We have yet to be asked to put scooter batteries in cabin. I dare say the day will come. It would be a good way of secreting a bomb on board regardless of whether the bateries are a liability.
Only applies to Li-on/Li-po... other dry cell/agm/sealed types are fine... although both BA and easyjet will now tolerate lithium in the hold at the Captains discretion. The reasoning behind lithium batteries is the same as not being allowed to check in laptops in hold luggage... to prevent undetected/uncontrollable fires in the hold. From a security perspective laptops, tablets and phones are all screened carefully by the xrays as you pass through security...
The important thing, beyond lithium fires is that the scooter cannot be accidentally switched on or put into gear once loaded... for most types this is simply a matter of removing the key or unplugging something (controller/battery).
The GoGo range is probably the most travel friendly, and not too heavy/bulky either... sealed dry cell with a key switch.
One further point of confusion, is that the fact that lithium batteries are technically a form of dry cell
