[RE-wrenches] Fwd: Fwd: Outback Grid Problems

[R Ray Walters]

Ah, now we might be on to something. If float voltage is temp compensated, and sell voltage is not, at cold temps we could see the sell voltage go below float voltage, which can cause "strange things to happen" as Steve mentioned in an earlier email.

Thanks,

Ray

Begin forwarded message:

> From: "Steve Higgins" <shiggins at outbackpower.com>
> Date: April 5, 2010 3:11:04 PM MDT
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Subject: Re: [RE-wrenches] Fwd: Outback Grid Problems
> Reply-To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
> 
> 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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