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Old 13-02-2013, 13:10   #16
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Re: Battery Charger Efficiency

I can't speak to the Victron in particular, but from the other inverter/chargers that I've used, the designers paid a lot of attention to the inverter efficiency, and pretty much punted on the charger efficiency. 80-85% is what I've seen. Let us know what you end up measuring, and maybe send the figures to Victron so they can publish them
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Old 13-02-2013, 14:31   #17
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In an inverter-charger, the charger efficiency equals the inverter effciency. The same components are used in reverse.


The Victron is the real deal with 94%, while things like Xantrex are at the bottom of the pit with 80-85% or so.
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Old 13-02-2013, 16:21   #18
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Originally Posted by s/v Jedi View Post
In an inverter-charger, the charger efficiency equals the inverter effciency. The same components are used in reverse.

The Victron is the real deal with 94%, while things like Xantrex are at the bottom of the pit with 80-85% or so.
94% efficiency, esp in a pure sine wave inverter is quite impressive. I would guess that falls at lower outputs somewhat, but I want one!

Chip
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Old 13-02-2013, 16:33   #19
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Originally Posted by SoonerSailor View Post

94% efficiency, esp in a pure sine wave inverter is quite impressive. I would guess that falls at lower outputs somewhat, but I want one!

Chip
Victron is good and the price confirms that unfortunately. Still, I think it's good value for money.
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Old 13-02-2013, 16:37   #20
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Re: Battery Charger Efficiency

Temperature can also be a factor in warmer climates.

The following is a coment about a Mastervolt combri, a similar inverter/charger.

Quote : "Anyone installing Lithium batteries may be expecting their 100 amp charger to provide a constant 100amps of charge .... In my case 200 amos of charge. But its not as simple as that.
On my Mastervolt Combi's the 200 amp charge dropped down to 65 amps today and on checking the chargers I found them to be at 50C so the massive drop was due to temperature compensation pure and simple.

At 30C I get a charge out of about 130 amps - that would be OK so I am now looking at changing the layout of the inverters away from the transformer that is generating all the heat. A combination of insulation from the transformer and better ventilation should do the trick.

At 20 C I should get most of the charge - probably about 160 amps.

I mention this to point out that whilst the batteries may be able to take up to 800 amps of charge the chargers themselves in the hot climate will probably put out nowhere near the rated charge. In the case of mastervolt their maximum capacity is at 10C which is pretty cold. AT 10c that gives 14.5 volts whereas I need 14.2 volts so lose some of the 100 amps before I begin.

On the other hand the batteries have no issue putting out 300amps - so we never have to think what we put on underway - a high load for a short time has little effect on the charge level of the batteries. "
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Old 13-02-2013, 16:52   #21
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Re: Battery Charger Efficiency

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Originally Posted by SoonerSailor View Post
94% efficiency, esp in a pure sine wave inverter is quite impressive. I would guess that falls at lower outputs somewhat, but I want one!

Chip
The efficiencies that are quoted in manufacturers specs are their maximum rates. As the state of charge increases, charge rate declines. Chargers have transformers that draw current even at no load. See magnetic hysteresis here: https://en.wikipedia.org/wiki/Hysteresis

This means that as the charge rate approaches zero, the efficiency also approaches zero. The message is that battery charging is not highly efficient.
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Old 13-02-2013, 17:00   #22
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Quote:
Originally Posted by St. Elsewhere

The efficiencies that are quoted in manufacturers specs are their maximum rates. As the state of charge increases, charge rate declines. Chargers have transformers that draw current even at no load. See magnetic hysteresis here: https://en.wikipedia.org/wiki/Hysteresis

This means that as the charge rate approaches zero, the efficiency also approaches zero. The message is that battery charging is not highly efficient.
Switch mode power supplies tend to change switching patterns as they approach idle current. The quiescent load of the switcher can be quite low often well below the supervisory circuits.


Retail price in electronics is not a great indication of quality.
Dave
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Old 13-02-2013, 20:28   #23
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The good units have a torroidal transformer which is more efficient. When output approaches 0 the efficiency becomes 0 but then the unit is still only consuming near zero amps, so this is nothing to worry about.
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Old 13-02-2013, 23:55   #24
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Re: Battery Charger Efficiency

I'm not sure the multiplus uses a switch mode transformer. It's a massive, heavy bugger (18 kilos) and I think there are some big toroidal magnets in there.
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Old 14-02-2013, 00:50   #25
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Re: Battery Charger Efficiency

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Originally Posted by downunder View Post
At 30C I get a charge out of about 130 amps - that would be OK so I am now looking at changing the layout of the inverters away from the transformer that is generating all the heat. A combination of insulation from the transformer and better ventilation should do the trick.
"
Some fan forced cooling works wonders for problems like this.

Get one, or two of the larger 12v computer fans and mount it/them close, or actually on the heat sinks. Often they can be just be cable tied in place at least to try out the idea.
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Old 14-02-2013, 01:02   #26
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Re: Battery Charger Efficiency

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The good units have a torroidal transformer which is more efficient. When output approaches 0 the efficiency becomes 0 but then the unit is still only consuming near zero amps, so this is nothing to worry about.
What does VICTRON say.

victronenergy.com says

A perfect transformer is 100% eff. in the real world the closest we get is less than 100%. So how can any transformer product really reach 94%, if you factor in all the other losses. Marketing

I agree a torrid is as close to the perfect transformer, but that depends, under some conditions an E-Core is the better choice.

I just had a custom built 3-phase toroidal/rectifier built (7 Kva). Price to build to a 20 degree temp, was just over $1,400.00. The final is built to a 40 degree temp, which added another $1,300.00 dollars to the end price.

Efficiency over the run period with a design build of 40 was well over the efficiency of a 20 doing the same job The 20 design wasn't in the ballpark.

Lloyd
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Old 14-02-2013, 06:29   #27
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What does VICTRON say.

victronenergy.com says

A perfect transformer is 100% eff. in the real world the closest we get is less than 100%. So how can any transformer product really reach 94%, if you factor in all the other losses. Marketing
Let me think about that.... may be because 94 is less than 100?
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Old 14-02-2013, 15:18   #28
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I was about to design one thats 100% efficient ..... but then I thought..... why not go the extra and design one thats 106% efficient............ to make up for all the years of using my Victron that is only 94% efficient.
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Old 14-02-2013, 17:59   #29
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I was about to design one thats 100% efficient ..... but then I thought..... why not go the extra and design one thats 106% efficient............ to make up for all the years of using my Victron that is only 94% efficient.
I'd put that idea up on kickstarter if I was you.

Dave
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Old 14-02-2013, 18:22   #30
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Re: Battery Charger Efficiency

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I was about to design one thats 100% efficient ..... but then I thought..... why not go the extra and design one thats 106% efficient............ to make up for all the years of using my Victron that is only 94% efficient.

The Victron is 94% efficient at one slice in time, now if we look at the PDF from Victron at 40C its rated output drops by 20% so how does that effect efficiency...because I'll guarantee it's not still operating at 94%.

What really counts is the end to end efficiency so if we are charging a large battery bank back up from 50% SOC, a unit designed to run 94% eff at 20C will exceed that by at least another 20C.

In the 60's industry standard was design to a 60C, then by the 80's it was 40C. Now we have some at 20C designs claiming 94%, and some designs at 40C only claiming 80-85%.

I'll just bet that 40C design has a better end to end efficiency then the 20C. especially if we are talking 2500-3000 what loads for extended periods

Lloyd
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