battery-chemistrylithium ionmosfetsolar cellsolar-charge-controller
I’m charging a Li-ion 3.7 V, 3500 mAh using a TP4056 charge controller IC and feeding a 6 V, 9 W monocrystalline solar panel to charge it.
When I connect the solar panel at good sun light at 2 PM in the noon, though what ever the programmable resistor I connect Rprog, 1k, 2k, 3k or 4.7k, the 4056 IC is heating very badly, at times my skin got peel off. What is the mistake we are doing?
I like the answer you suggested a lot. I think it is a good idea. I would suggest just a slight variation as follows:
Also, please work through the corner cases and unusual circumstances such as when the battery is dead, and arduino cannot power on. Will the charger be stuck in a zero charge current mode? Maybe a strategic pullup or pulldown somewhere, or a large resistor in parallel with RPROG and 100uF cap to insure small charge current even when PWM is off.
Great job!
McKenzie
You're about right
I've checked your numbers and it looks like you have done the calculation correctly. 150W per square meter is pretty good, most panels will be a bit worse than that, even pointed at the noon sun. I expect an average of 150W for 8h a day is a bit optimistic too. Here in the UK the average is about 10% of the rated output, so it would take about 20 days, not 7. With sun tracking panels and a sunnier climate, you'd do better, but 7 days would be impressive.
You haven't considered efficiency losses either. Some energy will be lost in transmission from the panels to the car (either becasue of the huge current flowing, or in the converters mentioned below) and in charging the batteries. Probably only 10-15%, so not worth worrying about if you're just getting a general estimate.
You might also choose not to charge the batteries at 12V/125A. That would require some very thick, heavy cables - probably 8-10mm diameter copper. Instead it might be better to connect the solar panels to a converter and step up to 100-200V, ac or dc, and convert back at the car. Since the car has a built-in converter for 120Vac input, it would make sense to use that.
Best Answer
As @winny says, there is no place for the heat to go without a heat sink, so the temperature will rise. This device detects its own junction temperature, and will automatically reduce its output current to maintain the junction temperature at 145 Celsius. So with no heat sink, the chip will reach this temperature regardless of Rprog.