Battery Mounts

FrodoBaggins

Pedelecer
Jun 2, 2017
70
25
47
West Yorkshire
I need some out of the box advice! (no pun intended)
My battery saga continues. I purchased a 17.5Ah 48V Hailong battery. Its great and works well. I have 2 Ebikes, so my bright idea was to buy a smaller one for when friends come over and also double it up as a spare if I do some longer journeys.
I looked around and bought what I thought was an identical case and mount from PSWPower, turns out it wasnt quite the same so I sent it back.

I researched and found something that looked the same on ALiExpress, allbeit another 17.5Ah battery. It arrived yesterday and guess what! Not the Same

I am not sending this back as I cant be bothered and it was a good deal.

So does anyone know anyway I could fashion a system that allows the 2 batteries to be interchangable. Maybe some creative method of adapting the mounts or the packs.
All I can think of is to find a replacement case and try and move the cells, but that feels like a job that could be quite hard!

Any bright ideas or great ones?