[RE-wrenches] 24V Rolls Charging Parameters?

Tue Apr 30 14:17:22 PDT 2013

If you run them thru the formula...

Time=.42 * C20/I...

Time = .42 * 3280AH/170amp (Max Current)

That's 8.1 Hours Absorb... But you DON'T want the inverters hitting a premature absorb because that will throw the FNDC SOC meter/timers off.

Also I didn't mention that they were only using a 5000 Watt Honda genset... so max current is almost halved in this example..   If so yes you are looking at an incredibly long absorb time.

This is why you have to go back and make sure that you have about 10-15% Charge rate capacity otherwise absorb times become way too long.   In most cases customer will stop the genset after just three hours of total runtime, because they don't want to burn the fuel.

Last I checked replacing sulfated batteries ever few years is more expensive than running a genset a few more hours per month to make sure the batteries get to a full state at least once per month.

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Kirpal Khalsa
Sent: Tuesday, April 30, 2013 1:03 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] 24V Rolls Charging Parameters?

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<mailto: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<mailto: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<tel:%2B1.206.790.5840>
F: +1.902.597.8447<tel:%2B1.902.597.8447>
Surrette Battery Company
Exclusive manufacturer of
<http://www.rollsbattery.com>
 <http://www.rollsbattery.com>
 <http://www.rollsbattery.com>

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