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 > Converter Left On Powered by Inverter--Measurements

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BFL13

Victoria, BC

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Posted: 02/10/13 02:24pm Link  |  Print  |  Notify Moderator

I often forget to turn off the converter when starting off on inverter. The Trimetric tells me -45 amps or somesuch, which is a CLUE [emoticon] and also the converter's fan comes on , so I say, "What's that noise?" Another CLUE! So eventually I turn it off. But what does that cost in battery meanwhile? I ran a test.

On battery bank at 50% (thirsty iaw) on shore power, turn on 7355 converter- Trimetric says: + 42.2 amps tapering--normal

Shut that all off, plug shore cable into inverter (1000w PSW)
Turn on converter- Trimetric says: - 43.2 amps rising slowly per "inverter creep"

So I am wondering why I don't see net amps on the Trimetric--or is that what I am seeing?

Inverter watts readout says: 1003 watts. So that should mean a 100 amp battery draw using the divide by 10 rule.

Ok so Tri says -44a instead Of -100 so maybe the converter is at its 55amps approx so the Trimetric is showing net amps after all.

Means as long as that converter is running on inverter, the battery bank is losing a bunch of AH as in this case 44 in an hour.


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pianotuna

Regina, SK, Canada

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Posted: 02/10/13 02:51pm Link  |  Print  |  Notify Moderator

Hi BFL13,

Yes the trimetric is showing net amps.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

Canadian Rainbirds

Vancouver Island (Winter: Mainland Mexico)

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Posted: 02/10/13 03:59pm Link  |  Print  |  Notify Moderator

That's why I run the Xantrex Prosine 2 inverter/charger! [emoticon] Almost Fool Proof. Though as my father often said, Fool Proof doesn't mean Damn Fool Proof! [emoticon] As I have demonstrated once or twice. [emoticon]

time2roll

Southern California

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Posted: 02/10/13 04:13pm Link  |  Print  |  Notify Moderator

Or use a transfer switch to avoid powering the items that should stay off the inverter.


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pianotuna

Regina, SK, Canada

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Posted: 02/10/13 04:53pm Link  |  Print  |  Notify Moderator

Hi BFL13,

My default setting for my converter is unplugged. That saves me from remembering to disconnect it.

BFL13

Victoria, BC

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Posted: 02/10/13 05:07pm Link  |  Print  |  Notify Moderator

PT, the 7355 is hard-wired. I did rig a house type light switch for turning the converter on/off, so I can see if it is up or down. But you have to remember to look at it!

I have it on when battery charging and batts disconnected, then I have to turn it off when that's done and I go back to normal off- grid on inverter. Too many procedures for my tiny mind. Somehow we manage to go camping and get back alive anyway. [emoticon]

I suppose it is a fluke that the 1000w inverter I plug into actually runs the 7355 converter at 55amps/13.8v at 1003w. If you had a smaller inverter and higher VA converter and a bigger battery bank at low SOC, I guess the numbers would be different or the inverter would alarm, no idea.

HiTech

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Posted: 02/10/13 09:05pm Link  |  Print  |  Notify Moderator

Interesting. What is the efficiency of the inverter? How about of the converter? A net 40% or so loss of power seems high.

Jim

pianotuna

Regina, SK, Canada

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Posted: 02/10/13 09:11pm Link  |  Print  |  Notify Moderator

Hi Jim,

Power factor of 0.7 on the converter, if it is the same as mine. Not sure about efficiency of the inverter--but probably running flat out 88%.

I have two "tell tales" that I've left something on that should not be on. The inverter resides behind the driver's seat--so can hear the fan on it.

I have a Hall Effect Ammeter that measures current flowing to and from the alternator to the house battery banks. It measures up to + or - 70 DC amps. If it starts flashing zero it means I'm drawing more than 70 amps, letting me know I've been a "bad boy". I only have a 40 amp PD converter with wizard so it would not max out the Hall Effect necessarily.

BFL13

Victoria, BC

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Posted: 02/10/13 09:32pm Link  |  Print  |  Notify Moderator

Not sure where that 40% comes from. Anyway the converter is probably about 80% efficient like most of them, with maybe a 0.7 PF or a bit less, not measured.

The inverter spec 85% efficient, but at full draw like that it is not at peak efficiency on its curve (don't have the curve, but AFAIK peak would be around 70% of the watt range?)

I don't know what voltage to use--the rated 13.8 of the converter or the actual battery voltage the inverter was seeing under load--11.6v--to go with that 1003watts it showed on its read-out. or what.

If draw should have been about 100a, then the 44 means the converter was at 56a which makes sense. I have had it doing that when used on a battery bank that had an inverter drawing 90 amps running a kettle. So let's say 56 amps at 13.8v = 773w with 0.7 PF is 1104VA so that is too high.

56a and 12v is 672w and 0.7 makes that 960 VA. just under the 1003w. So you can pick 12.x volts to get that 1003w to come out right [emoticon]

Not a clue how to do this stuff. Not sure what would mean if the numbers all did fit together.

HiTech

Texas

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Posted: 02/11/13 05:36am Link  |  Print  |  Notify Moderator

I may be doing it wrong, but i believe power factor does not affect efficiency, except that it draws more current than it would at a power factor of 1, and the higher momentary draw creates a little more loss in the wiring than it would at a power factor of 1. PF<1 does not remove power from the system, it just phase shifts it.

My thinking is that out of 100amps, if the net is 44 out, that is 44% loss. So 56 amps in to charge the battery from the converter, out of 100 being pulled to run the inverter which powers the inverter. Ball park that's not too far off for a little under 80% efficient on the inverter making the AC, and then a little under 80% of that charging the battery from the AC.

Where to measure the voltage is interesting in this case since there are two power sources - the battery and the converter output.

Jim

* This post was edited 02/11/13 05:56am by HiTech *

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