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BQ24650: Dual input charger; DC input from AC/DC converter and input from 100W solar panel.

Ivor Kruger15
Prodigy 160 points
Part Number: BQ24650

Hi, I have a new application that is rather cost sensitive due to volumes. The planned roll out is for 40k units in 1year.

The product is in two variants, one with solar/AC and one only AC. (AC = 220V 50Hz).

The solar panel is 100Wp, Vmp=18V and Voc=22.2V

The battery that must be charged is 75Ah 12V Gel Lead Acid.

From my brief readings on the BQ24650, the MPP voltage is configured for the device and panel.

I have also seen on the forum that the AC/DC converter input can be OR-ed with diode as input to BQ.

My concern/question is about the setting of the MPP voltage on device when using the AC/DC input. This PSU will probably have 12V (or maybe 24V) output.

How will the device react to the different input voltage?

Of course, I would like to use only a single board for both variants.

Looking forward to some expert advice.

  • 0
    TI__Mastermind 20570 points

    If you set your MPPT resistor divider according to the solar panel, the charge current will be reduced  when using AC/DC converter since the converter's output voltage (12V) is lower than the solar panel voltage. If MPPSET is pulled down below 75 mV, then charge is disabled.

    If the AC/DC converter output is higher than the panel output voltage, then it should be fine.

    Also, the bq24650 is a buck charger, which input voltage has to be higher than the battery voltage. If the input is 12V, and you have a 12V battery, then the battery cannot be fully charged.

  • 0 in reply to Jing Zou
    Prodigy 160 points
    Thanks for the prompt reply.
    So if I make the AC/DC to be 15V (or 18V), the charge current would remain high?
    And use a diode OR?
    Is it possible to prioritize the solar input?
  • 0 in reply to Ivor Kruger15
    TI__Mastermind 20570 points
    If your panel VMP is 18V, you probably want to use AC/DC higher than that. It would be better if your AC/DC can be around your VOC.
    A diode OR is typically used.
    I think it is possible to prioritize the solar input if using MCU and switches to select input source.