charging battery

if you charge battery with exterinal charger do you need to disconnect positive termal, will external charger back feed converter if show power is hooked up?

Hmm, why would you want to add an external charger when the converter/charger is working?
Faster charge, maybe?
And I would always disconnect the negative cable first. Once that is off there is no chance of a short to ground.
If you are working on the positive anode with the negative still hooked up, and accidentally short to ground, that wrench will get real hot real fast.

Peace
Dave