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Need some advice - connecting small generator to inverter


Nuno
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Hi folks!

Due to some unexpected problems with my Axpert Inverter, I got myself a small (2kva) generator for backup power, as I'm living offgrid.

It's fine for emergency usage, but now that my inverter is back up, I was wondering if its ok to connect this generator to the inverter to use it as a backup charge for the batteries. In this way I can have my house fully powered instead of using cords from the generator.

I never did this before, so bare with my with some basic questions :)

My generator doesn't have any AC output terminals (no idea if its common or not), just two typical AC outlets to plug cords.

So I was planning to do as follows

  1. Plug in an extension cord to the generator, cut the other end, and connect the wires to the AC IN terminals of the inverter (including ground wire)
  2. Switch the generator AC switch off
  3. Power the generator and leave it running for a few minutes (as per instructions)
  4. Switch the generator AC switch on

Is this ok and safe, or can I blow up my inverter? :)

thanks in advance!

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2 hours ago, Nuno said:

connect the wires to the AC IN terminals of the inverter (including ground wire)

It should not be a problem to run inverter from generator, but lots of inverters don’t like generators so I’m not sure about the

 

2 hours ago, Nuno said:

I can have my house fully powered instead of using cords from the generator.

You could also fit a change over switch for selecting between generator and inverter that way you can still power everything.

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It is safe to connect the generator; that's how these off-grid inverter-chargers are intended to operate.

Make sure that setting 03 (AC input voltage range) is set to APL not UPS. Even so, the inverter may reject the generator (no AC input symbol appears on the display). If so, try plugging in a small load (around 100-500 W) to the generator before switching on the outlet to the inverter. With the small load, it may settle enough for the inverter-charger to trust it. Once it starts charging the battery and/or powering loads, it should be OK to turn off the small load. Perhaps keep it plugged in but switched off (assuming it's a switched outlet or the appliance has a switch) in case it's needed again later.

Use output priority (setting 01) at UtI, so that as soon as the inverter-charger sees the generator, it will use it to power your loads and charge the battery. Obviously, you would not run the generator in the middle of a good solar day or (probably) if the battery is full. Charger source priority (setting 16) can be set to SNU to allow charging from both solar and utility. Choose maximum utility charge current (setting 11) to be something comfortable for your small generator, and allowing some spare capacity to power loads at the same time. Setting 02 (maximum total charging current) is presumably chosen to match your battery, and need not be changed.

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Ok, I got everything connected and working.... kind of!

I need some extra advice with the hopes that I didnt buy a terrible generator :)

The AC breaker in the gen was tripping after a minute or so. Being a 2300W gen I configured max AC In current to 10A. But upon checking the manual, I discovered the max current output is actually 9.2A. So it seems the inverter is pulling too much current and eventually the gen disconnects AC output.

Unfortunately for me, the only setting lower than 10A is 2A... which is extremely low :(

I tried playing up a bit with the inverter settings, changing the priority to SOL, but still it eventually disconnects when it needs more power from the gen.

Any advice on how I can use all these settings to reach the best possible setup for this?

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14 hours ago, Nuno said:

So it seems the inverter is pulling too much current and eventually the gen disconnects AC output.

I read somewhere (can't find it quickly now) that the manufacturer does recommend a generator rated at 1.5x or more higher than the expected power requirement.

But remember that the 10 A maximum utility charge current means 10 A into the battery, not 10 A from the generator. So 10 A is only ~500 W. It doesn't sound like that's your problem.

Perhaps you should increase the maximum utility charge current setting (setting 11) to 20 A (1000 W) or even 30 A (1500 W); the generator may be more stable at moderate loads. This document says that the maximum frequency slow should be 0.3 Hz/second, which sounds pretty low to me.

Try and keep your house loads low during this time; the generator is also supplying all the loads. You may have trouble starting fridges and the like with a small generator also charging the battery. A fridge's surge power could briefly be as high as a kilowatt. The resultant brief slowdown of the generator could be enough to get it rejected.

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