240v inverter

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240v inverter

Postby cfinlay96 » Wed Feb 08, 2017 11:20 am

Hi guys!
New here, basically i just want to know why my 24v to 240 volt inverter drops out everytime i plug something new into the system. for instamce i have a fridge running off it, now if i plug my laptop in to charge, the the fridge cuts out and restarts itself.
any ideas why it does this or anything i can do to fix this from happening?
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Re: 240v inverter

Postby Gordon-Loomberah » Wed Feb 08, 2017 12:33 pm

Firstly, welcome to the Energy Matters Forums :)

If a small load such as a laptop power supply is causing the inverter to restart, I'd suspect either the inverter or battery (or both) is not large enough for the loads. For a better understanding of what is happening, you'd need to tell us your system details.
Inverter specs, battery brand/model and capacity in AH, cable size between inverter and battery, charge controller and panels if you have any, or 240V battery charger details.
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Re: 240v inverter

Postby cfinlay96 » Thu Feb 09, 2017 10:53 am

[Moderator, no need to requote the whole post, it is just up there ^^^ ;) ]


So I have got 1kw of panels on the roof, going through a Schneider 150/60 controller, through to 4 90ah 12 volt batteries wired in 24v. Then got very very thick cable only 30cm short to a 2000w (4000w peak) inverter
Now the inverter is only a cheap one but it has 3 outlets and the fridge is only drawing 250 w.
Last edited by Gordon-Loomberah on Thu Feb 09, 2017 2:02 pm, edited 1 time in total.
Reason: removed unnecessary quoting
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Re: 240v inverter

Postby cfinlay96 » Thu Feb 09, 2017 12:22 pm

The fridge turns back on and everything runs fine it's just that one second of cutting out
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Battery

Postby cfinlay96 » Thu Feb 09, 2017 12:26 pm

So I've got a 24 volt system. Now when the sun goes down the batteries sit on around 25.8 until you use something. Even a low wattage light or something. Then it drops to 23.6ish pretty instantly. But the thing is all of the power is down low. The battery's last for ages but it just seems all the storage is down in the lower volts haha
And reason for this?
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Re: 240v inverter

Postby Gordon-Loomberah » Thu Feb 09, 2017 1:13 pm

It will be voltage sag at the 240V output, but a really small load like a laptop causing that to happen means there is a problem somewhere. Assuming the batteries are in good condition (have you measured the battery or AC voltage when the fridge cuts out?) then there may be a poor electrical connection somewhere, either battery interconnects, or battery to inverter. Check all these connections thoroughly, and also any fuses/breakers/switches you may have.
Even a cheap inverter should handle a laptop power supply start without issue if it has a good supply, but a poor connection will cause problems.

Does this problem happen at any time of the day, or only when the batteries are partially discharged? Your batteries could be going well below 50% SOC in hot cloudy weather with only 1kW of PV. Do you monitor battery voltage at all?
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Re: Battery

Postby australsolarier » Thu Feb 09, 2017 2:03 pm

that's why they are called 12v batteries and not 13v batteries. it has just something to do with acid lead battery chemistry and should be perfectly normal. like when you let the car engine run, the voltage is up somewhere 14.4 v then after you turn off the enigne the voltage will drop fairly quickly to some 12 odd volt. at the other hand a lifepo4 battery has a much stiffer voltage. different chemistry.
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Re: Battery

Postby Gordon-Loomberah » Thu Feb 09, 2017 2:08 pm

If a 20W light is causing the voltage to drop to 23.6, then you probably have a stuffed cell somewhere, or a bad connection. How old are the batteries?
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Re: 240v inverter

Postby Gordon-Loomberah » Thu Feb 09, 2017 2:11 pm

cfinlay96 wrote:Now the inverter is only a cheap one but it has 3 outlets and the fridge is only drawing 250 w.


What brand and model is the inverter? Cheap inverters tend to be very inefficient, particularly at low loads, due to high self consumption, so it could be draining your batteries a lot faster than you expect.
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Re: 240v inverter

Postby Bthree » Thu Feb 09, 2017 3:41 pm

How old are the batteries ?

180Ah of batteries are going to get a good flogging with the fridge 250W = 11Ah intermittent running over night
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