I just store most of mine horizontal but ..... DH uses 801 auto batteries with attys/carts. (Those carts are huge and hold a lot and work great with the tiny straw mod.) Before charging we clean the batteries well and then store them, after charging, hole side down in a small straight sided liqueur glass. Actually we store all the regularly used batteries, auto and manual, that way. He's been vaping about 6 weeks and just presented to me a battery, tonight, to check out as it "doesn't seem right". It might be a flooded battery but haven't checked it out yet. I ordered two "overstock" batteries from, can't remember, for about $5 US, but this is not one of the cheap batteries. DH doesn't like manual as he uses hard, flat tips, that he holds between his teeth for "no hands" vaping.