[villagetinker]

Originally Posted by Arctic Fox

The auxiliary electrics in my cart - lights, horn etc. - appear to be connected to just two of the (6v) batteries, as if they need only 12v. Is that correct and, if so, what is the work-around when using just one 48v battery?

As noted on a previous reply, you need to get a 48 VDC to 12 VDC converter.

Double check the MAXIMUM voltage on the new battery and make sure the convert will handle this voltage. For example a "48 vdc" battery can see 56 vdc during charging, no idea of the range for Lithium Ion batteries.
Next you need to determine the 12 VDC load of your cart, the easiest way is to disconnect the positive lead, install an ammeter 20 amp or higher range and turn on ALL of your auxiliary equipment and see what the current draw is, then order a converter with 50% higher rating.