Battery Charger Wiring

[ran Y-KNOT 396]

I am about to install a xantrex 20 charger. I read the manual but I don't understand why hooking up directly to the batteries is better than the 1-2-both switch. Is voltage drop that big a deal? Is'nt there voltage drop in a 5 foot run of 8ga. wire?

[Ran139]

Thanks Ron. I realize now that if wired to the 1-2-Both switch while running any DC load, the charger would be the primary supplier. While this might work for a while, (up to 20amps) it would beat up the charger pretty quick.
  Something about being a child of the 60's causes me to ask why...

 - Fair Winds