Derelict cabin to borg cube conversion

[chasingentropy]

Greetings all, i thought i would share my small off grid experiment. We have a large plot in the mountains with derelict buildings and raw woods. Rather than demolishing the buildings I figured I would use them!

I'm converting this old cabin to a mini solar power station. My priority for the project is to power my 37ft camper (or should i say glamper) and eventually power smaller cabins that Im building.
Camper has
1.8kw AC (summer only)
800w+500w+1500w total resistive heat load from three heaters. We do not burn propane for heat.
1.9kw water heater (20% duty cycle)
150w(50% duty cycle) peremiter and road lighting (must remain on at night for safety)
400w(intermittent loads) interior Lights, laptops, fans
180w(always on) media server/NVR, POE cameras, internet modem
360w(intermittent) 3d printer


So far I've finished 32 100w panels of various brands each connected to independent 40a mppt controllers which charge 10kw lipo4 bank and 2 kw sla bank (surge capacity) power bank. They power two 4kw inverters.

I also have a 2kw 4 stroke inverter generator and a 1kw 2 stroke generator for backup power. The generators feed 120->24v directly to the batteries. I'm working on a system to collect their exhaust heat to melt snow from the panels in the winter.

I plan to add multiple smaller substations scattered out over the property which all feed the prmary station.
Currently the equipment is in a box out front but once I've worked out all the kinks so it's less likely to catch fire i will put it inside the cabin.

Yes, those are power lines draped over edges of metal roofing. I am open to suggestions on how to gracefully route them into the house next to the front door.

 

[chasingentropy]

Update on basics because i havent worked on anything else...
Lighting
Currently lighting only an acre or so of the property, total consumption is 110w total for 14 10w flood lights and two sets of 150' string lights across 500 feet of 16ga. Obviously the flood lights aren't consuming 10w.

I'm budgeting 800whr to light all 19 acres.

 

[400bird]

Wow, that's a lot of tiny 100 watt panels! Mounting the standard, larger, residential panels would be easier, in my opinion.
For the wiring off the roof, put it on conduit and either run it around the edge or with a penetration through the roof, straight down to where you want it.

With electric heat, the constant night time loads, have you done the math, is 3.2 kw of solar and 10kWh of battery enough?
If the battery runs flat, it doesn't look like the 2kw generator can cover the loads.

Looks like a good project!

 

[scrubjaysnest]

I'm going the 100 watt panel route, no way can I lift a 47# panel onto a roof. No neighbor to help and $40k for an installed system.

 

[chasingentropy]

My priorities for the microgrid are redundancy, modular(cheap) repair, scalable, safe, (low VOC), and never needing to bring the entire system down. With that in mind, cheap 100 watt panels are a no bainer. Each bank is 100w*4p panels feeding a mppt controllers with redundant channels.
Only the primary bank is 6kw, the subststions that feed the primary (120v transmission, stepped down to 24v-14v at the receiving end) are between 2 and 6kw with their own banks of 1.2 to 2.4 kw or solar panels. I'll probably post some gore pictures once i resize them.

 

[chasingentropy]

Wow, that's a lot of tiny 100 watt panels! Mounting the standard, larger, residential panels would be easier, in my opinion.
For the wiring off the roof, put it on conduit and either run it around the edge or with a penetration through the roof, straight down to where you want it.

With electric heat, the constant night time loads, have you done the math, is 3.2 kw of solar and 10kWh of battery enough?
If the battery runs flat, it doesn't look like the 2kw generator can cover the loads.

Looks like a good project!

Thanks for the tip, i think a conduit around the edge will match the borg theme.

Total solar production is currently 4.3 kw and 19kwhr storage between the primary array, the one substation I've built, and the camper's power bank. With both the 1kw and 2kw generators running there would be an additional 1.5kw of DC power available. Theres a pic of the 1.1kw substation array in construction attached.

The substation has it's own 6kw bank and transmits power to the primary at .5kwhr through the evening. I attached a photo of the prototype charging system. Efficiency measurement will be a fun update for the future.

Agree absolutely not going to be able to heat our living areas on electric, it looks like we can maintain a delta of +25 degrees over ambient with an energy output of 3.2kw split between two space heaters and the electric central heat. That's 30kwhr for a night of heat! Since it gets to 20s here that's still insufficient temperature wise.

Because my wife refuses to sleep with combustion inside the building we have migrated to 5kw and 8kw diesel heaters located outside and ducted into buildings


It's fascinating to think that ONE gallon of diesel outputs more heat than my combined storage capacity and generator output for several hours.

I left a bunch of lipo cells outside and one had water penetration. Surprised it was a nice one with power button and lcd. Any suggestions on probability of salvaging the cells?

 

[400bird]

Good looking Borg assimilation progress!

If you haven't already tried it, heated mattress pad (or blanket) makes a +25 delta much easier on the body, battery, and diesel bill. I don't know if your equipment would allow a timer to start warming the interior back up to a more comfortable temperature just before the alarm clock says it's time to wake up.

No idea on the cells, water damage can be rough on the electrical connection and BMS. The cells should be pretty well sealed, but the terminals are exposed.

 

[Rednecktek]

I'm going the 100 watt panel route, no way can I lift a 47# panel onto a roof. No neighbor to help and $40k for an installed system.

Used house panels sound fantastic until you're the one slinging them on your own, then they become less cool right quick!

 

[chasingentropy]

Update: Heat
although not really solar related, its an obvious issue that most solar households face. It's also 12v and is powered using the Camper's solar power and battery.

I went with a 5kw diesel heater, removed the primitive propane death trap furnace, and ducted the diesel heater right into the existing ducting from outside the camper.
It is excellent on efficiency. 25 degree delta even when pulling outside air and pumping it into the camper. The fresh crsip dry air is great but I don't want to burn a gallon of diesel every night so there will be recirculation eventually.
External:

Internal ducting:

The cabinet sits right under the refrigerator and gets really hot which is obviously not good for efficiency so iattached a 120mm fan to one duct which vents the compartment.

So basically removed a $800 furnace; installed $100 heater and $60 in duct.

Future plans:
Duct exhaust heat to the water supply pipe to use to keep the line from feezing
Cut recirculation hole to mix with fresh air.

 

[chasingentropy]

Update - negative temps and bms triggers.

The temperatures dipped to -6 and I observed the bms charge protect working. Charge protect triped completely around -2 c ambient for the assortment of 100ah lipo4 batteries but i see less than .5kw draw at 0c from a 14kw bank that's nearly empty which to me implies a solid state circuit linked to a thermistor. I've disassembled one of the batteries that was water damaged to look at the bms and confirm this after it dries.

I began assimilating the cabin and repositioned the inverters to drive exhaust heat over the battery bank. Now sits 4c over ambient with no supllemental heat. Capturing generator heat will probably make it habitable in snow. Can't wait to move my lcds and haphazardly drape more cables across the room.

Also started my glass good substation. Edge to edge panels sealed with silicon flush mounted. Picture attached

 

[chasingentropy]

So following up on the shentek 100ah lifepo4 battery that filled with water. I ripped out a fire isolated ground mount array with some old panels to create another danger zone project.

Failure cause:
Water penetration at the battery meter or button allowed water to fill the container with approximately 5" of water causing the micro relay on the bms to fail(the bms and external volt meter still work, photo of failure element attached).

Salvaged three 4ga jumper cables, half a dozen NPN and PNP mosfets, 10w heatsink, volt meter, and four 3.2v prismatic cells.

The cells were completely unaffected by a few weeks in water. They supply around 89ah from 13.6v float to 11.5v under 100w load. Since there is no longer a bms i set it to cycle between 11.8v and 13.4v supplying .5kw/hr to the main power station. I'd like to code a cell balancer and temperature protection circuit using an arduino eventually. (Photos of the temperature and balance leads are attached)


Curious to see what a lifepo battery will do with no balancer, no temp protect, and no current protection charged by an 800w array and powering a 1.6kw inverter? Stay tuned to the danger zone

 

[400bird]

Curious to see what a lifepo battery will do with no balancer, no temp protect, and no current protection charged by an 800w array and powering a 1.6kw inverter? Stay tuned to the danger zone

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