A low cost way to add a second battery -- with all the details

[NeedSomePower]

I just added a second battery to my Rad City 3 Step-Thru. Here's a little photo essay showing what I did.

https://mrochkind.com/bike/battery/

[Veggyhed]

I've always thought about adding a spare battery that is not connected under my rack of my runner ?.
I was just going to use the battery rack and then slide the battery on it but I didn't know how to securely attach the battery rack to the underside of the rack. The battery would also be hidden from view due to the large  panniers I carry. I also want to use my bike as a commuter on city streets.

Sent from my TB310FU using Tapatalk

[NeedSomePower]

...  how to securely attach the battery rack to the underside of the rack. ...

Can't say for sure without seeing the bike, but if there's a way, it probably involves bolting the tray/plate to the underside of the rack, assuming there's room for the battery between the rack and the rear fender. If your tray/plate if like mine, it's not necessary to use the screws that came with the tray/plate. Get some longer screws that still fit into the holes in the tray/plate and run them through the tray/plate, the rack, and some large metal pieces the go on top of the rack. I'm not sure what metal pieces might be needed, but browse in a good hardware store and look for very large washers with appropriately small holes (fender washers, I think they're called) or mending plates or whatever the hardware store might have. If you can't find anything, go to a machine shop and have them make you a metal plate the fits on top of the rack. Or, get some strong wood (e.g., oak) about 1/2 - 3/4 inch thick, cut it to fit on top of the rack, and run the screws through the wood. Then bolt the tray/plate to the rack. It may be hard to slide the battery into the tray/plate, depending on how much room there is underneath the rack.