[RE-wrenches] High Voltage MPPT units

[Gary Willett]

Larry & Darryl:

Intriguing possibility using a DC transfer switch to toggle the PV array 
between the grid-interactive inverter and the "off-grid" battery-based 
inverter. Effectively, the battery-based inverter is functioning as an 
UPS for the Critical Loads, and the battery bank size is driven by the 
critical load needs.

The problem is getting a high voltage DC rated UL / NRTL listed transfer 
switch. I've seen AC / DC rated ATSs, but the DC rating is typically 
150V - versus 600V for the AC rating.

The current rating of the ATS with DC is usually listed the same as the 
AC rating, which results in a significantly lower DC Voltage rating.

Here's a link to an example:
http://www.lake-shore-electric.com/products/transfer-switches/molded-case-transfer-switches/single-motor-automatic-transfer-switch/

High Voltage PV source circuit strings are typically 10A or less. The 
example ATS has 4 switched connections. The manufacturer would have to 
certify its application as an ATS for 2 HV PV strings (Str #1 +/- and 
Str #2 +/-).

Also, the battery-based inverter should be configurable to automatically 
activate the ATS when it determines a grid failure has occurred, and 
then switch back when the grid is restored.

Regards,

Gary Willett

On 11/6/2011 21:40, Darryl Thayer wrote:
> Larry. I have used a 600 VAC transfer switch from Sq. D I never had 
> needed for it to be DC; however the insides are similar to the 600 
> VAC-VDC, it snaps open and snaps closed in both positions.  I will ask 
> my SQ D supplier, he is usually good.
> BTW Nice idea, thanks.
> DT
>
> *From:* "larry at starlightsolar.com" <larry at starlightsolar.com>
> *To:* RE-wrenches <re-wrenches at lists.re-wrenches.org>
> *Sent:* Sunday, November 6, 2011 1:45 PM
> *Subject:* Re: [RE-wrenches] High Voltage MPPT units
>
> With 4800 watts and HV input, it seems to me that a simple battery 
> backup can be formed from an existing PV grid tie system. Block 
> diagram attached. Where can one find a 600 volt rated DC transfer switch?
>
> Larry
>
>     -------- Original Message --------
>     Subject: Re: [RE-wrenches] High Voltage MPPT units
>     From: John DeBoever <jdeboever at trojanbattery.com>
>     Date: Sat, November 05, 2011 6:09 am
>     To: "'re-wrenches at lists.re-wrenches.org'"
>     <re-wrenches at lists.re-wrenches.org>
>
>     Todd,
>     It is 2,560 Wp for 24V battery banks and 4,800 Wp for 48V battery
>     banks.
>     John
>
>     *From*: toddcory at finestplanet.com [mailto:toddcory at finestplanet.com]
>     *Sent*: Saturday, November 05, 2011 12:42 AM
>     *To*: RE-wrenches <re-wrenches at lists.re-wrenches.org>
>     *Subject*: Re: [RE-wrenches] High Voltage MPPT units
>
>     what is the max wattage the unit can handle? (it can't be 80 X 600?)
>     todd
>
>
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