Saturday, Jan 24, 2015
I recently experienced some issues with the cabin solar system due to a few weeks of mostly cloudy days combined with low temps. Due to the holidays I was unable to visit the cabin for a three week period and the batteries reached the system's low voltage disconnect state on Tuesday of the third week. I was also having a problem with the compressor on the refrigerator not able to start when it is cold. While these circumstances are atypical, I took the opportunity to perform a few upgrades to the cabin electrical system.
The biggest change was to transition the system from 12V to 24V which will cut the current draw of loads in half and greatly reduce voltage drop in wiring. Ideally this will allow the compressor in the refrigerator to start more easily (it will run on 12 or 24V).
Rewiring the batteries to 24V was simple. Instead of four 6V batteries in a serial/parallel arrangement, I now have four 6V batteries all wired in series for 24V. An added benefit is that only having one battery bank eliminates any potential for uneven charging.
So I went from a 12V 440AH bank to a 24V 220AH bank, which is obviously an identical amount of stored energy but more efficient overall.
Most of the current system components run fine on 12 or 24V, such as the cabin control system, power supply for the security cameras, etc. The two items that were specific to 12V were the inverter and water pump.
I've replaced the inverter with a new Exeltech XP600 24-volt 600 watt sine wave inverter which seems to be working great so far. I haven't yet replaced the water pump.
I also added an IOTA battery charger to the system so I can charge the batteries with the genset if/when the solar panels are unable to charge the batteries.
For additional monitoring of the system I installed a "Whiz Bang Jr" which is an add on device for my charge controller which measures all current going in or out of the batteries. It uses the same current shunt and essentially performs the same function as my existing Trimetric monitor but by being integrated with the charge controller I'm able to remotely monitor the data via the modbus/network interface. I've updated the cabin controller software to report on this data.
Another slight improvement was to wire the router/3G modem to run directly from the batteries (via the 12V power supply) so that the cabin controller can function remotely with the inverter powered off. This will allow me to power the inverter on and off remotely. For this I used a "power over ethernet" dongle that uses two of the unused ethernet cable wires for power so that I didn't need to run any additional wires.
I also made a couple of bus bars from copper rods and added a couple of switches so I can disconnect the battery charger and control system when needed.
Finally, I installed the remaining two solar panels I had originally purchased for the cabin. This brings the total to six panels and 870W.
Wednesday, Dec 17, 2014
The past few months I've been working on a control system for the cabin. Initially I wanted an easier way to turn on and off the video motion detection when I arrived and left the cabin instead of having to boot up the laptop. I wanted to be able to switch it on/off it with my phone. Then I wanted to be able to view the snapshots remotely. And monitor the temperature in the cabin...
Well, you get the idea. The project as it stands today consists of:
- 2 Control boards, one for the motion detection and to run the local web application (Odroid U3) and one to control all the inputs and outputs (Udoo Quad)
- 3 temperature sensors (inside, outside, utility room)
- 8 relays
- 1 voltage sensor
- 5 current sensors
- 2 power supplies (5V and 12V)
Everything is mounted on din rails with a plywood backing.
The web application operates in two modes, local and remote.
In local mode, the web app runs on the Odroid and communicates directly with the motion capture service, also on the odroid, and a web service on the Udoo to control the inputs/output. The web service on the Udoo talks to the onboard Arduino Due via serial. There are also two services on the odroid which upload the camera snapshots and sensor data to the remote version of the web application (via 3G modem).
The remote web application stores the snapshots and sensor data in a database so has access to time series data. Otherwise it functions the same as the local app other than it uses the MQTT protocol to send commands to the local application so it can control everything remotely.
The only feature the local application has that the remote application doesn't is a live feed from all the security cameras.
Here are photos of the controller being constructed and installed in the cabin.
Here are screenshots of the remote web application.
Sunday, Jul 06, 2014
A couple of weeks ago I added a 5 cubic ft. refrigerator to the cabin. It runs on 12V directly from the battery bank and stays on all the time. It has a small freezer section that will make ice. It's nice that I no longer have to lug a cooler full of ice and food/drinks every trip.
I've been using the propane range and propane tankless water heater regularly. I especially like the water heater as I set it at a specific temperature and it will maintain that temperature. I currently have it set at 109 degrees and when showering I only need to turn on the hot water, no fiddling to get the correct mix of hot and cold. So far it's worked flawlessly.
Last weekend I stained the stairs but it didn't really turn out like I wanted so I'm probably going to install actual stair treads. The stairs are douglas fir and the stain didn't turn out splotchy like I feared but the color is a lot darker than it should be. I used a red oak stain but the result is more of a mahogany color.
I also re-stained the porch because it was starting to look fairly worn. They didn't have the color I use originally so I bought a "redwood" stain so the color turned out quite a bit different. I also didn't like the brand of stain I used (Cabot) in spite of good reviews, but it may have been more due to absence of any kind of preparation of the surface on my part. In any case, next time I'll use the Messmer's stain I used originally. Primarily I just wanted to get something down to protect the wood from any further degradation.
This weekend I added some cedar trim around the doors and front windows so they finally look decent.
For a long while I've been pondering what to do with the area under the stairs. I've been using it for random storage bit it's also where I installed the refrigerator (no room in the small kitchen). I finally made a plan and closed in that area with a full height partition wall and some sliding doors that give full access to the under stair area. I covered the exposed back side with some pine T&G siding (normally used for wainscotting I think) which matches the look of the siding upstairs. I used a similar T&G siding for the front, but in white mdf. There is not to much wall area on the front.
I was concerned adding the closet wall would make the room seem smaller but it actually seems to have the opposite effect. I guess hiding the stuff under the stairs makes the room seem less cluttered. Also having the stairs enclosed makes them feel a bit safer. I'm really happy with the result. I still need to add some corner moulding around the beam and door opening but I'll do that when I trim everything else, hopefully in a few weeks.
The down side to projects like this is that I have to load and haul a lot of equipment out including the big generator, air compressor, chop saw, and table saw.
Tuesday, Jun 03, 2014
It's been a few months since my last post due to a combination of factors but largely because of the despicable actions of thieves and vandals. The cabin was burglarized twice over the span of a few weeks. Nothing of great value was taken but both cabin doors were damaged and these incidents prompted a re-examination of cabin security. It's a cliche, but it really is the feeling of violation that's more traumatic than the loss of property, although having to clean up all the shattered glass from the front door was not that fun either.
In any case, I spent quite a bit of time working on making the cabin more secure. New features include:
- The addition of four high resolution IP security cameras for 24 hour video security
- New steel doors with double cylinder dead bolts on the cabin and utility room
- Motion detection LED lights on the front of the cabin
- Steel cable locks securing all the outside items (i.e propane tanks)
- Installing a lock on my battery box
Adapting the security cameras and recording system for 12V low power operation was the biggest challenge but was ultimately very successful. All four cameras constantly detect and record motion and the entire system uses about 25W.
Here's a video where I stitched together images from three of the cameras taken on a day I was at the cabin.
One other project I've completed recently is the refinement of my water supply system and the installation of a propane tankless water heater. I replaced the large water tank with a smaller tank that I can easily drain and refill in the winter. The large tank contained an 80 gallon block of ice from January to May despite my efforts to keep it from freezing.
I recently purchased a 12V DC refrigerator for the cabin which I will be installing in a few weeks. Because I now have several items running directly from the battery bank I also installed a dedicated DC breaker panel, replacing the marine switch/fuse panel I was using previously.
Tuesday, Dec 10, 2013
It's been unusually cold here this past week with overnight lows below 0 degrees and highs in the single digits. We've also had a good bit of snow.
My plan to use excess solar power to keep the utility room above freezing was still not working very well and I don't think it would have been enough to deal with temperatures below zero in any case. So I made an emergency trip to the cabin last Wednesday and moved a small propane heater I had in the mini-cabin over to the utility room. It keeps the room plenty warm. In fact, on the lowest thermostat setting it stays about 70 deg. in the room. I wish I could set it colder.