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Electric inverter problems  RSS feed

 
Gregg Taylor
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I have a Tiny Home that I built and I have 2-250 solar panels, A 48 VOLT battery bank and a 4000 watt inverter. I didn't realize how much draw there would be from my inverter. The inverter uses a continuous 75 watts when there isn't a draw.  Does anyone know how I could have a system that would turn off when there isn't a draw.  I realize now that you can buy inverters that have a sleep mode but already spent too much money on this one. Could I create an relay system that could turn the inverter off when there isn't a demand?

Thanks in advance for any advice.

Gregg
 
Glen Apollo
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Auto turnoff is challenging. If the inverter draws 75W idleing you will have to have a sensor that only turns on when maybe 100w is asked for.
I don't think this can simply be added to the inverter input wiring?
Doing some math, 75w at 48v = 1.5A idle current.
15A for 10 hours of darkness.
A simple option would add a power relay in the inverter input that can switch 100A. If my math is correct 4000W is 89A at 48v.
The relay can be switched via a wired or inexpensive wireless switch.
Ebay or Banggood sells 12v coil 100-150A power relays. Use a regulator to drop 48v to 12v.  The relay coil draws maybe 1/4A 250 ma. When energized.

The power relay would simply be installed in series with the + inverter input wire.
These power relays come with connection typebolts with nuts to accept cable lugs.
The relay coil sw would switch power to the Buck regulator set for 12v output from the 48v battery. When the sw is off, no current would be drawn for the relay coil control.
Another option is to use the voltage from one 12v in the bank for the 12v relay coil voltage source eliminating the regulator.

Typical 100A power 12v relay.
https://www.ebay.com/itm/282068085904

48v in:12v out adjustable regulator
https://www.ebay.com/itm/171247024835


 
Sebastian Köln
Posts: 97
Location: Germany · Schleswig-Holstein · Eutin
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Hm.. I have doubts that adding more electronics will solve the problem.
What if you would add a lamp (10W?) that is wired to the inverter input/output, so it is impossible to miss the fact, that it is running.
And then convert as much as possible (at least the lights and possibly pumps) to 48V or 12V. led lights are not that expensive if buy the correct ones.
 
keith s elliott
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Location: Ruxton Island
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Hi Gregg, very sorry to hear of your problem.

I'm no electrical expert, but your question seems to have been answered already.

What I don't understand is why doesn't your inverter have a sleep mode built in?  That seems odd to me.

I lived for nearly 20 years off grid and had a 3,600 watt inverter, with a sleep mode of course.  When things get quiet at night and you turn the last light off you can hear the little "bong" that the inverter makes, so you know that it is sleeping.  I honestly can't imagine how bad that's going to be for your battery bank.  I used to get around 7 years life from my battery banks, but that was because they could "rest" every night.  That constant draw with no rest isn't going to help at all.  Honestly, I think you need to do whatever it takes to change that inverter for a different one.  Good luck!
 
Chris McLeod
Posts: 57
Location: Cherokee, Victoria, Australia
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Hi Greg,

Yes, not all inverters are the same in that regard and many of them have very high standby current draws. I've been off grid for about eight years now and I use a locally (Australian) made Latronics inverter 24V / 3000W which has only a 0.6Ah draw (24V x 0.6Ah = 14.4Wh).

There is no easy way to resolve your issue other than:
- Replace the inverter;
- Add more panels to compensate for the high standby current draw; or
- Switch the inverter off say at night when it may not be as essential.

Mind you, I leave mine running 24/7.

Incidentally, if you are hearing a lot of buzzing noises from your inverter, the capacitors may be on the way out, so try not to let the unit get too hot as that dries out the inverters capacitors. Also a huge amount of radio interference also means that the unit may pack it in in soon-ish.

Sorry mate!

Chris
Fernglade Farm
 
C Jones
Posts: 59
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75W / 1.5 A definitely sounds high!  What are the make and model of the inverter?  I'd check it against the manual's rated numbers...or is that where you got the 75W number?  Sounds like it's fairly new?

Personally I'd be EXTREMELY wary of $6 eBay relays, especially at upwards of 100A.  That's a lot of current!  And a quick Digi-Key search, unless I'm missing something, shows prices in the tens to hundreds for a proper brand of electromechanical relay in that range.  link

And for solid-state, hundreds: link

Cheap Chinese stuff tends to have all kinds of quality and especially safety problems...

Glen, do you have any direct experience with those kinds of cheap relays?  I don't, so those are just my initial concerns.  Might be worth trying anyway though, for $6.
 
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