If you need to replace battery for CED 7000 timer [1] you can either buy a HLP 443450 3.7V 800mAh 2.96Wh accumulator [2] or dedicated inexpensive Power Bank [3] that contains two accumulators inside – one for quick replacement of the timer battery and the other to charge timer over the USB cable – this way you can also safely carry a backup and replacement power source at hand :-) One thing that could be improved here is using both accumulators in the Power Bank so capacity is doubled and both are always charged – that should also prevent self-discharge below safe point of the unused unit.