MPP LV6548 offgrid Wiring Question

derekja

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Mar 5, 2021
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6
Thanks for the great LV6548 AC discussion in the recent MPP LV6548 AC Wiring Question thread. I wanted to start a new one with a different scenario.

I am completely off-grid. I was going to use a pair of LV6548 units for split phase, but I have managed to remove my need for 240V (through gas appliances and a 120V slow well pump into a cistern.)

This is in a house I just had moved to my property, so there is an existing panel that is expecting split phase power. I will be having this inspected, so Canadian Electrical Code 2018 applies.

questions:

My Whisperwatt 7000 generator has two 25A outputs, one at 120V and one 120/240

When the sun is shining and the batteries good, I want to run off inverter. When it gets low I want to run off the generator.

Off mains power, the LV6548 wants a 60A feed to service both battery charging and load. My generator can’t supply that. Is there a way of using my two 25A circuits to supply that?

I do have a less efficient generator with two 30A circuits, but my actual load is low enough that I would prefer to design around the whisperwatt if possible.

Any thoughts? I will put together a diagram of my planned system.

Thanks!
 

FilterGuy

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Nov 26, 2019
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Location
Los Gatos CA
1) I found this in the manual:
1633376226010.png
That tells me they expect pulling power from multiple receptacles.

Technically, I would think that if you used the same 'hot' phase from the generator you could tie them together to get the 50A. However, I am not sure that would pass inspection.

2) The manual says to tie to a ground rod. Do not use a separate ground rod from the grounding system of your house.
 

derekja

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Joined
Mar 5, 2021
Messages
6
1) I found this in the manual:
View attachment 67481
That tells me they expect pulling power from multiple receptacles.

Technically, I would think that if you used the same 'hot' phase from the generator you could tie them together to get the 50A. However, I am not sure that would pass inspection.

2) The manual says to tie to a ground rod. Do not use a separate ground rod from the grounding system of your house.

Thanks, that helps. There are some LV6548 settings that allow one to set a max utility charging rate, I’m wondering whether that would allow me to essentially de-rate it in software.

Another option might be to not use the LV6548 as a charger, to just initiate charging from it’s dry contact when the batteries get low and use a 48V charger more suited to my generator’s 6kW limit.
 

FilterGuy

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Messages
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Thanks, that helps. There are some LV6548 settings that allow one to set a max utility charging rate, I’m wondering whether that would allow me to essentially de-rate it in software.
Yes..... that is probably a good idea. In fact, if you have a lot of solar charging as well you may need to limit it to keep from charging the batteries too fast.

Another option might be to not use the LV6548 as a charger, to just initiate charging from it’s dry contact when the batteries get low and use a 48V charger more suited to my generator’s 6kW limit.
That is an option, but I have to believe you could make the LV6548 work for you.
 

Samsonite801

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Oct 15, 2020
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I will start following your thread here derekja, as I will be having basically a pretty similar setup like you with my 6548's. I am building an off-grid property and would like to sometimes use a 6.5kW Onan 1800 rpm generator to charge with, and other times may use my Prius hybrid converted APC 5kW inverter to charge off of the car if ever needed, I don't think either of them put out quite what MPP Solar says they require for a generator input.

In the meantime, I did buy an AIMS 48v charger just for some bench charging on my 48v packs and testing around with. I still haven't wired up anything on the property yet, hopefully I get a chance to play with it soon.

There is another thread on here where one of our members was posting about finding a charger that has a very high efficiency, I don't remember which thread right off the top of head, maybe I can search a bit for it.

At any rate, post back with your findings and discoveries for sure. THANKS ✌️
 

Samsonite801

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Yeah it wasn't hard to find, it was this thread:

 

derekja

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Joined
Mar 5, 2021
Messages
6
My solution hurts the efficiency a little, but I got a 2:1 7kva transformer so that I can pull the full 50 amps out of the generator rather than just 25 amps on each phase. Then I am going to turn down the charge rate a bit from the max 90 amps so that I can fit on 50 amps rather than 60.
 

schmism

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the full 50 amps out of the generator rather than just 25 amps on each phase.
It really doesn't matter. fuel burn rate is proportional to load. ie you burn twice the fuel at 50 amps as you do at 25. So overall you still end up useing the same amount of fuel.
 

740GLE

Solar Addict
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Apr 30, 2021
Messages
1,144
Are you using the generator for charging the battery at 50a? or just suppling house load under 50a?

50a at 120v, that’s close to 100% rated capacity of the generator, many economy gen sets don’t like to be run that hard for constant loads and is tough on the unit.

I’d invest in more panels that you seasonally cycle to capture more power during winters to be less reliant on loading up the generator except for 5-7 days of heavy overcast or something.
 

Sanwizard

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Joined
Feb 2, 2021
Messages
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Thanks for the great LV6548 AC discussion in the recent MPP LV6548 AC Wiring Question thread. I wanted to start a new one with a different scenario.

I am completely off-grid. I was going to use a pair of LV6548 units for split phase, but I have managed to remove my need for 240V (through gas appliances and a 120V slow well pump into a cistern.)

This is in a house I just had moved to my property, so there is an existing panel that is expecting split phase power. I will be having this inspected, so Canadian Electrical Code 2018 applies.

questions:

My Whisperwatt 7000 generator has two 25A outputs, one at 120V and one 120/240

When the sun is shining and the batteries good, I want to run off inverter. When it gets low I want to run off the generator.

Off mains power, the LV6548 wants a 60A feed to service both battery charging and load. My generator can’t supply that. Is there a way of using my two 25A circuits to supply that?

I do have a less efficient generator with two 30A circuits, but my actual load is low enough that I would prefer to design around the whisperwatt if possible.

Any thoughts? I will put together a diagram of my planned system.

Thanks!
Each LV6548 can use a 30amp feed from grid, so as long as it sees 120V, you should be ok.
I use a transfer switch to feed my loads, and a breaker from the grid( in your case generator) which i never usually turn on.
So far the sun has been enough to keep the batteries charged.
I have a whole house generator with an ATS connected to the main. So to the inverters, the main and generator are the same. I use a breaker to the inverters to supply that power, but always leave it off. I dont want grid or generator to charge batteries, but I can if I want.
You can use the inverters in simple parallel mode to feed 120V to each side of your critical loads panel, or put them in split phase for 240V. Both ways seem to work ok.
 

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mesquito_creek

Solar Enthusiast
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Feb 8, 2021
Messages
145
A simple solution I applied to my LV6048 was to connect my underpowered generator to a EG4 Battery charger and then from the Battery charger directly to the Battery Busbar. It will not keep up with my max load potential but it will supplement my battery inputs long enough to get me to the next sunny day.... You may have described something similar in post #5, but regardless its all I needed to get me through a hot night running AC fully offgrid.
 

JakeinCanada

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Nov 17, 2019
Messages
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I’ve been looking at many options and found a 2kw auto start dc generator that looks very promising. The V5 has dual fuel option, monitors battery voltage and automatically starts when the battery is low. The price listed was just over $2000, this might not be the most efficient, but certainly the most convenient

I’m using dual LV6548 feeding a 60 amp 120/240 panel.
 
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