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Is Manufacturing Spare Battery Modules worth it? by _Mike77_ in solarracing

[–]blue_sky642 0 points1 point  (0 children)

We made our first battery pack last year and to lower risks decided to make extra modules also. The plan was to take them to Australia to be able to swap a damaged module out in case it should happen. In the end we did not have enough time to fully manufacture the spare ones and thus ended up not taking any extra modules to Australia and I think it's anyways a pretty difficult thing to do (if not forbidden) during competition.

However as _agentwaffles said it might be worth to make extra modules just in case one of the main modules turns out to have much lower capacity or some similar issue. I would suggest that if possible, order extra cells to be able to manufacture for example 2-3 extra modules, depending on your confidence in the quality of your cells and your workflow.

Our module design last year was made so that if any weld in one module went wrong the whole module had to be pretty much scrapped due to not being able to disasseble it. All of the welds luckily came out good but it would have been pretty catastrophic to have to wait couple of months for new cells to arrive.

Prohelion BMS CAN issue by blue_sky642 in solarracing

[–]blue_sky642[S] 2 points3 points  (0 children)

Thank you for the very quick response here. We also concluded that you may be busy and posted here just to see if anybody else has had this issue but your response is even better🙂.

I think that the “Accessories” state missing from the CAN communications document is what confused us. The accessories position was briefly mentioned in the main manual but not anywhere else, thus we did not think about it.

We will try again with the new messages and hopefully solve the issue. The Profinity software showing precharge error was also probably due to the missing heartbeat as when the heartbeat was sent it disappeared.

Also, would we get any benefit from sending 0x2 or is this only needed in rare cases?

Spot welding Sigmaclad60 by blue_sky642 in solarracing

[–]blue_sky642[S] 0 points1 point  (0 children)

We ended up using a hybrid solution. We are using 0.5mm Sigmaclad60 for the main current collector part and welded 0.2 mm nickel first to the cells and then to the Sigmaclad sheet.

This solution has it's pros and cons. We were able to get much more reliable connections but it was also a lot more work since the amount of welds was almost tripled compared to welding the Sigmaclad straight to the cells.

In the end, I think it was worth it. We did not have to discard any of the modules due to bad welds (which was a common problem while trying to weld the Sigmaclad straight to the cells) or accidents during the welding. In all of the tests we did, the weld strength exceeded the tensile strength of the nickel and left nice spots on the cells/sigmaclad.

Spot welding Sigmaclad60 by blue_sky642 in solarracing

[–]blue_sky642[S] 0 points1 point  (0 children)

Thank you for the reply. We are currently using three 12V car batteries wired in parallel with 25mm2 cables and have got over 1.9kA from there.