bq24074 charger not providing over 0.75 A

[wag10]

Trying to use this charger with a solar panel project. Testing the charger with the Lithium-Ion Polymer Battery - 3.7V 10050mAh (10 Ah) Product ID: 5035 and monitoring the charging current using USB Voltage Meter with OLED Product ID: 2690. I am using a Samsung Galaxy S8 fast-charger base which is rated to provide 5V 2A to supply the bq24074 through the USB port.

The charging current has never exceeded about 0.75 A even though I cut the 1.0 A jumper and soldered the 1.5 A jumper. Is there something else I need to check or do to get the highest charge rate?

[mikeysklar]

Setting up the 1.5A jumper (as you have done) should be all you need to do.

I suspect the battery voltage is not low enough to go into “bulk” charge mode at full current. You are probably just “topping” off in trickle mode.

[languer]

I think @mikeysklar identified what you are seeing.

A reliable LiPO charger will include the following:

1. Constant Current Pre-charge Mode.
2. Constant Current Regulation Mode.
3. Constant Voltage Regulation Mode.

Phase 2 will be "skipped" if the LiPO has not discharged much before you expose it to another charging cycle. In the constant-voltage regulation the LiPO will see reduced current; in my mind it looks more like a top-off stage.

The following are some good resources (certainly two of many):
https://batteryuniversity.com/article/b ... ithium-ion
https://circuitcellar.com/resources/qui ... -charging/

Even though I had read about this, it did not really "sunk in" until I saw a plot of my own system and the LiPO voltage looked nearly identical to those plots shown.

[wag10]

Thank you for the responses - very helpful information. I will take measurements again once the battery is discharged more fully.

[wag10]

Tried with a discharged battery and still not getting more than 1A charging rate. I confirmed that the 1A jumper is cut and there is continuity across the soldered 1.5A jumper - got around 0.97A:

1.5A.jpg (781.64 KiB) Viewed 102 times

Also tried with unaltered charger (default 1.0A jumper still in place) - got around 0.9A:

1.0A.jpg (646.68 KiB) Viewed 102 times

I can try to reflow the solder for the 1.5A jumper or try to modify the other charger to 1.5A and see if it performs any differently. Any other ideas? Charger is getting warm with 1A. 1.5A might be interesting if it ever gets there.

[languer]

Given that all the pictures show the current limited to 0.9A; and 0.9A is one of the current limits on the USB-C standard (0.5A/0.9A/1.5A/3A/5A), it may be that the "smart" USB brick is limiting the current to 0.9A.

[wag10]

Yes I was also thinking that the power supplies could be part of the problem. I've tried several phone bricks but the one being used in the picture is an Anker PowerPort 5 https://www.amazon.com/Anker-5-Port-Cha ... B00VH8ZW02 which supposedly can supply up to 2.4A to each port, but it could also be considered a "smart" charger, I guess.

I will check with a laboratory power supply connected into the solar panel jack later today to completely eliminate that possibility.

[mikeysklar]

Good to see you getting .9A now. Some improvement just by having a drained battery pack.

The power supply you are using seems to have plenty of current being rated for 2.4A and the OLED USB Voltage Meter can handle up to 3A.

The only unknown in the connection is the USB-A <--> USB-C cable. These cables normally have a maximum value of 5v @ 2.4A, but can be less.

A quick way to retest everything would be to use a USB-C <--> USB-C eliminating the USB-A connections and manually time the charge period.