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| Current for a buck boost converter. |
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| Siddhat:
Hey everyone, I just finished designing a buck boost converter. The converter is implementing a Maximum Power Point Tracking (MPPT) algorithm at its input. Now I would like to charge a 12 Volts lead-acid battery with the buck-boost. The voltage at the output of the converter is held by the voltage of the lead-acid battery. But in order to charge the battery properly, the current into the battery from the converter is to be controlled. I could not figure out a way to control the output current of the converter. How can the current be controlled? |
| Vovk_Z:
We change the charging current by changing the output voltage. If current is too large - lover the voltage and vice versa. The limits of charging voltage are somewere in between 12V - 16 V (it depends on additional parameters). |
| Ian.M:
You cant control the output current independently if you are running MPPT at the input - the system is over constrained and cannot magically make the input power different from the output power + losses. However you can and should implement output current and voltage limiting. If either limit is exceeded it should drop out of MPPT mode. For lead acid battery charging applications the voltage limit should be temperature compensated, and its advantageous to track charging/discharging history and state of charge with a MCU so it can vary the limits to run a more effective lead-acid charging algorithm and reduce wear on the battery. How to implement that lot is highly dependent on your buck-boost topology, and whether you have built the controller from scratch or are using off the shelf controller ICs. |
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