We are trying to find the right backup battery replacement for Legrand MicroRex D21 037 87. The battery has no voltage when the device is switched off. Then powered we measure 1.78 Volt over the terminals of the dead battery.
Then we search for documentation (below) we find under the type number V65HT a 1.2 Volt Nickel Metal Hydride 70mAh battery. Also the size of the battery suggests 1 cell of 1.2 Volt. This size matches exactly the original battery. No other battery in the Farnell database comes close to this dimensions of the original battery.
Varta also has an application note which suggests this type of battery.
We assume the Voltage of 1.78 Volt is measured because the circuit is not loaded with a healthy battery.
The new Legrand MicroRex D21 has a 3V replaceable battery (manual right, click for full pdf)
The battery can be purchased at allekabels.nl
