Chassis Battery Bank Service and Replacement for NEWMAR BAY STAR (Gas Class A)
This comprehensive guide will walk you through repairing chassis battery bank service and replacement on your NEWMAR BAY STAR (Gas Class A). Follow each step carefully and gather all required parts before beginning.
Required Parts
- AGM or Lithium chassis batteries – Part Number: Optima Yellow Top D31A or similar Group 31 AGM, Quantity: 2-4 batteries depending on configuration, Alternative: Battle Born 100Ah lithium (requires different charging setup), Price Range: $250-$350 per AGM battery, $900-$1100 per lithium
- Battery terminal cleaner and protection spray – Part Number: CRC Battery Terminal Protector #05046, Price Range: $8-$12
- Battery hold-down brackets and hardware – Part Number: Replacement if corroded
- Battery interconnect cables (if replacing) – Part Number: 2/0 AWG copper welding cable, Lugs: Heavy-duty copper ring terminals
- Battery charger/maintainer – Part Number: NOCO Genius or CTEK multi-bank charger, Price Range: $150-$300
- Battery load tester – Part Number: Schumacher BT-100 or equivalent, Price Range: $30-$60
- Baking soda for neutralizing acid
- Wire brush
- Dielectric grease
- Voltmeter/multimeter
- Battery hydrometer (for flooded batteries)
- Safety glasses and gloves
Step-by-Step Instructions
Step 1: Battery System Configuration Assessment
Class A motorhomes like the Newmar Bay Star have complex electrical systems with multiple battery banks serving different purposes. The chassis battery bank (typically 2-4 Group 31 batteries) powers the engine starting system, chassis lights, and some 12V accessories. This is completely separate from the house battery bank that powers interior lights, water pump, and appliances. Understanding your specific battery configuration is the critical first step in any battery service or replacement. Locate the chassis battery compartment, which on most Class A motorhomes is in the front chassis area, often accessible from inside a front storage bay or behind a panel in the cockpit area. Open the battery compartment and identify how many batteries are present and how they’re connected – they may be wired in parallel (all positive terminals connected together, all negative terminals connected together) to increase capacity while maintaining 12V, or in series-parallel for 24V systems (rare on modern RVs but possible on older models or heavy-duty chassis). Take photographs of the existing battery configuration and wiring before disconnecting anything so you can replicate the setup with new batteries.
Step 2: Battery Testing and Diagnosis
Before rushing to replace batteries, perform comprehensive testing to determine if replacement is actually necessary. Using a digital voltmeter, measure the voltage of each battery with the engine off and all accessories off – each 12V battery should read 12.4-12.8 volts when fully charged. A reading below 12.4V indicates the battery is discharged; below 12.0V suggests the battery may be damaged. Next, perform a load test, which is the most accurate method to determine battery health. A battery load tester applies a heavy electrical load (typically half the battery’s CCA rating) for 15 seconds while measuring voltage. At the end of 15 seconds under load, voltage should remain above 9.6V for a healthy battery. If voltage drops below 9.6V, the battery has failed and cannot provide adequate starting power. Test each battery individually to identify which batteries in the bank have failed – often only one or two batteries are bad while others remain serviceable. However, when replacing batteries in a bank, best practice is to replace all batteries simultaneously because mixing old and new batteries causes the new battery to try to charge the old battery, leading to premature failure of the new battery.
Step 3: Safe Battery Removal Procedure
Battery removal must be performed in a specific sequence to prevent dangerous electrical arcing, short circuits, or damage to the RV’s electrical system. Always disconnect the negative (-) terminal first from each battery. This is critical because if you accidentally touch a wrench or tool to the chassis while working on the positive terminal, nothing happens if the negative is already disconnected. Conversely, touching the chassis while the negative is still connected creates a direct short circuit that can weld tools, start fires, or cause explosions. Loosen the negative terminal bolt using the appropriate size wrench (typically 10mm or 3/8″), then twist and pull the cable off the terminal post. Move the cable away from the battery and secure it so it cannot accidentally touch the terminal. Repeat this process for all batteries in the bank. Only after all negative connections are removed should you proceed to disconnect positive (+) terminals. Remove any hold-down brackets or clamps securing the batteries in place. Lift each battery carefully as Group 31 batteries weigh 60-75 pounds each and the weight is unevenly distributed. Use proper lifting technique (bend at the knees, not the back) and consider using a battery carrier strap to make lifting safer.
Step 4: Battery Compartment Cleaning and Preparation
With all old batteries removed, this is your opportunity to thoroughly clean and inspect the battery compartment, which prevents corrosion problems with your new batteries. Battery compartments often accumulate acid residue from battery off-gassing, which creates corrosion on terminals, cables, and mounting hardware. Create a neutralizing solution by mixing 1 cup of baking soda with 1 gallon of water. Wearing safety glasses and gloves, use this solution and a stiff brush to scrub all surfaces of the battery compartment, paying special attention to battery cable ends, terminal posts (if they’ll be reused), mounting brackets, and the floor of the compartment. The baking soda neutralizes any acid residue, which you’ll notice as it fizzes when contacting acid. Rinse thoroughly with clean water and dry completely with shop towels. Inspect all battery cables for damage – look for cracked insulation, corrosion extending into the copper strands, or damage to the terminal lugs. Any cables showing significant damage should be replaced. Clean cable terminal lugs with a wire brush until bright and shiny. Inspect battery hold-down brackets and hardware for corrosion or damage and replace if necessary. Allow the compartment to dry completely before installing new batteries.
Step 5: New Battery Installation and Connection
Before installing new batteries, verify they’re the correct type and size for your application. Group 31 AGM batteries are the most common replacement for RV chassis applications, offering 100-125 amp-hours capacity and 900-1000 cold cranking amps. Lithium batteries are increasingly popular due to lighter weight and longer life, but require compatible charging systems – verify your motorhome’s alternator and battery charger are lithium-compatible before installing lithium batteries or install a lithium battery protection system. Place new batteries in the compartment in the same positions and orientation as the old batteries, ensuring the positive and negative terminals are positioned to match your cable configuration. Install and secure all hold-down brackets or clamps to prevent battery movement during travel – batteries that shift can cause cable damage or short circuits. Before connecting cables, coat all battery terminals and cable lugs with dielectric grease or a commercial battery terminal protector to prevent corrosion. Begin connecting cables in reverse order from removal: connect all positive (+) cables first, tightening terminal nuts securely but not excessively (typically 10-12 ft-lbs torque). Finally, connect all negative (-) cables and tighten securely.
Step 6: System Testing and Verification
With all new batteries installed and connected, perform comprehensive testing before closing up the battery compartment. Using your voltmeter, measure voltage across each battery – it should read 12.6-12.8V for new fully-charged AGM batteries or 13.2-13.4V for lithium batteries. Now measure the total bank voltage by testing from one end of the battery bank to the other – it should be the same as individual battery voltage if they’re connected in parallel (which is typical). Turn the ignition key to the “ON” position (but don’t start the engine) and check that all dashboard lights, gauges, and electronics power up normally. This confirms the electrical system recognizes the new batteries. Start the engine and observe the voltmeter/ammeter on the dash – you should see charging voltage of 13.6-14.4V with the engine running, indicating the alternator is charging the new batteries. Let the engine run for 2-3 minutes, then turn it off. Attempt to restart the engine, which should crank strongly and start immediately. If cranking is slow or labored despite new batteries, there may be problems with the starter motor, cables, or connections that need professional attention.
Step 7: Charging System Verification and Maintenance Setup
New batteries need to be properly integrated into the RV’s charging system to ensure longevity. Most motorhomes have three charging sources for chassis batteries: the engine alternator (primary charging during driving), the battery separator that allows house battery charger to charge chassis batteries when plugged into shore power, and potentially a solar system if equipped. Verify each charging source is working correctly. With shore power connected, use your multimeter to measure chassis battery voltage – it should increase slightly (to 13.2-13.8V) indicating the battery separator is allowing charge current to flow from the converter/charger to the chassis batteries. If voltage doesn’t increase, the battery separator may need adjustment or replacement. For alternator charging, drive the motorhome for 15-20 minutes and monitor battery voltage – it should remain in the 13.6-14.4V range while driving. Install a battery monitor system if your motorhome doesn’t have one – these devices track battery state of charge, charging current, and battery health. Establish a maintenance schedule: check battery voltage monthly, clean terminals annually, equalize flooded batteries quarterly (AGM and lithium batteries don’t require equalization), and load test annually. With proper maintenance, AGM batteries last 4-7 years and lithium batteries 10-15 years.