bq24650 Charging a SuperCaps (3000F @ 2.7V)

Is the charger in precharge or fast charge with the MOD?  What does the charge current look like?

What does the FB look like with a scope.   Does it stay above 1.6V?

The  FB line is clean and steady. The charge current according to the limited digits on my bench supply was somewhere between 10-20mA.

I did leave the unit running last and eventually it did charge. I'm discharging the supercap now for another run, but this time not draining it so completely.

  -Ben

The bq24640 is a super cap charger with the precharge removed.

but doesn't handle solar panels apparently.

See: http://e2e.ti.com/support/power_management/battery_management/f/179/t/253055.aspx

This is the client who handed me the PCB to test...

So being used with a panel (eventually) is this the device we want?

 -Ben

The bq24650 is for a solar panel input.

I understand that... That's why I'm told this was the device chosen.

So the question becomes -- how to modify it so that it works with a superCap.

Thanks,

 -Ben

You are on the right track clamping the feedback to make the part think it does not get into precharge.

There may be a short circuit mode where the part protects itself and just provides a small recovery current.

I would run a normal charge test starting at zero volts on the battery and monitor the current while raising the battery voltage up toward regulation and see what the charge current profile looks like.  We expect to see precharge at CC/10 and fast charge at CC until regulation, but it would be interesting to see what comes out of the charger at very low voltage.

Please remember this chip was design for li-ion cells which should have a protector. Tpically the Li-Ion cells open their protection below 2.5V/cell, so below this voltage the charger is not characterized for charge current in detail.  Most charges put out a recovery curernt when below a certain minimum voltage.  This voltage may be monitored by the SRN pin which is not modified by the divider.

Well, the SuperCap has been discharged to near zero volts.

I'll let the client know (who now has the demokit PCB with the needed mods on it)

 -Ben

Thank you!

Hi,

I know this is an old thread, but I thought that opening another thread would be unnecessary.

I just want to know if someone managed to build a supercap solar charger with this IC. If not, is there another option for this? 

Thank you.

I'll try with these settings.