OffGridInTheCity Build

[OffGridInTheCity]

Updated Jan 2026....

Living off-grid can bring to mind moving to the country... but the 'country' has it challenges so why not transform my city home to be off-grid capable? Water via rain-harvest (20,000g/year), Solar power to run a 100% electrified home (15,000kwh/year). Wood based heat (unfortunately) is not an easy option - and winter months are not enough power - not sure how to overcome this yet.

The Solar power design goal is to consume all that is produced. Its an ongoing, off-grid, power production focus. I'll use later posts to show details/pics. If there's additional metrics you're interested in, let me know and I can add here or share.

Power / Water / Maintenance:

Powerwall Cycles:

Powerwall Detail - 52v@260ah = 13.5kwh per battery x 8 batteries = 108kwh Powerwall

2026 Goals
* Wood based heat - boiler or forced-air or even fireplace (as city allows). During winter months (Nov, Dec, Jan, Feb) there isn't anywhere near enough PV for the heat-pump to keep things warm.
* More powerwall

 

[OffGridInTheCity]

========= Currently.... ==============

48 Panels in 2 arrays...
- Roof array is 24 SolarWorld 285w panels:




- Yard array is 20 x Mission Solar 345w panels + 4 x REC N-PEAK 365w panels (the 23+24th Mission Solar panels are off to the right on a gazebo):

4 x Midnite Classic 150s - Each handles 4 x 3s (12) panels for total of 48 panels.




Batteries/Batrium/SGP 12,000w and AIMS 12,000w (240v@100a) Inverters - 10 x 100-120p14s at 260ah@48v each = 135kwh battery bank.

ATS+UPS (Go-Power + APCs) for 6,000va of power for computers, tv, coffee-pot (things that cannot be interrupted during PV/Grid daily switch-overs)



The APCs have 18650 7x7 battery packs with iSDT balancing/BMSfrom left-over cells





ATS (Progressive) + MTS (Reliance) combo for mainhouse panel.




Solar/Battery workbench

 

[cowpen]

Great job... that's a lot of wall!
If you need to remove a pack that's misbehaving, do you just unbolt a pair and slide them out to get to the backside series connection?
Would love to see a diagram of your ATS / MTS setup.

 

[OffGridInTheCity]

Great job... that's a lot of wall!
If you need to remove a pack that's misbehaving, do you just unbolt a pair and slide them out to get to the backside series connection?
Would love to see a diagram of your ATS / MTS setup.

>If you need to remove a pack
Yes, unbolt and slide out. Since the + and - are on opposite ends, I have to slide them out inpairs as the back end (against the wall) are bolted as well as the front.

Here's a loose drawing on ATS / MTS. The MTS is just hooked up as you would any MTS with generator input. Then you feed the output of the ATS as input to the MTS. The ATS has grid power in one side and inverter power in the generator side. All #6 awg, 240v/120v (split phase US) power/wiring. #6 AWG is standard for 50amps.

You might think there is some kind of risk of wire short thru shore power -> ATS -> MTS -> panel, but the MTS takes care of that. The Reliance Pro/Tran MTS has 2 modes per circuit depending on how you flip the switches on the top row....
* GEN mode - Power comes from the ATS instead of the panel. The ATS gets power either from Shore (240v@50a bottom right circuit breakers) or AIMS 12,000w Inverter (also 240v@50a). So shore and inverter inputs to ATS are matched - either one has same power. The ATS automatically takes Generator (Inverter) power when it senses it's present... so it automatically switches to the Inverter when the inverter is on/delivering power.
* LINE mode - e.g. MTS connects the panel circuit breakers -> Circuits. This bypasses the ATS as if it weren't there - ignores it.

This setup let's you choose how much load is on the ATS by switching between GEN and LINE - as you can have some circuits on GEN and some on LINE and re-arrange by simply flipping the switch on that circuit.

Here's a loose drawing




Here's a shot with some wiring exposed...

 

[cowpen]

Thanks for the detail. Very ingenious setup.

 

[Maniac_Powerwall]

Do you charge the Batterys with the chargers inside the UPSes? Lithium ion 7S7P? Or do you charge them external?

 

[OffGridInTheCity]

Do you charge the Batterys with the chargers inside the UPSes? Lithium ion 7S7P? Or do you charge them external?

I create 7s7p battery packs out of 7s8p cell holders that have the same foot-print and Anderson plugas the original battery:




And plug them in the same as the the original battery - e.g. the APC does the charging. You can see one charged up - the float is27.7v (3.95v/cell) +/- a .1 depending on the particular APC.

 

[Maniac_Powerwall]

I'm always afraid of using charging made for lead batteries. Also I've seen many, like you doing it. Without any problems. Very cool. That's for sure.

 

[OffGridInTheCity]

I'm always afraid of using charging made for lead batteries. Also I've seen many, like you doing it. Without any problems. Very cool. That's for sure.

No need to be afraid. Lithium-ion does not care about float etc.. you simply need CC (constant current) up to float level where you go to CV (constant voltage - e.g. current goes lower and lower in a curve as the float voltage is reached). This is standard for all batteries.

Lead chargers 'may' have a function called "Equalization" - which temporarily raises the voltage high - so just make sure that's turned off or set to 0 minutes. Of course you must avoid chagrining when temp is too low (may be a bit different for lead compared to 18650) OR if the charge current exceeds the max charge of the cells.

The APCs only charge at 50-70watts which is only 400ma/cell in a 7s7p - which is quite modest.

 

[OffGridInTheCity]

2nd AIMS 12,000watt inverter arrived. With the 2nd PV array up/running, I will have enough to power the whole-house AC this year. The AC compressor (by itself) draws 35a@240v on hot days - so I need the 2nd AIMS for this. Eventually I hope to replace the gas-furnace/AC with heat-pump heat/AC... and maybe I can even do a little heating in spring and fall when sun is shining (lots of PV power) but its cool at night.

In any case.... Getting the 2nd AIMS into place was quite an effort - these things weigh 174lbs.

First up was tobuild a universal strut rack, to get the 1st AIMS up about 8" off the concrete so the 5th battery can be slid in (to the left) AND to create a place to put the 2nd AIMS....




Next, position the 2nd AIMS to go on top of the rack...




Pull it up with block and tackle..




And rock it intofinal position....





Since this is thefirst time I've used block and tackle(and recent 50Hz mistake)I was extra nervous. However, its in place and Iable to test that it works- so I'll call it good for today.

 

[OffGridInTheCity]

GOALS MET, OVERLOAD, and interesting GOVERNMENT OVERREACH tidbit...
-------------------------

GOALS MET:
2nd AIMS, 5th Battery, 400a ABB shunt-trip, and Batrium tidy-up in place. After 2 and 1/2 years its coming together! This take the system up to
- 45 x 285w panes for a 12.8kw array.
- 5 x 260ah batteries (70 packs) for a 1300ah@48v Batrium monitored battery bank.
- 2 x AIMS 12K for a total of 24,000w (100a@240v) AC output.

For orientation, here's a long view and a cross view of the solar control room...

---

OVERLOAD!!!

The new heat pump is scheduled for next week. Meanwhile, I just couldn't wait to try out the new AIMS. Its just getting warm enough to run the 23yr oldAC for a couple of hours in the afternoon - so I turned AIMS #2 on and wa-la, it seemed to work find for the last week until yesterday.


Now remember, this 4 ton AC Compressor is 23yrs old and it blows motor capacitors every year - I learned how to replace them 7 yrs ago and have put in 5 new 'starter motor' capacitors in last 7 yrs. So the AC Compressor is old / suspect!! - but I didn't expect this.

Today my new AIMS inverter powered-up and then WHAM, shut-off. After much fear, I discovered that the 250a breaker between the battery bank and the inverter had tripped. At 250a * 56v that means the Inverter was attempting more than14,000watts!. Look at what I found on my Omega power monitor log:



You can see the inverter turn on at 4:28:12 PM... and then 15sec later the automatic transfer switch changed over from grid to inverter power and WHAM - 95.4a @ 196.4v = 18,736 watts. No wonder the 250a @ 48v circuit breaker tripped.

Shows the value in having proper circuit breakers.


SO... I'm going to leave it alone and wait for new Lennox XP24-048 heat pump install next week. I was assured by the installer that this thing has variable speed 3-phase motor technology with has a couple of benefits.....
-It is soft start. So I shouldn't see anything like 100a @ 240v!!
- It takes in AC, converts it to DC, then to 3-phase AC, which give the variable speed motor control.... which meansthe ATS (and the whole 60cycle syncing issue) will not cause any problems.

I'll report back next week with good news I hope

---

P.S. GOVT OVERREACH: An intersting tid-bit on Lennox equipment according to the installer. Lennox specifically made their modern heat-pumps to connect directly to solar panels... BUT, in Oregon USA, they can't install the solar featurebecause Oregon requires a 'special' solar certificate - which requires journeyman+test to get. So Solar technician cannot do HVAC and HVAC cannot do solar - so the feature sits 'wasted' in Oregon. Thank you government!!

 

[OffGridInTheCity]

Finally, after 1.5yrs of manual monitoring - the Batrium is actually hooked up thru 48v->24v step-down thru relay #1 to ABB 400a shunt-trip to disconnect the battery.




Big shout-out to @LithiumSolar youtube:"Connecting an ABB Shunt-Trip Breaker to the Batrium WatchMon 4 BMS" -https://youtu.be/5xSFy13AEtQ
All I had to dowas 'follow along'. Thank you sir!

 

[OffGridInTheCity]

NEW HEAT PUMP: Brand new, whole house heat-pump install completed yesterday, first morning of heat,and look at this...

Only a 4,000watt draw heating a 2600 sq ft home up from night-time 19C/66F to day 23C/73F. This snapshot is mid-process (69F) at 5:30am, dark, andoutdoor temp of 4C/39F. Its an iComfort S30 'thermostat' using the 'IQ Schedule" to transition from night to day and the system is set for 100% heatpump when outdoor is >= -9C/15F - so heatpump may be limited due to outdoor temp and/or the "IQ Schedule" transition is programmed to raise the temp slowly over several hours - I don't know.




I live in "Zone 4 (moderate)" climate and the specific equipment is
- Lennox "SLP98V" ...SLP98VUH090XV60C:5 ton Furnace/Air-Handler dual fuelw/gas as 2nd fuel, indoor unit. -https://www.pickhvac.com/gas-furnace/lennox/
- Lennox "XP25" ... XP25-048: 4 ton HeatPump, outdoor unit -https://www.pickhvac.com/heat-pump/lennox/
- System is SEER 20, HSPF 9.5 according to the installer

We'll see over time and of course AC is not yet in play..but this very first 'solar powered', 'whole house heat' experience is*fantastic* (to me)and exceeds my expectations as I was estimating more like 6000watts from googling. The heatpump 'soft start' is very nice - you can see it ramp up slowly from 3amp @ 240v to 6a to 11a to 15a over a couple of minutes which is gentle on the inverter.

 

[OffGridInTheCity]

HEAT PUMPUPDATE- FIRST 18 DAYS

The numbers show an average of 23kwh/day thru last 1/2 of March for a 2600sq ft home. That's fantastic (to me) as my average solar production was 40kwh/day - which means there is enough power to heat my house. Here's the National Weather info for March to help quantify what the 23kwh/day is doing- its a mild climate...




More Detail:
We let it go down to 68F at night, so in the morning the system needs to raise the temp from 68F to 73F (5deg). This takes about 1-3hrs depending on the outside temp.At 30F the heat pump can barely raise the temp of the house (e.g. 3hrs). At 35F or above, it's adequate (2hrs). In the 40F(s) its much more responsive in raising the temp (<2hrs).

One thing that jumps out at me - is that in a serious WTH... it would be smarter to wait till late-morning for temps to raise before trying to warm the house. Itsonly <30F during the day for 'a few days' a year on average here. The rest of the time, its always >30F.

 

[Ricky786]

Thank you for the valuable information.iam very much impressed with this one.
Looking forward for the good posts.

 

[OffGridInTheCity]

APR 2020 Recap. Remember this is 100% off-grid, cannot sell excess to power company.

Generated 1862kwh perMidnite Classic and consumed 1475 kwh per meters onAIMs inverter output. Averaged 79% efficiency.

Key Notes:
- Efficiency drop. Since adding the 2nd AIMS, average efficiency has dropped from 86% to 79% and I'm not sure why.
- Heat Pump. The whole house heat pump used 389kwh for heat/cool. Set for electric only (so not gas involved) See weather info below.
Note: HeatPump functions down to 30F outside temp - below that it struggles, cannot raise the house temp/minimal heat.
- Generated more PV power than can be consumed...
*Midnite Classics aretransitioning to float early afternoon most days... leaving 15/day on the table leaving estimated (15kwh * 30days)= 450kwh lost.
* Inverter was off 80hrs (out of 720 possible) for the month. At 2300w/hour average consumption that's 80 * 2.3 =184kwh lost due to lack of battery size.


[size=small][size=small][/size][/size]

Next Up:
- A new (6th) 260ah@48v battery is nearing completion toboost the battery bank to 1560ah@48v (e.g. 80kwh battery bank). This should let me capture some of the lost PV power described above.


Observation so far...
For 2020, I wanted enoughPV array to heat/cool the house 9months out of 12. So I nearly doubled the PV array and battery bank BUT the consumption of the heat pump is 'less than anticipated' so far - so I'm 'wasting' PV input power. Maybe the hotter temps will cause Heat Pump to pick up the slack - not sure yet.

 

[daromer]

2 units have 2x the idle load than 1 have. So if 1 have 60w you now have 120w in losses. Thats why going with bigger or more units arent that efficient unless you really need it.

Get your self a Pool so you can waste the power into som nice warm baths Im just about to start up my pool soon. Though i heat it mainly with firewood but the lazy days i dump excess into the pool

 

[OffGridInTheCity]

2 units have 2x the idle load than 1 have. So if 1 have 60w you now have 120w in losses. Thats why going with bigger or more units arent that efficient unless you really need it.

Get your self a Pool so you can waste the power into som nice warm baths Im just about to start up my pool soon. Though i heat it mainly with firewood but the lazy days i dump excess into the pool

The AIMS 12,000w have 200w/hour idle power consumptionso I have the distribution panelswired so that they have load 24/7 have load all the time - e.g. they are never idle. The single AIMS ran at 86% all last year.

Based on that I was expecting toget86% efficiency from each inverter... and 86% overall.This logic....

[Battery] ----- (1000w) --> Inverter1 --> 850w --> 1700w total out of 2000w input --> 1700/2000 = 85% overall effeciency.
----- (1000w) --> Inverter2 --> 850w

But I'm wrong somewhere.

Side Note:
I can't use power saver modebecause this 'probes for load' instead of affirmatively supplying load to the ATS to cause it to take power from the inverter instead of the grid.

>dump excess into the pool
Yea... I already have the Hybrid Hot Water Heater and the Heat Pump fully supplied. I'm literally powering the entire house except a few low-power odds and ends. The only things left are the Dryer & Oven and we use those once a week (not much)

I do have a spa but it looses its settings on ATS switchover if I hook 'the whole thing' to the system... so i need a way for it to keep it settings OR just ATS the heating coil alone - but its a bit of work. We'll see.

 

[OffGridInTheCity]

UPDATE:
- Batteries 5 and 6 in place Brings the battery bank up to 80kwh (6 x 260ah@48v)





- Lennox whole house heat pump (2600 sq ft) in moderate climate, May was 382 kwh, Jun was 405kwh. Continue to be fantastic numbers. Here's the ATS powering the outside unit:





24/7 POWER ACHIEVED....
- The 12.8kw PV array is producing 80kwh/day. Highest was 83.7kwh on Jun 25th. 70kwh/day'ish is powering thehouse 24/7!! I'm running weeks at a time continuously on off-grid solar as long as the day is mostly clear - inverters never shut-off. In fact, I'mloosing 5-10% of the available PV power because I can't consume it. The efficiency of the whole house heat pump is so low compared to the previous AC that I overestimated the number of panels.


Added the dryer into the off-grid wiringso that once or twice a week we use an extra 5% - considering adding the dishwasher as well - but I'm really down to low hanging fruit and don't want to 'jigger' the wiring into non-code hookup for just a bit of excess power.

Here's a typical day with full sun that the power company sees:




The 2 spikes are the spa on a 12hr cycle. The rest is a background 200-300w/hourbecause I don't have *all* the circuits on off-grid. The MTS only supports 10circuits - 2 are directed to dryer and the other 8 to higher usage circuitslike the kitchen - but there are several others (spare bedroom, garage lights, ....)and its just not worth it to add a 2nd MTS. In a real emergency I could double up circuits at the MTS- but that's not OK per code so not good for regular living.

HAVE REACHED GOAL of 'powering the house comfortably'for 9 months of the year - so fantastically pleased to be able to do this.

FUTURE -
* Building battery #7 and #8 from RING packs... Will try to fit into camper and/or hook to house system.




*Stockpile30'ish panels for Nov, Dec, Jan (low power) months. These could bepropped up in the back yard and fed into the existing infrastructureif there ever were a Puerto Rico styleemergency during winter. This would bring the system up to1000kwh/month- enough to heat/operate the house 20 of 30 days / month. Not perfect but could work with that..

* 7 x 14 Cargo Trailer conversion to a camper. Can stay warm in that thing for those 10 days/month with not enough power for heating house?? We'll see... stay tuned.

 

[cowpen]

Wow! Great work. Congrats!
Thanks for the project update. Very interesting.
Couple of questions:
What's a RING pack?
Do you have any issues with different charge / discharge characteristics of the 6 batteries you've built over time? Do they all pretty well stay in sync for SOC?