Piranha Housing and Battery swap

[lostsheep]

Starting my own thread here so as to not derail others.

I appreciate any and all questions, comments, and concerns about what I'm doing here.

I got a piranha a couple of years ago with the original battery, and it's starting to show it's age. According to my "Watts up" charger monitor the most my battery has ever taken is about 280Wh even though the battery is supposed to be ~400Wh. After about 75 minutes at cruise it starts to die and it's become the limiting factor for me so it's time to step it up. I've never been a fan of the multiple sealing surfaces nor am I fan of stacking more batteries so I decided to attempt to make my own housing and I sourced a ~stock battery from battery space. I got a 777Wh battery from battery space and started making chips.

Here's the plan:

Milled a nose cap:

Used the laser to cut 1/4" acetal to hold the battery; I'm hoping friction will keep it in place:

Cut the housing on the engine lathe (sorry for the blurry pic):

Ready for welding and ano tomorrow!

 

[lostsheep]

The tube was not even remotely round and hanging out ~13" was a bit sketchy so I made an adjustable spud so I could indicate the tube in as accurate and as concentric as possible. ID was ~7.50" and I was aiming for 7.575", was able to get it to TIR of about .007". OD isn't perfect with the piranha tail but it would take some really good eyecrometers to notice...good enough:

 

[OTF]

Nice work!

 

[lostsheep]

Welded and out to ano:

 

[Oldbear]

Welded and out to ano:

View attachment 639752

Nice looking bead

 

[lostsheep]

Ready for vacuum testing and then sea trials :

 

[FIGJAM007]

Super cool to see, I need a short body for my cuda for boat diving . You where spot on in other thread. Absolutely no reason to reinforce 6mm alloy.

 

[lostsheep]

I didn't want to be swapping the handle so:

 

[211ratsbud]

I put the smart dpv in my sierra, they suggest some efficiency gains are seen with the new controller. Something to consider.

 

[Jimchris]

Looks awesome. I'm planning on using that same pack for one of my Sierras