Category Archives: off the grid system

Cabin WiFi is here

1.5.2019 – Saturday

Since the very beginning the Ol’ man and I have dreamed of ways to add surveillance to the offgridcabin. The easiest, and first method we utilized, was to use trail cameras. Initially this system relied on cameras with a visible flash. This provided a clear photo night or day but wasn’t very covert in the low-light hours. Then invisible flash cameras hit the market and could take photos undetected. Too bad most of the black-flash cameras yielded photos that were grainy, over/under-exposed, and low resolution. The first camera to produce useful black-flash photos (with a fast trigger speed) was the Reconyx Hyperfine HC600 and we started using it shortly after its introduction in 2011. Look it up; it was at least 5 years ahead of the competition and is highly regarded for night-time image quality. Initially, the HC600 retailed around $550 for a single camera. Today I added 5 Blink XT cameras to the cabin for a total cost of $299. These cameras rely on a WiFi connection to function – that was also added today. Poor reception at the offgridcabin meant a cellular booster was also needed.

Here follows the cellular booster / wifi hotspot / wireless surveillance installation. The total project cost just under $1000 and the only recurring fee is for the Verizon Jetpack® MiFi® 8800L, which costs less than $15/month for 1GB of data.

I have used Blink cameras at my house for nearly 2 years and was an early adopter. The hardware is well designed and only recently has the software caught up with what the hardware is capable of. I’ve enjoyed the product and have eight cameras at my house and use Life360 and IFTTT on my iPhone 8 to automatically arm and disarm the cameras. First person home disarms the system, last one to leave arms it. It works really well. For now, the cabin cameras will be manually armed and disarmed. The one weakness of Blink is that the cameras require a reliable internet connection at all times in order to function properly. Solving that problem is where most of the budget was spent on this project.

The first step was to find a cellular booster that would function off of 12VDC. The Surecall Fusion4Home 3.0 met my specifications. Their customer support was responsive to my questions about power-supply requirements, and detailed specifications were listed for each booster model online. After that, the next step was to find a cellular hotspot. I have AT&T for my phones and share an unlimited plan with my parents. Unfortunately AT&T was a dead end on two fronts. Their best hotspot has a tendency to overheat and the workaround for continuous use is to plug it in to USB power and remove the battery – not good signs when I need reliability. I can’t walk over and simply restart the hotspot when it goes funny. The second shortfall was the requirement for a separate data plan in addition to a monthly line charge… $50/month total for the smallest data plan of 3GB. The only other option was Verizon. Feeling defeated I investigated and was beyond surprised that I could get 1GB data for less than $15/month after all fees and taxes. Holy wah! With all the pieces on the board I poured over fine print for a few days and then placed some orders.

As the kit began to arrive my thoughts moved on to how the installation would look. In the shop I was wrapping up the Sobotta River Table and had some free space on the workbench. A wide hickory board and two ash batons made the perfect mounting panel. Cords were securely mounted onto reverse of the board, and keyholes routed into the batons, which made for a fast and efficient mounting solution. On the front of the board I used Festool 5mm dominos painted black to cradle the Blink camera hub and Verizon MiFi hotspot. An 12V accessory/USB outlet was mounted to provide power to the three units. I’ve noticed that some of the older USB 12V chargers, when in use, cause violent fluctuations in the 12V power supply of the cabin and cause lights to flicker and pulsate. Newer chargers labeled as fast chargers do not cause this. In order for any device in the cabin to be in continuous operation (including this accessory/USB outlet) is has to have some sort of overload protection built in.

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Once the mounting board was built and all the components were tested it was time to head to the cabin for the installation. The mounting board was hung on the wall with two screws and then power was supplied from the 12VDC fuse block left of the breaker panel. That was the easy part. The hard part was running the coaxial cable across the basement and out the far wall to the TV antenna pole. An 18″ drill bit was needed and even then it was barely long enough to span the thickness of the sill.

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The yagi antenna was mounted up as high as was reasonable and aimed directly at the AT&T tower with the strongest signal. This also happened to be ideal for Verizon as well. The correct aim was very important. Trial and error revealed that the yagi is very fussy about being aimed directly at the tower. Aim wrong and the booster is essentially useless. Speed tests revealed that a reliable 5+ mb/s was achieved for both Verizon and AT&T. Not bad! In my testing 2mb/s was the minimum for the Blink cameras to work reliability.

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The rest of the installation was easy. Walk around and find a place for each of the five Blink XT cameras. Each camera mounted easily and the Ol’ man and I had fun playing with live mode and arming and disarming the system.

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The Blink XT is perfect for the offgridcabin. Each camera is wireless and uses 2x AA energizer lithium batteries. With normal use each set of batteries should last 15 to 18 months (in my experience) before needing to be replaced. Rechargeable batteries are not recommended because the camera cannot accurately determine low-battery status on NiMH batteries (LiFeS2 has 1.8V open current voltage, and NiMH is about 1.25V). Also, LiFeS2 batteries like Energizer Ultimate Lithium AA’s have about 6.3 Wh while NiMH like envelop AA’s have about 2.5 Wh capacity. In other words, the lithium AA’s last 2.5x longer than a high quality NiHM AA. Whatever battery is used, the cameras have excellent endurance and are very easy to install and to relocate.

The Sync module is also very low power. I haven’t measured the total energy use of the booster, sync module, and MiFi hotspot…yet (I have a clamp meter). Prior to installation I used a 12V/2amp power supply to test the components and it worked without issue, implying that total power consumption is less than 24 watts.

Each camera has a built in thermometer and programmable temperature alerts. One camera is in the cabin and set to send alerts if the temperature drops too low. In the event of a failure in one of our propane heaters we can respond before the pipes freeze. The Ol’ man is also interested in the weather. How much snow did the cabin get? No need to wait until a neighbor can check and text back – check the cameras. Will the rain turn to ice? – check the temperature on one of the outdoor cameras.

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Blink XT features:

  • HD Video (1280×720 @ 15fps)
    • quality settings (saver, best, enhanced)
    • options to stop clip early if motion stops
    • retrigger time (10 to 60s)
    • clip length (5 to 60s)
  • Motion Sensors
    • programable sensitivity (1 to 9)
    • 25 zones that can be active or inactivated
  • Built-in Microphone
  • Infrared Night Vision
    • illuminator has three modes (low, med, high)
    • illuminator can be set to off, on, auto
  • Temperature Sensor
    • hi/lo alerts range from 40 to 90°F
    • records to temperatures well below 0°F
    • can be manually calibrated

A 30 second clip on best quality is less than 2.5MB. With the tiny 1GB/month data plan Blink should be able to upload about 200 minutes of video each month, or about 600 clips 20 seconds long (20 clips per day).

UPDATE (1.6.2019)

Deer. Everywhere. Here are two videos captured after we departed the cabin yesterday. They don’t look too spectacular when viewed on a 5K computer display. However, pulling up a live feed on an iPhone at any time, any where is pretty cool – and it looks a lot better on a smaller screen.

 

The active zones have been updated on the porch camera. I’m hoping that this reduces the number of videos trigged by passing deer yet still records if anyone gets curious and decides to walk up on the porch and take a look.

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This is the home screen for the Blink App. If a camera is offline the thumbnail will be greyed out. Quickly opening the app and seeing that the thumbnails are normal and the little camera icon is connected with a green line to the cloud let us know everything is operating normally.

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This post was not sponsored. I can say whatever I want 🙂

 

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battery monitor upgrade

5.10.2014 – Saturday

Through a bit of luck I somehow managed to acquire a Victron BMV-702 this Spring (big thanks to Matthijs & John). The current BMV-600s has served the cabin since July 2011 and performed like a champ. For a technical overview/run-down on the BMV-702, check out John’s post: BMV-702 insights | Victron Energy. I’ll share some photos and impressions from my specific application.

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The packing is compact and tidy and the box includes everything necessary for installation (clockwise from bottom):

  • Quick installation guide (featuring tidy diagrams)
  • User Manual
  • 500A/50mV shunt
  • 2 meter battery cable with fuse (red)
  • Faceplate for front mounting
  • Meter (with rear mounting ring, in anti-static packaging)
  • 10 meter RJ 12 UTP data cable

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Upon close examination the shunt is different from the BMV-600s shunt that it replaces. The BMV-702 features two quick connect PCB on the current shunt where the BMV-600s featured only one. So… what to do with an extra quick connect PCB? After a leisurely read through the user manual I uncovered a few different uses. The one that peaked my interest involves an optional battery temperature sensor that can automatically adjust battery capacity as temperature decreases. Once the sensor becomes available in the United States I’ll be installing it in short order (hopefully before October concludes and winter begins again). Due to our battery placement in an unheated garage, this alone is reason enough for the upgrade at the cabin.

Fore reference, the BMV-600s was programmed as follows:

  • 85% CEF (charge efficiency factor)
  • 1.20A Ith (current threshold)
  • 1.25 PC (Peukert exponent)
  • 13.5V Vc (charged voltage)
  • 1500Ah Cb (battery capacity) — use 850Ah for winter
  • 50% DF (discharge floor)
  • 0.8% It (tail current)
  • 4 min Tcd (charged detection time)
  • 1 Tdt (time to go)

Having to not reprogram for winter (<50°F) would simplify and increase the accuracy of the readings. I’m happy to pass this adjustment off to a computer. For now I carried over all the settings from the 600s to the 702. To install the shunt I simply cut power to the system and swapped in the new shunt. After install I replaced the bus bar shield and headed in to the cabin to swap out meters.

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The 702 retains identical physical dimensions to the 600s, making for a seamless upgrade. I spent more time taking photos than installing this time around. The “+” and “-” buttons toggle through the following displays:

  • Amp hours
  • State of charge (percentage)
  • Time to go (hours)
  • Battery temperature*
  • Voltage
  • Current (Amps)
  • Power (Watts)*
  • State of charge icon (lower right of display)*

*Added feature

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The added features to this meter (temperature, watts, fuel gauge style state of charge icon) only add to the utility of the meter in our application. Programming is straight forward and the text scrolls across the screen on the 702. You no longer need to program with the user manual in one hand like on the 600s, where a displayed abbreviation corresponds to a definition in the manual. I recommend setting the scroll speed just a bit faster than factory preset on the 702 for faster programming.

In everyday use I usually leave the display on the percent readout and toggle between the amp hours and watts displays. An easily missed convenience on the 702 is the backlight. It can be set to “always on” or programed to turn on for several seconds once a button is clicked. When set to turn on after a button click the first click does not toggle through screens – it only turns the backlight on. I really like this small touch (ie, not having to toggle back to the screen I was on before turning the backlight on).

UPDATE: 5.28.2014

Just the same as on the BMV-600s, the 702 produces an error in its readout under a very specific condition. When multiple large (>300 watt) loads are applied the meter will get stuck reading out 85 watts / 6.5 amps. The voltage will remain accurate however. Observed loads at time of error:

  • Kurig K10 MINI Plus Brewing System running
  • Oven on (300 watts)
  • LED lights (100 watts)
  • Well pump turned on (water running)

Once the error was in effect, several different approaches were attempted to reset the meter and remedy the situation. This took some time to perform since after several of the attempts the meter had to be reprogramed to the desired settings.

  • synchronisation
  • meter reset to default settings
  • cut power to meter 5 seconds
  • cut power to meter 30 minutes
  • cut power to shunt 5 seconds
  • cut power to shunt 30 minutes
  • disconnect Solar input (zero input)
  • disconnect Inverter and all loads (zero output)
  • disconnect solar and all loads (zero current at shunt)

All failed. I reprogrammed to desired settings and then waited… After about 12-16 hours it resumed normal operation. I’m still attempting to figure out what is happening. Again, this is a very specific situation and though it has been reproduced reliably, it only happens when there are multiple large loads and at a frequency of about 4 or 5 times a year. The glitch first occurred when we ran an air conditioning unit off battery power. Now it appears that the well pump and the Kurig can do the same. The exact cause is unknown and under investigation. I would really like to be able to hit a button and reboot the meter instead of waiting 12-24 hours for the meter to fix itself.

Bottom Line: I would buy this meter again. The feature set and build quality are second to none. And while the glitch is nuisance, it occurs infrequently. I’m confidant that a solution will eventually be uncovered (I’ll review my wiring, it could very well be my fault). Also, look for a new post this winter once a battery temperature sensor is added.

 

 

off-grid system :: diagrams

CURRENT DIAGRAMS:

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4.12.2014

  • off-grid inventory 5: (ADDED 4/12/2014) – I’m 18 months behind on this but I finally updated the inventory to include our conversion from CFL to LED lighting in the cabin. The update cost $486.10 for just 22 LED emitters. Wow how the price has changed. Non-the-less, we remain happy with the upgrade. LEDs in my observation offer much better lighting characteristics than CFLs and a wider choice of spectrum choices than incandescent.

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8.26.2011

  • Cabin DC wiring 2 (ADDED 8/26/2011) – updated; now includes battery monitor
  • Cabin Power System Schematic 2 (ADDED 8/26/2011) – Completely reworked and updated! This is a huge improvement over the old schematic. And that big blank spot on the LED diagram – that is reserved for the technical drawings of the 12V LED install planned for the cabin. The wire has been run from the garage and the bulbs have been ordered. We’re going to use standard E26 screw in bulbs specifically designed for 12V DC with a wide 180° coverage with 400 lumen output at 5.6W – in other words: we can use a standard light fixture and wire it for 12V DC instead of 120V AC.

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3.7.2011

Throughout the research and design phases of the project I created and updated this schematic: Cabin Power System Schematic (UPDATED 1/27/2011). Please note that the DC switches used in the LED light diagram are standard 110V AC light switches and not the toggle switches in the diagram.

  • Each item purchased in the construction of the system was also briefly catalogued in order to keep track of expenses: off-grid inventory 3 (UPDATED 7/31/2011). In this new inventory I’ve added pie graphs and itemized expenses by project.
  • I also created a DC wiring diagram (ADDED 3/7/2011) to better show how the panels, inverter, fuses, and breakers are connected.

I will continually update this post to reflect the current set up of the off-grid system.

Previews of the most recent documents (open PDFs above for easier viewing):

Overview Inventory

batteries :: cold weather

3.24.2014 – Monday

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There has been little doubt that these past few months have been Winter. Little chance of mistaking it for any other season. Records are adding up and it’s reasonable to say that it has been consistently cold. The silver lining has been the lake ice of Lake Superior. More ice means the liquid water is locked away and we have more sun and fewer lake-effect snow showers.

2014 data from NWS Marquette:

  • February averaged 5.6°F
  • 78 consecutive days were below freezing
  • 5 days this winter the high was below zero
  • 20 days in February had a low below 0°F
  • -28°F was recorded on 2/28/2014

The off-grid tech we have in the un-heated garage faired quite well this winter. As a result, I think we can endure future winters without much worry. Despite the cold, the lowest recorded temperature at the battery terminal (where the sensor is bolted on) was still in the twenties. The garage is fairly well insulated and the generator exhaust vent gets closed off when we depart – sealing up the garage quite well. An interesting observation the Ol’man and I noted was that the exhaust fans for the generator (two 100 cubic-feet per minute 110V muffin fans) were not working as efficiently as hoped. The solution was to crack the service door just a bit to let fresh air in to displace the air vented by the fans. The garage is very tight with doors shut and windows latched.

Before departing we like to make sure the batteries have a charge somewhere between 85-100% in the winter months. After some data mining I assembled the table and drew up the graph in this document: Freezing Point Depression. Below is the graph.

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The document was my effort to determine what it would take to damage our battery bank. The short answer is that it is almost impossible to freeze-damage our batteries given the lowest observed temperature in the garage.

We charge up to 85% or more before departure because of the lake-effect skies. It may take 10 days for our panels to collect 100 Ah in winter. The 12V LED lighting requires about 30 Ah (at 12V DC) to operate each day. In 10 days without sun (not an uncommon event) we’d find our battery bank down 300 Ah! The battery bank is rated at 1540Ah at 80°F. Ever wonder why batteries get ratings at specific temperatures? I recorded some data from our battery bank (via amp-meter and specific gravity) and found that at 30°F the batteries are down to roughly 50% of the 80°F rated capacity! The reaction required to transform chemical energy to electrical energy gets inefficient as the temperature drops. In deep winter, 300 Ah becomes 40% or more of the battery bank capacity.

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My data set only has three samples and it would be nice to get another point below freezing. However, given how well this graph has aligned with casual observation, I’m not too enthusiastic about drawing up below-freezing electrolyte in a glass bulb for an additional dot on a graph.

While cold batteries may last longer, warm ones sure work better. If you happen to be in the process of deciding where to place batteries in an off-grid system, hopefully I’ve given you some useful information. To finish up, here are a few parting shots of winter. Despite the cold I enjoyed winter this year and the lake ice made for some fun family outings. None-the-less, I’m happy to move on to maple tapping.

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12V :: fan box

2.27.2014 – Thursday

Sure was nice out today… except for the temperature. The sun was warm and bright but the wind dulled my sense of touch to the point that taking off my gloves to gain more dexterity for strapping a car seat into the Honda Pioneer was a foolish decision.

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But inside the cabin the weather was much the better. Wood heat. Wonderful, radiant, wood heat. A rolling flame softly rising against the glass pane. As much as I could while away the day sinking into the couch next to the fire, the latest cabin project required my attendance in the basement. The Ol’man had already run a surrogate wire up the wall behind the gas stove from the floor to the ceiling – which we would use to pull the lamp cord through and up the wall. In the two weeks previous I was able to acquire some things:

  • $17.62  – KingWin Four Channel Turn Knob Multi-Fan Cooling Controller FPX-001 (LED Indicator for Power On/Off, Control 4 Sets of Fans, 3 Pin Fan Connections)
  • $5.00    – 2x Neodymium Magnets 1/2 x 1/2 inch Cylinder N48 (26 lbs pull force each)
  • $1.51    – 2x Neodymium Magnets 1/4 x 1/4 inch Cylinder N48 (6.3 lbs pull force each)
  • $27.80  – 4x Evercool 60 x 25mm High speed 3 pin fan EC6025H12CA (Dimension (mm): 60 X 60 X 25, Bearing Type: 1Ball Bearing, Speed (RPM): 5000, Rating Voltage (VDC): 12, Power Current (AMP): 0.24, Air Flow (CFM): 26.5, Noise (dBA): 30, Pin Type: 3 Pin Type / 3 wire)
  • $0.85   – 5 amp blade fuse
  • $6.20   – 4x male &  female insulated connectors
  • $0.35   – 1x butt connector
  • $9.00   – 50 feet of lamp cord (18-2 copper stranded, $45/250 feet roll)

I had some extra parts as well – that’s just what was used in the final installation. The actual construction took about 5 hours start to finish with some additional time invested in gathering measurements from the stove. The total for this project was $68.33 and 5 hours.

 The fan box is an alternative to a $260 factory accessory. The factory accessory plugs into exiting connections on the stove and requires access to a 110V outlet for power. The objectives that had to be met by the fan box were 12V DC power, easy installation, ability to use existing wiring on stove, and to force enough air between the fire-box and firewall to increase heat distribution throughout the basement. 12V DC power means that we can heat up the basement without wasting power idling an inverter. The magnets allow for easy installation and adjustments. I purchased wire connectors that mated with the existing wiring on the stove for installation. And lastly, the fan controller allows for each fan to be individually adjusted for output (which is nice for fine-tuning the airflow to noise ratio).

Design wise, the fan box is glued together with a few plugged wood screws. The fans slide in from the open end and all the wiring connections are enclosed.IMG_1786

Sliding everything into the box allows for easy maintenance and fewer screws. The fit is snug so there is no rattling. IMG_1783

Once the cord cover panels and controller plate is slid in the end cap is magnetically held in place by small 1/4″ x 1/4″ cylinder magnets that mate up with screws counter sunk and adjusted for a perfect fit. IMG_0254

The two large magnets are quite powerful. As a test I was able to easily support two hammers over the fan area without failure of the magnetic  bond. IMG_0259

I had thought that a rheostat was pre-installed on the stove, but when I started the install I discovered that there was a space for a rheostat and not actually a rheostat. The stove has an aesthetically pleasing ON/OFF rocker switch for the front flame. The flame turns ON and OFF with the switch, but also turns ON when the stove fires up and starts to produce it’s 20,000 BTU output. I suppose in a house it would be nice to see a constant flame without having the stove run at 100% in order to see the flame. For the time being the switch has been repurposed as the ON/OFF switch for the fans (instead of the rheostat switch like originally planned). The install went reasonably smooth, making this the 3rd 12V accessory added to the cabin after the LED lights in the kitchen and the charging station automotive outlets. Three of the six slots on the 12V cabin fuse block are now in use.

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The blue LEDs are visual indicators that the fans are on. They do make sound as well, but if we decide to slot in quitter fans in the future it may be nice to have a visual indicator that something is running. IMG_0300

Two additional accomplishments for today were the replacement of the energy hungry 42″ plasma TV with a much more conservative 42″ LED TV, and the discovery of a battery charger that does not make LEDs on the 12V system pulse. The unofficial drop in power for plasma to LED is from 15 amps to 2.5 amps (multiply by 12V for watts). The charger we now use at the cabin is better designed for utilizing 12V power and uses a constant current to charge batteries instead of a pulse wave. The result is no more voltage fluctuation on our 12V system. The charger appeared in the previous post and is the Nitecore IntelliCharger i4. The charger is able to charge our AA, AAA, CR123a, and 18650 flashlight batteries. A $5 car cable makes it ideal for our charging station. At about $20 street price, it replaces the Lacrosse BC-700 Alpha that we’ve been using with a 12V to 3V automative transformer and charges the batteries in about 1/3 the time – still acceptable to promote longevity of the battery, yet quick enough to provide a useful upgrade to the current charger.

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Now at night we can charge our flashlight batteries, have only the 12V kitchen lights on, and watch shows on a 42″ LED TV and only use a total of 6.5 to 7 amps! (or about 80 watts). Add just 0.5 more amps and the basement can be warmed up using the fan box to push hot air out of the gas stove. IMG_0298

 

Remember how I mentioned it was cold? It reached 0.0°F at the cabin in the sun. Right now, at midnight EST it is -21°F and dropping (without windchill). This is a winter for the record books. I’m glad I’m not a yearling deer this winter.

battery checkup late-2012

11.14.2012-Wednesday

It has been a little, while but I’ve collected enough data to assemble another battery update post. The first topic I’d like to cover is battery capacity and changes in temperature. I’ve seen theoretical charts for capacity vs. temperature, but due to variables in battery composition, size, manufacture process, etc… I needed to experimentally find the relationship with our batteries and temperature. I have collected only three samples of capacity and temperature but I consider these to be very good samples given how much trouble I endured to start from a fully charged, rested battery, with a reasonably stable 20-30amp draw (TV and a few lights with the occasional power spike from the well-pump). I used to battery monitor to record how much power was used (Ah) and then took corresponding specific gravity readings to get an estimate. I used specific gravity before and after discharging to determine the change in state of charge.

What’s very interesting about this chart (other than dropping to 50% rated capacity at about 30°F) is how quickly capacity drops off when temperature drops below 60°F. I now consider “Summer” as the season when the batteries are >60°F and “Winter” to be anything below that. It would have been nice to keep the batteries in the basement, but in our situation an insulated garage works. I simply adjust the battery monitor to 850Ah in winter and then back to 1540Ah in summer.

I’ve begun to track the to amount of water I add to the batteries. I had a brief scare a while back when the plates were just barely exposed on a few batteries. The PV charger was running a bit high for voltage – I thought the low capacity of the batteries in the cold was due to not getting enough charge to the batteries so I jacked up the charger set-points. While this did not risk harm to the batteries directly it cooked off the water pretty quick when the weather got warm. Combine a particularly busy time in my life (graduation, first child, moving, new job…) and we were close to doing some real damage to the batteries. Luckily I had a weekend in June to give the batteries the once over. I also recently started tracking equalization dates. The new plan for maintenance is:

  • Water as needed,
  • Visually inspect every 4 months
  • Equalize every 4 months
  • Take S.G. of every cell yearly (once before, once after equalization)

The most recent battery health assessment was interesting. It’s been a long time since the last equalization. I may have record of it somewhere but it’s not in either of my two core battery spreadsheets. Here is the S.G. before equalization. Note that the batteries were at 87% charge.

How to read my tables:

  • Each battery is 6V and has 3 cells
  • One temperature reading is taken for each battery
  • Top table is actual readings
  • Bottom chart is the variance from average S.G. and standard temperature
  • My algorithms flag variances: white is normal, brown is OK, red is greater than ±0.007 from average – which is generally considered an indication to equalize

Here are the effects of equalization (before watering batteries)

I’m happy with this. One cell is just outside of factory specification. I’m not going to worry much since the batteries were cold and the quality of an equalization could be considered questionable because of that. I’m fairly sure a summer equalization would do the trick and leave my tables with all white cells (maybe a few brown ones).

It looks like at 3 years our battery bank is still fairly healthy and that having a maintenance plan is going to pay off long-term. Also, I’m almost ready to declare the off-grid system a success, and stop referring to it as an experiment. I’ll decide that at the five year mark (early 2015). It also looks like the batteries require about 1L water each month and that anything over 5L puts the batteries at risk for exposed plates. This will probably drop to 1/2L water each month in winter due to temperature drop.

Downloads: Battery AnalysisBattery Records

off-grid system :: settings

11.19.2012-Monday

Some fine-tuning has been going on. The battery monitor has been super accurate the past few weeks. I have marked the changes with an asterisk. The charge efficiency factor (CEF) has been adjusted and through trial and error 85% has been reached as the appropriate charger efficiency. This is after trying 74%, 80%, and 95% before arriving at 85%. Current threshold (Ith) was increased to cancel out noise from the 12V timer, garage sensor, and two outside LEDs – we need at least a 1.2A load to register anything other than zero current on the battery monitor. Only when the timer is “ON” and the kitchen lights are on will the current draw register on the battery monitor. Tail current (It) has been increased from 0.5% and should now be about 12A as cut off for charged (when charge current <12A and >13.5V has been achieved monitor registers batteries as “charged”). Charged detection time (Tcd) has been adjusted so the battery monitor more easily registers a charged battery bank as 100% full sooner. Time to go (Tdt) has also been lengthened to 1 minute to more conviently show time remaining to 50% at a one-minute average load. Battery capacity (Cd) has been adjusted for winter – the batteries are cold (25-40°F).

Victron BMV-600s

  • *85%-  CEF (charge efficiency factor)
  • *1.20A – Ith (current threshold)
  • 1.25 – PC (Peukert exponent)
  • 13.5V – Vc (charged voltage)
  • *850Ah – Cb (battery capacity)
  • 50% – DF (discharge floor)
  • *0.8% – It (tail current)
  • *4 min – Tcd (charged detection time)
  • *1 – Tdt (time to go)

3.9.2012 – Friday <PREVIOUS SET POINTS>

The off-grid system is now approaching the two year mark (sine the install date of the solar panels). With a second winter on the way out I’ve had a chance to learn some of the subtleties of our particular battery/inverter set up and have now arrived at a reasonably set list of device settings. A common question I’ve observed from those wanting to install their own system is, “what settings should I use for my charge controller?” From this many more device settings questions arise. The finer points of choosing device settings will rely on manufacturer specifications, particularly those from the battery manufacturer. With that in mind, here is a complete list of the settings I’m using:

 Xantrex C60

  • 13.8V – FLOAT (CHG)
  • 14.7V – BULK (CHG)

Xantrex MS3000

  •  20A – Power Share
  • 100% – Max Charge Rate
  • 10.5V – Lo DC Volt
  • FLA – Batt Type
  • 1540Ah – Batt Size
  • 85W – Sense Below
  • 8s – Sense Interval
  • 3 – # Chg Stages
  • 15.5V – Egz Volts
  • On – Force Charge
  • 85V – Lo AC Volt
  • 45Hz – Lo AC Freq
  • 135V – Hi AC Volt
  • 65Hz – Hi AC Freq

Victron BMV-600s

  • 74%-  CEF (charge efficiency factor)
  • 0.10A – Ith (current threshold)
  • 1.25 – PC (Peukert exponent)
  • 13.5V – Vc (charged voltage)
  • 1500Ah – Cb (battery capacity)
  • 50% – DF (discharge floor)
  • 0.5% – It (tail current)
  • 45 min – Tcd (charged detection time)
  • 0 – Tdt (time to go)

CEF (Victron BMV-600s) is a particularly tricky setting. I may return to this post and edit that value from time to time. So far I’ve only been able to determine that 90% is too high, 50% is too low, and 74% is my best guess at this time.