Solar/LiPo Charger

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philiplgraitcer
 
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Solar/LiPo Charger

Post by philiplgraitcer »

I am trying to solar power a remote weather station: arduino, Sparkfun weather shield, xbee series 1 pro. I have the adafruit solar/LiPo charger and adafruit 2200mah LiPo battery. I have a couple of 5x5inch solar panels in series that produces about 6 volts in full sun. When in full sun, the charger works great: the power and charging lights are on most of the time, sometimes I get the green done. When the solar panels are shaded, the power and charging LEDs flash and continue to flash, even though battery voltage reads 4.6 and the load voltage output is 4.6. But the weather station does not work. It stays in this state until sun hits the panels again.
I have the charger hooked up per your tutorial. I am running power into the 3.3 terminal on the Arduino, and have the xbee on a breakoutboard, with 3.3 line going to a 3.3 v on shield. What am I doing wrong.

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adafruit_support_mike
 
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Re: Solar/LiPo Charger

Post by adafruit_support_mike »

The Arduino's 3.3v pin isn't a power input. It goes to the 3.3v voltage regulator's output.

The 3.3v regulator has a built-in diode to protect it from reverse current (just checked with a meter), so when the Solar Charger's output is around 6v, power will flow through that diode to the Arduino's 5v rail and power the microcontroller. When the voltage drops to 4.2v (normal for a fully-charged LiPo), power might not flow back through the regulator as well.

It's possible to run an Arduino from 3.3v, but you'll want to replace the voltage regulator as shown in this tutorial:

https://learn.adafruit.com/arduino-tips ... conversion

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philiplgraitcer
 
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Re: Solar/LiPo Charger

Post by philiplgraitcer »

Thanks, Mike, for the information. Didn't realize the 3.3v pin was an output. Do I understand correctly that the coaxial jack and the USB jack are the only inputs? Is there any reason why I couldn't feed the output of the solar charger into a buck board and then send those 5 volts into the coaxial jack? It is designed to take 5-12 volts, right?

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Re: Solar/LiPo Charger

Post by adafruit_support_mike »

The positive pin in the DC barrel jack is connected to the Vin pin, upstream of the onboard voltage regulator. You can connect any voltage between 7v and 12v to that. The 5v pin is connected to the regulator's output, so you can connect a well-regulated 5v supply to that.

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Re: Solar/LiPo Charger

Post by philiplgraitcer »

In July I ordered the Solar/DC/LiPo Battery charger and in October, when I got the 6000mah battery from you, I put the two together and into an outdoor weather station.

When in full sunlight, the red power and the yellow LEDs are illuminated. When there are clouds, they flash. In sun, eventually the yellow LED goes out and the green LED goes on. I think this is exactly how it should work.

The station has been operational about a week, but yesterday, it stopped working. I decided to check the battery voltage. It was 3.2 volts.

I pulled the charger and battery and brought them indoors and plugged the charger into my computer’s USB. Nothing seemed to happen. No LEDs. I left it plugged in overnight and this morning the battery and load voltage still read 3.2.

I took the battery and charger outside and hooked up my 3W Voltaic solar panel. After about 8 hours of full sunlight (and no load), the B+ is now 3.6, and at the load terminals, measured in full sunlight, it is 4.7v. The solar panel is putting out about 6.5volts.

I think there is something not right with the USB charging part of the charger. Am I correct, or is there something I am doing wrong?

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Re: Solar/LiPo Charger

Post by adafruit_support_mike »

Post a photo showing the charger and the LiPo and we'll see if anything looks out of the ordinary. 800x600 images usually work best.

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philiplgraitcer
 
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Re: Solar/LiPo Charger

Post by philiplgraitcer »

Charger and LiPO battery (plugged into USB). No LED lights. When solar panel attached, RED and YELLO LED light. Battery voltage is at 3.841 V
Charger and LiPO battery (plugged into USB). No LED lights. When solar panel attached, RED and YELLO LED light. Battery voltage is at 3.841 V
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philiplgraitcer
 
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Re: Solar/LiPo Charger

Post by philiplgraitcer »

Here are two pictures of the charger. It does not seem to charge when under USB power - there are no lights. When under solar power, both RED and YELLOW LEDS are lit. When fully charged, GREEN comes on.

Please advise.
Attachments
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FullSizeRender.jpg (256.41 KiB) Viewed 800 times

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Re: Solar/LiPo Charger

Post by adafruit_support_mike »

Hmm.. nothing obviously out of place.

The symptoms are unusual because the USB jack and the DC barrel jack are connected to the same pin of the MCP73871. The USB jack is actually a little closer because there's a polarity protection diode that goes to the solar panel.

Try connecting the USB cable and measuring the voltage between the DC IN holes next to the USB jack.

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Re: Solar/LiPo Charger

Post by philiplgraitcer »

I have connected the USB CABLE and measured the voltage at the DC in pads; it is zero. Unplugging the USB and plugging in the solar panel, the yellow LED lights.

The 6000mah 3.7v battery that I purchased from you is now dead as well. Hooking up the solar panel to the charging board, does not seem to charge this battery.

Is there a fuse in the battery? Is there a short in the charger?

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Re: Solar/LiPo Charger

Post by adafruit_support_mike »

Let's see if we can sort out the power connections before declaring the LiPo to be dead. I think there might be a bad connection inside the DC barrel jack, so let's test that.

With no cables connected to charger, measure the resistance between the DC IN ground pad and the metal shell of the USB jack.

Then connect the USB cable and measure the voltage between the DC IN positive pad and the metal shell of the USB jack.

The USB jack's ground connection is controlled by a switch built into the DC barrel jack. Plugging the barrel connector in disables the USB power connection. If that switch has gone bad, it would produce the symptoms you're seeing.

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Re: Solar/LiPo Charger

Post by philiplgraitcer »

resistance between USB Shell and DCIn positive = Open
resistance between USB Shell and DCIn negative =Open
Between USB Shell and DCIn positive with USB powered, measures 5.019v
Across the DCIn pads measures 0.20 with USB powered
Battery connected, no USB power, measure on battery pads 3.183v - same if I measure directly on battery
Battery connected, USB powered, measure 3.183 on battery pads and load pads
LED lights do not go on when charger connected.

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Re: Solar/LiPo Charger

Post by adafruit_support_mike »

Yep.. that's a bad plug-detection switch in the DC barrel jack.

Send a note to [email protected] with a link to this thread and the folks there will get you a new Solar LiPo Charger.


(#390)

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philiplgraitcer
 
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Re: Solar/LiPo Charger

Post by philiplgraitcer »

Ok, I have ordered a replacement LiPO charger. Thanks! But what about the two batteries I used on this charger? I have a 6600mah and a 2200mah battery, ordered from Adafruit, that were used in this LiPO/Solar charger. At different times, they were set up with this charger and a Voltaic 3W solar panel. Both discharged to 0.0 volts in the charger. I've checked my circuit for shorts. Now I am wondering, since the LiPO charger has been deemed defective, could it be responsible for the complete discharge of the battery? I thought the charger had a limiting circuit that prevented the complete discharge of the batteries. Yet, in the circuit, which consisted of solar panel, charger, boost converter, hooked up to an Arduino/Xbee combination both batteries ran to zero.
Your thoughts?

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Re: Solar/LiPo Charger

Post by adafruit_support_mike »

The charger doesn't prevent full discharge.

As long as the LiPos drained to 0v gradually, you can probably recover them. All of the MCP738-series LiPo chargers have a low-current preconditioning phase when they see a battery voltage below about 2.9v. If the polymer is good, it will charge to that level in a few seconds, and the regular charging process can take over.

The main risk is that metallic lithium can plate out of the polymer when it's close to 0v, and that produces conductive paths that can short the battery. A few seconds at low current can't plate enough metal to matter.

You don't want to make a habit of letting LiPos drain completely, but it doesn't kill them instantly.

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