I have sold an electronic item where manufacturer indicated battery life of 3.5hrs but it lasts 1.5hrs. Do I have to refund?

[vicdealz]

Hello,

I have sold a brand new electronic item where the manufacturer (Motorola) says the battery life is "up to 3.5hrs" and I wrote the same on the description of the item. The same is written on the box of the item.

Now the buyer claims the battery lasts for 1.5hrs only and wants the full refund or would lodge a complaint to eBay/Paypal.

Considering the manufacturer's statement of "up to 3.5hrs" does it mean the battery should work for 3.5hrs and if not then it is faulty?

My understanding is that "up to 3.5hrs" does not mean "minimum 3.5hrs" or "at least 3.5hrs".

As per eBay / Paypal am I supposed to give a full refund to the buyer? 

My item was marked as "free shipment" and I myself absorbed the shipping cost. If I give a refund, can I ask for a shipment and handling fee?

Thanks