Why does it need 2 batteries? Are these regular truck batteries?
one battery has a hard time charging grid heaters when it's cold out among other things. while one would work, it has to work harder, so they wire two in parallel. the two then share the load.
The bigger the truck is and the more components is has that need to be charged, the more battery power it will need. I am a truck driver, and my semi has four batteries.
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