question

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multiplus rebulk voltage threshold

Hello,


I couldn't find anywhere the re-bulk voltage offset threshold that the algorithm of a Multi (MP-II, or Multigrid, whatever) in an ESS system with DVCC enabled with unmanaged batteries (nickel-iron batteries in our example) is applied ? For example, we have a bank of 24V NIFE with 31.5VCC for absorption, with the following parameters :



The bulk-abs-float cycle starts all over again once the voltage of the batteries drop below the float voltage, or below a pre-determined voltage threshold, or minus a certain % of the float voltage, andfor example for how long ? 1 min ?


Couldn't find the info on the Victron documentation (it is clear for MPPT charging algorithms though, but not for internal Multi's DVCC algorithms). We've set up those settings depicted above in order to be able to restart a full charging cycle with a 2h absorption cycle, if the voltage of the array drops below a certain limit (2x times a day max = 0.5 days absorption interval). It would be helpful to manually override the threshold, just like you can do when you have non controlled MPPTs charger (in which you can specify the re-bulk voltage). In any case, knowing the default value would help us in having more prediction over the conditions that trigger a new charging cycle.

Based on our experience and .csv log, it seems like the Multi restart a full charging cycle once the battery voltage drops at the nominal voltage (~ < 25VCC). Can anyone confirm this ?

Thanks in advance for your help !





ESSbattery chargingDVCC
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1 Answer
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Mark answered ·

The Multiplus re-bulk voltage is as follows (depends if 'Lithium batteries' is the selected 'battery type' in the VEConfigure 'charger' tab):

  • Lithium: Re-bulk Voltage = Vfloat - 0.2V (max 13.5V) - for 12V system, multiply by 2 for 24V systems & by 4 for 48V systems
  • Others: Re-bulk Voltage = Vfloat - 1.3V (max 12.9V) - for 12V system, multiply by 2 for 24V systems & by 4 for 48V systems
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