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

[Jeff Clearwater]

Hi Drake,

A GENTRAN or equivalent is standard equipment for adding a backup 
generator to a house or small business as an alternative to one main 
manual or automatic transfer switch.   It's simply a box with 8-12 
individual transfer switch breakers some 120 and a few 240 - mostly 15 
and 20 amp.  They sell plug-in types and hard wire types where the 
output of a small gas generator is either plugged into the face of the 
unit or hardwired into the buss.


Then there is a bundle of wires that run from the GENTRAN to the house 
breaker panel.  For each house circuit you want to backup you simply 
interupt the load line coming out of that main panel circuit breaker 
with the 2 lines from the individual transfer switches in the GENTRAN.  
So on the GENTRAN you switch each circuit between "GEN" or "Utility".  
Then you simply use the output of your new off-grid solar inverter to 
feed the GEN side and during a power outage you can not only switch your 
house over to your solar inverter with no dedicated critical loads 
subpanel but you can control how much load you want to put on your 
backup solar.


I've used 2 GENTRANS to cover all the circuits in a house - so IMHO it's 
better than a dedicated subpanel or an all-house automatic transfer 
switch in that you can pick and choose how much load you want to expose 
your inverter and batteries too.  The only disadvantage is they only 
usually come in 15 and 20 amp circuits and usually offer only one or 2 
240 Volt circuits.  If you want to empower a 30 or 50 Amp 240 circuit - 
there are other companies that sell GENTRAN type switches with 
customizable breaker options but they are much more expensive.


Do watch your neutral and grounding circuits though.  Since the neutral 
is bonded at the Main panel you want to be consistent with the "grounded 
conductor grounded at one and only one point rule" when the GENTRAN is 
installed and switched - a point many electricians miss when they 
install backup generators.


Hope that helps.

Jeff Clearwater
Village Power Design
NABCEP^(TM) Certified PV Installer
C-46 CA Solar Contractor


Drake wrote:
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 switchDone. 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 dur

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

[Darryl Thayer]

We are getting a little wild here, but take the 600 volt line and run one leg 
at least through the high voltage relay (tyco kilivolt EV2000 series), then use 
a 3 pole 240 V transfer switch, using one pole to control the series current 
through the relay coil.  When the 240 volt switch is opened the relay breaks 
the circuit, and the transfer switch finishes opening without current.  The 240 
volt switch is safe with no load just like a do not open under load other 
devices we use.  
Darryl



From: Jeff Clearwater 
To: RE-wrenches 
Sent: Thursday, November 10, 2011 1:32 AM
Subject: Re: [RE-wrenches] High Voltage MPPT units; Adding battery  backup


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 switchDone. 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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Re: [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 switchDone. 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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Re: [RE-wrenches] High Voltage MPPT units; Adding battery backup

[Jeff Clearwater]

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 switchDone. 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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Re: [RE-wrenches] High Voltage MPPT units; Adding battery backup

[Darryl Thayer]

this is a 240 volt transfer switch and also shown is a 600 volt safety switch 
single pole single throw




From: "maver...@mavericksolar.com" 
To: RE-wrenches 
Sent: Wednesday, November 9, 2011 9:55 PM
Subject: Re: [RE-wrenches] High Voltage MPPT units; Adding battery  backup


I googled "600 volt switch dual throw" and found a cutler-hammer DT363URK.

From http://www.alliedelec.com/Images/Products/Datasheets/BM/EATON_CUTLER_HAMMER/416-0447.PDF

Not sure if it carries a DC rating all the way to 600v. 

 
 




Thank you,

Maverick


Maverick Brown
BSEET, NABCEP Certified Solar PV Installer ®
President & CEO
Maverick Solar Enterprises, Inc.
Office:     512-919-4493
Cell:        512-460-9825
Sent from my HondaJet!

On Nov 9, 2011, at 6:07 PM, "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 switchDone. 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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Re: [RE-wrenches] High Voltage MPPT units; Adding battery backup

[maver...@mavericksolar.com]

I googled "600 volt switch dual throw" and found a cutler-hammer DT363URK.

From 
http://www.alliedelec.com/Images/Products/Datasheets/BM/EATON_CUTLER_HAMMER/416-0447.PDF

Not sure if it carries a DC rating all the way to 600v. 


 



Thank you,

Maverick


Maverick Brown
BSEET, NABCEP Certified Solar PV Installer ®
President & CEO
Maverick Solar Enterprises, Inc.
Office: 512-919-4493
Cell:512-460-9825

Sent from my HondaJet!

On Nov 9, 2011, at 6:07 PM, "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 switchDone. 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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Re: [RE-wrenches] High Voltage MPPT units; Adding battery backup

[Larry Crutcher, Starlight Solar Power Systems]

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 switchDone. 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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Re: [RE-wrenches] High Voltage MPPT units; Adding battery backup

[Drake]

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


On Nov 9, 2011, at 6:14 AM, Drake wrote:



I vote for the AC coupled system.  But if you 
need to make a 600 VDC transfer switch, I think 
you could likely make one from Tyco relays and 
voltage controlled relays.  http://relays.te.com/datasheets/ev200.pdf


At 03:16 PM 11/7/2011, you wrote:

Ray,
Yes, the idea was for a low cost way to add 
battery backup to existing high voltage PV 
grid tie systems, not new construction.


The second inverter does not need to be able 
to sell since that is handled by the grid tie 
inverter. It simple passes grid power to loads 
and maintains the battery. That means any 
off-grid inverter/charger or even low cost 
separate inverters and chargers may be used, a 
very economical solution. However, the idea 
may be of no value because it appears no one makes a transfer switch.


Larry Crutcher
Starlight Solar Power Systems




On Nov 7, 2011, at 11:32 AM, Ray Walters wrote:

Just curious, what's the advantage of 
switching at the array vs. just using a Sunny 
Island or Outback system? Seems this would 
cost more, and have less efficiency, since 
you would still have the battery float 
losses, backup inverter idle losses, in 
addition to the 2nd grid tie inverter losses. 
Are there site specific conditions driving this that I'm not understanding?
I've done quite a few GT systems w/ battery 
backup, so I'm always up for new ideas though.


Ray


On 11/7/2011 12:15 PM, Larry Crutcher, 
Starlight Solar Power Systems wrote:

Hi Glen,
That model is a disconnect switch. What the 
system needs is a 4 pole transfer switch, 
automatic or manual, to connect the PV source to the charge controller.


Hello Gary Willit,
Yes, you've grasped my concept precisely and 
I agree, getting a high voltage DC transfer 
switch may nix this design. Sounds like a product for Midnite Solar to build.




Larry Crutcher
Starlight Solar Power Systems


On Nov 6, 2011, at 1:42 PM, Glenn Burt wrote:


Siemens makes a line that are UL listed.
Their VBII series like HNF361PV – 30A

-Glenn

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Drake Chamberlin
ATHENS ELECTRIC LLC
OH License 44810
CO license 3773
NABCEP Certified PV
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Re: [RE-wrenches] High Voltage MPPT units; Adding battery backup

[Larry Crutcher, Starlight Solar Power Systems]

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


On Nov 9, 2011, at 6:14 AM, Drake wrote:

> 
> I vote for the AC coupled system.  But if you need to make a 600 VDC transfer 
> switch, I think you could likely make one from Tyco relays and voltage 
> controlled relays.  http://relays.te.com/datasheets/ev200.pdf
> 
> At 03:16 PM 11/7/2011, you wrote:
>> Ray,
>> Yes, the idea was for a low cost way to add battery backup to existing high 
>> voltage PV grid tie systems, not new construction.
>> 
>> The second inverter does not need to be able to sell since that is handled 
>> by the grid tie inverter. It simple passes grid power to loads and maintains 
>> the battery. That means any off-grid inverter/charger or even low cost 
>> separate inverters and chargers may be used, a very economical solution. 
>> However, the idea may be of no value because it appears no one makes a 
>> transfer switch.
>> 
>> Larry Crutcher
>> Starlight Solar Power Systems
>> 
>> 
>> 
>> 
>> On Nov 7, 2011, at 11:32 AM, Ray Walters wrote:
>> 
>>> Just curious, what's the advantage of switching at the array vs. just using 
>>> a Sunny Island or Outback system? Seems this would cost more, and have less 
>>> efficiency, since you would still have the battery float losses, backup 
>>> inverter idle losses, in addition to the 2nd grid tie inverter losses. Are 
>>> there site specific conditions driving this that I'm not understanding?
>>> I've done quite a few GT systems w/ battery backup, so I'm always up for 
>>> new ideas though.
>>> 
>>> Ray
>>> 
>>> 
>>> On 11/7/2011 12:15 PM, Larry Crutcher, Starlight Solar Power Systems wrote: 
 Hi Glen,  
 That model is a disconnect switch. What the system needs is a 4 pole 
 transfer switch, automatic or manual, to connect the PV source to the 
 charge controller.
 
 Hello Gary Willit, 
 Yes, you've grasped my concept precisely and I agree, getting a high 
 voltage DC transfer switch may nix this design. Sounds like a product for 
 Midnite Solar to build.
 
 
 
 Larry Crutcher
 Starlight Solar Power Systems
 
 
 On Nov 6, 2011, at 1:42 PM, Glenn Burt wrote:
 
> Siemens makes a line that are UL listed.
> Their VBII series like HNF361PV – 30A
>  
> -Glenn
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> Drake Chamberlin 
> ATHENS ELECTRIC LLC
> OH License 44810
> CO license 3773
> NABCEP Certified PV
> 
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