Best way to start the inverter?

Started by Nomad1, September 07, 2018, 04:57:31 AM

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Nomad1

Hi guys,
I'm wondering, what is the best way to start an inverter to back up KID during nighttime/bad weather?
I have enough PV output to power my home during sunny day, but I don't want to drain battery power during the night, only if AC grid is down. So I tried to start the inverter with AUX relay and AGS mode, but it seems like KID powers down the relay when 'generator' is started. Later on I decided to use Low Voltage AUX mode and it sometimes fails when inverter decides to charge the batteries and raises Vbatt above the threshold. Right now I'm thinking about disconnecting the load and putting the relay these to utilize dusk/night load modes. And the very last option is to make a script that would monitor KID stats and make some assumptions based on PV power, battery voltage and possible SOC.

Does anyone have similar scheme? What is your scenario for Grid/Inverter switching?
Thanks!
Programmer

harryn

#1
My experience is entirely working on RVs and conversion vans, so slightly different.

If you think about a conversion van as being a mobile off grid home, it makes more sense of how they are similar.

In the field, very often the A/C power that is available is fairly poor quality, availability can be intermittent, in theory 50 or 60 hz - and wandering, spikey, generator acting up, etc.

As a result, I take the more brute force approach and convert everything to 48 volt DC, then invert everything as needed.  Obviously this is less efficient than a pass through, but it works when other approaches fail, which is more often than you might think.

Some chargers can be programmed to not kick in until the battery bank has depleted to xx volts.  As long as solar or other sources are keeping up, the AC chargers won't turn on until the battery bank has depleted down to that level.  I guess in theory you could also use an Auto gen start output to trigger the AC charger.

In your case, you are trying to avoid cycling the battery pack down, so you could set this "time to charge" voltage fairly high.

I know it isn't what you asked, but perhaps accomplishes something similar to the goal.

Rwbain

I have two Kids right now . I use the load control function of one Kid for my inverter switching right now.  I set  low disconnect to 11.9 volts. I wired in a toggle switch and a mechanical  (spring) bathroom fan timer for manual control in my cabin. I also installed a toggle and bath. fan timer for my generator and im using the AGS function. The problem I have is when I put a high amp temporary load on the inverter the DC voltage drop goes below the set load control function parameter and will disconnect or shut off my inverter until recovery. That's why I have a toggle that I can "override" that function. It was dumb not including a time delay for the load function. I was considering using my second Kid's AGS function as my load/inverter control but I'm not sure that would work how I want. Right now the accessory switches I installed make it work pretty good. I can set my inverter timer for an hour at bed time and preserve juice for the a.m. I used to fall asleep with the inverter on and sometimes have to wait for charge before using the inverter the next morning. I only have to worry in the winter months. Summer I leave it on 24/7 I believe both the AGS and Load internal relays are switched negative,  but I'm starting to forget.

ClassicCrazy

Quote from: Rwbain on November 13, 2018, 07:18:38 PM
I have two Kids right now . I use the load control function of one Kid for my inverter switching right now.  I set  low disconnect to 11.9 volts. I wired in a toggle switch and a mechanical  (spring) bathroom fan timer for manual control in my cabin. I also installed a toggle and bath. fan timer for my generator and im using the AGS function. The problem I have is when I put a high amp temporary load on the inverter the DC voltage drop goes below the set load control function parameter and will disconnect or shut off my inverter until recovery. That's why I have a toggle that I can "override" that function. It was dumb not including a time delay for the load function. I was considering using my second Kid's AGS function as my load/inverter control but I'm not sure that would work how I want. Right now the accessory switches I installed make it work pretty good. I can set my inverter timer for an hour at bed time and preserve juice for the a.m. I used to fall asleep with the inverter on and sometimes have to wait for charge before using the inverter the next morning. I only have to worry in the winter months. Summer I leave it on 24/7 I believe both the AGS and Load internal relays are switched negative,  but I'm starting to forget.

What kind of inverter ?  I am assuming you are using a remote switch option for the inverter and not trying to break the  DC input connection to the inverter ?
I have a timer switch on my Outback inverter in parallel with a regular switch ( to the inverter  remote shut off connection). So in normal operation I leave regular switch closed, then when I want timer I turn that on and open the regular switch . When timer runs out it shuts off the inverter ( it is still on but in very low power sleep state until I turn manual switch back on - I guess I could hook that up to contacts on my Kid or Classic like you do if I needed that ) . Anyway works fine when I want to watch TV at night but have inverter shut off and save some power after I fall asleep.

Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable

Rwbain

I'm using a Tripp lite 2kw cont. 4kw max 12volt . It feels like it weighs 80 pounds. I am controlling it through the remote jack , which is kinda funky on my inverter. The remote "receptacle " is a 1/8" phone jack that uses the tip for the conductor . And the thing is switched positive..kinda lame but it works. It has "sensitivity adjustment " thats adjustable with a small POT that shuts it off when there's no a/c load present, but I can't get it adjusted correctly.  Some of my lights and other items are such small loads they don't turn it on. I used a DPDT relay as an ATS between my  gen and inverter. I switch one leg and the neutral. I have a dedicated 220 circuit as well. I'm currently brain storming using a similar set up for two inverters. As in , transferring loads between inverters . Light loads I could run through my small , more efficient inverter then switch over to the larger, less efficient inverter for heavy loads. I'm not sure it's worth the effort yet though because I'm not really sure what the efficiency is for either . I haven't thought of how to switch based on amperage draw (not that I've have this too much consideration  ). I'm sure there's a PLC or some kind of microprocessor controlled switch around but I haven't seen it. Sorry I guess I kinda rambled! !

ClassicCrazy

Might be more savings in energy on the smaller inverter for the no load current draw compared to the bigger one.

Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable