Not to draw this topic out too far, but I thought I'd post an image
that shows what I inherited when I bought the conversion truck and
began removing the cells for installation in my car.
This is large image, but I left it in the original resolution after
cropping so that the details wouldn't be lost:
http://www.westlanetv.org/~sharkey/evgfx/Old_Thundersky_Installation.jpg
This looks like a Sunday Funnies "How many problems can you spot in
this picture?" puzzle. The strap that I just operated on is one of
the two shown in the photo.
The controller in this rig was set to limit current to 350 amperes.
Even with that, there were burned spots where some of the straps
contacted the tarnished/oxidized cell terminals. The general fit and
finish of the installation invited problems. No particular effort was
expended to make connections low resistance, or even to produce a
close fit. Look at the distortion on the left hand strap end where
the copper has been pulled up by the oversized BMS ring terminal
being compressed by a stainless flat washer under the terminal bolt.
Or the interface of the other end of the strap with the rectangular
copper bar that runs through the Hall effect current sensor.
All of this is a testament as to why Tesla chose to have robots weld
their battery cell connectors.
That said, at least NEC fabricated the Leaf cells with copper
contacts that are backed up by steel captive nuts so that the bus
bars can be drawn down tight. The copper contacts have a little bit
of "float" in the module cases so that they have at least a limited
amount of position adjustment when the modules are assembled into a battery.
>> Bob Rice used to weld his connections
Some years back, I was contacted by a new owner of an SCT conversion
like mine. He described his lead-acid pack as having copper braid
soldered to the battery terminal posts as jumpers. I thought it was
some kind of desperation move by a previous owner, but given the
"super cooled liquid" that lead terminals represent, it was probably
a good move. Glad to be past that phase of EV technology. I can't see
ever going back to lead.
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