Trickle Charging

[Zzonyx]

For Golf MK7.5 gasoline engine start-and-stop owners:

Should I disconnect the battery (negative terminal only) before connecting the 3 A (max. output) trickle charger/maintainer?
Can I use the solar charger connected to the rear 12V socket in the car (not controlled by the key)?

I would appreciate your personal hands-on experience.

 

[hooville]

No need to disconnect the battery. I'm not familiar with the solar charger you are referencing, make sure overcharging is not an issue with the one you will be using. You will also need to move a fuse to make the 12v socket hot when the key is off - there is a DIY on here IIRC.
I have used a Battery Tender and now a BatteryMinder for the last 15 years or so and they make a difference on battery longevity.

 

[Zzonyx]

Thank you hooville!
I know from personal experience that in other and/or older cars the process is a nobrainer. The MK 7.5 has the sophisticated control modules which may be a bit delicate under certain conditions and an entirely different battery due to the S&S. Then there's the battery control cable attached to the neg terminal cable. The car's manual doesn't say a word about it all, making owners' lives more miserable in case of problems and keeping us dealer-dependent.
I've used trickle chargers on my 2005 SKODA Octavia TDI (a Golf 5 clone, wasn't exported to the US) with no problems at all, but the 15-year difference in cars means several tech generations have gone by...
On the other hand, when using jumper cables or boosters, the starting current drawn from the donor battery goes into hundreds of amps - if nothing pops then, it is unlikely to do so while using a trickle charger.
I had no particular solar charger in mind, but may decide to buy one in the foreseeable future - seems a good idea for longer idle time imposed by the pandemic.