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I have a 12 V, 24 Ah lead-acid battery that I have to charge using a solar panel.

My initial solution to the problem was to implement a buck or a buck-boost DC-DC converter with MPPT and control the charge by sensing the output voltage and current. I then realized that when implementing MPPT I can not keep the output voltage constant.

The alternative to this is to use a casacade boost-buck converter to charge the battery, that way I can simultaneously implement my MPPT and charge controller independently. I can use the boost to control MPPT and the buck to control the charging, is this a feasible solution? If not, are there any alternatives, especially any involving single-stage configuration?

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  • \$\begingroup\$ No need for more than one stage! Just buy a GENASUN GV-4-PB-12V and be done with it? \$\endgroup\$
    – winny
    Sep 4, 2020 at 15:30
  • \$\begingroup\$ Reopened after editing by ocrdu. \$\endgroup\$
    – Russell McMahon
    May 31, 2022 at 12:46

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You don't want to charge lead-acid from a constant voltage, and if you do, you need to change the voltage depending on the state of charge of the battery (switching from constant voltage "second stage" charging to trickle charge).

Google "lead acid charging algorithm".

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  • \$\begingroup\$ I want to charge it with the constant current constant voltage charge method, I want to extract maximum power from the PV panel and also use the three stage charging method \$\endgroup\$
    – Kevin
    Sep 4, 2020 at 15:22
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Never done this, but I think it could work: you could control the DC/DC converter's input for MPPT during CC charging, and control its output during CV charging and float charging.

You would only have MPPT in the CC stage. You would still have to monitor the voltage and current to decide which stage to start (and end).

If you want MPPT in all charging stages, I see no other way than building a MPPT and a separate charger fed from the output of the DC/DC converter. I do hope somebody else does see a way of doing it, though.

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