I've never needed an extended warranty, but much depends on how far you are from them. There's a standard collect and return charge in the extended warranties which those living very far away might feel a good insurance, not just for expense reasons but convenience as well.
The standard bike warranties have to accord with the law of course, one year minimum, but batteries are consumables, so exempt from that. As Ian says, the battery warranty is six months on the eZee models.
Their Kalkhoff/Panasonic battery has a two year manufacturer warranty, manufacturers being free to extend standard warranties if they wish.
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