Disconnect battery when charging?

[jroswell]

My owners manual (2000 C2 Cab) says to disconnect the battery when using a charger or the alternator could be damaged. Is this for real? I would have to reset my clock, radio presets, radio theft code, etc. - a real pain.

How about for a low amperage charger, say 2 to 5 amps?

Can I use a battery maintainer/tender without disconnecting the battery? I'm going into my 1st New England winter with this car and its already cranking slowly.

[FPB111]

Really? I used a battery tender on my 2003 and now use one on my 2004. I have never disconnected the battery while charging or using the maintainer either. Maybe it is in reference to a high amp charger?
Battery Tender Plus 12 Volt Smart Charger
Or if you have extra $$ to burn this one.
https://www.gaudinporscheparts.com/oe-porsche/95504490054?origin=pla&gclid=CNOvpcnijdACFUtahgodCbwFvQ

[KNS]

I would think a trickle charger/maintainer would be fine.

It's probably the units that are charging at much higher rate that may be a concern. If your voltmeter is still running between 13 and 14 then you're alright.

[JFP in PA]

Originally Posted by jroswell

My owners manual (2000 C2 Cab) says to disconnect the battery when using a charger or the alternator could be damaged. Is this for real? I would have to reset my clock, radio presets, radio theft code, etc. - a real pain.

How about for a low amperage charger, say 2 to 5 amps?

Can I use a battery maintainer/tender without disconnecting the battery? I'm going into my 1st New England winter with this car and its already cranking slowly.

That is referring to when higher amperage commercial chargers are in use (a good shop charger can put out between 30 and 200 amps, which can fry the voltage regulator or diodes in the alternator). Good quality battery maintainers are under 5 amps, and usually are only running at a fraction of one amp. We store cars over the winter for some customers using very good maintainers, and never disconnect the batteries.