Trips, Troubleshooting


Results inconclusive

During our difficulties is May and June, we were trying to clarify the charging times for the Roadtrek E-trek battery. According to  Roadtrek, “while driving, the under hood generator will be providing 3300 watts at 24 volts with 2000 RPM.”  (This is slightly different than the Roadtrek E-trek Owner’s Manual which states 3500 watts.)

In addition, we wanted to clarify some terminology from the manual, so we asked Roadtrek to define as a percentage what the E-trek manual (p. 85 FAQ: Electrical) means by “moderately depleted,” “adequately charged,” and “minimum battery charge.” 

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

Roadtrek could not provide the information in percentages; however, we are keeping a log so we can eventually create a table to show what battery percentages map to what battery volts.

Since the service at Mercedes-Benz in May and the dealer service in June, we had not driven more than 10-20 miles at a time, so we decided it was time to take a short trip to test the charging capabilities of the Roadtrek E-trek Battery and verify the information we received from Roadtrek. Our son was working as a camp counselor for the summer about 50 miles away, so we decided to visit him and do the charging test..

The battery reading before we departed was 89%/25 VDC (Volts DC). While we were driving the display on the inverter was 100%/28 VDC. After the 1-hour/50-mile trip, the reading was 94%/26 VDC.  After the drive home, we took another reading and 95%/26 VDC. According to Roadtrek, Volts 25.5+ indicate fully charged; however, we were surprised it had only moved up 1% during the second hour of driving.


For a full hour of driving at highway speeds we would have expected the battery to be 100% charged. Our next test will be to charge the battery by idling.




  1. Do you “read” the charge level on the inverter itself, or do you have another monitor wired into the cabin? It is difficult to read the inverter, over the sofa or walk around to the back.

    1. Hi Caroline, Thank you for your question. We would read the charge on the inverter. Often we were testing at home, so we would just open the back door to check the battery strength on the inverter. When traveling, I would lean over the sofa and take a picture with my phone. Hope this helps! Marjorie

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