Off grid in Joshua Tree, Inverter with auto restart functionality?

[thesundayranch]

Hey solar nerd friends. First time posting here - but I have been working on and installing my solar / wind hybrid off grid system in the remote desert of Joshua Tree for the past year.... and have learned A LOT. (will post more in other threads about some of the challenges I have hacked my way through)...

BUT - my most recent challenge is this: although I have (on paper) more than enough batter capacity and solar output to prevent this from happening (details below) - the power at the ranch keeps going out when I am not there to baby it. I know this because I have a SimpliSafe security system and Google Nest outdoor cameras hooked up to my Starlink internet and when the power goes out - I get notified by both Google Home and SimpliSafe that the wifi is out (meaning power to the wifi has gone out).

Powering the cameras and security system are 4x200ah 12v LifePO4 batteries and the draw from the security system is minimal - maybe 20watts. The draw from the starlink is from 50W-100W depending on how hard its working to connect to satellites.

So - maximum calcs would be:
100W x 24hrs = 2400W / day
20W x 24hrs = 480W / day

So to keep both of these powered and running 24/7 i would only need 2,880Wh and the system is 9600Wh. Even with this - I was encountering issues with power loss and HERE IS THE ISSUE: when my 120v inverter turns off due to low voltage disconnect it will not turn back on unless someone is there to turn it back on (I am only there on weekends to work)

Hoping to fix the situation - I removed the Starlink from the main power supply above and hooked it up to it's own independent power supply which consists of 2x12v 100Ah Gel batteries. So - this gives me the 2400Wh I need to keep the starlink running 24 hours a day and allows for more than enough capacity for the SimpliSafe to run off the original system above. (the starlink does not run at 100W consistently so 2400Wh should be enough to keep it on?)

Anyways this is really annoying because there are desert thieves out there and every time the power goes out I end up having to make a 3 hours trip out there to turn it back on - for fear if I leave it off I will get robbed.

Are there any 120v inverter options out there that have an auto-restart feature? Even one with just a manual switch on/off would work - since I would keep it in the ON position and in theory once the batts charge back up in the morning it should kick back on. I have not found anything that fits this need but I know there has to be something... so that's why I am here!

Anyone have any good reccos for a 120v inverter that will kick back on automatically in the morning when the sun comes back out and starts to recharge the batteries???

 

[MichaelK]

Which inverter do you have? Some of the AiO units have background idle draws in the 60-100W range. That's 2400Wh just leaving the inverter on.
How many watts of solar is charging this?

 

[v_green57]

I found your story intriguing, so...

I took a Whistler 400W 12V MSW "el cheapo" inverter I had around here and connected it to a bench supply set to 13VDC.

Reduced the voltage until the "voltage too low" tone started up. Then pulled the power altogether. Left the power switch ON.

Turned the bench supply back up to 12V. Reconnected the inverter. It started right up.

Tried it multiple times to make sure it was repeatable.

Then, tried a more real-world scenario.

Turned the voltage slowly down to 6V and set off the LV alarm. Then slowly raised the voltage back to 12V.

The inverter LV alarm stayed ON and the inverter itself was not putting out 120VAC. A ON-OFF of the power switch OR a disconnect-reconnect of the power was required to regain AC out.

So, to answer your question, there are inverters out there that will power up on their own. But they need a solid ON-OFF of the voltage source or the power switch to make that happen.

I would suggest looking into separating your "critical" loads to a separate inverter that you have confirmed will come up when power is applied when it is already switched on. Then look for a Low Voltage Disconnect like this or similar:

https://www.amazon.com/Blue-Sea-Systems-Voltage-Disconnect/dp/B00GZOP53M

to get the positive ON-OFF required when your batteries get too low then recover.

Even though LVD also exists in charge controllers, I would NOT use the CC to do this. Inverters have a big draw on startup that can blow FET's and kill CC's.

 

[thesundayranch]

Thank you for such speedy responses! The original "main" inverter for the cabin I am using is this 3000W inverter: but this is a main power source area so that makes sense (I now have a fridge, TV, lights, etc)... however the independent starlink setup I just created is using this smaller 1000W inverter (less draw).

After posting, I started researching ways to connect straight to DC from Starlink - since the modem runs on DC anyways I figure why not remove the energy loss from conversion 12v to 120v back to 12v... so now im wondering if I should just bypass the inverter all together and run straight DC to the battery? https://www.starlinkhardware.com/tutorial-12v-dc-power-supply-for-starlink-rv/

I would imagine the efficiency gains from not converting up and down again would more than make up for the delta I am experiencing on days where the power goes out.. does anyone know how much loss there is when you convert from 12v to 120v and back down again?

I am hesitant to have a direct connect to the battery because I do like the fact that the inverters have safety built in.... but I think I can find a way to go direct to the batteries with a fuse block that has the same protections.

I assume if I connect direct to the battery there would be no issue of "booting back up" in the morning if there were a total battery shut down... since it's direct connect I think once the battery gets back above a certain voltage the starlink would automatically kick back on?

Thanks again... already really appreciating the support from this forum! Excited to share some of the stuff I have been able to figure out through "desert engineering"

 

[v_green57]

Running stuff directly off DC is always an option, BUT:

What will that stuff do if it sees 10VDC or less? It might be unhappy about that...

Electronics don't "just shut down" gracefully when faced with low voltage, they sometimes soldier on with bad results.

Take a look at the FAQ page for the Blue Sea:

m-LVD Low Voltage Disconnect - FAQ - Blue Sea Systems

Senses low battery voltage and disconnects non-critical loads to save power for engine starting.

www.bluesea.com

That should help you understand how they work. Your "direct connection to the battery" should be fused or breakered for sure. The LVD module makes sure that the inverter (or other connected equipment) will never see a potentially damaging low voltage:

Factory Default Disconnect Voltage 12.1V
Time Delay to Alarm The unit waits 5 mins after the voltage goes below the set point before it starts the warning. Then an additional 5 mins to disconnect, 10 mins total.
Alarm Time Before Disconnect 5 mins
Reconnect Voltage 13V DC

 

[goldserve]

Would the Victron battery protect work to protect dc loads?

https://www.victronenergy.com/upload/documents/Datasheet-Battery-Protect-65-A--100-A--220-A-EN-.pdf

 

[thesundayranch]

I gotta be honest at this point the batteries are not my concern (outside of fire hazard)... im not really trying to preserve them since I've already upgraded to LifePO4 but these gel batteries should still have a couple years of life in them to power a low draw system like the Starlink.

Here is my other option: I also have a 14kW BigBattery.com Rhino battery (powerwall equivelant) but even with that system only powering LED lights and a water pump I am showing voltage drops from 55V to below 50V overnight.

Is it potentially the fact that I do not have enough solar panels to properly charge to the correct 100% voltage for LifePO? My controllers read 100% but when I look at the voltage tables none of my batts are at true 100%.

Perhaps I should remove all loads completely for a week and let the sun charge my banks to the true 100% mark and go from there?

TL;DR here are the 3 setups I have:

1) 14kW BigBattery Rhino
- 6kW Growatt inverter / charger
- Load: 100W max (mostly lights and a propane water heater) x 24hrs

2) 4x 12v 200Ah LifePO4 batteries in parallell
- 6x 100W solar panels in parallell
- 3000W inverter (always on)
- Load: variable but max 300W when I have my big speaker and college fridge plugged in

3) 2x 12v 100ah Gel batteries in parallell
- 2x 100W solar panels in parallell
- 1000W inverter (always on)
- Load: Starlink only: 50W (100W max) x 24hrs

Another thing I would like to figure out with this setup (we have built multiple structures on the land with independent power at each) - I would like to build a redundency system where as if the smallest bank hits a low voltage warning the next biggest bank will kick on and supply charge to keep it above shut down. If both of those hit low voltage - the big batter 14kW will then kick on to charge the middle bank which in turn charges the smallest bank.

So it would be like this: #3 hits low voltage and #2 kicks on to support. If #2 doesn't have enough to keep it above voltage over night and they both go down - the big battery #1 kicks in and charges #2, which then charges #1.


Or am I better off just having completely independent systems at each building location with no connection between them?

 

[thesundayranch]

Running stuff directly off DC is always an option, BUT:

What will that stuff do if it sees 10VDC or less? It might be unhappy about that...

Electronics don't "just shut down" gracefully when faced with low voltage, they sometimes soldier on with bad results.

Take a look at the FAQ page for the Blue Sea:

m-LVD Low Voltage Disconnect - FAQ - Blue Sea Systems

Senses low battery voltage and disconnects non-critical loads to save power for engine starting.

www.bluesea.com

That should help you understand how they work. Your "direct connection to the battery" should be fused or breakered for sure. The LVD module makes sure that the inverter (or other connected equipment) will never see a potentially damaging low voltage:

Factory Default Disconnect Voltage 12.1V
Time Delay to Alarm The unit waits 5 mins after the voltage goes below the set point before it starts the warning. Then an additional 5 mins to disconnect, 10 mins total.
Alarm Time Before Disconnect 5 mins
Reconnect Voltage 13V DC

Is there a real fire hazard with low voltage here? What technically happens when a system breaches the low voltage shut down point?

 

[v_green57]

Is there a real fire hazard with low voltage here? What technically happens when a system breaches the low voltage shut down point?

The below applies ONLY to running stuff directly off DC, NOT via an inverter. Apples and oranges.

I would say low fire hazard, larger "busted electronics that no longer work" hazard. And the possibility that even if the voltage is restored, they didn't come up cleanly from 0 and are scrambled in some undefined limbo state. Example is the test I did above where I brought the inverter slowly back from LV to nominal (such as would happen if the battery ran low overnight then got sun the next morning) yet it wasn't working. But if you do a "clean" power cycle it's fine. A "limbo" situation takes you right back to the original problem of your remote stuff being offline.

It's not the solar system components that you need to worry about, they USUALLY deal with LV OK, it would be Google Nest, etc. and Starlink. They assume you're running them from the "Factory Approved" AC power supply ONLY.

My gut feeling is that you are undersized on both systems #2 and #3. There are online sizing tools to help figure this out.

If you have unlimited funds, you could just keep increasing battery and panel capacity until the problem goes away ;-)

 

[v_green57]

Another possibility:

Use the charge controller LVD/Load output to operate a big-ass contactor with a 12V coil or an SSR:

https://www.amazon.com/irhapsody-Continuous-Starter-Current-Control/dp/B07T48QKQB

https://www.amazon.com/SSR-100DD-3-32VDC-Output-5-240VDC-Plastic/dp/B08GP328LH

Same functionality as the stand-alone Blue Sea option but leverages some stuff you already have. Also LVD options in CCs are probably more tweakable than the Blue Sea.

You would probably need to wire in an override switch so that when you are in residence at your desert place, you don't kick things out with the occasional big load. And of course remember to de-override when you leave.

 

[NC_hydro]

Seems like the biggest problem is you only have 800Watts of Solar.....

 

[MichaelK]

Looking at the specs of your systems, I'd say you are making design mistakes here. Sticking with 12V I think is your single biggest problem. Four parallel strings of batteries is NOT a good bank design. You also have marginal charging amps going into the bank, which in part is a result of sticking with 12V.

One thing that is unclear is how system one gets charged? Is it connected to the grid, and gets charged via AC only?

What I would do first is immediately get more solar for both system 2 and system 3. Even at a very conservative value of 1/8th C for charging system 2, with 800Ah of battery, that's 100A of charging current. And Li can really take much more. With only 600W of solar, assuming you get 85% out of your panels, that's (600W/12.5Vcharging) X 0.85 = 40.8A. What charge controller do you have? What is it's amp limit?

For system two, since you have 4 batteries, I suppose you could rewire them in series to make a 48V bank. In that respect, you would be making something cross-compatable with system 1. Then charge that with a minimum of at least 1500W of solar.

Here's a guy in Yuma that's marketing panels. You might want to consider driving there and picking up a load of his panels. Would that be too far for you to drive? There are other closer locations like Norco that are offering panels, but these look like a really good deal. If this guy's panels are good enough, you might consider getting even more panels to charge system 1.

Used Peimar SG High Efficiency SG290M 290W 60 Cell Mono Solar Panel...

"I have recertified PEIMAR 290W solar panels available for a limited time. These were recently decommissioned from a working system, processed by Solar Steals technicians, meticulously inspected,...

inlandempire.craigslist.org

 

[thesundayranch]

thank you for the heads up on the panels - not too far at all and worth the drive for those savings!

I like the idea of rewiring into a 48v bank that i can connect to system 1 14kW 48v via DC-DC charger so that if the 4 battery bank ever gets too low the 14kW will kick on to keep them at a certain charge level. Only problem is the charger and inverter I have in that system is 12v to 120v and cost a pretty penny so I guess i've been skirting the 48V series conversion (thought about it) so I don't have to drop money on a new 48v inverter... since the one I would get is Victron and runs $1400.

A similar but slightly different question / subject but another thing I have been trying to engineer in my head would be a 2-way connection between all of the independent solar systems I will eventually have. This campground will have 15 independant sites (RVs, Vintage trailers, Yurts, Etc) and rather than have one central bank of panels and batteries which I then have to run wiring from across 15 acres - I thought it would be better to have independent solar at each site as well as the common areas (which is where system 2 is), Vintage RV bar (system 3) and on our common bath house / outdoor kitchen area (system 1 14kW).

So this means in theory I could have 15 sites (small systems for charging phones and lights) plus 5 larger common areas (larger system requirements).. and ideally I would find a way to connect all of them across the 15 acre property so that each independent solar array charges those batteries - but when those batteries are full it sends charge to other nearby systems... which in turn all send power to the larger systems - and back again where on cloudy days the larger systems with more storage would keep all of the smaller systems charged.

Do they make a 2 way DC-DC charger where if I connect 2 systems to that charger they will work together to charge each other? What if I ran longer wiring from the major common area systems at 48v then measured the voltage at the destination point... assuming there would be a decent amount of loss during transit so if the end voltage is lower I could plug that directly into cheap battery charger?

I am also working on integrating 48v wind into the system because the wind out there is almost constant +10-20mph (gusts of 80-100mph LOL)

Anyways thanks again for all the help - I will be back out there in a week or two and will post more photos of the setups and the property so y'all can see.

 

[thesundayranch]

Seems like the biggest problem is you only have 800Watts of Solar.....

sorry i forgot to mention that system 1 has it's own 48V 600W system as well as the independent solar arrays on system 2 and 3

 

[thesundayranch]

I wanted to close the loop on this in case anyone else here finds the thread and is looking for a solution... happy 4th of July weekend!

Problem: running independent solar systems at multiple locations in a harsh desert environment; critical loads that may power off during periods where solar is not sufficient to charge batteries to 100%. Specifically I was looking for a 120v inverter that would auto-restart if batteries cut off at low voltage over night.

I was having a hard time finding an inverter that would simply shut down at low voltage and then power back up automatically the next day once batteries were back up and running. This was very difficult to find... but I FOUND ONE!

Leave it to Victron to come through in this case - and for having incredibly high quality (expensive) products. BUT - this Victron Pheonix 12 / 500 I just got delivered DOES AUTO RESTART after a low voltage shut down... meaning my critical load (Starlink in this case) might go down overnight once in a while (which impacts my security system) but the next day will power back online once the batteries start to recharge (and so will my security system).... which solves my issue! (for now lol)

So for anyone looking to solve the issue of critical 120v AC powered loads going out when you are not there and in a remote location - this inverter will solve that issue. (still need appropriate storage and solar) https://www.amazon.com/dp/B01N4J9OOM?psc=1&ref=ppx_yo2ov_dt_b_product_details - less than $200!

The product itself is high quality right out of the box. VERY heavy for a 500W inverter (almost heavier than my 3k watt). Designed in Europe, made in India (not China). Great warranty, ability to monitor with bluetooth and impressive built in safety features.

Photos attached as well of the specific manual page where it calls out the auto-restart functionality: "To restart the inverter, switch it Off and then On. OR recharge the battery and as soon as the battery has risen and then stays above the charge detect level for 30 seconds the inverter will automatically switch on.