Thursday, March 27, 2014

Default Charge profiles

The past few days I have been pouring over different battery manufactures tech manuals and their recommended charge profiles.  What strikes me is the rather wide variation in approaches for charging, even the good old Flooded Lead Acid batteries, everyone seems to have a slightly different idea on what makes a Good Charger.

But one thing all  battery manufactures have in common is the idea of ending charging when the battery is truly fully charged, and with the exception of LiFeP04 batteries - that all really depended on measuring the Amp the battery is accepting.

I have posted many of the technical manuals I found on the Google drive, click on the 'Reference' tag above.

It was interesting to research the LeFiP04 batteries.  These have the look to becoming a standard in a few years, prices need to drop a little, but they have lots of good reasons to use them over FLAs.  With a proper Battery Manager on each cell, most all issues of the past go away.  Charging them looks to also be simple:  LiFeP04 batteries exhibit a rather flat discharge curve - holding their voltage constant until they are just about exhausted.  When recharging, it is about the same - they hold a steady voltage until they are full, then the volts start to rise quickly!  I placed in a default LiFeP04 profile that seems to match a few of the larger batteries out there, but truth be told I thin the profile will need to be customized for each battery and BM combination.

Here is the default table I have as of now:

Click for larger view.

This is a large table, click on it to get a larger view.  (And see the source code for more details, ala how to drop out of Float mode and get back into Bulk mode)

If interest is #7, this was an advanced charge profile recommended by one manufacture for their large industrial batteries.  Not the 4th phase which is Amp limited, letting the voltage rise.  Also of key note is the Exit Absorption phase  by Time and/or Amps.  Almost without exception, battery manufactures prefer using Amps as a trigger point for deciding the battery is fully charged.  In fact, many will recommend a dramatically shorter max time (like 3hrs) if Amps are NOT being measured, to prevent overcharging.

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