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Dreaded Prior Owner
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Discussion Starter #1
Many of us keep our cars battery on some sort of maintenance charger for part of the year. I was wanting to have a port that would disconnect without damage if I forgot it was attached, and was inconspicuous enough to place it where it was easily accessed. I got a magnetic USB phone charger cable (rated at 3 amps if you believe the ad copy, $3 on EBay), opened up the male end, soldered on some leads and made a little bulkhead fitting to epoxy the end into. (I had an F style television cable fitting on hand that was already threaded that worked for me.) I was reluctant to drill a hole in the body shell, and the bumper cap limited my access to place it vertically under the plate overhang, so I placed it in one of my license plate light housings. Terminate the other end of the cable with a connector to match your battery charger. Under $10 for a magnetic charger port!

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- You'll need wire connectors that are small enough to fit through the nut securing the connector housing
-One caution is that both ends of the cable are magnetic so they will grab any ferrous bits that come close, so you need to add a low amperage fuse to the wiring for when it tries to short itself.
-Get a cable that does not have an LED that lights up in the connector. It won't be happy with 13 volts instead of the 5 expected.
-This is only for trickle chargers, which typically run .5 to 1.5 amps. More than that will challenge the small gauge wire in the cell charger cable.

Mod, if you think this should be in the general Lotus/Battery section feel free to move it.
 

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Wow, awesome idea. I just found a cable on Amazon Prime for $3.98 and it will be here Sunday! Gotta give it a try. USB 360 degre Magnetic Cable with Led We need more inovation like this on this site!
 

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2020 Evora GT in Formula Red, coordinated black+red interior, windowed engine hatch
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433 Posts
When I get around to doing this, I plan to put it in the side or bottom of one of the bumperettes. The upper screw holes for the license plate can reach inside the boot so no holes need be drilled in the body. The bumperettes are plastic so easy to mod and easy to replace if that's ever desirable. I'll secure the license plate via its lower holes.
 

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I bought one of these (12v 3 Piece Magcode Set POWER Magnetic Connector POWER CLIP PORT & COVER) off of eBay and 3D printed a mount that sits above the license plate (Magnetic trickle charger license plate mount by fjohn624). More expensive, but a very nice solution, and dead simple to install (the wires come out with the license plate light wires). Easy on an Elise; not as easy on an Evora, I hear.
 

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Dreaded Prior Owner
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735 Posts
Discussion Starter #5 (Edited)
"The upper screw holes for the license plate can reach inside the boot " Good idea, this is the case with the Esprit as well, If i was to do it over I would try to fab a skinny version, or make one plate bolt a 8mm.

RapidLotus- the LED on that cable may cause you problems at higher voltages, mine got quite hot at 13 volts. I took it to 30 Volts to try to hopefully burn out the LED to an open circuit, but it's stubborn and still is hanging in there dimly.
 

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"The upper screw holes for the license plate can reach inside the boot " Good idea, this is the case with the Esprit as well, If i was to do it over I would try to fab a skinny version, or make one plate bolt a 8mm.

RapidLotus- the LED on that cable may cause you problems at higher voltages, mine got quite hot at 13 volts. I took it to 30 Volts to try to hopefully burn out the LED to an open circuit, but it's stubborn and still is hanging in there dimly.
I did not even notice the LED, bummer. I can easily return it. I love Prime. The other problem with the one I ordered does not state the length of the cable. How long is your cable?
 

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I was a daily driver snob that sneered at trickle chargers - if you need a trickle charger, you ain't drivin' it enough!

However, Covid 19 and the impact has vastly reduced my driving time and forces me to consider trickle chargers (getting tired of full charging 4 cars in rotation every 2 weeks during these trying times).

How times have changed.
 

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I put a plug in the right side fuel door. On the '99 V-8 they sealed it shut because you only get the left side filler. I cut the blobs of glue to get the door to open, cut a small hole to fit a plug in and wired it to the battery with a fuse.
David Teitelbaum
 

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You can get the bare connectors here: Magnetic Power Connector-Magnetic Power Connector Manufacturers, Suppliers and Exporters on Alibaba.comConnector


 

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Dreaded Prior Owner
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735 Posts
Discussion Starter #10
I did not even notice the LED, bummer. I can easily return it. I love Prime. The other problem with the one I ordered does not state the length of the cable. How long is your cable?
Mine was a 1 meter, they come in 2 meter as well. My battery tender has plenty of cable on it anyway.
So far my cable LED is still glimmering, but passes the voltage through just fine. As I looked for a non-LED cable I see that some cables show a circuit embedded in the cable plug, maybe that was what was heating up on me. I'll test it some more with more current and see how it behaves.
 

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2005 Lotus Elise
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Is the end that stays on the car well recessed/shielded to protect against accidental shorts? If not (or maybe anyways), add an inline fuse! Less of a big deal for usb, which doesn’t have 400+ CCA.
 

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2020 Evora GT in Formula Red, coordinated black+red interior, windowed engine hatch
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3D printed a mount that sits above the license plate
Very nice job! I considered the same thing but it looked like a centered magnetic connector would interfere with my rear view camera. I might print up your part and give it a test fit. Worst case I could offset its mount enough to get out of the camera's field of view (if that's possible, the camera has a VERY wide angle lens).

The next problem would be how to secure it if I'm using one of the top screw holes for the wires. Maybe it can mount at the bottom. I could add a channel behind one of the arms to hold the wires which could then disappear behind the license plate, snake up to the top hole, and vanish into the boot. There's space behind my plate, I space it away from the car panel using 1/4 inch adhesive backed neoprene (adhesive side toward the plate, of course). If/when I do this I'll report back on how it turns out.

Again, nice job on the 3D bracket!
 

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2020 Evora GT in Formula Red, coordinated black+red interior, windowed engine hatch
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OK, got it. I figured there aren't a lot of us Lotus owners out here in the first place, so presumed you had to be the one who designed it. {grin}
 

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Wingless Wonder
1988 Esprit Turbo
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5,901 Posts
@glb has commercially-available magnetic connections for the battery maintainers on both his cars.
 

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2020 Evora GT in Formula Red, coordinated black+red interior, windowed engine hatch
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That is pretty clean, for sure. My goal is to do it with no permanent alterations to the vehicle (or at least none visible). That's why I'm looking at wiring through a license plate screw hole, using a 3D printed holder for the connector, etc.
 

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My magnetic connector solution:
 

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Dreaded Prior Owner
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Discussion Starter #19
Back to DIY & Cheap-
I was curious about the heating I was seeing with the previous cable, so I bought a 3-for-$10 pack of cables


and sacrificed one to see what "chip" might be in the magnetic end. Now these are a generic item, so they may vary from vendor to vendor, but what I found in this model was just an LED across the connector. The green and white wires are paired to the center pin and the red (which I would like to think is positive) is actually the negative to the outer magnet, so check your polarity if you make one of these.
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The soldered and shrink wrapped "phone" end will fit also easily in a bored out 3/8"/M10 bolt.
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I would have the connector hang vertically if I did it again to make it less likely to be disconnected if the cable gets moved.
 

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2020 Evora GT in Formula Red, coordinated black+red interior, windowed engine hatch
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I have always presumed that in the "magnetic, not energized when physically disconnected" connectors, the magnet itself closes the circuit. That would be the easiest and simplest solution. Have a pair of contacts which are closed by a lightly-springed magnet moving toward them when the mating connector (containing some ferrous object to attract the magnet) approaches. Otherwise you'd need a Hall switch to detect the magnetic field, likely a FET to close the circuit, etc. all of which is needlessly complex and expensive. A circuit-based solution would also require constant power, whereas a moving magnet would consume zero current.

I suppose you could have a circuit in the receptacle that gets powered by the charging cable when the latter is connected, and then THAT closes a circuit to the outside world. That would consume zero quiescent current. A solenoid-like coil arrangement would work. However, it's still considerably more complex than the moving magnet technique, and would require that a specific side of the connector system is always the one with constant power. The moving magnet would just be a set of dry contacts, like any switch, able to accommodate any connection scheme. Simpler is almost always better.
 
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