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How to charge a battery without the charging port!


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7 replies to this topic

#1 IowaGuy

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Posted 16 February 2013 - 01:31 PM

Photo link: http://flic.kr/p/dVk9X3

 

Here is a photo (turns out I dont know how tp post a photo here!) of the inside of a Maylong m270 tablet. It has a sheared off micro USB charging port. I am wondering of anyone knows what terminials I can use to recharge the battery. The tablet says its dead. In the photo going from left to right  starting with the rectangular blank terminal is labeled B+. The red wire is labled P+, Blue wire is T, Black wire is P-, and the other blank is B-. If put my volt meter on the terminals I get:

 

               B- to B+ is 4.8v

               B- to P+ is 4.8v

               B- to T is  4.4v

               B- to P- is 4.4v

 

Any combo of the 3 middle terminals I get 0 volts. 

 

Obviously the battery isnt dead, but the part the tablet uses must be. The back side of the battery pack says 3000 mAh 3.7 volt.

 

If any one knows what terminals need to be used to charge I'd appreciate it!


Edited by IowaGuy, 17 February 2013 - 12:16 PM.


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#2 Uncle Rim

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Posted 17 February 2013 - 03:00 AM

If you plan to attach wires to charge the battery, you might be better off looking at the USB connection rather than the battery connection. The USB standard is pin 1 is +5V and pin 5 is the ground. Pins 2 and 3 are data. Pin 4 is either connected to pin 5 in type A and unconnected in type B.

 

At a guess, P+ means power positive and B- is battery negative. The red and black wires confirm this (not that standards are closely followed internally these days). These probably have close enough to a direct connection but connecting here will bypass any charging circuits and could lead to over charging the battery.

 

I can't imagine how an internal socket got sheared off. Perhaps I don't want to know!



#3 IowaGuy

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Posted 17 February 2013 - 12:15 PM

My guess is the guy or kid dropped it while the charger was plugged in and landed right on that side. I was gonna try to re solder the port back in only concentrating on the pos and neg terminals, but there just isnt enough there and far to small to do it. Plus it took part of the circuit board with it. I realize I could over charge the battery, but plan to be careful and hopefully can just watch the battery indicator rise.

 

I get 4.5 volts at the terminals P+ and B- that you said to charge from. (I just realized in the original post I had the black wire labeled as B- but I meant P-. I get zero volts at those two.) Did you mean to use the red and black wires to charge from? Does the tablet still consider the battery dead at those volts? Or is it more of an amps thing. I cant remember how to measure those anyway!

 

Thanks for your input!


Edited by IowaGuy, 17 February 2013 - 12:20 PM.


#4 rotor123

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Posted 17 February 2013 - 01:25 PM

Hi, This might help.

 

Inserting An Image Within A Post

http://www.bleepingcomputer.com/forums/t/14738/inserting-an-image-within-a-post/

 

Sample: badcaps.jpg

Uploaded with ImageShack.us

 

Hope this helps

Roger


Edited by rotor123, 17 February 2013 - 01:26 PM.

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#5 Uncle Rim

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Posted 18 February 2013 - 05:47 PM

Sorry for taking so long to get back to you.

 

The tablet should not be declaring the battery dead at 4.5V. This is higher than the nominal capacity of the battery, usually 3.7 - 4.2V. I would suspect that the part of the board which broke off contained more than just the USB port. In order to achieve the small size, multilayer boards are used with connections running through them.

 

I wouldn't be concerned about the lack of voltage on charging points. There is probably a diode to prevent the charger taking power from the battery. It also serves to prevent reverse polarity if a faulty charger is used.

 

At this stage, just connect the charger to the posiitive and negative you find. It doesn't sound like you hjave much to lose!



#6 IowaGuy

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Posted 18 February 2013 - 11:17 PM

Ok one last question, and thanks for your input! You are correct that I dont have much to loose! Well except the 100 bucks ebay BUYER protection screwed me out of!

 

What spots do you recommend I attach to? Originally you had said P+ and the B- that I miss labeled. Are you thinking the red and black wires that are P+ and P-? Correctly this time, from left to right I have:

 

B+, P+, T, P-, and B-



#7 Uncle Rim

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Posted 19 February 2013 - 07:14 AM

The Pand B connections essentially connect to the battery and either will provide charge. The difference is the P connections have protection that I described in the previous post. If you are sure about polarity, either will do. I have no idea what the T connection is (perhaps a thermister to prevent overheating?).

 

You have measured 4.5 volts in circuit. Even though this is without load I would expect the tablet to boot with that. You can try futher charging the battery, but I don't feel this will achieve anything. While you are down a hundred bucks, a few minutes soldering is worth a try.

 

It is almost impossible to break the USB connector off the board by dropping the tablet. The cable is thick enough to hold the tablet so that the other side will hit the floor first. There is something more sinister in the history of this tablet.



#8 Sneakycyber

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Posted 21 February 2013 - 04:59 AM

If you feel up to replacing the usb port, I order from here atleast monthly


Chad Mockensturm 
Network Engineer
Certified CompTia Network +, A +




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