Modifications Req. to use Gen 2 modules in Gen 1 Battery

I'm pretty sure that your problem is that you're not squeezing the modules together to get the screw holes lined up. If you simply stack them in there you won't get the screw holes to line up, at least not for long.
The gen 2 mods only have a screw hole on one end, so you'll only use 1/2 the screws. And they will line up, though they have to be "persuaded", especially the farther you go. I use a bar clamp, a couple of small blocks of wood, and a rubber mallet. The bus bars will definitely work as well. As for the temp sensor, I use a small zip tie to hold them in place. I think 2 bar clamps would work a little better than 1, but I just make do. Use the wood to spread the force of the clamp (as minimal as possible) over the module and pull it in to line up the holes.

 

Do you need to replace other things besides the battery cells when going from Gen 1 to Gen 2 cells? I suppose the Gen 2 battery tray cannot fit in a Gen 1 vehicle? I thought I might just buy a whole Gen 2 battery pack if I can fit it in the Gen 1 vehicle.

 

Gen 2 battery packs are not compatible with the Gen 1 Prius. They have 10 fewer modules and run at a lower voltage than Gen 1.

 

You can replace the cells with gen2 cells, as has lredy been shared, but the gen2 battery assembly will not be compatible with the gen1 hybrid system. At least a couple of the ECUs will be thrown off by the lack of voltage and the missing number of sensors that normally come with the gen1 battery assembly.

 

I am currently running a general with mixture of general and general batteries. Working just fine and has been for ages.
The g2 are slightly wider so I made the mounting holes wider, the temp sensors clip in ok.
As do the breather tubes.
No ecu issues