You should be okay for cable length. You may need an additional cable to go from the positive side of one battery to the negative side the other battery.
Before you buy batteries consider purchasing a battery load tested. Any automotive parts store has them. This tool should be part of your kit bag. My tester is rated at 130 AMPS.
1. Make sure if flooded cell batteries the water level is correct.
2. Fully charge the batteries.
3. Disconnect the batteries from each other and the coach. Batteries are connected to nothing.
4. Follow the tester instructions. The test take about 15 seconds per battery.
5. The reading will tell you the state of the power in the battery(s). The power in the battery is really what you want to know.
2005 Newmar KSDP 3910 + GMC ENVOY XUV 37K lbs Moving Down The Road
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