From my measurements, the input to the Sterling is more like 60-65A, the output is more like 47A. The newer Sterling (green stripe) seems to handle low alternator voltage better. The efficiency is more like 80% with alternator voltages in the 13.3-15.5V range.
Regards,
Mark
Calbiker, John61ct and Mark and others,
Thanks for the "real world input". Sterling's specs are incomplete it seems, because they say the BB1260 is 12v input at up to 60 amps and output is 12v at up to 60 amps; yea, right. No efficiency is provided making you all's data really good. I've seen a 25% safety margin used for protecting solar chargers, so 60 x 1.25% = 75 amps. Don't know fi this application would be different. But Sterling says a 60 amp output, then calls for a 100 amp fuse. Confusing to a novice like me.
John61ct recommended Bestboatwire.com for cable, so I'm doing the tinned, UL1426 cable with a 105C rating (BC5-W2).
Thanks for the cable input calbiker. I'm going to crawl under and pull some cable loom along the same path and get a real good distance estimate on the Sterling to chassis battery run. I'm guessing installed it's 11 feet one way. The Sterling to house battery is only about 4 feet one way. I prefer to run new cable between the sterling and the chassis batt, rather than reuse the existing 1AWG. The existing one has open ended lugs, is 13 years old, and has the solenoid to be eliminated in it also.
With the sizing tool:
http://www.bestboatwire.com/wiresize
Please check my inputs
Sterling to chassis batt: 11 feet one way, single conductor, 12V, 60A. Result: 1AWG is a 1.4% voltage drop.
Change above to 70 amps = 1.63% drop.
Sterling to house batt: 4 feet one way, single conductor, 12V, 60A. Result: 1AWG is a .51% voltage drop.
Change above to 70 amps = .59% drop.
Unless you guys say no, I'll get enough 1AWG to wire it all. I plan to use the bolt on 100 amp fuse in my PDC at the Sprinter's chassis battery and one of these holders with the same fuse between the sterling and house batts:
https://www.amazon.com/gp/product/B004T1VYLA/ref=ox_sc_saved_title_3?smid=ATVPDKIKX0DER&psc=1
Per John61ct's comments, I'll update the install diagram to tomorrow. I still must confirm how to eliminate the existing 1AWG cable Winnebago installed, which includes the boost solenoid shown on the drawing I posted.
There is a "battery disconnect" solenoid next to the "boost solenoid". Subject to confirmation, I believe I'll be eliminating the old cable from my house battery back to the disconnect solenoid. This eliminated section will include the boost solenoid (and the 5 amp Tric L Start chassis battery maintainer). This will leave the old 1AWG cable from the chassis battery to the motorhome's DC load center in place, which includes the battery disconnect "kill switch" solenoid.
I do not suppose there will be a "kill switch" on the Sterling's connection to the chassis battery. I may have to pull a terminal off or remove the fuse; not sure.
Next step: post revised install diagram.