The way I figure, it would be better not to tell people how easy ( or hard ) it is to steal a battery. Because if it happens to be easy best not to tell people least some fools get ideas in their heads. I figure if you can't afford to lose it and decide to leave it on your bike and then some dolt steals it, you have nobody to blame but yourself for leaving it on the bike. I own a Shimano Step system and the battery on those lock to the bike with a built in key lock. Regardless, If I were to park the bike somewhere and leave it for a prolonged period of time I would consider taking the battery with me since it is perhaps the most expensive piece of removable equipment on the bike other than the motor. ( key locks can be picked if you have the know how).

I like these ebikes I see where the batteries are built into the frame ( along with the motor ). I love me some stealth design! With those I would think the opening where the batteries go in would be secured with some kind of locking mechanisms making it even better ( If...I'm correct ). I would love to have an e-mountain bike designed like that. You almost can't tell they are electric assist ( unless of course you are familiar with newer e-bikes ) I was looking at one online the other day but "Oh MY!", are they expensive!