Need to put trickle charge in this spring. Any suggestions. 90 T Cab https://share.icloud.com/photos/0nVCwwsrq1ClQZSs_nOBP2J8Q
Just attach the two alligator clips of the battery tender to the terminals of the battery (black to -m red to +). (Maybe I misunderstood your question.) I never start the car when it's in winter storage, BTW. Just let it sit with a sump full of fresh motor oil. A simple formula for winter storage for all my cars: full tank of gas with fuel stabilizer, park the car on a sheet of plastic on the garage floor (to prevent condensation), tires to 40 psi, oil change at the very end. In my other cars I remove the battery and bring it inside the house. In the Mondial replacing the battery is enough of a pain that I simply connect the battery tender to it while in the car.
The battery tender has a cable that attaches to the battery then you connect/disconnect the battery tender to that quick connect fitting.
https://www.aircraftspruce.com/catalog/elpages/tenderchgr6.php?clickkey=4088 This is a nice litle battery tender, used one like it for 15 years, comes with the ring terminals you connect to the battery and then can plug in and unplug the tender when you need to. Might be avilable on Amazon as well, but Aircraft Spruce is a nice source for other products for aircraft that can be useful to know about for car maintenance. These tenders actually desulphanate the battery while maintaining a charge, and that is what extends the battery life. It is a tender, so is not meant to charge a battery that has been seriously run down, it would do so but would take a long time. I have used it on regular lead acid batteries and AGM batteries, it is rated for both types. To install the wiring ring terminals, you probably want to get at the battery through the wheel well, remove the wheel and there is a panel with a few screws that you remove and the battrery posts would be right there to easily attach the terminals to after losening the attachment nut, putting on the ring terminal and tighening back up. The wire extension would then poke out over the battery and be accessible from in the trunk to plug in the charger.
I went with the CTEC Multi US 7002 which cost me $118+tax on Amazon. Comes with the terminals you can mount to the battery and also alligator clips if you don't want a fixed installation (though with the battery position in my Mondial 3.2 Cabriolet, I would not trust alligator clips to stay put). I had some cheap brand battery tender on my Jag XK-8 and it actually destroyed the battery within a year - I recommend to not cheap out on this. CTEC consistently has the highest ratings for their battery tenders. No issues so far in 3 months of use.
All of these are great suggestions. Just another nod to the Deltran Battery Tender Plus. I have had one on my Mondial and another on my '71 Mustang Mach 1 429 CJ for years. I just go direct with the alligator clips to both, and you can find a way to make the connections with the front bonnet closed. Sure beats trying to remember to start the car frequently enough in winter to keep the battery charged. Still waiting for what's left of 26" of snow to melt here in eastern PA. Spring can't come soon enough!
We use a Battery Tender. I removed a screw from the front air valance on the driver's side and mounted the connector underneath. With just one screw it will pivot and release the plug if I forget it and back out of the garage. I knew if I had to open the hood or walk to the passenger side that I would rarely plug it in.