BQ24232: Is the BQ24232 suitable for charging a small Lipo cell e.g. 200mAH from a very small solar panel e.g. 70mm x 50mm

Hi Ron,

Do you have information on the power output of the panel? 

The BQ24232 does not have MPPT or Battery Tracking VINDPM like other chargers have that are intended for solar charging. In low light conditions, the panel may be held at the VINDPM threshold on the BQ24232, only allowing for a set amount of current to be provided while the other devices would allow the voltage to be regulated down further. 

For a low charge battery, the BQ25176M may be good unless you're looking for a powerpath device. 

Best Regards,

Anthony Pham

Hi Anthony, thank you very much for getting back.  One panel that we've been trialling is the Ixolar SM141K09L, which is 5 volts out at maximum power, with a peak power of 277 mW.  We are looking to support several wireless sensor devices, although a key one is a cow tracker, where the panel won't always be ideally oriented and will often be in the shade.  An issue is that the BQ24232 has already started to be incorporated in several prototype devices, so changing this would be a relatively significant shift that would need to be justified.  Thanks for the BQ25176M reference.  I was also looking at a BQ25504, although now see that its maximum voltage 5.5 is insufficient. The key point though is whether increased efficiency is likely to be worth what would be seen as another delay in replacing the device.  Power path is also important to optimise battery life, possibly more so than dynamic power point tuning. For such tiny wattages does power point tuning have much impact.  Is it 1 or 2 percent or 10s of percentages? A view on this would be very much appreciated.

Hi Ron,

Let me take a look and see if we have any comparisons. Do note that we don't have any linear chargers with MPPT so this may not be a 1-1 comparison. 

Best Regards,

Anthony Pham

Hi Anthony

Thanks, that would be very much appreciated.  Am unsure what you mean by 'linear chargers'.   Apart from dynamic power tracking our interest is in a charger that can supply the load directly from the solar source whenever there's sufficient power, avoiding the battery being continuously discharged and charged, which will tend to reduce its life.  If we can only have power path or MPPT but not both, the question is which is of more value in reality (rather than necessarily theoretically).  There are some references that indicate that whilst MPPT is a significant advantage at higher wattages it makes only a very small difference at mW levels. So I'd be keen to get a TI view on this.  

Hi Ron,

Ron Segal1 said:

Apart from dynamic power tracking our interest is in a charger that can supply the load directly from the solar source whenever there's sufficient power

This would most likely be a power path scenario. I also sent you an email last week. Let me know if you'd like to take this offline.

Best Regards,

Anthony Pham