[RE-wrenches] questions about solar charging 72v UPS

[Mick Abraham]

Hi, Ron~

The Midnite Classic PV controller shows 72 volt nominal as one of the
battery choices on its menu screen. That's about the only option I know of.
Even though the HV controller from Apollo can accept a similar range of PV
input voltage I think that unit stops at a 48v battery--maybe because of
code problems with battery strings above 50 volts.

For charging a 72 volt lead battery, consider a minimum of 36 X 6 = 216 PV
cells in each charging string. Confirm that "cell count" suggestion with
someone who knows more than I do about the Midnite controllers...such as boB
Gudgel who is a frequent List contributor. I just unboxed my first Classic
controller and I look forward to learning more about this item.

With a 72 volt lead acid battery bank it will be difficult to maintain equal
state of charge on the 36 chemical cells in each battery string. As you
know, Ron, one can only add/remove energy through the whole battery
string--barring new developments--so if some of those critters get out of
line it will be tough to re-establish good discipline.

Jolliness,

Mick Abraham, Proprietor
www.abrahamsolar.com

Voice: 970-731-4675


On Tue, Feb 8, 2011 at 8:07 PM, Ron Young <solareagle at solareagle.com> wrote:

> Hi All,
>
> I recently acquired some UPS units that are a high end portable units (GE
> GT3000). They are nearly new and I would like to rig them up as a standalone
> emergency back-up power source with a solar (or wind) charging option. These
> units have sine wave output and are a double conversion type, i.e. power out
> is isolated from power in by ac to dc to ac conversion. The main problem I
> have is that the battery pack is 72v. It is expandable and I can add up to
> four additional packs to increase the runtime to over three hours at half
> power (1200 watts). How do I charge this type of battery pack with solar? Is
> there a charge controller out there that will provide nominal 72v?
> http://www.gedigitalenergy.com/PowerQuality/catalog/gtseries.htm
>
>  Best Regards,
> *Ron Young*
> earthRight Products - Solareagle.com
> Alternative Energy Solutions ~ Renewable Energy Products
> 1-877-925-2929
> *blog*: http://www.earthrightsolar.tumblr.com
> *website*: http://www.solareagle.com
> *email*: sales at solareagle.com
> 79F North Third Ave
> Williams Lake, BC
> V2G 2A3
>
>
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