[RE-wrenches] 24V Rolls Charging Parameters?

Kirpal Khalsa solarworks at gmail.com
Tue Apr 30 13:03:16 PDT 2013


Steve.....15 hours of Absorb charge!?  Is this just during the initial
charge during commissioning? to set the Flexnet DC calibration?
Thanks for the clarification...
Cheers,
Kirpal Khalsa
Renewable Energy Systems LLC



---------- Forwarded message ----------
From: Steve Higgins <steve at surrette.com>
Date: Tue, Apr 30, 2013 at 12:31 PM
Subject: Re: [RE-wrenches] 24V Rolls Charging Parameters?
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>


 Wayne, ****

** **

Sorry about the delay!… I’ve been in wonderful sunny Nigeria dodging
kidnappers and car bombs… ****

** **

** **

All Rolls batteries require a bit hotter voltage when charging and
especially when you are using multiple parallel strings. ****

** **

With that system I would suggest if you are using the Outback Temp
Compensation.****

** **

Inverter: ****

Bulk/Absorb 29.2 (2.45vpc)****

Absorb Time 15 Hours.  (I’ll explain why below)****

Float 26.4 (2.2vpc)****

EQ 31.8 (2.65vpc)****

** **

Charge Controllers: ****

Bulk/Absorb 29.4-29.6. ****

               Normally I set the controller a bit higher than the inverter
just so my charge controller don’t back off if my inverter is also charging
the battery.****

Absorb Time 4.5 Hours (Time=.42 * 3280 (C20 Rate) / 320amps (max current of
charge controllers) =4.13… Rounded up to 4.5 Hours.   This can be adjusted
depending on monthly SG measurements and or water use. ****

Float 26.4****

EQ 31.8****

** **

Flexnet DC****

** **

End Amps 2% of Battery bank Cap.  65 amps. ****

Charge Voltage 29.0****

Met Time 1-3 min. ****

** **

Battery Charge Factor 90%****

               This means if you take out 100 amps it’s going to put back
110% before it determine the batts are full. ****

** **

The reason for the longer Absorb time is the Flexnet DC determines full
charge by three parameters. ****

** **

**1.      **Absorb Time Completion****

**2.      **End Amps/Charged Voltage****

**3.      **Battery Charge Factor. ****

** **

IF ANY ONE OF THESE (OR Statement in the Logic) PARAMETERS ARE MET, AND THE
FNDC SEE’S A 60 SECOND DISCHARGE IT WILL RESET THE SOC METER TO
98,99,100%.   It’s better to set the Absorb timer longer and force it to
use the End Amps or BCF%..****

** **

The absolute worst way to charge a battery is by running a timer, all the
inverter manufactures do it because it’s a cheap (but somewhat effective)
method of charging a battery that works as long as you set the absorb timer
correctly.  Plus a sulfated battery will rise in voltage too early
potentially causing issues with charging. ****

** **

The best way is measuring the amount of current and shut off the charger
when you hit about 2% (New battery) of the battery bank capacity. ****

** **

Many people make two mistakes when setting up the flexnet dc…  ****

**1.      **Leaving the absorb timer set at default… this will cause the
flexnet dc to think the batts are full and will reset the soc to 100%
early. ****

**2.      **Not forcing a manual full charge prior to connecting the
Flexnet DC… The Flexnet DC when first powered up will assume a full 100%
state on the batteries.  Many battery guys know that when they first
install them they are usually only at 60-80% SOC.   This will cause
incorrect measurements of SOC from day one. ****

** **

Hope this helps. ****

** **

** **

** **

** **

*Steve Higgins
Technical Services Manager
***M: +1.206.790.5840
F: +1.902.597.8447
*Surrette Battery Company
*Exclusive manufacturer of
 <http://www.rollsbattery.com>
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