

So, one of the first problems we ran into with the RV was a steady drain on the engine battery. One of the main reasons for getting the RVwhisper all setup was to monitor this data remotely and see if it was real or just typical lead-acid battery flakiness.
After replacing the batteries to eliminate old batteries as a cause, I started collecting data, and noticed the following pretty quickly. Here’s a graph of the House battery (2 6V Batteries in series) and the Engine battery.
(Green in House Battery, Red is Engine Battery, grey bars indicate nighttime so you’re seeing the voltage over about a week).
Nothing was on or running during this period, the RV was just sitting in storage and the RVWhisper & Modem were plugged into a portable battery (another article). You can see pretty clearly that there’s a substantial drain on the engine battery here, dropping about 0.3V in a week compared to the House Battery.
To some, this is a known problem. Lots of things in the RV continue to run when it’s "off", things like smoke detectors and such. To avoid showing up to a dead battery, many people recommend disconnecting the battery. That seemed a bit extreme to me, so I moved onto the next solution: Solar Suitcase.
Solar Suitcases are popular in the RV world for this very reason: Small portable solar panels with the charge controllers and all integrated, that you can hook up via giant gator clamps to your battery and provide some offset current during the day. After a bit of research, I went over board and bought a big 200 watt/20 amp Renogy panel.
With that hooked up, I’ve never had any more battery problems. But I did notice a new interesting quirk in the charging graph, that looks like this.
Every day there’s a swift uptick in voltage to a peak just under 14.5V, then it falls back to just under 13.5V to spend the rest of the day, before falling back down to 12-and-change at night. What’s going on here?
I suspect that the first 14V spike is the actual charging step. Measure a running car battery with the alternator going and you’ll read something similar. This is when it’s actually pumping a fair bit of juice into the battery to charge it up. Given that I went overboard with a big 200W solar panel, it doesn’t take long. Then it drops to this 13.5V range, where the battery is basically "full" but it’s still absorbing a tiny bit of power to counter whatever drain is coming from the RV. Then it simply quits charging overnight when there’s no sun for the solar.
Seems legit, but can I monitor this more usefully? A bit of python and SQL query later, and I’ve added a new tool to the RVwhisper-Monitor package, solar.py
. You can run it independently or have it added to the output of the slope
tool, and get a chart like the following.
This shows the hours of sunlight in the day (actually seconds, I need to fix that sometime) as the faded red bar (Yes, the days really are getting shorter now). It also shows the time spent in that 14V Peak range (in green), and the 13.5V "sustained" range (in blue).
You can see that on days after a trip when I hook the solar panel back up for the first time in a while, there’s a lot of green. That makes sense, as it has to recharge from the few days of running the battery down. As things recharge over the first day or two, you see the blue begin to dominate as it’s now just having to recharge the continuous draw. And given the size of this solar panel, I can also power my Netgear Nighthawk & the RVwhisper module directly from the engine battery.
Hope you find this useful!
A few months back, Laura talked me into buying an old RV from a friend of ours. WE thought it would be a great way to get our elderly Mother-in-Law back home to Mississippi to visit relatives. It's been an interesting few months.
So the RV in question is a 1994 Fleetwood Bounder 34C. Chevrolet engine, 34 feet long, and almost entirely original. Original carpet, original wallpaper, original electrics. Needless to say, she's needed a lot of work. We've been taking it out regularly to work on it. So far we've replaced the flooring (some old stained carpet, switched out for vinyl flooring), replaced the wallpaper, repainted the cabinet, replaced the power inverter, replaced the water pump, replaced the awning, replaced the AC Compressor... It's been a big project.
Over the course of all this, it's been important to monitor all the variables of the RV and see if things are improved or getting worse. It didn't take long to stumble across a product called RV Whisper
The RV Whisper is a low power communication devices that runs a local webserver and low-power communication network that can talk to a wide variety of sensors. I bought some temperature sensors (to monitor the temp inside the RV, as well as the fridge and freezer to make sure they work), door open sensors (To work like an alarm for the front door, and to allow me to correlation temperature inside the RV to the opening of the door), and some battery sensors for both the Coach & Engine battery (the batteries were one of the first main problems we tackled).
The device generates a weak wifi network that you can connect to directly to monitor the device, or you can connect to a larger Wifi and the RVWhisper company offers (for a small annual payment) a reverse proxy from their website to your device. They don't store any of your data, which is nice. However, this also means that if you have an interruption in your network then you can't get any data.. Not even historical.
Me being me, I wanted something a bit more robust.. And while I'm at it, if I could get some more sophisticated visualization and analysis I might be able to get more information on what's going on inside the RV.
Introducting "RVWhisper Monitor", freely available on Github.
I'm running this at home on my Raspberry Pi. Every 30 minutes it pulls an hour of data (the overlap helps with small network problems) and stores it locally in SQLite databases. There are also a few scripts there to visualize the data as static HTML files uses Chart.js for some basic interactivity. Check out an example here.
Once the data is stored locally, I can start calculating some more advanced visualizations. The most important one I've come up with so far is the Battery analysis visualizations that show the slope of the battery state, as well as things like min/max/average over select periods (daily). You can see some of those visualizations here.
I'm still working on it. It's been a great help so far, particularly since I'm forced to park my RV at a storage lot a few miles away from home. With the help of a decent solar panel to charge up the engine battery I can keep the Nighthawk modem and RVWhisper unit powered, and then monitor it from the comfort of my house between visits.
If you have any ideas or recommendations, don't hesitate to let me know!