2x older model Piranha's....what to do here?

[Jacob BV]

Unrelated question, do you get a small buoyancy change at depth? I've only used mine a few times but it seems slightly more negative at depth

 

[PEDiver]

Thanks for that! If you have any pictures or are able to get hand of the specs some time would be amazing to see.

Here are some pictures from during the building phase. We used 18650 cells and purchased a newer BMS from Amazon. I found that using the saltwater plate added just enough weight to make it neutral in fresh water without adding any additional weight inside the housing itself (since the new battery was lighter than the original). If I use it in saltwater, I will probably have to adjust the weight so it's not positive. But I rarely dive saltwater so not as much of a concern for me.

These pictures don't represent the complete and final battery, but shows how we approached building it and sizing it with the amount of space we had. Definitely be careful when building a battery like this, especially when using lithium. Fire is always a hazard if not done properly.

 

[Jacob BV]

Here are some pictures from during the building phase. We used 18650 cells and purchased a newer BMS from Amazon. I found that using the saltwater plate added just enough weight to make it neutral in fresh water without adding any additional weight inside the housing itself (since the new battery was lighter than the original). If I use it in saltwater, I will probably have to adjust the weight so it's not positive. But I rarely dive saltwater so not as much of a concern for me.

These pictures don't represent the complete and final battery, but shows how we approached building it and sizing it with the amount of space we had. Definitely be careful when building a battery like this, especially when using lithium. Fire is always a hazard if not done properly.

That's really so helpful. So do you have some 18650s not in the main center block? It looks like you have put some on the sides too? Did you put the metal cover back on top of this? I was wondering if it was worth loosing the motor side battery cover to save some weight (and hence get more cells in)

 

[PEDiver]

That's really so helpful. So do you have some 18650s not in the main center block? It looks like you have put some on the sides too? Did you put the metal cover back on top of this? I was wondering if it was worth loosing the motor side battery cover to save some weight (and hence get more cells in)

We did end up wiring some cells outside of the main block to maximize capacity. If you get creative, you can probably add more cells within the module. We just calculated the number of cells needed for a certain capacity to more or less mirror the specs of the P1 from the factory. We did put the metal cover back since it encapsulates everything nicely in the module.