Battery Voltage Monitoring for Golf Cart

I want to periodically measure the voltage of a 44v lithium battery that sits in a golf cart 3 hours away. A charger is installed and functioning but trusting it is a single point of failure I cannot accept.

My thought is to use a voltage meter with the proper voltage range and a bluetooth switch like the MHCOZY zigbee relay to manually connect the meter for a sufficient period of time to obtain an actionable reading.

I am aware of the Shelly Uni device from this thread by @Cobra and others but the range is not suitable for my application.

Is anyone aware of a compatible DC voltage sensor with a range up to or greater than 44v?


The 44v should not be a problem you could (and IMHO should) use two resistors to reduce the 44V down to something below 5v or perhaps below 3.3v.

My reasoning is the first resistor should be located at the 44v connection. Then the 2nd resistor near the measurement device. Here the goal is to reduce the 44v making it easier to handle AND provide current limit so any failures in the measurement wiring will not have the full energy of your 44v batteries.

If you want to consider this approach let me know and I will suggest specific values. Actually a rather simple calculation.

As I'm writing this I had a crazy idea. Get a simple contact sensor with battery level reporting. Use the resistors to bring the 44v down to the 3v required by the sensor. Power the sensor with the resistor divided voltage. Read the voltage in HE.

Thanks for the idea @JohnRob.

Ohm's Law should get me there but EE not my forte.

Yes, if you wouldn't mind fleshing out your idea a little further I'm interested to look into this a little further...


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BTW, it seems like these Zigboat guys are doing something similar to what you have suggested...

What voltages would you say are:

Maximum when charging.
Minimum you wish to sense.

Interesting..... too bad its so expensive ( €160). However it is a Marine accessory so they can charge 3x the worth :slight_smile:

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Thanks JohnRob for the offer but I've decided to use a bluetooth device with no HE. Not the ideal solution but I can access the analog data from the Victron Battery Sensor remotely using their software and one other sub-optimal technique.

Thanks again!

Happy you found a solution. Good luck with your project :slight_smile:

@david4 / @JohnRob

There seems to be affordable Arduino/Zigbee DYI projects for this kinda thing out there...but few turnkey solutions using ZIGBEE.

We're a year later, is this really all there is given the utility of this kind of monitoring and the ubiquitous use of 12 & 24V DC batteries? (I know there are other comms protocol solutions)

EDIT: Been using a number of MHCOZY relays and have had good luck with them, might consider picking up on the idea the OP had but I'm not sure on the what & how to get that DC voltage reading to HE. Actually, the relay isn't necessary if a device that reads the voltage could also communicate it right?

Fibaro FGBS-222 and a properly sized resistor to divide the voltage down to <10V on the analog input. I believe its a 9bit ADC so your resolution from 44v wont be the best but maybe acceptable. I use one to monitor my 24V battery solar system.

As the OP, my monitoring problem was solved via the new remote vpn feature on my Ubiquiti UDMP at the remote location in conjunction with my udmse. I just remote into the remote Mac and open the Bluetooth app for my remote device and get visibility to real-time data on the battery. This ubnt feature is less than a month old and also allows me to forego the Expense of the Hubitat remote monitoring service. :grin:

Yeah thats cool. I have a Victron charge controller in one of my sheds and can see everything on my phone thru bluetooth within 30ft, its a great app. Cant get into HE though.

Shame. Best HA platform imo. Been thru a few. Detailed-oriented Engineer. Very happy wit these guys. Just waiting to the other buy-out shoe to drop. :moneybag::unamused:

this has been my upgrade charge controllers, but....I'd really like this info available further than what Bluetooth can reach and more importantly, where it could be monitored/acted on through HE there are HE connected devices that are sitting on (relying on) that solar charged battery.