The older brown version takes a pp9 replacable battery. The newer grey version has a lithium battery soldered to the circuit. The manufacturers technitcal dept. says they don't know the battery number and that it is expected to last the life of the timer - 15 years and they don't recommend trying to replace it.
Of course they don't they just want to sell a new timer every 15 years. Drayton CONtrols are the manufacturer.
Brian Andrews
March 2012
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