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Old 25-09-2018, 19:10   #16
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Energy solutions onboard a live aboard

A decent correctly sized inverter is actually very efficient.
It’s using a big boy to charge a laptop is where they are not.Click image for larger version

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Source of chart in link below
https://www.e-education.psu.edu/eme812/node/738
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Old 26-09-2018, 09:12   #17
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Re: Energy solutions onboard a live aboard

for small items like computers, cell phones, etc. you are best getting 12v charging adapters or replacing things like reading lights with 12v versions.. adaptors tend to be inexpensive and widely available. for larger items you need an inverter and to closely watch the status of your house bank. the problems are the same weather you use 120v AC or 230v.
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Old 26-09-2018, 10:59   #18
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Re: Energy solutions onboard a live aboard

Quote:
Originally Posted by john61ct View Post
No. Inverter is from DC to AC.

DC to DC is a converter.
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Originally Posted by hellosailor View Post
A car adapter for a laptop is indeed an inverter. The marketing folks just try not to use three-syllable words because it confuses and scares the buyers. .....
Correct hellosailor - to make a DC converter that amplifies the DC it has to go via on inverter to get to AC and then converted back to DC at the higher voltage.

From RS components:
'The basic DC-DC converter will take the current and pass it through a "switching element". This turns the signal into a square wave, which is actually AC. The wave then passes through another filter, which turns it back into a DC signal of the appropriate voltage necessary.'.
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Old 26-09-2018, 16:19   #19
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Re: Energy solutions onboard a live aboard

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Originally Posted by john61ct View Post
Many people using inverters are wasting a very large percentage of the total energy consumed.

Yes it can be done relatively efficiently, but doing so is a challenge.

Some people run a mains charger powered by an inverter into large batteries, just silly to me.

Avoiding inverter usage when possible is a sound strategy.

DC to DC conversion is much more efficient.

Inverter/chargers are just two devices combined. 1) an inverter and, 2) a charger. When connected to shore power, it's only a charger. It's just convenient to package the two devices together.

I use my inverter to run my microwave oven, and I switch it off when I'm not using the microwave. Since my power is generated by solar, I'm "cooking with sunshine." Heating a cup of water for tea takes 5 Amp/hours. A can of soup, 10 amp/hours. So I avoid having any of that diabolical propane on board (I don't trust any fuel that's constantly trying to escape from a pressurized cylinder). And I never have to make a trip to the store to buy a tank of sunshine.

As other posters here note, it's very wasteful to power a DC device by first converting power to AC and then back to DC. But if you examine how 12 volt plug-in USB chargers actually work, that's exactly what they are doing on a small scale. They are DC (to AC) to DC converters that use an internal switching regulator. The efficiency of that method is much higher than using an old school series regulator. Example: 1 amp at 5 volts (5 watts) using a series regulator will consume a little more than 12 watts, but only a little more than 5 watts using a switching regulator. The downside: switching regulators are notorious for generating radio frequency interference (RFI). Series regulators don't have that problem. Nearly every power supply you get these days is a "transformerless" switching power supply. View all of them as suspects for generating RFI.
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Old 26-09-2018, 17:15   #20
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Re: Energy solutions onboard a live aboard

I usually separate the charge buss from the loads buss for LFP bank management, can isolate one independently from the other when voltage goes too high or low.

Therefore all charge sources need to be a separate standalone device, and inverters are on the load side only.

One rig we went for a very large Victron combi unit, sweet system especially the PowerAssist feature, but tgat was a lead bank, no BMS required.

In general I prefer to separate the functions, and try to avoid inverters AMAP
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Old 26-09-2018, 17:48   #21
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Re: Energy solutions onboard a live aboard

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If you get an AH counter between your inverter and battery, and compare to a Killawatt reading on the other side,

you will find the actual inefficiency losses to be much greater IRL than the best-case "optimistic" specs claimed by the vendors.

If you have plenty of surplus power of course who cares, but for a mostly-solar setup often every AH counts.

Like most things not all inverters are equal, good one's ( not necessarily expensive ones) do meet the efficiency claimed but poor ones may not. I have a sterling power 1500 and the efficiency loss is so low I cant measure it on a meter with .1a resolution. I recon about 2a/hr per day If I leave it on 24x7. Inverters are far more efficient at running low continuous loads than a gen-set giving a fraction of its output. I do agree that it is useful to have a small unit to run things like a laptop and phone if they are usually plugged in and I have one that just has a 4way running directly off it that sits on the chart table. It is largly because the main inverter is 240v and now being in canada I need some small 120v stuff.
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Old 26-09-2018, 17:55   #22
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Re: Energy solutions onboard a live aboard

Your 1500 W inverter, just being on, it pulling about an amp.
Leave it on 24/7 and that is of course a little over 20 AH.
My 2800 W inverter pulls 20 W just being on, I used to leave it on 24/7 and then figured out just how much power aid was wasting, just turning the inverter off when I wasn’t using it and buying a baby inverter to run low power things, saved me about 10% of my total power usage.
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Old 26-09-2018, 23:55   #23
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Re: Energy solutions onboard a live aboard

Unless a 12 volt TV has an inverter built in that I don't know about, that for me is the answer when I want to use a television for either free to air or DVDs. I haven't measured the power drain, but the cost is very reasonable for the ones designed for use in RVs.
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Old 29-09-2018, 18:42   #24
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Re: Energy solutions onboard a live aboard

Inverters convert d/c power to A/c power, converters convert a/c power to d/c power, sounds like you need a converter if you want to go from a/c to d/c
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Old 29-09-2018, 18:49   #25
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Re: Energy solutions onboard a live aboard

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Unless a 12 volt TV has an inverter built in that I don't know about, that for me is the answer when I want to use a television for either free to air or DVDs. I haven't measured the power drain, but the cost is very reasonable for the ones designed for use in RVs.
they even make a 32 inch tv that is 12v dc if you really have to have a tv .
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Old 29-09-2018, 22:16   #26
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Re: Energy solutions onboard a live aboard

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you can use an inverter but they are incredibly inefficient and use up your house bank faster. ok for occasional things but not efficient to use as a frequent thing
What is "incredibly inefficient" in your book? Our Victron is 94% efficient in converting 24v DC to 230v AC, and runs 24/7 when we're off shore power. This is not an unusual use pattern.

Overhead is 10 watts.
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Old 29-09-2018, 22:19   #27
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Re: Energy solutions onboard a live aboard

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DC to DC conversion is much more efficient.
If you look at actual numbers, I think you'll find there's not all that much difference, in single digit percent.
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Old 30-09-2018, 09:34   #28
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Re: Energy solutions onboard a live aboard

Does that 94% hold measuring yourself IRL?

If so, at what % of max capacity?
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Old 30-09-2018, 09:42   #29
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Re: Energy solutions onboard a live aboard

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Does that 94% hold measuring yourself IRL?

If so, at what % of max capacity?

I don't know, but Victron specs are pretty reliable. A highly reputable company.


The overhead is 10 watts, so you should be able to calculate the real efficiency at partial loads by taking that into consideration.


So at 50% capacity, say 1.25kW, you would expect something like 6.4% loss, at 25% capacity about 7.2% loss, and so forth.


In real life, it's not a big deal. I would be very inefficient to use the inverter for loads of 100 watts, say, but once you have a few laptops and phones charging, it already doesn't make such a big difference whether you do it via the inverter or with direct DC-DC converters. I have a DC-DC charger for my own laptop, and ship's computer and monitor work off DC power. I have a DC powered USB charger. But I decided not to install multiple DC powered USB chargers because I understood that there's nothing to be gained if multiple devices are being charged at the same time. I just leave the inverter on.
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Old 30-09-2018, 11:00   #30
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Re: Energy solutions onboard a live aboard

How big is it? I doubt the overhead is ten watts, but maybe since it’s a 24V inverter?
I say that cause if you look at quality inverters, 10 Watts for each 1.5 KW seems to be a standard, but I’ve only looked at 12 V inverters
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