[RE-wrenches] Fwd: Outback Grid Problems

[Steve Higgins]

Sell RE and Refloat are not Temp Compensated, 

Absorb, Float Voltages and EQ are temp Compensated. 

 

Older Grid tie inverters using firmware revision 75 utilized temperature
compensated voltage with the Sell RE, but new versions such as 76 and
above don't.

 

"2)What is the difference between refloat and rebulk?"

 

For the purpose of the GT units, it's really the same.  Just when
Refloat, is triggered it's basically going into a Re-bulk mode. 

 

Steve Higgins. 

Sr Application Engineer. 

Sub-Saharan Africa Business Dev Mgr. 

Outback Power Systems. 

 19009 62nd Ave Ne 

Arlington Wa 98223

360-618-4313

 

 

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of R Ray
Walters
Sent: Monday, April 05, 2010 12:13 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Fwd: Outback Grid Problems

 

Thanks very much Steve;

 

I still have 2 questions: does the temp sensor control all voltage set
points  or just absorption and float voltage?

2) I'm still a little confused about the absorption time, and refloat,
rebulk features. for instance, what is the difference between refloat
and rebulk?

 

Apparently his system was getting stuck in a mode where it couldn't
quite satisfy the absorption time, and would cycle back and forth into a
refloat mode, etc. Is it possible that the temp sensor was causing the
sell voltage setting to drop below the refloat voltage? or that, as the
temp of the battery rose through the day, the set points kept changing
and never quite get met?

 

R. Walters

ray at solarray.com

Solar Engineer

 

 





 

On Apr 5, 2010, at 11:02 AM, Steve Higgins wrote:





Here is a bit more on how RE-BULK and RE-FLOAT interact with the ABSORB
timer. All battery voltages are default and are given as 12VDC nominal,
multiply by 2 for 24V and 4 for 48V systems. All of the following is
true for grid-tie GV or GT FXs only. 


After the battery voltage reaches the Absorption set point, the
absorption timer starts counting down and maintains absorption voltage
for the absorption time. Watching the absorption time is the indication
of how long the FX will be in the absorption mode. 

After the absorption mode is finished, the next stage is Sell RE. Sell
RE is a target that the FX cannot charge too, but can export renewable
energy if the source is powerful enough. Towards the end of the day,
typical renewable energy, like solar, is not available so the FX cannot
export any more power. In this event the FX will go silent/passthru,
which means it stops any power conversion. 

The battery usually still has small DC loads, so battery voltage may
slowly fall during the night. If the battery voltage falls below the
RE-FLOAT setpoint (12.5 volts) then the FX will transition to the FLOAT
stage and charge the battery to the FLOAT target (13.6 volts) for the
FLOAT time (1 hour). After the FLOAT timer has expired, the FX returns
to the SellRE stage and/or silent/passthru. 

If the battery falls past the REFLOAT setpoint, below 12.4 volts (which
we call RE-BULK), the FX will change to the BULK stage and the
absorption time remaining will start counting up. The absorption time
remaining will count up in real time as long as the battery voltage is
12.4 volts or below. The absorption time remaining counts in double time
if the battery voltage is less than 12.0 volts and counts in quadruple
time if battery voltage is less than 11.6 volts. In other words the
lower the battery voltage goes the more time the system will have to
remain in the absorption stage up to the absorption time setpoint. 

 


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