DC-DC MPPT Battery Charger monitor not working.


New Member
Apr 5, 2020
Hey everyone, haven't posted anything in a long time because... well, everything was working well Lol. So, I'm on the road full time living in a converted Astro van. About a year ago I installed a aux battery so I could run a fridge, I was getting tired of soggy food. Anyway, I installed the Renogy DC50S to charge my aux battery while driving and of course with the MPPT using my solar panels as well. At that time Renogy did not offer a hard wired monitor and I really dislike Bluetooth because in my opinion, IT SUCKS! IMHO BT way too finicky to be monitoring something as important as this alternator charger/charge controller. I coudln't beleive Renogy developed this thing without a hard wired monitor so, I installed one of the 0-100 amp AiLi Battery Monitors using a shunt and it's has worked well most of the time. It gets a bit wonky when I'm plugged into shore power and charging the battery using my NOCO 10 amp charger. The readings get flaky and I have to shut down the system and restart for the monitor to read the proper voltages that agree with my multi-meter. Also, I hate the fact that the light flashes whenever there is a draw or when it's charging, gets really annoying at night when you're trying to sleep in a fairly small space. Anyway, long story short I purchased one of the "new" RMS-DCDC-US monitors because it doesn't flash like the AiLi and it's actually made to work with my system. I disconnected my old AiLI monitor, made a Battery Voltage Sensor lead as per the specs in the Renogy RVSCC manual, attached the ring connectors to the correct positive and negative terminals of the battery (again, as per the Renogy RVSCC manual) plugged in the opposite end which has the green plug going into the DC50S, plugged in the RS 485 line that was supplied with the monitor and the display lit up... Yeah... I went through all the settings and set them for my battery and the parameters I wanted and then got to thinking, shouldn't this thing be showing me current voltage of my battery? So I got out my multi-meter and checked the battery, battery is at 12.88 volts checked all the connections to see if there was anything loose no problem. Checked to see if I somehow reversed the polarity of the voltage sampler wire, nope that is exactly to what Renogy spec'd in the RVSCC manual. Everything else in my system works exactly the same as it did before and is wired exactly the same as it has been for over a year without any issues. Something as simple as this plug n' play monitor will not show voltage, anyone have any guesses as to what is going on? I can post a schematic of my system and some photos showing my actual setup if that will ve of any help, but there really isn't much, it's a very simple system.