Victron Inverter - power consumption

[PeterV]

I am trying to calculate daily battery power consumption and have most of the figures but I am not sure how the 3kw Victron inverter performs.

 

I have to leave it running as the fridge is 240v and it looks from the handbook as if it consumes 6w.

 

I have assumed that means it consumes 6w per hour x 24 hours = 144w = 12 amps per day just because it is switched on without any load. Is that correct?

 

Does that "background" consumption vary when load is applied such as when the fridge cuts in, and if so is there any way of calculating the additional consumption?

 

Peter V

[chris w]

I am trying to calculate daily battery power consumption and have most of the figures but I am not sure how the 3kw Victron inverter performs.

 

I have to leave it running as the fridge is 240v and it looks from the handbook as if it consumes 6w.

 

I have assumed that means it consumes 6w per hour x 24 hours = 144w = 12 amps per day just because it is switched on without any load. Is that correct?

 

Does that "background" consumption vary when load is applied such as when the fridge cuts in, and if so is there any way of calculating the additional consumption?

 

Peter V

 

I have cut and paste a relevant piece I just posted on another inverter question.....................

 

The only issue with using a pure sinewave inverter is that the current needed to run the inverter (its "quiescent" current in the jargon) can be 5-7 amps whereas for a modified sinewave inverter it's more like 1 amp - this is wasted power. (There will still be inefficiency losses on top of these figures for both types which will run at around 10% of the supplied current).

 

There is some clever marketing, with pure sinewave inverters, whereby you may see a low "standby" current for a pure sinewave inverter maybe less than an amp. Looks good eh? Not so......... what they do is that the inverter goes into a kind of "sleep" mode when no load is detected - this is the "standby" current. However when you are actually running some equipment, the quiescent current is as stated above and represents wasted battery power...............

 

The 6W to which you allude is the "standby" power not the power that will be wasted when the inverter is connected to a load (Not sure where you got this figure as the Victron spec states 15W with zero load). Note also that the Victron is not rated as 3000 watts but 3000VA. Further it is specified as 3000VA @ 25degC not 40 degC like some others (eg: Sterling). The Victron's continuous output power in WATTS is 2500W at 25degC and at 40 degC is specified to be only 2000W. So ensure you compare apples with apples.

 

Your calculations are not correct I'm afraid. The 6W equates to around just 0.5 amps or approx 12 ampere-hours per day. However, this is if the inverter is not connected to anything so is pretty meaningless because if there's no load, you'd probably switch the inverter off anyway and have zero losses!

 

The consumption of a pure sinewave inverter can be approximately calculated by dividing the appliance's power (eg a 60W refridgerator) by 10 (not 12) which will give the actual current flowing from the batteries, in running the appliance, including losses.

 

So in this example about 6 amps ie: 60/10). Spread over a day at say a 50% duty cycle (ie: the fridge thermostat switches ON for 50% of the time), this equates to approx 72AH per day. On top of this (for a pure sinewave inverter) there will probably be another 70AH in other wasted power which will stay constant approximately regardless of how many appliances it is running. Hence the efficiency goes up the more you run from it.

 

If anything is unclear please come back to me.

 

Chris

Edited September 13, 2007 by chris w

[DHutch]

I think a crude estimate of 6watts lost current, plus a factor of about 0.9~0.8 for it only being 80/90% effeinent maybe.

 

- Im sure gibbo and the others will be able to advise you with more authority.

 

 

 

Daniel

[chris w]

I think a crude estimate of 6watts lost current, plus a factor of about 0.9~0.8 for it only being 80/90% effeinent maybe.

 

- Im sure gibbo and the others will be able to advise you with more authority.

 

 

 

Daniel

 

 

Clearly Daniel you don't know the technical differences between pure sinewave and quasi sinewave inverters. The figures to which you allude above would be appropriate for a quasi NOT a pure sinewave inverter.

 

Chris

[Gibbo]

I am trying to calculate daily battery power consumption and have most of the figures but I am not sure how the 3kw Victron inverter performs.

 

I have to leave it running as the fridge is 240v and it looks from the handbook as if it consumes 6w.

 

I have assumed that means it consumes 6w per hour x 24 hours = 144w = 12 amps per day just because it is switched on without any load. Is that correct?

 

Does that "background" consumption vary when load is applied such as when the fridge cuts in, and if so is there any way of calculating the additional consumption?

 

Peter V

 

The 6 Watts you refer to is if the inverter is allowed to go to sleep (idle mode). If it doesn't go into idle (ie it's on all the time) then the wasted power is more along the lines of 35 watts = 70 Ahrs per day!

 

And there is a slight problem with idle mode and fridges. Often the fridge will not try to fire up unless there is 230 volts available (which there won't be if the inverter is in idle mode). And the inverter won't come out of idle mode unless a load is put on it. Catch 22. Many people have to keep the inverter out of idle mode in order to run a fridge. As you can see from the above this can get rather wasteful of power.

 

But not all fridges do this.

 

Gibbo

[Ernie]

QUOTE:Many people have to keep the inverter out of idle mode in order to run a fridge. As you can see from the above this can get rather wasteful of power.

 

And it’s not just fridges.

When we bought our boat, the inverter was set to switch into idle mode when it detected no load.

Unfortunately (or fortunately – depending how you look at it) our hard disk drive video recorder draws very little power when in timed record mode. The inverter would think there was no load and would turn off removing power to the recorder causing it to loose it’s clock settings. Also, the Sky satellite receiver did not draw enough power to keep the inverter on either.

 

Likewise, chargers for mobile phones etc. would not turn the inverter on.

 

We very quickly switched the inverter out of power saving mode and into the mode where it is on all the time. The problem with this, as Gibbo has pointed out, the inverter is fairly inefficient and wastes a lot of power even if there is no or a very low load on it.

 

The inverter in question is a Synergex 1500W pure sine wave job which so far, we have been very happy with.

[PeterV]

Thank you, I think this has identified my apparent shortfall between the charge I thought I was putting in to the batteries and the consumption.

 

Peter V

[DHutch]

Clearly Daniel you don't know the technical differences between pure sinewave and quasi sinewave inverters. The figures to which you allude above would be appropriate for a quasi NOT a pure sinewave inverter.

Quite certainly not.

- Im a partially trained mechaincal enigineer, with a minor dislike for electronics. So thats not too supprising.

- Ours posts crossed, and had i noticed yours before i would proberbly have removed it, but still, whatever.

 

 

 

Daniel