Charging with bq24074 while load is active never completes?

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sigwx
 
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Charging with bq24074 while load is active never completes?

Post by sigwx »

Trying for a simple solar setup with charging a backup battery.
Set up the bq24074 (Product ID: 4755) with the 6600mAh battery (Product ID: 353) and the PowerBoost 1000 Basic (Product ID: 2030) as the 'load'.

With the battery on the bq24074 and the PowerBoost connected to the Load (the PowerBoost itself has -nothing- connected, so its loading is minimal), with a 2Amp USB-C charger the Chg light never turns off on the bq24074.

If I disconnect the PowerBoost, the Chg light will turn off, so the bq24074 does appear to charge the battery when there is -0- load.

So should the bq24074 be able to charge the battery while a load is active?

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Re: Charging with bq24074 while load is active never complet

Post by adafruit_support_bill »

That sounds about right. The last phase of the LiPo charge cycle is a constant voltage 'trickle' charge to level out the charge across the cell. It completes when the current falls to zero. With any load connected, the current will never quite get to zero.

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Re: Charging with bq24074 while load is active never complet

Post by sigwx »

Good to know, thanks!

Now, then with 6600mAh, and an approx 300ma load after the PowerBoost, I get about 3-4 hrs after the sun goes down.
Any information on the operating efficiency on the PowerBoost? It seemed like things should have lasted longer.

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Re: Charging with bq24074 while load is active never complet

Post by adafruit_support_bill »

What are you using for a solar panel?

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sigwx
 
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Re: Charging with bq24074 while load is active never complet

Post by sigwx »

An HQST 10w panel that claims 9.8V operating but 12v open. I've run that through a converter to get it down to 5V since the bq24074's protection circuit would shut it down if the panel ever did reach over 10V.

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Re: Charging with bq24074 while load is active never complet

Post by sigwx »

Though what I've noticed lately is that I can remove everything, connect the battery to the bq24074 and power the bq24074 from its USB-C connection, and the charge light isn't turning off anymore, even after 48 hours on a charge.

The battery is the Lithium Ion Battery Pack - 3.7V 6600mAh (Product ID: 353) which I thought has over-discharge protection, and the bq24074 should be handling over-charging. Is there a way to determine if there is a battery problem?

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Re: Charging with bq24074 while load is active never complet

Post by adafruit_support_bill »

Disconnect the battery from the charger and measure the voltage on the battery leads. All our cells have protection circuits, so they should not go below about 3v.

48 hours on a USB power source with no load attached should be more than enough to charge that battery if it is healthy.

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Re: Charging with bq24074 while load is active never complet

Post by sigwx »

Battery is showing 4.1V with my meter, so it seems charged.

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Re: Charging with bq24074 while load is active never complet

Post by adafruit_support_bill »

So it is charging, but the charge never finishes. Full charge should be 4.2V. But I have seen meters off by more than 0.1v. What voltage do you measure between the GND and VBus pins?

And with the battery connected and the charger powered, measure the voltage between the GND and LiPo pins..

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Re: Charging with bq24074 while load is active never complet

Post by sigwx »

Well, I tried a discharge test where I plugged the battery to the PowerBoost Basic 1000, and that to a ~100ma load, using a USB Voltage tester to track mAh consumed and the battery stopped at 3554 mAh

So it is definitely in a state where it will be charging, and for that I see 4.55v on VBus/Gnd and 2.78v between LiPo/Gnd waiting to see what that looks like after a few hours

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Re: Charging with bq24074 while load is active never complet

Post by adafruit_support_bill »

VBus should be much closer to 5v. If the voltage of your power supply is sagging, most likely it is not able to source sufficient current.

You did not specify whether the LiPo/GND measurement was with the battery connected or not. But in either case, would not expect it to be below 3v.

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Re: Charging with bq24074 while load is active never complet

Post by sigwx »

After a few hours now, VBus is 4.9V and LiPo is 3.55V, battery connected.

The previous LiPo reading was with the battery connected.

Power is USB-C, 2Amp tested at 5.05V

Without a battery connected, VBus is 4.51V and the LiPo output is all over the map, ranging from 0.55V to 3.55V

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Re: Charging with bq24074 while load is active never complet

Post by adafruit_support_bill »

Without a battery connected, VBus is 4.51V and the LiPo output is all over the map, ranging from 0.55V to 3.55V
VBus should only be a Schottky diode drop below your USB supply voltage. That would be about 4.7v.
The LiPo connection on the charger will vary as it attempts to detect whether there is a chargeable batter connected.

What is the voltage across the battery itself now (disconnected from the charger)?

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Re: Charging with bq24074 while load is active never complet

Post by sigwx »

After an overnight charge, the battery disconnected is 3.87V

Putting it back on the bq24074, the LiPo output shows 3.87V and the VBus is 4.88V

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Re: Charging with bq24074 while load is active never complet

Post by adafruit_support_bill »

We can try replacing the charger. If you purchased directly from us, you can contact [email protected]. Otherwise contact the seller. In either case, please include a link to this thread as authorization for a replacement.

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