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Topic: Charging this Li-Po battery? (Read 514 times) previous topic - next topic

karl101

Hello
I have a ASUS C11-ME307T 3v7 4325mAh battery recovered from a broken tablet. I would like to recharge it with a Sparkfun Single Cell LiPo USB charger, this uses a MCP73831T chip as the Charge Management Controller.

Will this work? I'm asking as there are two extra wires coming out of the battery, a yellow and white. Can I ignore these when using the Sparkfun charger?

Thanks
Karl

raschemmel

#1
Feb 10, 2016, 08:57 pm Last Edit: Feb 10, 2016, 09:01 pm by raschemmel
Did you measure the voltage across the two extra wires ?
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

pwillard

If no voltage... check for resistance.  Since its not a higher voltage than 3.7V, it is likely just  parallel cells which of course can be charged as 1 cell... but the extra wires could be a thermistor, for temperature monitoring.

karl101

I've measured the wires, both the yellow and white appear to have the same output, but don't show continuity so are not connected together.

I measured a resistance of 16.16K between negative and the wires. The reading goes down when I place my hand over where the wires are connected to the battery, I guess this is a thermistor.

raschemmel

Quote
I've measured the wires, both the yellow and white appear to have the same output, but don't show continuity so are not connected together. 
WHAT IS THE OUTPUT ?
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

karl101

WHAT IS THE OUTPUT ?
As I said: "I measured a resistance of 16.16K between negative and the wires. The reading goes down when I place my hand over where the wires are connected to the battery, I guess this is a thermistor."

raschemmel

#6
Feb 10, 2016, 11:19 pm Last Edit: Feb 10, 2016, 11:20 pm by raschemmel
no voltage ?

Put it in the fridge for 15 minutes and measure the resistance again.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

MarkT

The extra connections might be a temperature sensor, might be serial interface to the cell's own
battery management unit, or something other...  Try to see if its temperature response is consistent
- that would probably confirm a thermistor.

Ask ASUS?
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

karl101

no voltage ?

Put it in the fridge for 15 minutes and measure the resistance again.
The voltage between the yellow and white wires is about 20mV. This drops to 0V when I cover and warm the connector end of the battery with the palm of my hand.

I'll try it in the fridge later today.

raschemmel

It's probably a thermociouple.. Thermisters don',t generate voltage.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

karl101

It's probably a thermociouple.. Thermisters don',t generate voltage.
OK, Thanks for that. Is it safe to ignore this for use with my battery charger?

raschemmel

I wouldn't say that. The reason it's there ( IF it IS a Thermocouple is to provide an input for an amplfier circuit. It sounds like a Negative Temperature Coefficient but won',t know till you try the fridge. Lipi batteries can heat up and catch fire if overcharged. Don't ever charge it unattended. If you plyg in the charger and go to a movie , you may come back and find a smoking pile of ashes where your house used to be. If you thinking I'm kidding Google "LIPO FIRES"
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

MarkT

#12
Feb 11, 2016, 02:59 pm Last Edit: Feb 11, 2016, 03:00 pm by MarkT
20mV from a thermocouple at room temperature?  Are you kidding?  That's usually 100's or 1000's of degrees.

The 20mV is probably rectified pickup - placing hand on battery brings its potential to match
the hand holding the multimeter!

Measure the resistance at different temperatures?
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

raschemmel

#13
Feb 11, 2016, 03:13 pm Last Edit: Feb 11, 2016, 03:20 pm by raschemmel
Quote
20mV from a thermocouple at room temperature?  Are you kidding?  That's usually 100's or 1000's of degrees.
 
Thanks for the clarification on that.


According to this lookup table , 39 mV corresponds to -1 degree C
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

Zapro

#14
Feb 12, 2016, 05:31 pm Last Edit: Feb 12, 2016, 05:33 pm by Zapro
It's a good thing that we have google. The Nexus 7-tablet is quite known and the schematics are available if you know where to look.

First off, no battery pack in a consumer item would use a /thermocouple/ - the amplifier/frontend for that would cost way too much, and be WAY overkill.

I post an excerpt from the schematic which shows the connections to the battery. It's a "smart battery" with a fuel guage built-in.

I guess you can use the cell as a "dumb" cell without the smart-battery comms, but i warn you - there probably isn't any over-discharge/overcharge-protection built in.

// Per.

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