Voltage drop musings [RE-wrenches]

[jay peltz]

Hi Joel,

One way is to increase the number of batteries in the system.  This increases the
operating voltage ( more watts) without the need for a MPPT controller.  48v systems
are pretty easy as you add another 6v ( if you are using 6v batteries.  If you are
using 2v cells, then maybe 8v would work better?) battery to the system, works
pretty slick- cell voltage is lower, overall voltage is higher= more watts to the
grid.

And yes many people are using the MPPT controllers to get around this problem called
"batteries".

Jay
Peltz Power

Joel Davidson wrote:

> 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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