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I am trying to design an MPPT charge controller based on an interleaved buck converter. Per my design, I use the present panel voltage to compute the duty cycle that first outputs 14.4 V which is charging voltage for the battery, after which the relay that connects the battery to this 14.4 V voltage is activated. I have a few questions from this.

  1. Is generating 14.4 V before connecting to the battery the right approach?

  2. When battery gets connected, the measured voltage does not reflect the battery OC (open-circuit) voltage, neither does it reflects the charging voltage, why is this? Does this have to do with internal resistance of the battery?

  3. As the MPPT varies the duty cycle in an attempt to maximize current, this voltage measured while charging often increases and goes above 14.4 V, since I have a protection set at 14.6 V in the code to flag an error and restart charging when this occurs, the system continually tries to restart charging when this occurs. is this normal? Because I never expects the voltage measured to exceed 14.4 V?

What am I missing here related to battery charging?

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  • \$\begingroup\$ Is the battery hard connected or via battery clamps? Do you have any SSR to protect against reverse polarity, sparks/inrush current and similar? \$\endgroup\$
    – winny
    Commented Dec 12, 2023 at 15:16
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    \$\begingroup\$ What is the battery? Add the battery type, voltage range, current rating, etc., to the question. If it has a part number and datasheet, a link to it would be great. Also, add a high-level connection diagram. If you are designing the schematic, share that too. There could be a problem there. \$\endgroup\$
    – Saadat
    Commented Dec 12, 2023 at 15:26
  • \$\begingroup\$ If this is a 12 V lead-acid battery, 14.4 V is a normal full-charge voltage for those. \$\endgroup\$
    – Hearth
    Commented Dec 12, 2023 at 15:51
  • \$\begingroup\$ If the voltage rises too high, you need to stop attempting to maximize the current, since the battery is getting full and can no longer accept that current. Instead, you should switch to a simple voltage-regulating mode (float charging). \$\endgroup\$
    – Dave Tweed
    Commented Dec 12, 2023 at 22:11
  • \$\begingroup\$ Yes, the battery was connected through battery clamps, with necessary protections in place. \$\endgroup\$
    – Peace
    Commented Feb 9 at 10:26

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