[RE-wrenches] High Voltage MPPT units; Adding battery backup

[Drake]

The GENTRAN sounds very interesting.  The Internet has some for sale, 
but so far no detail.   Will the 12 circuit panel shed one circuit at 
a time?   In a nutshell, how does this work?


Thanks,

Drake



At 02:32 AM 11/10/2011, you wrote:
>Hi Wrenchies,
>
>Yes and if you use a GENTRAN or equivalent circuit-by-circuit 
>transfer switch add-on for the output from the offgrid inverter to 
>your AC panel -  then there is no need for a separate dedicated AC 
>loads panel and rewire like in Larry's original drawing.  I've used 
>this trick for years to avoid a dedicated subpanel for the output of 
>an off-grid inverter.  Combined with the DC transfer switch idea 
>that high voltage MPPTs enable,  (we've been waiting for this) you 
>have a really simple retrofit for an on-grid system.
>
>And now with Magnum and others offering low-power 120/240 split 
>phase outputs in one inverter - the grid-tie hybrid retrofit market 
>is getting more attractive all the time.  DC Transfer Switch to MPPT 
>Charger to 120/240 split phase inverter/battery to GENTRAN 
>Switch.  Getting cheaper all the time.
>
>And hopefully one day not too far off SMA will bring their "Backup 
>Set S" they show in their European catalog to the States- this is 
>basically a 2.2 KW version of the Sunny Island - 2 of them would 
>achieve 120/240 stacked and be a nice cheaper SB enabler as well.
>
>Also your standard 100 AMP 4 pole DPDT transfer switch may not be 
>rated for 600 VDC explicitly but think of it - the old knife style 
>units "throw" is like 12" - no way that won't work with 600 VDC.
>
>Hope that helps!,
>
>Jeff
>
>
>
>
>
>Larry Crutcher, Starlight Solar Power Systems wrote:
>>
>>Right.... a major rewire and many components...and sacrifices. The 
>>Outback is limited to 30 amps AC and cost much more than you would 
>>need to spend.
>>
>>With my idea you just add a transfer switch....Done. When the grid 
>>is down, PV feeds HV CC. Then you can use ANY size inverter, with 
>>or without a transfer switch. No rewiring the grid inverter. No 240 
>>volt transformers or dual inverters. No relays, switches or 
>>diversion controllers. Batteries are always properly maintained. No 
>>phantom loads. Very simple.
>>
>>Thanks for your input. Now if I can just find that darn 600 volt 
>>transfer switch.
>>
>>Larry Crutcher
>>Starlight Solar Power Systems
>>
>>
>>
>>On Nov 9, 2011, at 1:55 PM, Drake wrote:
>>
>>>
>>>Any amount of power will AC couple.
>>>
>>>If you use an off grid inverter, such as an Outback, to feed the 
>>>protected load panel, the inverter should be fed by grid AC power 
>>>to supply loads, when the grid is available.  Just feed  your grid 
>>>tie inverter into the protected loads panel.   You will need a 
>>>relay to shut off power from the grid tie inverter when the 
>>>batteries are full.  This can be triggered by the fan relay in the Outback.
>>>
>>>The on grid inverter will push power into the grid through the 
>>>battery inverter's internal transfer switch during normal 
>>>operation and AC couple when the power is out.  If your grid tie 
>>>inverter is 240 volts, you will need to use a transformer or two inverters.
>>>
>>>The phantom load of the inverter can be eliminated by using a 
>>>transfer switch to send PV power straight to the grid, during 
>>>normal grid availability, keeping the inverter turned off.  AC 
>>>coupling seems much easier than using a charge controller, but 
>>>there is no conditioning of the batteries.  The charge is just on 
>>>and off at the voltage set point. For a back up system, that is 
>>>not much of a problem, as the battery inverter can maintain the 
>>>batteries when power is available.
>>>
>>>
>>>
>>>At 02:04 PM 11/9/2011, you wrote:
>>>>
>>>>Nice Find, Drake! Thanks.
>>>>
>>>>What is the minimum system for an AC coupled inverter?
>>>>
>>>>Again, the idea is for low cost battery backup of an existing 
>>>>grid tie. The AC coupled schematics I have looked at require a 
>>>>major rewire and many components. I would like to hear if someone 
>>>>has a simple add on solution compared to just switching the array 
>>>>to the high voltage CC.
>>>>
>>>>Larry Crutcher
>>>>Starlight Solar Power Systems
>>
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Drake Chamberlin
ATHENS ELECTRIC LLC
OH License 44810
CO license 3773
NABCEP Certified PV
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