Voltage drop musings [RE-wrenches]

[Joel Davidson]

Yes, I have 32 each 70-watt modules 4 in series for nominal 48 volts. The C40 is
set at 54.8 volts so that voltage flows downhill to the inverter which is set at
54.4 volts.

Note that this is a grid tied net metered PV system with batteries - not a stand
alone or standby PV system.

The problem with a net metered PV system using the SW-series inverter with
batteries is that the inverter operates at the nominal battery voltage, not the
optimum PV array max power point. Since the batteries are just sitting there
being float charged and power passes through the inverter to the load and grid,
can the SolarBoost send max power from the array to the inverter? Has anyone
used a SolarBoost to get around this SW inverter shortcoming?

"Travis Creswell, Ozark Solar" wrote:

> Joel,
>
> Are you trying to say you have thirty two 70 watt modules?  8 strings x 4.?
> amps = 30 + amp array.  You will need two Solar Boost 3048's.  Better yet
> put 16 on the C40 and 16 on the SB3048 (you'll need a DVM option for it too)
> and compare the outputs.   Do you have a Fluke 36 ammeter?  If you don't
> borrow/buy one (~$250 and you really should have one) and compare it's amp
> rating to your C40's.  I almost always find the C40 DVM's to read amps ~10%
> low.  I have found the SolarBoost products to be very accurate.  (Never pass
> a chance to beat up on Trace, just kidding, maybe)
>
> Oh yeah, your question,  you should produce up to 30% more amps when its
> colder, say less than 40F.  In the summer you will only see a 10% (maybe)
> difference when the batteries are under 50 volts in the cooler mornings
> which you won't see since you are grid tied.
>
> Travis Creswell
> Ozark Solar
>
> ----- Original Message -----
> From: "Joel Davidson" <joeldavidson at earthlink.net>
> To: <RE-wrenches at topica.com>
> Sent: Wednesday, May 02, 2001 6:51 PM
> Subject: Re: Voltage drop musings [RE-wrenches]
>
> > Is the SB3048 a current boosting battery charger or a PV array max power
> point
> > device? I have 8 each 4-module series strings of Siemens SP70 modules
> feeding
> > into a C40 and then into a net metered SW4048 with a small backup battery
> bank.
> > The batteries just sit there (pulling the inverter off max power point),
> but the
> > net metered load is the grid so it can take all the PV I produce. Right
> now
> > (4:30PM) my C40 digital meter says 16 amps at 54 volts equals 864 watts.
> Will I
> > produce 19.2 amps at 54 volts or 19.2 amps at 45 volts with the SB3048?
> >
>
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