tyrel
New Member
Posts: 6
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Post by tyrel on Feb 2, 2021 21:18:46 GMT -8
I have a SunAirPlus (part of the SkyWeather kit) that I'm not sure is working right, or maybe this is by design? I have an external power source connected via USB, and a battery connected to the battery connector. My expectation was that the battery would get charged by the external power source, and if that source went away, then the battery would power the device until it was depleted or external power (or solar power) returned. However, it doesn't appear to be charging the battery. The battery is actually discharging while external power is supplied.
At this moment my load is reading 0.736 W, my battery is providing 0.443 W, with no solar power. So I guess it's pulling 0.293 W from the USB cord, for some reason. Why doesn't it pull more and charge the battery?
In addition, there doesn't appear to be a way to read the external power information from the device. There are only three "channels" used in the code in SkyWeather.py: LIPO_BATTERY_CHANNEL, SOLAR_CELL_CHANNEL, and OUTPUT_CHANNEL. Is there something hiding I could use?
Thanks!
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Post by SDL on Feb 3, 2021 8:47:19 GMT -8
The usual reason for this is that your USB power supply isn't providing enough voltage / current to really charge the battery. Try a better USB power supply and check to see your USB power supply is supplying at least 5.2V.
You can't read the power coming from the USB Power supply. It gets mixed in with the solar and battery charge.
BP
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tyrel
New Member
Posts: 6
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Post by tyrel on Feb 4, 2021 8:40:01 GMT -8
The USB spec is 5.00V with an acceptable range of 4.40V to 5.25V. My USB power supply is outputting 5.06V, well within this standard, and can do up to 3A (which is more than the standard). How can you expect a USB cord to supply at least 5.2V when this is barely within the spec?
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Post by SDL on Feb 4, 2021 8:55:09 GMT -8
Due to the protection diode drop and the way solar chargers work, you need to have more than 5V (~5.1V to ~5.2V)to charge the battery when you have a load present. And it's not linear. You will get a lot more charging at 5.2V versus a lower voltage. If you unload the system, you should be able to charge the battery, albeit slowly. The USB input is really designed to supply power to a load with a secondary benefit of charging the battery (with load removed).
Inexpensive cables also drop a large amount of voltage. When you measured the voltage, was it at the power supply or at the end of the cord? A good cord will drop less voltage. Good USB power supplies generally output 5.2V to compensate for inexpensive cords.
Another way of charging the battery would be to use a variable power supply and supply ~5.5V to the solar panel inputs.
BP
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