Interesting, very interesting... [RE-wrenches]

[Todd Cory, Bald Mtn. Solar]

Hey everyone,

This fits into the "learn something new every day" category. I will
share it here, so perhaps you can avoid the "school of hard knocks".
This was also an "ahh-ha" for Ron & Michael at Array Technology too.

I finally discovered why a recently installed tracker refused to go East
in the morning. System details:
The PV's are 150' from the batteries, so to reduce wire size I decided
to run the PV's at 48 Volts, and use a SB3048 at the other end to shift
to the 24 volt battery pack. Everything worked great with this
configuration... except the tracker refused to return East in the
morning. Once the sun was on the PV's (around 11:00 AM)  everything
operated normally.

Here is what was going on... with no sun on the PV's the MPPT was
squeezing everything it could out of the array and dragging the 48 volt
panel voltage down to basically just above battery potential. The
tracker was running array direct with the supplied 36 volt to 24 volt
converter. With no sun on the panels the 3 PV's in series were running
at about 18 volts, which is insufficient for the tracker to operate.
When the PV disconnect was opened, or sun got onto the array the tracker
operated normally.

Moral of the story:
If you are using a BS3048 in the 48 to 24 volt configuration, with a
tracker, you MUST run the tracker off the battery directly. It will not
work array direct.

Todd

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