Obviously you need to wrap it more so it's fucking bosh, in there and not coming out unless you really yank the bastard out. I don't know how to explain that in watts per square rage but it should be tight enough that you do a man grunt to get the battery out of the seatpost and then feel like a beer.
A kitcken scourer with the scourer bit cut off works well, you need something that'll expand in the seatpost, bubble wrap and rags don't really do that
Obviously you need to wrap it more so it's fucking bosh, in there and not coming out unless you really yank the bastard out. I don't know how to explain that in watts per square rage but it should be tight enough that you do a man grunt to get the battery out of the seatpost and then feel like a beer.