Disconnecting Negative = Install Battery Disconnect?

[2Highplains]

I have a battery tender I use on the two AGM batteries I am storing in my garage until we put the AS in use. I intend to use the battery tender when the batteries are put back in the box on the trailer.
QUESTION: Does (1) disconnecting the negative terminal when the batteries are installed in the battery box and subsequently using the battery tender accomplish the same thing if (2) I install my own battery disconnect switch at the battery box, and then use the tender?
Too many parasitic loads now on Airstreams sucking the fun out of batteries.
Thank you.

[Zil]

Yes you can use a battery disconnect switch on the negative. I have a Blue Sea M series 6004 single circuit switch. I switch the negative, and then pull fuses if i want just one circuit off the battery. Be sure to have the battery tender on the battery side of the switch.

[Bill M.]

For batteries in parallel. Whatever you do with the negatives, you have to do it to both.