Xantrex SW and battery configuration [RE-wrenches]

[William Korthof]

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Yes... I have a 54 volt pack on the grid-tied (SW inverter) PV system on 
my first house (installed in 2001). I later switched to an MX60. I'll 
probably replace the pack this year and I switch back down to 48 volts
at that time. There were a few problems with the 54 volt system...
-inverter defaults are set for 48 volt pack and each parameter has to be 
changed any time the inverter is disconnected
-voltage setpoints/levels are less intuitive for me (4 x 12v is easier 
than 4.5 x 12v)
-72 volt array circuits save a lot of wire and wiring compared to 48 
volt nominal... and once you have an MX60, why bother with an odd 
battery voltage
-you have to use 6-volt batteries or 2-volt cells, can't use 12-volters
-robust equalizing voltage for a 54 volt pack is right at the high 
voltage shut-down level for the SW inverter...

On the other hand, the system works. Due to the TOU rate schedule from 
my utility, I used the buy/sell function on the inverter (to discharge 
the pack during on-peak daytime hours).

/wk



William Miller wrote:
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> 
> 
> 
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> 
> Marco:
> 
> In the 1990s when MPPT controllers were not available, this might have 
> made sense.  Now there here, why not stick with a 48 VDC battery bank 
> and configure your PV for 72VDC with a Blue Sky or MX60?  (Will the Blue 
> Sky do 72 VDC PV array?)
> 
> William Miller
> 
> 
> 
> 
> 
> 
> 
> 
> 
>> I don't know how many of you tried this back in the olden daze of the 
>> late
>> 1990s, but I remember being convinced by a Trace tech to try a 54 volt
>> battery bank with a 4048 or 5548 in order to allow the nominal 48V 
>> array to
>> spend more time at its MPP.  (This assumes the use of a non-MPPT charge
>> controller.)  So, I did several systems with a 54V battery bank.  
>> Well, for
>> the first time in years, I'm doing a SW4048 NEM system here in Hawai'i 
>> and
>> am wondering if it will make much of an appreciable difference in 
>> terms of
>> overall system output over time if I go with a 54V battery rather than 
>> 48V.
>>
>>
>> Any thoughts or actual experience comparing output between the two
>> configurations?
>>
>> aloha,
>> marco
> 
> 
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