deep battery discharge [RE-wrenches]

[Rick Cullen - Blue Sky Energy]

Gentleman,

Assuming the SB50 is not damaged it will operate with battery voltage down
to ~9V. If output current is low, first confirm that both the unit is in
Bulk and battery voltage remains low. If the battery is very very
discharged, damaged, or sulfated it may have a very high series impedance
such that voltage rises to the charge voltage setpoint but little current is
delivered. If this is what is happening the SB50 is likely OK and the
batteries are the problem.

If battery voltage remains low with the SB50 in Bulk and there is still
little current, then the bypassing the controller test is the next step. If
the bypass test produces the high current you expect then the problem is
likely with the SB50. If it does not then the problem is likely with the
PV's or their wiring.

The 40A Isc recommended limit is to comply with NEC 1.25 derating. With
typical modules this translates to ~670W into a 12V battery or ~1340W into a
24V battery. The 50 rating is also the current limit value. If array power
is such that output current would exceed 50A, the SB50 will go into current
limit and not let more than 50A flow.

Regards,
Richard A. Cullen
Blue Sky Energy, Inc.
760-597-1642 x102
Fax 760-597-1731
mail; rick at blueskyenergyinc.com
www.blueskyenergyinc.com


----- Original Message -----
From: "Allan Sindelar" <allan at positiveenergysolar.com>
To: <RE-wrenches at topica.com>
Sent: Friday, July 28, 2006 11:05 AM
Subject: Re: deep battery discharge [RE-wrenches]


>
> Ron,
> Not certain, but you may need a higher voltage to "wake up" the SB50.
> Certainly the batteries will accept a charge. Try bypassing the SB (both +
> and -) and leave it that way until voltage rises.
>
> Also, a single SB50 is a poor choice in this situation, as it can't handle
> 750 watts at 12V. Blue Sky suggests a maximum of 40A input, as that allows
a
> 20% boost to 50A output, and current is limited to 50A output at whatever
> battery voltage you have. 50A at 12V is 600W of array. Any more than that
is
> only going to help in early/late charging hours and overcast skies. I
don't
> know the degree of overcurrent protection built into the controller; it
may
> have been damaged by consistent overloading. Try bypassing the input
> directly to the batteries, while leaving the battery connection in place;
if
> it doesn't wake up after the voltage rises, it may be the toast.
>
> At a C/30 rate (750/12 = 62.5; 1900/62.5 = 30), his array is too small for
> those batteries anyway. It can't fill them completely or equalize them.
>
> Allan at Positive Energy
>
> ----- Original Message -----
> From: "Ron Young" <solareagle at solareagle.com>
> >
> > Hi all,
> > I've got a client who inadvertently discharged his relatively new set
> > of 1900 a/h lead acid batteries (left a light on that was directly
> > wired for about three weeks). The voltage reading is 10.5v, I can't
> > even get a reading on a hydrometer so it looks like the electrolyte is
> > pretty much water. The 750 watt 12v array is only registering .4 amp in
> > bright sun -through an SB50L -is this because the batteries can't
> > accept a charge now? Are they toast or can they be recovered?
> >
>
>
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>


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