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Topic: Small Inverter Efficiency (Read 539 times) previous topic - next topic

Small Inverter Efficiency

I am far from an expert on inverters and their efficiency. However, to add to the mix I will offer what we have on our coach. These were installed by the previous owners (along with a solar system) who enjoyed dry camping. We haven't changed the system and do relatively little dty camping, but have been pleased with the system they had installed. I'll leave it to others to review the manufacturers' documentation and determine whether or not the mix of small and large inverters is a good solution.

Our large inverter is a Magnum,
2800W 12VDC Pure Sine Inverter Charger MS Series | Magnum Dimensions
while the one we use for our TVs and other small loads is a Morningstar SureSine 300,
SureSine - Morningstar Corporation

David and Carolyn Osborn
1995 U320C SE 40' Build 4726 Feb 1995
FMCA 147762
Motorcade 17186

Re: Small Inverter Efficiency

Reply #1 –
Four separate issues when evaluating an inverter or inverter/charger:

Is is sufficiently large (in watts) to handle the loads, including starting loads of what you will be running on it?

What is its draw in amps or watts (remember amps times volts= watts so either amp or watt draw can be converted to the other for comparison) in standby-mode (i.e. when no 120 VAC items are being run)? For most residential refrigerator- an important consideration, as close to 50% of the time the refrigerator will not be running.

What is its efficiency when running the loads you will be running (i.e. load once started, not the momentary load when starting)?

Cost?
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Small Inverter Efficiency

Reply #2 –
Your magnum is  90% or over efficiency  at 300 to 700 watts.  The smaller one is 90% at 100 watts.  85% at 300 watts.

One amp less draw at 300 watt output to use the Magnum. Seems to be  24 amp hours per day? 

Minus the power loss from the extra cabling.

Both  have a  chart showing their efficiency. 

A Victron at low power levels maybe even more efficient as it has a smaller transformer than the Magnum
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Small Inverter Efficiency

Reply #3 –
Some put small inverter close to batteries, in my case under bed , and use the standard fwd 110 electrical wiring and outlets to run electronics. So no loss from cabling. The SureSine mentioned above only seems to use about 5 watts when on with no load. So perfect for leaving on all the time to maintain all the memory in your electronics.
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.

Re: Small Inverter Efficiency

Reply #4 –
Quote from: Caflashbob –
Minus the power loss from the extra cabling.

There is no "power loss from the extra cabling." The small inverter is mounted as close to the batteries as is the large inverter, and there is large cabling to the small inverter.


David and Carolyn Osborn
1995 U320C SE 40' Build 4726 Feb 1995
FMCA 147762
Motorcade 17186

Re: Small Inverter Efficiency

Reply #5 –
cabling aside.  As Brett said the inverter needs to match the load at its max efficiency point.

The 500-1000 watt loads the Victron may well save at least an amp per hour. 

At higher loads and internal  temps it's limitations would be the possible derating that could occur under heavy loads most here would rarely do.

Learned a lot on this.

If the max efficiency was paramount the special construction of the Victron would save a lot of battery power meaning less gen run time. 

Need a chart to verify the actual efficiency at the intended load

"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: Small Inverter Efficiency

Reply #6 –
I have been full timing off the grid for 15 years. The only inverter I had for 10 years in my 1981 Foretravel was a 400 watt modified sine wave inverter. I've been in this 1993 Foretravel for 5 years and use a 750 watt Schumacher that costs $45. I have an identical spare on board in case I ever need it. I have no idea how efficient these small inverters are but they do what I need to do and I have plenty of battery left at the end of the day even in the short days of winter.
I use the generator if I want to use the microwave, pizza oven or AC.
1993 U225 Build #: 4285
500 Watts Solar
Honda CRV AWD
Former 1981 Foretravel Travco
Retired, Full Time Off Grid Snowbird

Re: Small Inverter Efficiency

Reply #7 –
Quote from: Caflashbob –
As Brett said the inverter needs to match the load at its max efficiency point.

Need a chart to verify the actual efficiency at the intended load


I think a significant part of the overall efficiency in the real world would include the power consumption when inverting with no load. According to the manufacturers' data my large inverter consumes 30 Watts when inverting with no load, while my smaller inverter consumes about 6 Watts. That appears to me, at least, to be a rather significant difference--particularly if it's powering a load that's not on continuously. 
David and Carolyn Osborn
1995 U320C SE 40' Build 4726 Feb 1995
FMCA 147762
Motorcade 17186

Re: Small Inverter Efficiency

Reply #8 –
Had it in another post but if your Magnum has the BMK monitor you can look at the amps it;s using and know exactly,if you don't
have the BMK would sure get it,easy to install.
96 U270 BUILD 4810
85 380SL
Drummonds TN.