Is Your Motorhome’s Engine Charging Your House Battery?

Welcome to another Todd’s Two-Minute Tech Tip Tuesday, brought to you by the National RV Training Academy—the largest hands-on RV training academy in America. This week, we’re tackling a common question from @turdbowman, who owns a 2023 Entegra Quest 24L, a motorhome on a Sprinter 3500 chassis.

Issue: Upon arriving at his campsite, he found that his 230 amp-hour lithium house battery was dead. He had to jump-start it from the cab battery (also known as the starter battery) to start the generator. According to Entegra, the alternator doesn’t charge the house battery while driving, but many RVers on Facebook, who own the same model, claim that it does. Turd is left wondering who’s right and how to solve his problem.

Let’s break down the issue and how to troubleshoot it.

Does the Alternator Charge the House Battery?

In most motorhomes, the alternator typically charges both the starter battery and the house battery while driving. This is done using one of two common systems:

1. Solenoid-based System: A solenoid is activated when the ignition key is turned on, allowing the alternator to charge the house battery as you drive.
2. Battery Isolation Manager (BIM): This is an automatic relay system that manages the flow of electricity, allowing the alternator to charge the house battery while also preventing the house battery from draining the starter battery when the engine is off.

Now, although Entegra may have told Turd that the alternator doesn’t charge the house battery, the people on Facebook say it does. Based on my experience, I’d side with Facebook here. Most motor coaches have the capability for the alternator to charge the house battery—it’s just a matter of figuring out what might be causing the issue in your particular case.

Potential Causes of the Disconnect

If the alternator should be charging the house battery but isn’t, there’s likely a disconnect somewhere between the cab (starter) battery and the house battery. This could be caused by several things:

1. Blown Fuse: A fuse might be blown between the alternator and house battery. A fuse protects the electrical system, and if it blows, it will prevent the alternator from charging the house battery.
2. Faulty Solenoid or Relay: If your system uses a solenoid, it might be stuck or malfunctioning, preventing power from flowing to the house battery. Similarly, if you have a battery isolation manager (BIM), it could be faulty and not allowing the charge to reach the house battery.
3. Corroded or Loose Connections: Over time, connections can become corroded or loose, causing a break in the electrical flow. This could prevent the alternator from properly charging the house battery.

How to Troubleshoot the Problem

If you’re comfortable doing some basic troubleshooting yourself, here’s how you can track down the issue:

1. Follow the Red Wire: Start by looking at your house battery and following the red (positive) cable. You should see more than one red wire coming off the positive terminal:
   • One wire likely goes to the fuse panel to power your 12V systems.
   • Another may go to your landing gear or other specific components.
   • The wire you’re interested in is the one that leads to either a relay/solenoid or a battery isolation manager. This wire eventually goes to the starter battery.
2. Check for a Fuse: Once you locate the wire that runs to the alternator/starter battery, check for any in-line fuses along the way. If you find one, inspect it to see if it’s blown. If it is, replacing the fuse could solve your problem.
3. Inspect the Solenoid or Relay: If you have a solenoid or relay system, check to see if it’s functioning properly. If the solenoid isn’t engaging when you turn the ignition key, it might be stuck or broken, preventing the alternator from charging the house battery.
4. Look for Corrosion or Loose Connections: Make sure all connections between the alternator, starter battery, and house battery are clean and secure. Corrosion can break the flow of electricity and prevent charging.

What If You’re Not Comfortable with Electrical Work?

If this all sounds a bit too complex for a DIY fix, don’t worry. A qualified RV technician can quickly diagnose the issue for you. They’ll be able to follow the wiring, check the fuses, solenoids, and connections, and identify the exact cause of the problem. This way, you’ll know whether it’s something simple, like a blown fuse, or if there’s a larger issue at play.

Final Thoughts

It’s likely that your 2023 Entegra Quest 24L does have the ability to charge the house battery via the alternator while driving. If it’s not charging, there’s probably a simple disconnect between the two systems, whether it’s a blown fuse, a faulty solenoid, or a loose connection.

The good news is that once you identify and fix the problem, you should be able to keep your house battery charged while you’re on the road, avoiding the need to jump-start the battery or manually start the generator.

If you have any further questions, feel free to leave a comment, and I’d be happy to help. Don’t forget to subscribe so you never miss a Tech Tip Tuesday!