grid intertie [RE-wrenches]

[Carl Emerson]

Hullo there...

I have just commissioned phase 2 of a 25 kW/day system.

This consisted of 28 x Canon EF2-64 roof modules in groups of seven on adjustable
frames.

These fed into 4 x AERL 600B MPPT units through fuse/disconnects directly to 8 x
L16's. This part of the project uses a SW4548E inter tied but providing essential
backup in the case of a power down.

Now I first checked that the 600B's were regulating at the factory setting of 57
Volts float. To do this I left the SW settings at default and operated in FLT mode
(menu 9) for the test.

Sure enough each of the 600B's "Battery charged" LED came on at about 57 Volts to
57.5 volts.

I did this to test the functionality of the units and make sure that they would
regulate well above the sell setting of 53.4 Volts. I disabled the Equalize
function of the 600B's as I consider the default of 61.5 a little high for L16
Equalize.

Then I changed to 'Sell Mode' and as expected the battery volts came down to 53.4
and we started selling back.

Great so far... but after an hour or so, my sparkie noticed the "battery charged"
LED's coming on on the 600B's and the Bogart Monitor indicating that the battery
volts had climbed to 57 again despite the fact that we were in sell mode and no
settings had been changed.

By this time I was on the motor way back to Auckland so he called me on the cell
phone and asked for advice. I thought that the only way that could happen is if he
had disconnected the AC1 feed to the inverter, even for a moment, to initiate a
bulk charge. He was sure that had not happened but at that point I ran ot of
ideas. The only other possibility I could think of is that there was a grid power
fluctuation, interrupting sell mode and stating a bulk charge.

Finally to reinstate sell mode he dropped the bulk and float setting to below sell
voltage setting to 'force' sell mode. This worked but should not be necessary in
my understanding.

 My questions then are:

1. Will the inverter do a bulk charge every time the grid has a small interruption
??

2.  Is this the whole deal including a 2 hour absorption charge period, if so then
we would seem to loose a lot of selling in the process, especially in areas prone
to 'power flicks'.

3.  I had intended to client to do a controlled Equalize every two months but the
inverter has no provision to equalize without a generator. (Not being able to EQ
from the grid seems to be a serious short coming of the unit) This would mean
turning the inverter off and doing an EQ with the MPPT on a good sunny day. Now
because the 600B has a fixed hysteresis between float and EQ and in my view the EQ
is too high I am left with doing an EQ at about 57 which seems far too low ??

4.  Would leaving the bulk and float settings down at less than the sell voltage
pose any problems ??  It would seem that doing this would prevent the unit from
doing the bulk cycle in the first place.

If anyone is still reading this and has some inspiration I would be most grateful.

--
Regards,


Carl Emerson
Manager
FREEPOWER LTD.  "Harnessing Natural Energy"  Auckland, NEW ZEALAND.



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