Our System

Backstory:

The story begins early 2015. Our family had acquired a 40 acre property that was bare land, meaning there were no utilities of any kind, simply just dirt. When we first moved to the property, we arrived after dark, with lights, chainsaws, and a couple of trucks – The driveway was overgrown with trees, and we had our 40 Weekend Warrior 5th Wheel that we were planning on dragging to the top of the hill. It was quite the introduction to the neighborhood considering the property had not ever been used.

When we bought the property, we climbed to the top of the hill, checked for cell coverage, and when we saw full service and this nice of a view, we were sold!

We were camping out on the weekends in a fifth wheel toy hauler. The main goal was to have more reliable power than the 2000 watt inverter in the RV paired with 4x 100 watt solar panels. We had fallen in love with being on the property, and for me it was equal distance to work as our old house was. I would stay at the property in the families 40 foot toy hauler during the week and my parent’s would stop by on the weekends.

One Friday night, my parent’s had arrived for the weekend, and packed the tiny freezer in the RV full of frozen peas/vegtables taking up any room for me to store my own food. This ultimately frustrated me due to the fact that my go-to dinner at the time was mostly microwave-meals. My Step-dad goes “You can get your own freezer”, which I was thinking I would locate in the garage of the RV…He then suggested that I get my own RV and park it on the property. Over time this was made reality.

I had built out my RV with a bigger 3000 watt inverter, 5x size 8D FLA batteries and 1000w of solar panels, which ran great for quite a few months as I started living on the property more and more. Trouble arose however, when I realized there were no provisions to do laundry! More power capability was needed, especially having 240 Vac.

Meanwhile as all of this was happening, we were talking to our local utility company, PG&E We had paid them a fee of around $2,200 to have the site evaluated for electrical power service. We had also contacted a well drilling company to have a water well drilled. The well site would be located in the meadow, around 1600 feet from the top of the hill where the future house (and currently RV’s) were located. The cost to have a 1φ 200 amp service drop at the well and a 1φ 400 amp service drop at the top of the hill totalled to be over $70,000 to PG&E plus additional cost on our end for a back-board, consumer panel as well as service enterance.

The absurd part with this is the fact that 3 of PG&E’s power poles were already running through the property! They literally would have only had to set 1 of their poles, 2 transformers and then ran the drops. After all this cost, PG&E has some of the highest prices for electricity in the country – Nearly $.50/kwh during peak demand times and an off-peak rate near $.30/kwh. It was outright absurd to follow this pathway.

Initial Build:

Our initial build had resembled the system we had built for my RV, except it was far bigger. We had utilized the same group 8D Lead-Acid batteries, however instead of 5 batteries at 12 volts, we had allocated for 32 of them at 48 volts. These batteries were charged by a pair of Outback FlexMax 80 Solar Charge controllers, and power was inverted to 120/240 volts by a 12kw Sigineer inverter. We had a 200 amp panelboard and 3 Honda Inverter generators – we were good to go…At least for a few weeks.

The system is housed in a 40 foot shipping container which the back 20 feet was framed with 2×4 studs. We insulated it with R19 insulation. The insulation is designed for 2×6 framing, however it fits into the highs and lows of the corrugated container walls beyond the studs. After framing, we put up plywood sheeting and painted the plywood white. We then installed some lights and went to town with electrical. In hindsight it would have been a good idea to put fire rated drywall over the plywood to reduce the flammability risk, while maintaining the backing material. Such is life and these learning lessons.

After a bit of tweaking and getting things up and running, we were good to go. We were now able to wash laundry on the hill and our quality of life improved with good quality power.

More information on the initial buildVideo of the initial build

Initial Issues:

Undersized Generators:

In the inital build, I had paralleled 2 Honda EU2000I generators with an additional EU3000I. Then, the voltage was stepped up to 240v for the battery charger function of the inverter. The problem here was that when the inverter was in charging mode, all of the loads on the inverter were then transferred to the generators. This usually is OK, however, the battery charger drew nearly the full capability of the 3 generators. If any additional load was added, the generators would overload and trip their output protection.

After overloading the generators tripped their overload protection, the inverter would then instantly transfer the loads back to itself, causing a huge inrush. Additionally any misalignment of phase angle would furter cause a surge, especially with any inductive loads (such as motors) running. One night, while charging the batteries, my step-dad had ran his microwave, leading to an overload condition. The loads transferred to the inverter, however at the same time one of the three generators did not fully trip out on overload. Some way, some how, one of the contacts within the inverter’s transfer switch had welded shut and the inverter was literally fighting with the last generator left, ultimately leading to the destruction of the inverter.

Battery Type:

Another issue, that was not made obvious until the system was in operation for over a year, was that the lead acid batteries were simply unable to stay healthy and keep up with our increasing power demand. I made a 4 part video series showing the issues as well as the removal of failed batteries. The batteries failed after just a year of being in operation. At a total cost of $6,400, I still to this day have a pile of batteries that are toast.

The issue with the group 8D batteries was two fold – Even though I had constructed the system with equal length cabling to each and every one of the 32 batteries I had installed, the state of charge of some cells tended to drift from other cells. We are talking on an individual cell level, not a individual battery (6 cells) level. When these cells sat at a lower state of charge, sulfation would begin to build on the plates. The only way to get rid of this sulfation is by running the batteries at a higher “Equalizing charge” voltage.

The amount of hydrogen gas produced during the equalize charge and the amount of water that would be consumed was incredible. After an equalization charge, each battery would need to have the water in its cells checked. Checking the water in 192 cells is a very time consuming task, however it was usually done at least once per month. This worked out fine, because I would take care of this regularly, that is, until I took a job out of state and the batteries went without maintenance for at least 2 months.

Manual balancing was also required from time to time – Batteries that had lower-charged cells would be removed from operation, manually charged, then returned to operation. This only worked so many times before complete failure of a battery occured. The other issue here was that only one of the cells within the 6 cell bank was at a lower state of charge, as indicated by a Hydrometer. Bringing only 1 cell up was impossible as all of the cells were enclosed within 1 battery case.

Ultimately, the amount of work it took here to keep the batteries happy was overwhelming and eventually the maintenance wasn’t being taken care of properly. Some cells went dry and batteries failed left & right. The biggest issue is if we replace a failed battery with a new one, the new battery would fail quickly – The other unhealthy batteries would suck the life out of the heathy batteries, leading into my record shortest 3 month battery life.

Upgrades:

As we continue to run our systems, we will always have shortcomings. If it’s not enough solar, it’s not enough battery storage. If it’s not enough of those, then our inverters are too small. There is a constant process of evolution to make things better. Luckily, since we had such a huge price to pay if we went with the local utility company, we also had a huge budget to beat. At our old house, we also had a very high montly bill that we now no longer have, thus, we now have a monthly budget for upgrades.

Power Distribution: Rebuild

To solve the issue of the undersized generators causing tripping issues and blown inverters, we acquired a Wacker-Neuson G14, 14kw 12/240v Diesel Generator. This unit can easily power the battery charger with headroom to spare. With this headroom, I do things like Heat a Hot Tub and . Instead of letting the loads transfer to the generator through the inverter, I have a second inverter of similar topology that all of the loads are constantly powered by. Then, when the generator runs, the power goes to charging batteries, but only after powering the loads first. This has it’s advantages as well as disadvantages. Primarily, I can have uninterrupted power at all times (no transfers), and I can limit the excessive load on the generator.

Ultimately, this lead to a full rebuild of the electrical wall in the room. Previously I had been running a 120 to 240 volt step down transformer, ran in reverse, in order to increase the voltage of the generator output to feed into the inverter. With the addition of the new generator, having this transformer was no longer required as the generator has 120/240 as its native output. In order to properly connect the new generator, I had to remove all of the wiring for this transformer. The new issue was that I did not have space to properly provide disconnecting means for the generator circuits.

I had a custom “split bus” panel built, which means it’s a regular panelboard with a break in the bussing in the center. This essentially split the panel in half. I used one half of the panel for my generator-only loads, and the other half of the panel for inverter-only loads. I also installed a regular 42 space panelboard to facilitate the main distribution of power. I made a multi-part video series covering the full reconstruction of the power distribution wall. Finally, I incorperated an Industrial Control Panel that facilitates the function of the generator. The worm hole that was opened by adding PLC control is one that we will later find is ever-growing.

New Battery Chemistry

If you recall, I had initiallly installed 32x group 8D Lead Acid Batteries. These were the same batteries that I used in my RV and I actually liked their performance at first. The symmetrical buss bar design alotted equal resistance to each battery. This was optimal for this system to be successfull with the large amount of parallel connections.

The problem was, however, that cell-level balancing on the group 8D batteries was not possible since each 12 volt battery was comprised of 6x 2 volt batteries put together. The only possible way to monitor if a cell was healthy or not was based on its specific gravity measured with a Hydrometer. This is impractical to measure when you have a total of 192 cells in the system. The result of this was that some cells of some batteries had a lower state of charge than the rest of the series string. To correct for this, an equalization charge would be required. Unfortunately, in order to equalize 8x 32 strings not only takes a significant amount of power (that ends up going to waste since the power is just breaking down the electrolyte in the healthy cells), it now means that the electrolyte level of each cell be carefully monitored.

At this point, the design of the battery racking is now detrimental to the proper maintenance of the batteries. Insufficient space was provided to see down into the cells to determine if they were properly filled. I was the only one to check the electrolyte on the batteries.

In November of 2018, I was hired at a job located out-of-state. I discussed this greatly with my parents since running the off-grid power system would now be their responsibility. Watering batteries, changing generator oil, monitoring battery voltage, etc. would be their responsibility now. Unfortunately, these maintenace items were not actually being performed. A few months after my departure, I returned home and checked on the system. There were complaints that the batteries were not performing well and that their nigh-time storage was very poor. I checked the voltages of a few batteries and learned that things were all over the place!

Shortly before my departure on this trip, I opened up a couple of cell caps and realised that the electrolyte on these batteries was far below the top of the battery plates. What happens when the electrolyte is at this level is quite simple – the plates dry out and essentially become de-activated, permanently. I had refilled a couple of the cells, but after going through a gallon of distilled water on 2 batteries, I now realised that it was an uphill battle that I could not win. I needed my parents to finish filling the rest of the batteries so I didn’t miss my flight! They did, and the total count was 18 gallons of water for around 24 batteries. It was too late and the damage was already done. So much capacity had been lost, the generator would run 6-7 times per night, the batteries would spike right up in voltage, then the generator shut down. A couple hours later it would start back up. So little power was being stored, it was quite unbelievable.

At this point, defeated, I was searching for a better option. Luckily I had a viewer from my YouTube channel send me an email – He really wanted to know why I wouldn’t install lithium batteries!

My concern from the very beginning of installing an off-grid system has been a fire destroying all of the progress built. Lithium batteries in general have a bad reputation for their flammability and are known for how spectacular as well as intense the flames they can produce when they do inevitably fail. Sometimes these thermal runaway fires are unfightable because the chemicals have what is called a negative temperature coeffecient of resistance. This means that once the fire is started, they are self fueling, including their own oxygen source.

What I did not know, was that not all “lithium” chemistries are the same. Chemistries such as NMC (Nickel Maganese Cobalt) and NCA (Nickel Cobalt Aluminum) support thermal runaway and in my opinion should be avoided under any circumstances. LiFePO4 however, is a very different chemistry that is inherently safe chemistry. After my viewer had written me a very inclusive email, we had looked more into LiFePO4 chemistry and ordered a 100ah bank that would replace 2000ah bank of lead acid.

The result was outstanding – The LiFePO4 batteries ran laps around the lead acid counterparts. The batteries that I purchased actually were from a chinese reseller that was selling Used product! Luckily, since the LFP batteries are such a wonderful technology, it didn’t actually matter that they were used. They had still met their capacity rating. Some manufacturers, such as CALB & Battleborn over-rate their batteries. For example, a CALB CA100 has a nameplate rating of 100 amp hours, however, if you capacity tested a new cell you would observe that they are capable of over 110% of their rating. The used cells had around 105% of their rated capacity. This bank of 100ah cells would be a test for me – I needed to learn how they behave, what their pros & cons are, and what the special operating requirements were.

Fast forward. August 2020 – After well over a year of heavy service, with around 2-3 cycles PER DAY, at C rates quite close to their maximum, the 100ah cells are going to be removed from service. I’m removing them not because their capacity has been lost (I’m going to see how the performance is after a year of heavy use compared to install performance) but rather, I’m removing them because I am ready to take off the training wheels. As preiously mentioned, the 100ah bank was the test, to get everything figured out, and if I made a mistake, I’m not destroying $10,000 worth of batteries (Or $6400 in the case of the group 8D Lead Acid batteries.) At this point we are installing 64x Calb CA180 cells. These are 180ah Nameplate rating, but realistically capable of 200ah.

I’m going to be building them in a 4p16s configuration, for a total bank size of (800ah realistic, 720ah nameplate). The great part of geting my parents used to the 100ah bank is that I can run the new battery bank at 80% capacity and they will still think the new battery bank is performing well. Unless they read this, what they don’t know won’t hurt them. My reasoning for this is that the batteries really like to operate in the 10% to 90% discharge range (unlike Lead acid that likes the 100% to 50% range). Running at the lower capacity will help stay out of the high voltage and low voltage ranges where any differences in cells show. There really is no need to abuse a battery bank, especially if running at 80% capacity still covers all of the demands.

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