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Old 10-07-2020, 12:24 PM   #1
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Victron smart charger/inverter - borrowing power

So with my Victron, the refit guy said (and I easily could have misunderstood) is that when on shore power if I need more watts than 2000 (my inverters limit) it can take those excess watts from my battery bank. So if I am running something at 2500 watts, 500 watts in excess of 2000 watts, the unit will go to the battery bank for the remaining 500 watts.

Is this the correct understanding?

He also said to do this only for a few minutes. Is this because he is worried the battery bank will drain excessively (6 fireflies) or is there some kind of heat concern?
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Old 10-07-2020, 12:33 PM   #2
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Yes, either you or your electrician are mistaken and may not understand what an inverter does. It takes all of its power from the batteries whether it is supplying 1 watt or 2,000 watts. If it supplies 2,500 watts for long (maybe 5-10 seconds sometimes a minute) it will trip off. The latter may be what he was saying and you misunderstood him.

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Old 10-07-2020, 12:35 PM   #3
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DavidM, I understood if you are on shore power, the inverter senses that and simply passes AC power through without taking it from the battery. Is that not the case?
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Old 10-07-2020, 02:24 PM   #4
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DavidM, I understood if you are on shore power, the inverter senses that and simply passes AC power through without taking it from the battery. Is that not the case?
Yes, if your inverter has an internal transfer switch.

If the OP were saying that the inverter was operating on shore power at 2,000 watts, its rated output, and you went to 2,500 watts, the difference would be supplied from the batteries, that also would be wrong.

In that case I think that shore power would be transferred through the inverter at 2,500 watts or maybe as much as 3,600 watts when the shore power breaker (30A) would likely trip.

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Old 10-07-2020, 02:41 PM   #5
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This has been discussed here recently. The inverter monitors shore power usage, and kicks in to supplement the power when a specified current is exceeded. So if you're on a 30 amp shore power the inverter allows your total AC draw to exceed 30 amps by drawing down the 12v supply.

See https://www.victronenergy.com/blog/2...urrent-limits/
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Old 10-07-2020, 03:05 PM   #6
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I stand corrected. I didn't catch the "smart" in the Victron thread title. Also I didn't realize that the shore power current limit was adjustable on the inverter, presumably down to 2000/120 amp level as the OP's question stated. I just assumed that shore power current would be supplied up to its circuit breaker limit through the transfer switch.

That feature which is only on more expensive inverter/chargers is probably used more often to boost generator supplied power with inverter supplied power syncing to it particularly when starting an A/C or similar and only for a few seconds.

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Old 10-07-2020, 04:26 PM   #7
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So I did go to the link but nothing is really mentioned about it should only be for a short period.

So back to my 2000 watt available, using 2500 watts, which is roughly 5 amps over. So my available usable power with my fireflies is 560 amps which allow the 2500 watts for almost 5 days before I went past the 20 % depletion of the battery bank. So why can't I do that, though I doubt I ever would, but what bad thing happens?
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Old 10-07-2020, 04:54 PM   #8
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QUOTE]
From the link the power assist is supplementing your shore power or generator. If you have 2000 watts of shore power (approximately 16 amps at 120 volts) and your demand is 2500 watts (approximately 21 amps at 120) then your smart inverter will take power from your batteries to give you 2500 watts rather than trip the 16 amp shore power breaker so your inverter is not outputting 2500 watts it is outputting 500 watts. If you have a standard 30 amp shore power at 120 volts you have 3600 watts available so the inverter supplies nothing for the 2500 watt load, but if you have a 4100 watt load then the inverter puts out 500 watts from your batteries to prevent blowing the 30 amp breaker. I havenít researched the Victron inverter but I believe like others it can probably exceed itís rated capacity for short periods to facilitate a starting load etc. youíd have to peruse your unitís specifications for how much and how long.
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Old 10-07-2020, 06:35 PM   #9
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So I did go to the link but nothing is really mentioned about it should only be for a short period.

So back to my 2000 watt available, using 2500 watts, which is roughly 5 amps over. So my available usable power with my fireflies is 560 amps which allow the 2500 watts for almost 5 days before I went past the 20 % depletion of the battery bank. So why can't I do that, though I doubt I ever would, but what bad thing happens?
I think you misunderstand. At 2000w output your inverter will draw something like 175 amps at 12v, so you can exhaust your batteries in under 4 hours. Watts = amps*volts

The 2000 watts has nothing to do with your shore power capacity, but can be configured to supplement it on demand. So you could have 3,600 watts available from shore power plus up to 2,000 from the inverter. But not for long.
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Old 10-07-2020, 08:28 PM   #10
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Originally Posted by rsn48 View Post
So with my Victron, the refit guy said (and I easily could have misunderstood) is that when on shore power if I need more watts than 2000 (my inverters limit) it can take those excess watts from my battery bank. So if I am running something at 2500 watts, 500 watts in excess of 2000 watts, the unit will go to the battery bank for the remaining 500 watts.

Is this the correct understanding?

He also said to do this only for a few minutes. Is this because he is worried the battery bank will drain excessively (6 fireflies) or is there some kind of heat concern?
Yes that is correct. Your inverter will draw from the batteries when needed to support the loads in excess of your shore power setting.
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Old 10-13-2020, 12:52 PM   #11
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Originally Posted by rsn48 View Post
So I did go to the link but nothing is really mentioned about it should only be for a short period.

So back to my 2000 watt available, using 2500 watts, which is roughly 5 amps over. So my available usable power with my fireflies is 560 amps which allow the 2500 watts for almost 5 days before I went past the 20 % depletion of the battery bank. So why can't I do that, though I doubt I ever would, but what bad thing happens?
Your math is off. To supplement 500 watts from the battery bank would be 42 amps (12 volts). You would take around 8 hours to draw 80% from the battery.

If you were not connected to shore power and the inverter was drawing the full 2500 watts from the battery bank you'd be drawing 208+ amps from the batteries (probably 10% more due to inefficiency in the inverter) and deplete the bank in less than 2 hours, probably closer to an hour (you won't get the full 560 amp capacity at that load).

P=EI (Power Watts) = E(Voltage) * (I Current)
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Old 10-13-2020, 06:34 PM   #12
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Your math is off. To supplement 500 watts from the battery bank would be 42 amps (12 volts). You would take around 8 hours to draw 80% from the battery.

I realized that after I posted my response. Thanks.
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Old 10-13-2020, 07:58 PM   #13
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Ok a question that I haven't found the answer to on these hybrid inverters.


If the AC source is where the neutral ground connection is made, in this case I will assume that his 2000 watt inverter is a pass through from the shore power and it is limited to 18amps around 2kw... when the demand for power increases and the inverter is now supplementing the pass through power. It becomes a power source.... What happens with neutral ground connection? does the inverter provide or does it continue to be provided by the shore power connection? or do they both provide it?
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Old 10-13-2020, 10:42 PM   #14
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Ok a question that I haven't found the answer to on these hybrid inverters.


If the AC source is where the neutral ground connection is made, in this case I will assume that his 2000 watt inverter is a pass through from the shore power and it is limited to 18amps around 2kw... when the demand for power increases and the inverter is now supplementing the pass through power. It becomes a power source.... What happens with neutral ground connection? does the inverter provide or does it continue to be provided by the shore power connection? or do they both provide it?
Excellent question! I have a hybrid in my motorhome. (Never use it) Same would apply there.
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Old 10-14-2020, 05:12 AM   #15
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I believe the bonding would remain with the shore power. Bonding in an inverter is typically part of the transfer relay, and that would remain in the "transfer" position, i.e. no bonding, even if the inverter is assisting.
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Old 10-14-2020, 10:07 AM   #16
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Ok a question that I haven't found the answer to on these hybrid inverters.


If the AC source is where the neutral ground connection is made, in this case I will assume that his 2000 watt inverter is a pass through from the shore power and it is limited to 18amps around 2kw... when the demand for power increases and the inverter is now supplementing the pass through power. It becomes a power source.... What happens with neutral ground connection? does the inverter provide or does it continue to be provided by the shore power connection? or do they both provide it?
Keep in mind Neutral and Ground are two different terms. Neutral being the return path for the electrical flow, and Ground being the safety reference line which should not be carrying any current. The Neutral on the inverter would have to return as much current as it is providing, eventually completing the circuit flow back to the batteries through it's complex electronics, and the Ground should continue to have no current flow (assuming no leakage exists anywhere).
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Old 10-14-2020, 03:37 PM   #17
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I believe the bonding would remain with the shore power. Bonding in an inverter is typically part of the transfer relay, and that would remain in the "transfer" position, i.e. no bonding, even if the inverter is assisting.

If the inverter remains in the pass through position, how does the power sourced by the inverter enter the circuit? I thought that the transfer relay needed to energized for the inverter become the source of AC.... The only thing I can think of that would allow this is a separate ground neutral relay that wouldn't energize in the assist mode....Maybe its best to think of this more inline with a typical grid tied solar system on a house.
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Old 10-14-2020, 05:09 PM   #18
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If the inverter remains in the pass through position, how does the power sourced by the inverter enter the circuit? I thought that the transfer relay needed to energized for the inverter become the source of AC.... The only thing I can think of that would allow this is a separate ground neutral relay that wouldn't energize in the assist mode....Maybe its best to think of this more inline with a typical grid tied solar system on a house.

For an inverter/charger, the inverter circuitry is always connected to the output. It's just a question of whether it's sourcing or sinking current. Older devices that don't have a power assist feature were but bi-modal. They were either sourcing current in inverter mode, or sinking current in charger mode. Most were/are smart enough to adjust how much they sink in charger mode to avoid overloading the power source.


Then someone got smarter and realized you can really infinitely vary the source/sink, and actually source current in parallel with the incoming power source. Clever buggers, eh?
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Old 10-19-2020, 01:54 PM   #19
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I really like the Power matching feature of the Victron Mulitplus inverter chargers. I used it often when connected to a 120 volt 15 amp shore power source which was insufficient to cope with the A/C inrush compressor startup. We lived on the boat at a friends dock in the heat of a Chesapeake 90 degree August using this power assist to have one A/C unit running, cooking, coffee machine, as well as the phone and computer chargers, Sat. TV, lights and fans. Note we did also practice power management to avoid too many simultaneous power demands. After two months we left the dock with full batteries. After the excess demand(momentary startup inrush current) is over the unit seamlessly transitions to charging with whatever is left in the power supplied. Note that we did add extra shading with insulation to the salon extensive windows and hatches to greatly reduce solar gain. We were very comfortable without ever running the gen set.
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Old 10-19-2020, 02:02 PM   #20
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From the link the power assist is supplementing your shore power or generator. If you have 2000 watts of shore power (approximately 16 amps at 120 volts) and your demand is 2500 watts (approximately 21 amps at 120) then your smart inverter will take power from your batteries to give you 2500 watts rather than trip the 16 amp shore power breaker so your inverter is not outputting 2500 watts it is outputting 500 watts. If you have a standard 30 amp shore power at 120 volts you have 3600 watts available so the inverter supplies nothing for the 2500 watt load, but if you have a 4100 watt load then the inverter puts out 500 watts from your batteries to prevent blowing the 30 amp breaker. I havenít researched the Victron inverter but I believe like others it can probably exceed itís rated capacity for short periods to facilitate a starting load etc. youíd have to peruse your unitís specifications for how much and how long.

The 2000 Victron multi has a peak power of 4000 watts
the 12/3000 Victorn multi had a peak power of 6,000 watts !
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