Replaced battery terminals

Sometimes you need to go back some steps to make sure you're happy with the build. That's what happened with my battery terminals.

As described in a previous article, I was using a custom MDF part to secure the bus bars and channel the BMS voltage sensing wires. After fabricating the MDF, buying the connectors and wires, and crimping around half the wires I just wasn't happy with the way it was going... I felt the wires were not tidy and, worst of all, they were dangerously close to one another; if (when) the bus bars got hot, I was afraid the wire insulator wouldn't cope and some cells could short circuit. With this kind of power, that's the last thing we want.

So, I've undone all that custom work and bought a used OEM battery terminal cover with the BMS wires. What a difference! Since I used the same layout as the rear most battery pack in a Nissan Leaf, the cover just fitted nice and tight! And all the wires are done.

OEM battery terminals
OEM battery terminal cover in place. Much cleaner and safer than my previous custom solution :P

I just had to adapt the cover from the original 24 modules in the Leaf for my 16 modules (32 cells). I was a simple and clean job.

 

One other thing I decided to change now was the bus bars. Previously, I laser cut them from 4 mm thick aluminium, since the laser cut shop doesn't work with copper. I've read that aluminium is a pretty good conductor, not far from copper. But I was afraid of some reaction between the aluminium in the bus bars and the cooper in the terminals and cables/connectors so I replaced those bus bars with some custom ones made from copper.

I bought a 4m bar of 5mm thick copper and used an angle grinder to cut it to size, using the aluminium ones as template. I drilled the holes and, overall, it wasn't a difficult job.

Copper bus bars
Copper bus bar vs the laser cutted aluminium version. Hand made from a 4m long copper bar :)

I think these tasks related to the battery are the ones I don't find as interesting to do. They are a bit tedious to work with and I see it as a "commodity". It's just a box that outputs around 100V DC :P
But it's very important to do it well because the safety of the project, myself and all others around depend on it. Let's just hope the whole build doesn't explode or burn to ground the moment I switch on the ignition for the first time :D

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