Battery Controller for high voltage Sunny Boys.

 I hear that SMA USA is planning on coming out with a Island inverter to
complement their grid inverters.  Has anyone come up with a device that can
keep batteries charged with a 240+ volt system.

Thanks

  High voltage battery strings are highly unreliable and furthermore it
is difficult to keep the battery states of charge balanced. You could
use a 48V to 300V DC/DC converter to add batteries to you system - but
why? The SMA inverters are not designed for back-up power as they are
a strict anti-islanding technology.

Even selling back at a higher $ time is silly as batteries cost about
$0.25 per KWh delivered in life costs alone.

The SMA island inverter is a battery-fed bidirectional inverter that
acts as the grid for mini-grid (eg islands) applications - an AC bus
centric technology. Many people argue that this may be a wasted
complication over a simple 48VDC bus centric configuration. We will
soon see how well it fares in the market place.

-andy

 Ken,

I have been hearing that story from them for quite some time from SMA. Every
time I talk to them, it will be available in 6 months (same story for most
of 2003).

I your are not committed to an inverter yet, I would suggest that you keep
an eye on the inverter coming out from Magnetek. They will have a SMA killer
called the Aurora. But most interestingly they will come out with another
inverter called the MWI (may have changed name since the last time I looked
at them).

IMO the MWI will revolutionize the solar backup system industry. This multi
input inverter will have a MPPT input of 400VDC (solar), another 300VAC
input  (generator, windmill...). It will charge 48V or 110V battery bank and
also re-sell excess energy to the grid.  All these feature in one box...

I am expecting that backup system using this inverter should have VERY clean
installations without boxes and wires hanging all over the place.

The big negative that I can think of is the unproven technology...  I know
Magnetek to be a very good competitor in my power electronics day, but this
technology is unproven.

If you are committed to an inverter, check out RV power products. They have
a MPPT charge controller. I have no opinion about its reliability, I did not
invest in one yet  (I find them a bit pricey).

-Luc