ECN Forum Forums General Topics of the Trade General Discussion Area Interesting.....

From the AOL news flashes....

Tesla Motor Company, maker of the Model S electric car, is recalling 29,222 wall charger adapters following reports of overheating in owners' garages.

The National Highway Traffic Safety Administration (NHTSA) announced the recall Tuesday morning. Tesla said the problem lies in the Universal Mobile Connector (UMC) adapters, which can lead to the adapter, cord or wall outlet overheating during charging. The danger was discovered when a garage caught fire in California in November. It has since resulted at least five incidents that were reported to NHTSA's complaint database.

"These are very rare events, but occasionally the wiring isn't done right," Tesla CEO Elon Musk said, according to Bloomberg. "We want people to have absolute comfort, so we're going to be providing them with an upgraded adapter."

The new adapter will include a thermal fuse that will shut off charging if overheating is detected, Musk said. Tesla sent a software update to its customers to deal with the overheating issue back in December, which was designed to trigger a 25 percent reduction in charge current when it sensed a potential overheating.

Tesla said about 2.9 percent of Model S buyers have returned their UMC adapters because of defects

I saw a charger that had a 100amp circuit going to it for a Tesla. Are these the ones that caught fire?

Tesla uses a non-industry standard connection.

The fundamental problem: Lithium-ion batteries are prone to run-away charging and discharging dynamics.

This is the source of the chronic fires:

Boeing's 787

Tesla's roadster battery array

Tesla's charging system

....

This tick gets even more pronounced as the batteries get better.

The current solution is to actively sense the temperature -- and to throttle the current via semi-conductor means.

(Probably an IGBT)

http://en.wikipedia.org/wiki/Insulated-gate_bipolar_transistor

These switches are changing everything on the load-side.

Eventually, three-phase motors will be commonly powered by single-phase circuits. IGBTs will permit 3-phase synthesis. This has already been proto-typed in hermetic refrigeration compressors.

The ability to throttle such compressors up and down increases their efficiency -- and makes them last three times as long. (It's virtually a solid state solution.)

I like manual reset thermal switches for stuff like this. I was collecting them for years at IBM. We used to have engineering changes where they got swapped for a different temperature quite often and I put the old one in my pocket instead of throwing it away.
I had one save me from a serious problem on my spa. I had a problem where a heater ran away and my thermal tripped it out at ~122f. I changed that to 110f because I decided that was even too hot.

If I had something like this I would have a thermal right on the charger.

The article I read about it said they were making a software upgrade to fix it and the new units would have a thermal fuse in the NEMA 14-50 plug.

That might be OK for an overload but the charger could burn up without actually overloading the circuit.