Planned System Improvements

The last few weeks the system has had outages a few times because of flat batteries. Most of the times it would stop in the middle of the night and come back on around 10AM after a little bit of sunshine. In this post I will describe some changes I hope to make very soon and why I didn't have some of them implemented from the start. 

Means of reducing power usage

There are two easy possible ways I would like to apply to reduce the amount of power used over the course of a single day.

1. Time based rules
2. Voltage based rules

Time based rules
When I analyse the general data usage over the course of several weeks and look for patterns. Especially when no data is going though the system, it becomes clear that after 1Am and before 7AM nobody uses the internet. This is a quarter of the day that the system is using power to maintain a connection but otherwise is not being used. I could save several Watts of power by automatically turning the antenna's off and on at these times.

Something similar can be done with the cameras. There is not really a need to watch the lights of Picton and Waikawa in the evening. If I turn of cameras off when it is dark and On when the sun comes up that would save a lot of power to. To do this I have created new cables to run power to the camera from POE instead directly of the batteries. The red Patch cable plugs into the POE port on the switch and the 24VDC splits out and is 

being stepped down to 12VDC and powers the camera through a barrel jack. If the switch turns POE off then the camera will turn off to. I have something similar for the weather station. 

Voltage based rules
I want to turn devices off and on automatically depending on preset voltage thresholds.
Further on in this I will talk about the hardware I plan to use for this.
First have a look at what the battery voltage tells you about the state of charge.​

I have two Gel batteries in series to create a 24V system so in my examples I will multiply these numbers by two. The manufacturing recommends to not go below 50% if possible. Which would be 24.7V in my case. 

The solar regulator has a Low Voltage Disconnect at 23V and a Low Voltage Reconnect at 25.2V. Unfortunately these thresholds can't be configured on the solar regulator I use. As you can see from the above chart 23V is way too low.

By using voltage rules I want to turn of lower priority equipment to reduce the amount of power used when the system is batteries a re getting depleted below a certain level.

At the moment I have three different priority devices:

1. WiFi antennas
2. Weather station
3. Cameras

So for example I would like to do the following:

• < 75% state of charge turn off cameras
  
• < 60% state of charge turn off weather station
  
• < 50% state of charge turn off antennas

These will work together with the time based rules and should reduces outages to the critical function of the system (providing internet) and improve battery life by reducing the amount of time it will go below 50% state of charge.

Switch with power management

Currently the system uses a Ubiquiti Toughswitch-5. This is a passive POE switch. It requires a stable 24VDC input. To run it from my batteries I use a DC-DC converter to create that stable 24VDC so not to blow up the equipment on a sunny summers day when battery voltage can go over 28VDC. The Toughswitch doesn't have any battery monitoring or power management settings because it doesn't know anything about the battery voltage. Unfortunately it also doesn't have any time based rule set you can configure.

When I designed the system I was looking at the Netonix WS-8-350-DC but it had already been discontinued. This is a smart switch with build in Voltage Regulator so it can run straight from the batteries, has build in power management/rules and time based rules.

Now over a year later they finally released its successor the WS-8-150-DC. Unfortunately it is currently out of stock in New Zealand. But I will try to get my hands on one as soon as possible.