Maintenance, Troubleshooting


Back to Mercedes-Benz for service

According to Roadtrek, idling charges the Roadtrek E-trek battery at a rate of 2000 watts at 24 volts @ 1000 RPM. On Friday, August 7th, we ran down the batteries from 85%/25 VDC to 20%/21 VDC to see if we could fully charge the batteries by idling. We started the test at 11:00 AM when the battery was at 85%/25 VDC. Then we turned on the battery disconnect, inverter, and AC with the temperature set at 60 degrees F. After one hour, the battery was at 65%/23 VDC. After two hours, the battery was at 50%/23 VDC. After three hours, the battery was at 20%/21 VDC and the CO alarm was beeping, indicating low battery, so we turned off the AC.

As a reminder, according to Roadtrek:

  • Full charge…..25.5 volts
  • Moderately depleted…..24 volts
  • Adequately charged…..23.5 volts and above
  • Minimum charge ……21 volts

After revving the engine and idling, we noticed that the battery did not display 100% as it should, but rather 83%/24 VDC. Karl moved it around the driveway, but the battery stayed at 83%/24 VDC.  When the battery went down to 68%/23 VDC after 30 minutes of idling, we sensed something was wrong. Karl popped the hood and noticed right away the fan wasn’t spinning. He turned off the engine and took a closer look. Sure enough, it looks as though the belt had slipped off again.

It was late Friday afternoon, so we immediately contacted Mercedes-Benz to see if we could drop it off so they could take a look at it as soon as possible. Karl spoke to the same technician who had serviced the E-trek in May, who will look at it first thing Monday morning and change the oil as well.


Unknown, since we could not complete the test. To be continued…


  1. Our E-trek is still at Mercedes-Benz. They are replacing the tensioner belt, bolt, and alternator pulley, which Mercedes-Benz said should prevent “belt chatter.” We will post the complete story as soon as the work is complete and we have our E-trek back. We have in the meantime heard from another E-trek owner who had similar problems.

    1. The work was completed yesterday (August 19th) and we will pick up the E-trek today. There was some confusion about which part was needed (the alternator pulley came in two versions, 12 volt and 24 volt), and the correct part (24 volt) wasn’t shipped to Mercedes-Benz until Monday. We brought it up to Mercedes-Benz on Friday, August 7th, so the service has taken nearly two weeks.

  2. I’m happy for you that you got your RV back! I’m sure that waiting was not fun.

    Hopefully, you’ll be able to finally do your battery study with everything functional now. Incidentally, since that heavy duty alternator is not a standard option on the chassis, would Roadtrek continue to cover that under their standard 6 year warranty beyond MB’s warranty period?

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