Inverter, Charger/Inverter standby draw current question

[MikeG]

Hi Guys and Girls

I have had to re create myself on the forum,  could not remember my password and Password Reset would not work, old age don't yer know ? 

But a quick question for the knowledgeable among you.  I am contemplating a new build and thinking about Inverters and Charger/Inverters and would like to source a reliable one with a very low standby current draw.  Is there such a thing and could you recommend one?

Cheers

MikeG

[Robbo]

Victron and Mastervolt are good makes with decent low standby.

[Alan de Enfield]

15 minutes ago, Robbo said:

Victron and Mastervolt are good makes with decent low standby.

Wasn't it reported in a thread "mysterious battery drain" (or similar title) that after problem-solving was carried out they found that the Quiescent current on their Mastervolt was around 4 amps (100Ah per day)

 

Although I think Nick Norman has a Mastervolt and gets 'fractions of an amp'

 

Maybe there are different Mastervolt models ?

Edited December 18, 2018 by Alan de Enfield

[mrsmelly]

Mine is brilliant but no longer available and draws 0.3 of an amp. I have had a couple or three cheapies including stirling and a couple of Mastervolt. I have a victron in my spare s box just in case mine goes bang. My choice from what is available on todays market would be Mastervolt every time. Lowish draw on standby, silent in operation and does more than it says on the tin.

[Robbo]

1 minute ago, Alan de Enfield said:

Maybe there are different Mastervolt models ?

I wouldn't trust the readings from with the "mysterious battery drain" thread.

 

Different models will have different standby's.  The more expensive the model doesn't mean the better the standby as it will probably have features that make the standby worse (Victron Quattro's are worse than the multis, etc).

[alan_fincher]

In my experience the higher the maximum output is the higher will be the standby current.

So I have had cheapie 300w inverters that draw very little in standby, but the same was not true of an 1,800W one. (Both were MSW).

 

Also aren't many configurable as to how easily and/or quickly they will wake up?  One that is configured to come fairly seamlessly out of standby will probably draw a lot more quiescent current than if it is not.

So I suggest there may be no "right answer" to this question without knowing things like maximum power required, (perhaps) whether it is MSW or PSW, and how important it is that it kicks in immediately there is any demand for power.

[Jen-in-Wellies]

It is one of those you get what you pay for things. Generally speaking a low standby current is associated with a higher price. You need to look at the detailed technical specifications for the inverter you are interested in. One problem is that different manufacturers call the standby current by different names and define them differently, making comparison difficult. If the tech spec doesn't show it, then beware, as it may well mean that it is very high. You are looking for standby current, what it consumes while switched on, putting mains out, but no mains appliances switched on and efficiency, usually a percentage, how much power drawn from the batteries ends up as mains power when appliances are drawing from the inverter. The rest ends up as waste heat. Easiest thing would be to draw up a short list of two, or three inverters and post us links to the specs and the electrical gurus can comment. My Victron, an obsolete model, draws around 0.3A no load too. Some inverters achieve low standby current by effectively disabling the inverter until they sense something trying to draw from it. This can cause problems for some appliances.

 

Jen

Edited December 18, 2018 by Jen-in-Wellies

[Jen-in-Wellies]

4 minutes ago, alan_fincher said:

In my experience the higher the maximum output is the higher will be the standby current.

So I have had cheapie 300w inverters that draw very little in standby, but the same was not true of an 1,800W one. (Both were MSW).

 

Also aren't many configurable as to how easily and/or quickly they will wake up?  One that is configured to come fairly seamlessly out of standby will probably draw a lot more quiescent current than if it is not.

So I suggest there may be no "right answer" to this question without knowing things like maximum power required, (perhaps) whether it is MSW or PSW, and how important it is that it kicks in immediately there is any demand for power.

Good point. Minimise the mains power required to minimise standby current. Mains fridges need around 800 to 1000W for a fraction of a second to start the compressor reliably. Up until recently, my highest power appliance was the vacuum cleaner at 1300W, which was near the limit of my 1600VA Victron. Now I have a battery vac, which recharges at low current over a couple of hours. Battery power tools used mostly now. I have a twin tub washing machine that draws only a few hundred Watts. Many people put in a 3000W inverter without really thinking if it is needed. Automatic washing machines are the biggest current draw when they are heating water. If you can avoid that, then a big inverter isn't needed.

 

[mrsmelly]

3 minutes ago, Jen-in-Wellies said:

Good point. Minimise the mains power required to minimise standby current. Mains fridges need around 800 to 1000W for a fraction of a second to start the compressor reliably. Up until recently, my highest power appliance was the vacuum cleaner at 1300W, which was near the limit of my 1600VA Victron. Now I have a battery vac, which recharges at low current over a couple of hours. Battery power tools used mostly now. I have a twin tub washing machine that draws only a few hundred Watts. Many people put in a 3000W inverter without really thinking if it is needed. Automatic washing machines are the biggest current draw when they are heating water. If you can avoid that, then a big inverter isn't needed.

 

Yes very true. My bro in law had a 3kva Victron fitted which he shouldnt have had, a 2 would have sufficed. In my opinion if its a modern engined new build I would ALWAYS have a Dometic travel power fitted, a brilliant bit of kit that does the heavy work and leaves the verter for the fridge etc when engine not running.

[Boater Sam]

A QUESTION

 

Why is it so important? When you don't need mains power, turn it off.

I suspect you want to run a mains fridge 24-7.

Consider wiring a dedicated inverter just big enough to start the fridge into just the fridge so that the fridge thermostat switches on the inverter only when it needs it. Easily done if the fridge has an ordinary capillary stat, just use it to switch the on/off switch on the inverter. Then there is no standby current at all.

Edited December 18, 2018 by Boater Sam
smellings & Added

[nicknorman]

3 hours ago, Boater Sam said:

A QUESTION

 

Why is it so important? When you don't need mains power, turn it off.

I suspect you want to run a mains fridge 24-7.

Consider wiring a dedicated inverter just big enough to start the fridge into just the fridge so that the fridge thermostat switches on the inverter only when it needs it. Easily done if the fridge has an ordinary capillary stat, just use it to switch the on/off switch on the inverter. Then there is no standby current at all.

If and when you live in a house, do you turn off the master switch when you don't need the power? I suspect not! Why should it be different on a boat? Well it only needs to be different on a boat if the inverter quiescent power drain is significant. On our boat, it isn't and so we leave it on 24/7. I did go through a phase of turning it off when we went to bed but didn't find any significant difference in the morning's SoC readings. So now I just leave it on.

 

From the Mastervolt 12/2500-100 spec sheet, the quiescent power drain is 9w (~0.75A) in normal mode, 8W in economy low voltage mode, and 0.5w (ie 0.04A) in idle mode (where it sends sniffer pulses twice a second and reverts to normal ops if it senses a load). We just leave it in normal mode. So 0.75A for 24hrs is 18AH which, out of 450AH batteries, isn't really significant for the convenience of sockets always working.

4 hours ago, alan_fincher said:

In my experience the higher the maximum output is the higher will be the standby current.

So I have had cheapie 300w inverters that draw very little in standby, but the same was not true of an 1,800W one. (Both were MSW).

 

Also aren't many configurable as to how easily and/or quickly they will wake up?  One that is configured to come fairly seamlessly out of standby will probably draw a lot more quiescent current than if it is not.

So I suggest there may be no "right answer" to this question without knowing things like maximum power required, (perhaps) whether it is MSW or PSW, and how important it is that it kicks in immediately there is any demand for power.

I would say a much bigger factor is the design of the device. Sterling ones seem to use a lot of juice. Mastervolt seem to be very economical, for a similar max output.

[WotEver]

5 hours ago, Alan de Enfield said:

Wasn't it reported in a thread "mysterious battery drain" (or similar title) that after problem-solving was carried out they found that the Quiescent current on their Mastervolt was around 4 amps (100Ah per day)

Yes it was, and I don’t believe a word of it. 

[ditchcrawler]

5 hours ago, Alan de Enfield said:

Wasn't it reported in a thread "mysterious battery drain" (or similar title) that after problem-solving was carried out they found that the Quiescent current on their Mastervolt was around 4 amps (100Ah per day)

 

Although I think Nick Norman has a Mastervolt and gets 'fractions of an amp'

 

Maybe there are different Mastervolt models ?

Mine is fractions as well, I can't actually measure it unless I disconnect and put a meter in series with it and then I a worried what the inrush would be

[Detling]

New ones are much better than older models. The new victron replacement for my 10 year old one uses 0.8A mine uses 2.1A so get the latest.

[Robbo]

13 minutes ago, Detling said:

New ones are much better than older models. The new victron replacement for my 10 year old one uses 0.8A mine uses 2.1A so get the latest.

My 10+year old multiplus (12/2000/120) uses around 0.8amp on stand by.

[Jen-in-Wellies]

5 hours ago, Boater Sam said:

A QUESTION

 

Why is it so important? When you don't need mains power, turn it off.

I suspect you want to run a mains fridge 24-7.

Consider wiring a dedicated inverter just big enough to start the fridge into just the fridge so that the fridge thermostat switches on the inverter only when it needs it. Easily done if the fridge has an ordinary capillary stat, just use it to switch the on/off switch on the inverter. Then there is no standby current at all.

This would give the minimum current drain when using a cheap mains fridge, rather than an expensive 12V one. It does rely on the person installing it knowing how to modify the fridge correctly and safely to wire the thermostat in to the inverter. Not hugely difficult, but does need a bit of electrical knowledge. Also a dedicated inverter plus mains fridge is probably not much different in cost from a 12V one anyway and you lose the advantage of having mains available instantly for other things. Depends on your circumstances and how you want to use your boat.

 

Jen

[Sea Dog]

Both Mastervolt and Victron have modes where the inverter is all but dormant until it senses (for example) the fridge kick in.  Both can cope with high starting current too, so that mitigates for the high initial current draw of items with a motor, so you may not need as a model with as high an output as you first think.  I'd recommend reading the manuals of the models which interest you - they're available online to download. You may find Mastervolt's manuals are usually better than Victron's but I've found that it's the reverse when it comes to technical support. 

[AndrewIC]

3 hours ago, ditchcrawler said:

Mine is fractions as well, I can't actually measure it unless I disconnect and put a meter in series with it and then I a worried what the inrush would be

Put the ammeter across the battery isolator then open the isolator. No inrush. 

[ditchcrawler]

1 hour ago, AndrewIC said:

Put the ammeter across the battery isolator then open the isolator. No inrush. 

Not easy to get to, I could possibly go from positive battery terminal to inverter fuse with long leads and then open the isolator but that would mean the wife holding things over an open battery bank while we did it, not a one man job