Hi,

Do you know if your kit will fit inside this box?

https://www.aliexpress.com/item/Free-Shipping-36V-electirc-bicycle-battery-box-with-5V-USB-plug-36V-HaiLong-Battery-plastic-case/32762997036.html?spm=2114.01010208.3.9.bthqLZ&ws_ab_test=searchweb0_0,searchweb201602_1_10152_10065_10151_10130_10068_10139_10136_10137_10060_10155_10062_437_10154_10056_10055_10054_10059_303_100031_10099_10103_10102_10096_10052_10053_10142_10107_10050_10051_5030017_10084_10083_10119_10080_10082_10081_10178_10110_519_10111_10112_10113_10114_10182_10078_10079_10073_10123_10120_10189_142-10120,searchweb201603_1,ppcSwitch_5&btsid=ac7137e7-0251-4732-b6b8-e5b6be496699&algo_expid=f79adfc8-11bc-4b1b-ac94-ad26ff52e71a-0&algo_pvid=f79adfc8-11bc-4b1b-ac94-ad26ff52e71a

I'm not sure, I haven't used that specific case. But you can see the size of the caps on a cell and determine for yourself.

The outer dimension of the box is 90MM, so I'm going to say no as there is the thickness of the walls and those screws posts. Do you know of a similar box that fits your caps?

I'm sorry, but I don't. I'm a bag guy myself, and prefer triangle frame bags to hard cases. I do know there are many different styles of hard cases out there, I'm just not familiar with the dimensions of each one. 

I've never had one, these appeal to me as it has a lock and is easily removable to charge inside. What are the benefits of a triangle frame bag style?

For me the main benefit is two-fold: 1) being able to put different batteries on (including different sizes and voltages), as well as being able to easily build multiple custom batteries.

I live in a city with significant ebike theft, especially batteries. If I know I'm going to a bad part of town, I'll toss on an old, beat up battery. My bag locks, but even so, I try not to leave my bike unattended for too long. Anyone could of course cut the bag. 

If I'm going on a longer trip, I'll use a bigger battery. If I want to go faster that day, I can use a higher voltage battery. 

For me, it's just more flexible. But the advantages for me are disadvantages for others. To each, his own.

Ok, thanks, I understand more and the bag attached to a rack above the tire?

I prefer a triangle bag that goes in the front triangle of the frame. A bag on the rear rack has many of the same advantages, but I don't like the weight being up so high, and it's also weird having it that far back. It can induce some weird handling issues sometimes. At least, that's the way it feels for me. Having the battery weight between your knees just feels much more naturally balanced to me.

Does anyone know where I can buy custom shaped battery bags to strap on my bike frame?  Or if you know how to make a custom durable bag?

The lunacycle and em3ev bags are both very reasonably priced and fit into a lot of frames.