I was watching a rocket launch video last summer, and was always amazed at how the umbilical cords would detach at just the right time. I'm sure NASA's systems are quite sophisticated, but I thought that a magnet(s) would serve the same purpose for a hassle-free trickle charger. I was looking for a way to charge without having to constantly open and close the boot and manually attaching and removing charging clips.

I used an existing hole in the bottom of the boot (I think it was a battery drain) and ran two wires through it, one to the + side of the battery, and one to the - side. these wires lead to two small aluminum plates. Behind each plate is a fairly strong magnet.

The "umbilical cord" side consists of a similar arrangement...two aluminum plates and magnets. The wires run to a charger in the garage. The cord is screwed to the wood trim next to the garage. So, when the car pulls away, the umbilical cord slides cleanly off the car. No need to open the boot and manually remove charging clips.

When I get back home, I back up to the garage (I have a stop placed behind the right rear tire so I don't back up too far), get out and reattach the umbilical cord...again, no need to open the boot at all.

Both the car side and the umbilical cord side are fused just in case. And the umbilical cord has sat out in rain and snow with no ill effects to it or the charger. Since it's fused, the charger would be protected in case something would crowbar the two aluminum pads.

I've had this system in operation for about four months to trickle the battery. It has sat out in rain, snow and cold with the only needed maintenance being a periodic cleaning of the plates, since the magnets attract small metal filings and such. And when the car is not attached to the charger, it's completely invisible unless you are down on your knees.

The paste on the pads is anti-seize compound. Since the pads are not perfectly flat, the paste seems to help with the electrical connection.

Here are some pics.

Thanks,

John
1987 XJ-S V12


Umbilical cord. The small bolt sits against a small bolt on the bottom of the bumper assembly, it helps with alignment.

Under the bumper. The HDPE sheet the pads are attached to is strong and weather resistant. You can see where the screws that hold the aluminum pads to the HDPE have been cut off and leveled.

View from the back. When the umbilical cord isn't attached you can't see any of the charging apparatus.

 

Great idea. Added to my project list!