I’m using an MP26101 in a 2-cell configuration with the sch suggested in the datasheet. It’s a remote data logger which is supposed to be charged with a 5W solar panel. Experimenting with a 12V supply instead of a solar panel I have the problem that the MP26101 doesn’t resume charging (ACOK and CHOK off, SW at Vbat level) if I disconnect the 12V for a longer period (longer than 30min seems to do the trick) and then reconnect it. The only way to get charging to start is to disconnect both the 12V input voltage AND the battery for a second or two. It’s as if POR is required for charging to resume and POR can only happen if the battery and input voltage are off at the same time. If this normal behaviour?
Hi Viktor,
When reconnecting the input (12V) back to system, were batteries were fully charged? or did you test this with depleted batteries? and did you give some time to observe the full charge cycle for the batteries through Trickle Charge > Constant current charge > Constant voltage.
With respect to POR, there are 2 conditions as per page 11 of datasheet regarding the Vin. 12V input meets both of those requirements.
Can you kindly confirm what is your Ctmr cap?
Best,
Nouman
Hello Nouman,
Thanks for your quick response.
I was trying to simulate normal solar charging conditions so the batteries were not fully charged. The 2S cells I used for testing usually had a voltage between 7.5V and 7.8V at the moment of disconnecting the 12V input and not much less at the moment of reconnecting it. The only time reconnecting the 12V would get the device to resume normal operation (LEDs on, activity on SW pin) was when the batteries were discharged under 5V.
I did wait 30min (and more) after reconnecting the 12V input for the LEDs to turn on and pulses on the SW pin, but this didn’t happen.
I made several boards with Ctmr=100nF and one with 10nF.
BTW shouldn’t the LEDs be active during trickle charge?
Cheers,
Viktor
Not to rain on the parade or anything, but is this the correct choice for a solar charger? What happens first thing in the morning as the sun comes up but the available solar power is far lower than the demanded charge power? At a guess the chip sits at 88% duty cycle and crunches the panel preventing it from operating at its’ optimum voltage the Vmpp. I would suggest adding an op amp that tugs via a diode on the I comp pin to regulate the imput voltage to no less than the Vmpp.
Thanks for the suggestion and don’t worry, my parade is thoroughly soaked already.
Until I get the MP26101 to restart charging at all the next time the sun comes up or a big cloud goes away, the MPP is the least of my worries.
My device uses very little power and a 5W solar panel with two 1500mAh LiIon batteries should be enough to not have to squeeze the most out of the panel. Again, if I can get the MP26101 to start without disconnecting the batteries.