inside the batteries a few moments to rest and rebalance.

Here is how that works in everyday life:

• Scraping off invisible dirt: When batteries sit in a toy or TV remote for a long time, an invisible layer of film or rust called oxidation builds up where the battery touches the metal springs. When you pull the batteries out and pop them back in, you physically rub that dirt away, making a cleaner path for the electricity to flow through.
• The chemical catch-up: Batteries do not hold pre-made electricity; they make it using a liquid chemical reaction inside. When you use a device, the chemicals right against the metal parts get used up first. Taking the batteries out pauses the drain, letting the unused chemicals inside drift over to where they are needed, like water leveling out in a bucket.
• Sharing the work: In a device that uses two batteries, one usually drains faster than the other. If you swap their positions, you are moving the slightly stronger battery to a spot where it can push through and help the weaker battery just enough to power the gadget one last time.