I am looking for an inexpensive way to monitor a 12V batteryās actual voltage to use to run a rule in Hubitat.
Some background:
I have a small solar panel and battery that I setup last summer. I have an inverter connected to it that drains the battery regardless of whether or not a load is connected to it. This is a problem in the winter as there is not enough sunlight here to replenish the battery, and it is being totally drained which is not good for it...
The inverter has a button to turn it off and I have connected it to Hubitat by welding 2 wires from the switch to a Zooz multi-relay.
What I want to do is to shut down the Inverter when the battery level is lower than a set (TBD) level and turn it on when it is higher than another set (TBD) level. The volt meter connected to Hubitat would allow me to monitor the voltage and determine the ideal voltage to turn off and on the inverter, and set a RM rule to do this automatically.
Note: Iāve seen @JasonJoelās recommendation 1 year ago to build something with an ESP8266, but Iām not sure where I would start to build something like that... Iām also wondering if something else would be available since them, or if there would be some way to connect a contact/motion/etc. sensor to it to detect the voltage - it would need to be relatively accurate though...
The Shelly Uni has an ADC capability
I use it to monitor the voltage of my motorhome leisure batteries (also connected to a solar system)
Normal lead acid batteries should not be ādrainedā to less than 50% of their capacity if you want to ensure longevity.
This equates to around 12.1v
Draining the batteries to below 10.1v may cause damage.
Keeping a battery below this state for any period of time is almost guaranteed to cause permanent damage.
The Shelly device uses wifi to connect to your lan and although there is no official Hubitat driver yet, I have one that I have adapted from a Shelly1 driver which reports voltage
Ouch! The device is priced right, but they want over $70 for shipping to Canada when ordering from Shelly.cloud! Will need to find somewhere that ships at a reasonable price...
This is from Shelly USA. They only ship to Canada via FedEx. Shipping is almost 4x the cost of the device... I donāt get how companies think that makes sense...
I checked out Amazon, EBay, Mouser, AArtech but none of them seemed to carry it.
I pre-ordered a couple before they were released and they have only been released a short while so atm i think you can only buy them from shelly direct.
I donāt know if they will sell them via amazon (as they do most of the other devices)
Do you power it from the same battery you are monitoring, or do you need something else? I have been looking for a similar solution for a hobby solar system for my garden shed. This is a great tip.
I actually put it into a little box that is designed to take two AA batteries (which is an indication of the size) and just had two leads coming from the box.
These leads both power the device and monitor the voltage.
During initial tests with a variable power supply, it still reported right down to about 7 volts.
@Sebastien You know I love the automations, but aren't you using a charge controller? They shut off the at either fixed or adjustable discharge cut-off levels. This one cuts out at 10.7 volts and it's only $12.70 CAD. Probably you would want something a little better if this is anything serious, but if just playing around with solar, this seems like it fits the bill nicely.
It is not advisable to pull current through a charge controller to power an inverter.
In fact, my mppt controller manual specifically states that you should not add an inverter to the āloadā connection (and I paid 10x the price of the linked controller)
I suppose you could use the load output to drive a relay
However; taking a lead/acid battery down to 10.x volts is not advisable and will reduce longevity
I'm not a solar user, so I yield to your knowledge on the subject. My brother in-law setup a small unit at their cottage that has no power. Used a small inverter on it last Summer with no issues. Controller was still working fine at the end of the season.
The cottage (actually not much more than an old hunting cabin) is presently torn down and a new one is going up. I'm sure I'll learn a lot from him about the new larger system going in its place.
Yea, I have one that is very similar and there is a port to plug in, but as @Cobra indicates, it is not advised to do so. I initially did connect it to the charge controller and it kept causing issues. It is connected directly to the battery now.
I have a very small setup (100W with 1 x 12V battery) that I wanted to setup to understand how it works, the issues, etc. I looked at updating to a 300W panel with another battery, but then I did some back of the napkin math and calculated I would save a whole 0.10$ on my electric bill with this ~1000$ āUpgradeā.
I have 4kw solar on my home roof and 300w on my motorhome.
Motorhome setup is connected to two 130ah 12v batteries which run the Pi and HE that I have setup there.
MH solar runs through a 30amp MPPT charge controller.
I have to say, since installing the MPPT charger (previous version was a PWM controller) I have noticed a significant increase in charge capability.
Yea, I was going to get a MPPT charge controller with the upgrade as I had read that. Maybe I should upgrade my controller anyway... Though to justify the update as this is really just for fun though...
Nice! I would also eventually like to supplement with solar. It would be great in the summer, but in the winter, my roofās slope is not sufficient so it would not be at the right angle, plus it is covered with snow...
