Ok, I still have my legs, but I am kind of obsessed with this battery thing.

It has been about a week since my last confes… post.

Some of this post will go back and forth, time-wise. I am more interested in covering each subject rather than rigorously maintaining a timeline.

The plan was to leave the new 100 watt solar panel in place as long as possible to see if it can catch up charging the new battery. Unfortunately, the weather saw through my ruse and has conspired to be cloudy and sometimes rainy, limiting the solar flux.

By Tuesday, I decided to help the battery along by connecting a mains powered battery charger, using a 800-ish watt-hour power bank. I knew it would not last all day, but I also knew it would be a powerful boost for the battery.

Wednesday morning, I pulled the voltage logger history, then put it right back on to continue logging.

There were a few key moments in the data:

When the battery voltage dropped to 11.3 volts by about 11:45PM, the charge controller shed the load, resulting in a small voltage boost. Interestingly, it did not restore the load until 5:45PM Monday, well after the peak battery voltage well over 12 volts.

By 11:45PM Monday night, it had again shed load, but it seems important that it shed load at 11.11 volts. This is, to a lead acid battery, significantly lower voltage than the 11.3 volts where load was shed the night before. Very curious.

Around 8:00AM, we actually had a sunny day the solar panel began adding a sharp rise to the battery voltage.

At 8:56, I connected the external charger. The screen display on the power box estimated 3 hours of runtime, but it was wrong. The box was depleted at just over an hour and a half. Since I had set an alarm to check on it in three hours, it was well shut down by the time I checked it. I pulled the charger off and put the power box in the garage to recharge it, but I left the logger in place until Wednesday morning.

When I reconnected the panel on Tuesday, I was smart enough to take my 2nd string cheapy meter up there to see what the open circuit voltage was on the solar panel, which was 23.9 volts. Ironically, I kind of noticed at that time that the charge controller and the voltage logger were slightly different and I remembered the voltage logger as being about 1 volt lower than the charge controller. However, with a meter in my hand, I did not think to check it and compare at that time. Typical.

Early Thursday evening, I took my good meter out there and compared the three readings. They were all close enough to not really matter, though the charge controller reads the lowest by 0.2 volts, possibly a significant number when dealing with lead acid chemistry.

The coolest development is something I have wanted for a long time, a way to monitor the voltage remotely. I had mentioned using an ESP-Home device, which would be inexpensive and pretty easy to build, plus I have already made a few similar devices and likely have everything I might need on hand.

Then again, I discovered that Shelly makes an affordable device that does what I need right out of the box.

For my purposes, it is a WiFi device that talks to Home Assistant using MQTT, runs on 9-28 volts DC and can measure 1-30 volts DC.

It also has two digital inputs, a pulse counter input, two digital outputs that can drive 300ma, and it can operate a variety of one-wire devices, such as temperature and humidity sensors. I see a Home Assistant gate opener in my future. I only wish one unit could monitor two voltages so that I could almost monitor the gate opener battery without deploying a second unit.

It was almost trivial to get it working. This is not really a tutorial, but… I put the Shelly app on my phone and give it Bluetooth permissions. I powered the UNI with a 12V battery pack that I use for various things. The app found the UNI device immediately. I configured it to join my IoT WLAN, then browsed to it to set it up.

First, I set up MQTT. All I had to provide was the IP and MQTT port of my Home Assistant and it pretty much immediately showed up in devices.

I noticed that there was no voltage sensor showing. To enable that, I had to go to Peripherals in the UNI setup menu, click the + button to add a peripheral and add Voltmeter. There are several useful settings, such as a friendly name, measurement range and some custom math and units that can be applied to the measurement before it is reported. For example, you might measure 4 volts, but 4 volts from a strain gauge might mean 9 pounds of grain left in a hopper, so you can do some math and report 9 pounds instead of 4 volts. You can also set up automations from within the UNI device itself

“Delta Threshold” is worth spending a little time on. The Triplett logger takes a voltage reading once every configurable time period. The longer the duration between samples, the longer you can collect data before the memory fills up. The Shelly UNI instead watches the voltage and only reports when the voltage changes a certain amount. The minimum and default is 0.1 volts. This makes for a much more efficient use of database space, but a blockier uglier graph.

Everything else was just minor tweaking of Home Assistant stuff.

I left it connected to the battery pack overnight.

It was several hours between 0.1V drops, from 12.14, to 12.03, to 11.92 volts.

This morning, I added a little more wiring and connected it to the gate battery. We’ve had a reasonably sunny day.

It’s only one day, and the first semi-sunny day in several, but I am disappointed in how rapidly the battery voltage is dropping. Of course, it didn’t peak very high, so that could be a factor as well.

I am thinking of running a cord out there and running the charger for 3-4 days to put a real solid charge on this battery so that the solar can really do just maintenance charging.

It is now Saturday morning and rather than add a whole post just for this, I though I would append to this one.

I took the 30 minutes or so that it took to build and attach the mounting brackets to the panel.

This is set to the reasonably ideal angle for a panel that is the same as the location’s latitude, 33ish degrees in this case, measured imprecisely with a speed square during assembly and using the holes that came closest to that imprecise measurement.

It is a cloudy day and it was a foggy morning, so I can’t expect a lot of energy today. I did find the little dip from the removal of the panel during construction of the brackets a little chuckleworthy.