Gary Hatt
September 25, 2022

I Didn’t Know My Batteries Were Dead

The FMCA 104th International Convention & RV Expo was over on Sunday, March 27th, 2022, and hundreds of RVers were packing their stuff away and getting ready to leave Pima County Fairgrounds south of Tucson.  There was the smell of diesel in the air as people were starting their engines and airing up their rigs.  They were also running their generators as they shut down the big show generators at 9:00 AM to encourage people to start leaving.

I packed away my power cord, checked my engine and generator oil and coolant. Then I cleaned my windshield and packed away my lawn chairs inside my bus. I hooked up my toad and checked all of the connections and verified my taillights were all working. 

I got in my driver’s seat and turned the start key to get ready to depart.  Not even a burp.  My batteries did not have enough voltage to even tell my Series 60 engine to turn over. I looked at the BatMon (battery monitor gauge) on my dashboard and the batteries were so low that there was no voltage reading showing at all.  Even the display screen was dead.  What to do?

I have a Noco battery charger/maintainer system connected to both my start batteries and my generator batteries to always keep my batteries charged when plugged in to shore power and when my generator is running, but for some reason, it failed to maintain my start batteries that day.  I am not sure if it was the Noco system or the 110V power outlet supplying the power, but something failed me that week.

BatMon start battery monitor showing no voltage or amperage.

BatMon start battery monitor showing no voltage or amperage.

I had been at the FMCA rally for five days and the electronics on board my bus that are usually energized by my start batteries such as a Dashcam, Sirius satellite radio, etc. were operating and they discharged the batteries down to a point that was below the threshold for starting a Series 60 electronic engine.  I turned the key and the engine brain (ECM) just said “No”.

Fortunately, my Wrico generator battery was fine as there was no draw on it for the days as I was plugged into shore power at the rally and my generator immediately fired up.  I then checked my Noco charger and the charging indicator light was on so I knew my three group 31 batteries were charging again.

I went back inside the bus and looked at my BatMon and saw that it now showed 6.9V on the display.  Not good, but at least now, there was a reading so I felt pretty good.  I decided to go back into the FMCA Vendor building to see who was still in there packing up and visiting with some friends.  This would give my Noco charger time to put some life back into my start batteries. 

About two hours later I walked back to my bus and checked the BatMon and it was now displaying 12.7V.  I cranked the engine and VOILA! The old girl blew a little smoke, sprung to life, and was running. After a short time of running, the voltage was back up to normal again.

BatMon start battery monitor showing the normal 12+V.

BatMon start battery monitor showing the normal 12+V.

This could have been prevented and will never happen again…at least not to me.

While at the FMCA show, I bought a monitoring system that will alert me if my batteries fall below a pre-set threshold.  This is not the first time this has happened to my bus, but I wanted it to be the last time.

The system is called RV Whisper and it can monitor several things in a bus (or any type of RV) and allows you to monitor everything from your smartphone or computer.

The brain of the system is the RV Whisper Monitor Station which can monitor up to 30+ sensors in your rig via Bluetooth and allows you to see all of the sensor information on your phone in one app.

RV Whisper Monitor Station.

RV Whisper Monitor Station.

The RV Whisper system works both with or without internet access, but when you have internet access in your bus or RV (like with a cellular Wi-Fi router) you will also have remote access to the sensor data on your phone, and you can also set it up to receive email and text alerts based on your threshold settings.

The RV Whisper system is always monitoring and logging various sensors information.  Based on the settings you defined using the RV Whisper phone app, it will display a status reading on the interface and it will notify you via email or text alerts to let you know that something is out of range based on your user definable alert threshold settings.  

For monitoring your engine starting battery voltage as I want to do, the BV2 Battery Voltage Sensor will continually monitor the voltage and transmit the data over Bluetooth to the receiver unit.  The BV2 sensor by default also send Alerts via email and text if the voltage falls below 13.0 Volts for more than 10 minutes.  You can also create your own custom battery voltage alerting thresholds.

RV Whisper BV2 Battery Voltage Sensor.

RV Whisper BV2 Battery Voltage Sensor.

The Bluetooth signal from the BV2 is seen by the RV Whisper Monitor Station.  The Monitor Station (in the RV) logs the data so you can always see it on your phone when you are in your RV.  That’s right, everything is logged and stored in the RV so you always have access to the data when you are “in the RV”.  

When your RV has Wi-Fi with internet access, your phone can also see the same data remotely, no matter if you are outside your rig, in another city or state, or even country if you leave your rig parked as I occasionally do when I fly to another country for a vacation.

This same sensor can be wired to your generator start battery or your house batteries to let you know their voltage as well. You can install up to ten BV2 sensors in one system. If you want more detailed information about your batteries, RV Whisper also integrates with two other Bluetooth battery sensors that measure volts, amps, and an accurate state of charge for your batteries via the Victron SmartShunt and the Thornwave PowerMon / DC Power Meter.  

This is also very useful if you have an auto-start system on your generator as I do. An auto-start system automatically starts your generator when the house batteries drop below a preset voltage limit, but can also be programmed to start your generator at a specific time of day for running your heat or air conditioning. If you have pets in your bus, RV Whisper will help you understand how well the air conditioning is working. The shunt-based battery monitors are also very useful if you rely on solar power and/or generator power to keep your batteries charged.

RV Whisper also has Bluetooth temperature sensors (BTH1) that will alert you if your bus gets above or below a preset temperature, which may be too high for your pets, or too low which would allow freezing of your water lines.  You can put BTH1 sensors in your fridge and freezer as well so you will know how your beer and produce are doing.  Nobody likes warm beer.  LOL.

If you were busy and were not paying attention to your App, or ignoring your email and text alerts, you can look back at the history of the voltage readings to view the voltage history.

Voltage readings.

Voltage readings.

As you can see, this system can prevent really bad things happening to your bus which can cost you hundreds or thousands of dollars while you are away, or even when you are there.  If I had wanted to leave the fairgrounds in a hurry that day, I would have been unable to, as without this system, I may not know until I was ready to leave that day.

If I would have had this system installed when my batteries were slowly drained at the FMCA Rally, I would have been alerted via a text message as soon as the voltage dropped below a preset limit, perhaps 12.1V, so I could have taken immediate action to prevent my batteries from becoming too discharged to start the bus. 

This system may also allow you to get more life out of your batteries as everyone knows that batteries that become discharged over a long period of time, do not last as long as they otherwise would if they were kept properly charged. With this system, as long as you can get to your bus, or have a friend check on your bus, you will be able to take corrective action before something become a more serious problem.

For more information about this monitoring system, and to protect your property and your pets, visit 

Article written by Gary Hatt

Since July 2012, Gary Hatt has been the Publisher of Bus Conversion Magazine. Gary does most of his own work on his bus with the help of mechanic friends. He has owned tents, truck campers, travel trailers, and stick-n-staple motor-homes until he bought his first bus in 1997 which was a 1972 MCI MC-7 Combo. When he had a chance to buy a 1983 MCI MC-9 Log Cabin bus with larger windows he jumped at the chance. On Thanksgiving of 2014, Gary bought a 1967 Model 08 Eagle and has since been living and traveling full time in that.

You may reach Gary Hatt at

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