If the BLACK and WHITE cables are the same slightly size then those are the main battery cables. You should be able to hand trace the WHITE CABLE back to a main trailer frame connection near the battery terminals... The BLACK CABLE should go all the way back to the CONVERTER CHASSIS which is probably an ELIXIR model. I need to look at some 1989 ROCKWOOD interior photos to see what is mounted in the cabinets. If I had the model number hopefully I can find similar photos of your trailer on the internet to look at.
You should have an converter close to the floor and probably looks like this.
The additional wires on my batteries are for the electric lift assy for my top. Some other trailers may have an electric tongue jack. We will probably need to hand trace those other wires at the battery and see where they go before hooking them up.
Pass along the model number of your 1989 POPUP... Depending how big it is will determine if it has electric brakes and what is installed inside... All the 12VDC items inside will run from the CONVERTER when plugged into shore power or from the BATTERY if you had one.
ALso if the trailer has electric brakes you really should get the battery installed as this is DOT SAFETY REQUIRMENT (Actually an state law) you should have on-board and working. The trailer battery is what will lock up your electric brakes if you are pulling the trailer and it becomes disconnected from the truck while being towed. You may have noticed a small chain coming from the BREAKAWAY SWITCH if you have ever hooked up to the trailer and towed it.
We all need a little more info on the trailer to provide good info for you...
Roy Ken
My Posts are IMHO based on my experiences - Words in CAPS does not mean I am shouting
Roy - Carolyn
RETIRED DOAF/DON/DOD/CONTR RADIO TECH (42yrs)
K9PHT (Since 1957) 146.52M
2010 F150, 5.4,3:73 Gears,SCab
2008 Starcraft 14RT EU2000i GEN
2005 Flagstaff 8528RESS