Solar to Shore Power inlet

I am about to buy some solar panels for my all-electric Olson 40.

This has been somewhat of a science experiment, and it has taken awhile until charging the LiFePO4 batteries using shore power has worked as expected. Rather than have yet another charging system, and working out the kinks in that technical duplication, I am thinking of using solar panels wired to micro-inverters (which use MPPT) to generate 240VAC, and wiring that split phase AC to the existing charger/inverter, a Magnum PAE 4448, to charge the 48v bank.

I have investigated this, and it seems like it will work. The Magnum PAE charger/inverter is currently wired for 30A 120VAC shore power, but can be wired for 60A 240VAC as typical for house service from the utility, where each hot leg is out of phase by 90 degrees (hence, sometimes called 208VAC). So it appears I can keep the 110V 30A shore power going into the PAE, and also wire the AC output from the micro inverters to the PAE.

And of course, a switch, so I only use shore power OR solar, not both at the same time.

Has anyone tried something along these lines? Any lessons learned?

 

IStream

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I have a Magnum shore power charger, solar on the boat, and a microinverter solar array at home, plus direct experience with the PAE series equipment from a previous job. I went through a similar thought exercise when designing my system and recommend you not do this.

For one thing, you'll take a much bigger efficiency hit from microinverting and then charging through the Magnum than you will just staying DC with a solar charge controller.

For another, you'll avoid having 240VAC wiring and fields running around topsides where people and potentially sensitive equipment are.

Finally, you'll lose the redundancy of having a separate solar charging system. 

If you decide to do it anyway, you'll need off-grid microinveters because most are designed to shut off if they don't sense utility power.

 
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El Borracho

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I have investigated this, and it seems like it will work. The Magnum PAE charger/inverter is currently wired for 30A 120VAC shore power, but can be wired for 60A 240VAC as typical for house service from the utility, where each hot leg is out of phase by 90 degrees (hence, sometimes called 208VAC). So it appears I can keep the 110V 30A shore power going into the PAE, and also wire the AC output from the micro inverters to the PAE.
208 V derives from 240V 3 phase service with 120 degree phase angles. Not typical home service which might be considered a 180 phase angle.

How do you limit the power demand from the charger?  You have 15 kWh of solar?

Am I missing something? Good idea, but seems unworkable. 

 

weightless

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How do you limit the power demand from the charger?  You have 15 kWh of solar? 

Am I missing something? Good idea, but seems unworkable. 
Uses the grid as a buffer like household solar? Not sure about the details of how that might work in a marina...

 
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Seems like the potential for brown outs would be high.  AC stuff in general doesn't like multiple drops would call Magnum and ask.  I'm with Istream the on paper simplicity doesn't really pencil out when you are jumping from DC to AC to DC.  Stand alone redundant system will probably be simpler and safer. 

 

2airishuman

The Loyal Opposition
This has been somewhat of a science experiment, and it has taken awhile until charging the LiFePO4 batteries using shore power has worked as expected. Rather than have yet another charging system, and working out the kinks in that technical duplication, I am thinking of using solar panels wired to micro-inverters (which use MPPT) to generate 240VAC, and wiring that split phase AC to the existing charger/inverter, a Magnum PAE 4448, to charge the 48v bank.
For this to work, the micro-inverters have to communicate with the inverter/charger (and with each other) to keep the power balanced.  In other words, if the panels are delivering more power than the inverter/charger can accept, the micro-inverters have to throw away some power by letting the panel voltage float up while dropping the current a little.   On the flip side the inverter/charger may have to reduce the charging current based on the amount power the solar panels can deliver (e.g. on a cloudy day or at dusk).

There are systems that will do this either using data over powerline, or by fiddling with the phase relationships between voltage and current, but they are something you have to seek out specifically and you generally have to get an inverter/charger and the micro-inverters from the same vendor because the signalling protocols are all proprietary.

I have investigated this, and it seems like it will work. The Magnum PAE charger/inverter is currently wired for 30A 120VAC shore power, but can be wired for 60A 240VAC as typical for house service from the utility, where each hot leg is out of phase by 90 degrees (hence, sometimes called 208VAC). So it appears I can keep the 110V 30A shore power going into the PAE, and also wire the AC output from the micro inverters to the PAE.
I think you're confusing several important points.

The 4448PAE, in charging mode, can be run either at 120v, 36 amps or at 240 volts, 18 amps.  It does not accept 120/208 volt three-phase input, which is important to note because there are some micro-inverter systems designed around 120/208.

And of course, a switch, so I only use shore power OR solar, not both at the same time.
Of course, a switch.  Or maybe a switch.  Most micro-inverter systems are grid tie and, unlike most yacht power systems, can use two power sources at once if desired.

Do your homework, and good luck.  I think you'll find that setting up your solar panels for DC and using DC charging will work better and cost less but I will admit that the micro-inverters are getting better and better.

 
Some more investigation ... including some time spent on the phone with technical support at Magnum.

The Magnum MS PAE 4448 inverter/charger accepts 120V (such as normal 30amp shore power), or 240V (split phase, 180 degrees between the phases of 120V AC between red & neutral, and black & neutral), but not 208V (which is three phase, 120 degrees between phases).

When using microinverters, the microinverters must output 240V split phase. The enphase IQ 7 does this, and works with Sunpower 170 watt semi flexible panels.

The output of the microinverters is connected to the OUTPUT of the Magnum inverter. Weird, right?

The way the Magnum controls the output power from the microinverters is interesting: the inverter alters the 60Hz frequency on the inverter output slightly: 60.6Hz turns off the microinverters completely. This is an international's standard for how microinverters are controlled. There is no separate signal anymore, its done by shifting the frequency of the AC **output** by the inverter.

 

IStream

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Connecting to the output isn't weird, it's how you fool the microinveryers into thinking they're tied to a live grid. It also means that if / when you turn off your inverter you'll lose your solar charging. 

Again, it can be made to work but that doesn't mean it's the best way to do it.

 
Thanks for your insight, ISream:

I have a Magnum shore power charger, solar on the boat, and a microinverter solar array at home, plus direct experience with the PAE series equipment from a previous job. I went through a similar thought exercise when designing my system and recommend you not do this.

For one thing, you'll take a much bigger efficiency hit from microinverting and then charging through the Magnum than you will just staying DC with a solar charge controller.

For another, you'll avoid having 240VAC wiring and fields running around topsides where people and potentially sensitive equipment are.

Finally, you'll lose the redundancy of having a separate solar charging system. 

If you decide to do it anyway, you'll need off-grid microinveters because most are designed to shut off if they don't sense utility power.
I may well follow your advice eventually. I have not yet bought anything, I may come to your side on this.

The reason I am starting with this thought experiment is because charging the lithium batteries has been a pain. So I want to use the same charging approach that I finally have. At least I understand the strengths and weaknesses of the current configuration.

The reason I might well change my mind about this, and follow your suggestion, includes all the reasons you mention. And because I may well rip out the current install, re-wire YET AGAIN, and use a single (or double) 48V battery for my high current loads (propulsion and inverting), and use the 4 x 12v LiFePO4 in parallel for the house low current house loads (mostly LEDs, refrigeration, and instruments). That will allow me to get rid of the buck converters I currently use.

 
Connecting to the output isn't weird, it's how you fool the microinveryers into thinking they're tied to a live grid. It also means that if / when you turn off your inverter you'll lose your solar charging. 

Again, it can be made to work but that doesn't mean it's the best way to do it.
That is a significant point!!!!

The inverter consumes 75 watts!!!! If I leave it on all the time, passively, then that is 75 x 24 = 1800 watt hours!! Holy smokes!

 
This is right up magnums alley, if they give you the green light on something I would go for it.

Nerds in Edmonds or maybe Everett got nothing better to do...

Enough time on here and you will bring in the full Arlington circle... pretty sure they have all worked together at some point...

 

IStream

Super Anarchist
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That is a significant point!!!!

The inverter consumes 75 watts!!!! If I leave it on all the time, passively, then that is 75 x 24 = 1800 watt hours!! Holy smokes!
Zactly! Roll in the inefficiency of charging via inverter and you're taking a real hit to the net effective output of your solar array, possibly even driving it negative.

 
Without going down the lithium well is there a cuttoff on voltage for charging?  I know from our stuff it's tough doing a 24v agm array even in tropical land so 48v on a boat would be tough.  Can you drop voltage and go to direct cell array at lower voltage to lower panel size needed?  Just curious

 

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