Emergency Battery Backup - Utility Mode

Thanks for filling us in, Fastnf. I wonder, would a transfer switch be a reasonable upgrade to your current setup? That way you can skip the extension cords/strips abuse and still be able to power a bunch of 120V circuits.

So I'm trying to make sense of these statements. If the LDC unit is limited to supplying 1200W, then in what scenario would cause it to operate in the 1500W to 1740W+ danger zone? Might a large surge on the 12V battery have anything to do with it?

 

The problem is that inexpensive inverters (like mine $275 ) have a voltage of 60 volts between the neutral and ground. If you tie them in to the transfer switch where the main panel neutral and ground are tied together this causes a dead short between the inverter neutral and ground and you burn out the inverter. If you leave off the ground, then none of the GFIC outlets work. So its not a good idea to connect this type of inverter to a transfer switch. More expensive inverters have a neutral to ground ability to be bounded when tied into a transfer switch. They however start at about $1200 and go up from there. Usual these will have a UL listing of 458 or 1741. If I needed the option more often then the current once in 5 years I would install a more expensive inverter. On the other hand I am hoping that within a couple of years Vehicle to House (V2H) systems will be available for CCS charge ports which would be my preferred option.


For the LCD 1200 watts is the maximum safe load with out a voltage drop. Above 1200 watts the voltage on the LCD low voltage side starts to drop and current goes up. If it reach about 1500 watts it blows the fuse. If you were to say put in a higher rated fuse the LCD would eventually over heat and fail. So I choose to limit the current to 100 amps with a circuit breaker rather than having the Kona blow a fuse if I accidently over load it. This way I can turn off the load and reset the breaker with no affect on the cars circuitry.

 

We had a power outage last evening, first one in several years, lasted 2 hours. Usually happens during storms with trees down, but wx was perfect, so assume must have been an accident somewhere taking out a pole or something like that. I have salt water tanks with corals and fish. If the water circulation stops for too long, it can be a real disaster with corals and fish dying.

Anyway, I have an 800W inverter at home, and was just starting to hook it up to the car and to my water circulation pump with a long extension cord, when the power came back up. So never actually used the back-up, but good to know it was there and available.

However, the outage also exposed another vulnerability. My computers, routers, modems, etc run off a UPS system. But it did not work, and everything just shut down. Will have to look at that now. I did get a new computer this spring, and maybe there is a UPS software set-up problem. Will have to investigate it further.

 

Unfortunately, those UPS batteries only have a reasonable lifetime of a couple of years.

 

Yeah, I might very well now have a battery issue. I did find out this morning what went wrong. Turns out I forgot to install the UPS software (only plugged in the USB) on my new computer earlier this year. I did the install this morning, but unfortunately it says the batteries are dead now, too, at 0%. I guess they don't charge unless they are not told to. It is charging now though, and will have to wait until it is 100% to see if they are still any good. I hate making mistakes like this...

 

We have a fairly complex system like this at the office - probably too complex. About 6 different UPS, of different sizes, and one daemon on one machine that monitors the state - if the batteries on any of them start to drop, it tries to initiate a controlled shutdown. But for this to work, all routers and switches need to also have power.

We had an outage at the office when the hurricane blew through - it took out *both* of our domain controllers. Each of which had RAID, but the hardware limitations of the thing were such that the machines couldn't boot if one of the hard drives was complete toast. In the short term, I restored from backup into VMs so things work again. In the long run, I think we moving everything to the cloud.

 

I just have a simple home office system, and the UPS has always worked in the past with power outages. I just got complacent. Luckily W10 is pretty good with recoveries, and no harm done. But yeah, in an office with lots of computers and networks, you need a more robust fail safe system.

So far I just do my own back-ups and don't use the cloud. With all the stories about ransomware, I am just waiting for the day, when they penetrate and take control of a cloud system. I understand that they now can lay dormant for many months, even years before they pull the trigger. So even your back-ups may not work. That is frightening. I wish the govts, FBI, CIA, etc would put a little more effort in nailing these bast***s. Potentially, they could hold up the whole world!!...

 

The electrical mystery never ceases to scare me. I went back to your posts in the original backup thread and saw one of the big inverter you had looked at:
https://www.sigineer.com/product/3000-watt-12-volt-to-120-240vac-double-phase-pure-sine-inverter-charger/
Does this inverter fit the bill of backing up a typical 120V/240V panel (via interlock kit) without the scary shorts and burnouts and stuff you warned about? The price for this inverter is suspiciously low but perhaps expected of an overseas Chinese unit which I'd imagine won't last long if run often.

While I don't expect to request a constant 1200W+ draw, the LDC can survive short startup surges past 1500W, right? My thought is that the 12V battery can absorb short bursts and thereby shield the LDC from overheating/failing as you warned.

I had the same issue with one of my UPS units during last week's outage, very disappointing as it's less than six months old so hopefully just a warranty issue. On another note, I want to caution you with my experience last week. During the outage I tried powering up computer stuff attached to a dead UPS unit with a modified sine wave inverter (hooked into the Kona 12V battery) and man, the UPS freaked out big time. I can only guess that it did not like eating the "fake" sine wave I fed it? I unplugged it real fast and it still took constant beeping over 12 hours for it to discharge whatever bad stuff it ate. Now I'm scared to ever use it again.

Can anyone comment on whether modified sine wave power is bad for feeding typical home-use UPS units?

 

I read the manual for it and could find a clear answer, which is one of the reasons I decided against it. The brands That I could determine capable of neutral ground bonding were Magnum, Schneider Conext, Outback Radian, and Victron all in the $2k-4k range

I haven"t tested beyond 1200 watts but those that I have read about blew the fuse in the car near 1500 watts. I am being cautious as I'd rather not damage the electronic in the car. My plan would be to put a second battery in parallel with the 12 volt battery that way half the current would come form each battery and the so that the LCD would not be overloaded and hopefully during times of low current it would allow charging of both the battery's. This set up should give you close to 2400 watts of surge. I haven't tested this yet though. I plan on testing when my schedule allows time.

 

Well, at least on my small 230VAC units they use a transformer for everything coming in and going out. A modified sine wave is marketing speak for a two-step square wave (in my experience) and not suitable for transformers or induction motors. A true sine wave type is going to be an improvement as it uses 6 steps if I'm not mistaken.

 

The quality of the sine wave varies from one brand of inverter to the next. Some are great, some aren't bad, some are horrid. If you shop by price alone, you will probably get horrid. The only way to know for sure is to put it on an oscilliscope.

 

Wow! We covered everything here from solar panels to UPS systems. But the actual use of the Kona HV battery as a backup home power got lost! I will spend the afternoon to read through this stuff.
Could someone sketch a block diagram of a tried solution?

Thanks

 

You basically just need a pure sine-wave inverter - roughly 1200W or so (and a good quality inverter at that). Personally, I wouldn't go higher wattage than that - it is probably wasted money for this application. You would need to attach it to the 12V battery on the car with jumper-cable type clamps (see post #5 and pay close attention to post #7 as to exactly where one should attach the clamps). That's enough to get AC power on the other side of the inverter.

Whatever you do, remember to put the car in "utility mode" before you do this..

It won't run the whole house, but you can run a few things like your fridge, WiFi router and a phone charger or two.

If you want air conditioning, honestly I would just sit in the car. The inverter can't produce enough electricity for anything but the smallest window unit.

 

Thanks ericy!
Here in the Great White North we are more concerned with missing heat in the winter.

Found a neat step by step description from a similar tread here

https://pmarks.net/konapower/

 

Checking in on this thread again after some recent storm outages. My Kona was rock-solid shouldering an overnight 200w to 700w load with a 2200w true sine inverter. I also did some sidebar tests with just a space heater that gave interesting results. At zero load, the Torque app reported a background 150w draw that I guess keeps the car alive in utility mode. With a 900w load from my space heater, Torque reported a total 1400w draw from the car battery pack, and with a 1300w load, the total draw was 2000w.

If the above Torque numbers are to be believed, then there's a ~40% overhead power draw from the car battery pack (after subtracting the background 150w draw) on top of my actual load. Ouch, but maybe that's what the LDC needs to do its job, however inefficient. Then again my test methodology could well be wrong, penny for anyone's thoughts.

Speaking of the LDC, Fastnf reported above that there's a post-LDC fuse that blows under a 1600w load. I seem to remember someone here discovering a LDC output PID, perhaps hobbit? Wish I had that PID during my test, though since my fuse didn't blow under a 2000w battery pack draw, that suggests LDC output is more in line with the actual load being put on the 12V battery.

Hey Fastnf, I wrote into Sigineer with your above concern verbatim about that split-phase inverter that we were shopping, below is their reply:

This comment is 90% correct.
Our AC output neutral is floating, so there is a voltage between the
ground, but the inverter willn't be damaged even you bond the output
neutral with the ground.
Many cheap inverters could be damaged in this way because the
factories doesn't know UL1458 or 1741, but we are very familiar with
it.
Welcome to order the APC3012D online
https://www.sigineer.com/product/3000-watt-12-volt-to-120-240vac-double-phase-pure-sine-inverter-charger/

I shall leave you to decode that, because I can't. How do you feel about their reply?

 

Based on what Sinineer said it sounds like the unit is compatible with a transfer switch. It also sounds like the build them to UL specifications however they don't test and certify them. (its probably a copy of a certified one they build for a different brand) Hence the cheaper price. My current inverter is doing the job I need the few times a year that I need it so I am probably not going to try their unit unless my current inverter goes out. It doesn't meet code with out the certification nor would it probably be allowed in an insurance claim if there was a problem. Still if my current system went out i would consider it again. I only need 240 volt for my well pump, but it only runs a couple of minutes a day to fill the pressure tank and for that I can just fire up the generator for now.

The post about the blown fuse was on reddit. I have posted a link in different thread along the way. If some one needs it let me know I will look it up again.

 

Thanks electriceddy! very helpful. Looks like there has been a little additional info added since the last time I looked at it but still the same results.

 

The moment the 12V system voltage drops under the approx 14.6 V that can only mean the LDC is in current-limiting mode, not a good part of the envelope to work in if you want any margin on your AC side.