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Adafruit USB Li-Ion/LiPoly Charger - v1.2
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Please be positive and constructive with your questions and comments.

Re: Adafruit USB Li-Ion/LiPoly Charger - v1.2

by Alli on Sun Feb 10, 2019 7:53 am

@Like

I am not an expert on the product and may not be of much help there but since you are not sure where the problme is, have you tried the following:
Have you measured the current to the battery when it should be charging ?
Have to tested the voltage across the battery terminals before charging and after the battery is connected to the charger (with the charger connected to a supply voltage)?
Have you tried charging a similar battery and was it successful ?
If you have, please share the results.

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Re: Adafruit USB Li-Ion/LiPoly Charger - v1.2

by luke1976 on Sun Feb 10, 2019 6:05 pm

Thanks so much for your reply. I had not realised lipo batteries were so sensitive (if that's the right word). I hadn't charged it in over a year, and it may be that I simply can't charge it any more and I need to try again with a new battery. Although from memory, it never did charge the battery (which was new when the charger was new).

I will get my meter out and post the results.

Thanks again.

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Re: Adafruit USB Li-Ion/LiPoly Charger - v1.2

by Alli on Fri Feb 15, 2019 9:52 am

@Mike

Is there a rule that states what the resistance should be in conjunction with the input impedance of the micro when measuring the supply voltage?

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Re: Adafruit USB Li-Ion/LiPoly Charger - v1.2

by adafruit_support_mike on Sat Feb 16, 2019 1:29 am

There's no specific rule for the resistor values, but 150k-150k is convenient.

When the LiPo voltage is 3.6V, the current through that voltage divider will be about 12uA. Current will always flow through those resistors, but it will take about 80 hours to consume 1mAh of energy stored in the LiPo.

If you dropped the resistor values to 150-150, the current through the divider would be around 12mA, which would drain a 1000mAh LiPo in about 80 hours.

Higher resistor values create larger errors when you read them with an ADC pin though. The pin draws a small amount of current from the divider to get its measurement, and that current creates an error voltage across the divider's resistors. The ADC current is around 1uA, and the current through a 150k-150k divider is about ten times larger than that. That keeps the errors small enough to safely ignore.

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Re: Adafruit USB Li-Ion/LiPoly Charger - v1.2

by Alli on Sat Feb 16, 2019 9:51 am

Thanks again Mike. Truly grateful for all your advice and assistance

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Re: Adafruit USB Li-Ion/LiPoly Charger - v1.2

by crazy1gadgets on Sat Feb 23, 2019 7:22 pm

Can this device be configured to charge a cell phone? Based on various articles I have read I have heard it is not always best to charge cell phones to 100% maximum, so I am trying to control charging rate so that I can limit the overnight maximum charge the cell phone receives (I usually plug in at night, and unplug 1st thing in the AM). So far I have not had luck. I have made my own JST to USB-Micro adaptor to plug into the cell phone and I get no indication the phone is charging at all. Any comments on this would be welcome

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Re: Adafruit USB Li-Ion/LiPoly Charger - v1.2

by adafruit_support_mike on Mon Feb 25, 2019 3:13 am

No, the phone has its own, built-in LiPo charger that wants a 5V DC power source.

Charging to 100% is okay as long as you don't leave the LiPo sitting that way for a long time (more than a week or so). The preferred level for long-term storage is 80%.

LiPos aren't subject to what's known as 'memory effect' in NiCads, so charging back to 100% is okay even if you haven't drained the LiPo all the way.

The LiPo charging cycle is kind of complicated, so LiPo chargers are careful not to overcharge a cell, or to start a new charging cycle when it could put unnecessary stress on the polymer.

If you want to exercise your phone's LiPo more (let its charge drop lower before recharging), you can do it by charging every other day, or just checking the battery level before plugging in the charger. If the battery level is higher than about 75%, you can skip that night's charge.

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Re: Adafruit USB Li-Ion/LiPoly Charger - v1.2

by crazy1gadgets on Fri Mar 22, 2019 2:37 pm

Thanks, this helps a lot!

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