Selecting the right charge controller

Check out http://www.ti.com/lit/pdf/slva437.  The bq24650 does not have to be powered from a solar cell.  The same concept should work with any of the bq2426x family.

Hi,

I was wondering if someone could help me find the best charger for my application. What i need are:

• Charger a 12V battery, from 6Voc, 4A Isc solar panel
• Charger that support both lead acid and Li+ batteries
• Easily adjustable output/charge current and voltage

Thanks in advace,

Best regards,

Miguel

You will need a boost converter.  The bq24650 can also be converted into a boost converter as explained here: http://www.ti.com/litv/pdf/slyt424.   Combining this app note with the one in the previous post is our best solution.

Thanks! Do you have any AN or something to help me with dimensioning of the componens?

Best Regards

I suggest reviewing the datasheet and online design tools for the TPS40210 for help sizing the inductor, power FET and Schottky diode for the bq24650 as a boost.

In the example shown on http://www.ti.com/litv/pdf/slyt424, it does't mention the TPS40210.
Can't I make my design with the example circuit shown on http://www.ti.com/litv/pdf/slyt424?

Thanks,

Miguel

In slyt424, L1, Q1 and D1 were sized for certain maximum current level. You would need to ensure that those components are rated high enough for your application.  The TPS40210 is a generic boost converter that has equations and tools to help you size and select those components.

However, with only 6Voc, your MPP point will be 80%*6V = 4.8V which is below the 5V minimum operating point for this device.  So, the circuit as shown in slyt424 would not work for you.  

In theory (meaning not tested), you could take a second, low switch current boost IC, like TPS61041, to provide a >12V power rail from the solar panel to VCC, removing R2 in the slyt424 schematic.  If you do this, then you don't need D2, U2, R17, U3, R20, C7 and D3 and R21 can be directly connected to SRP and SNP.  R11 and R12 will also need to change to set the 12V output regulation level.  Since your power level is slightly higher the design in slyt424, you will likely also need to increase C3 and C4 to better filter the output current and therefore get a more accurate current measurement.  Good luck!

Hi Jeff,

Thak you very much! Now I think i can do it.

Best regards,

Miguel