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Thinkpad will only re-charge if it is "off"  (or sleeping)

chinman asked
Medium Priority
Last Modified: 2008-03-06
Concerning a 755c ThinkPad.
I have owned many different models of ThinkPads and have never had this problem with any other unit. Plus I have 2 of these 755c Thinkpads, and both of them are doing the same thing. IBM service center indicates that it may be a battery problem. I think it very strange that I bought two seperate units and both are experiencing the exact same problem?????????
Anyway - All works well except that neither of these units will re-charge the battery while being used... It will only re-charge if the unit is is either off or in standby mode.
Do any of you very smart and nice people have any advice for me? I can return them to the seller but I really want to keep them. And I've worked very hard loading my software on them and all. By the way - They are running win95.
Watch Question

This is "normal" behavior on this laptop as well as many others.  It is actually charging when powered on but at a VERY slow rate.  The problem is that the external power supply is designed to be as small and light as possible.  The benefits are fairly obvious but the drawback is that the amount of power that it puts out is quite limited.  When the unit is turned on, there is not much excess power provided to charge the battery.  This is why switching to standby or powering down makes the battery charge.  My Toshiba 730 laptop will charge the battery in about 24 hours when powered up but will charge in about 2 hours when turned off.  If this is a big issue, there are 3rd party suppliers who can set you up with a beefier power supply that will give you enough power to run the computer and charge at the same time.


Your explanation sounds logical but in this case is not correct. IBM not only told me how the unit should charge, I have owned a lot of other Thinkpads and have never experienced this with any other. A IBM document (on this unit) clearly states that 1.5 hours are required to charge the machine when not in use and that only 2.0 hours are required to charge it when it is in use. And for what it is worth - It can be left on all night and will not charge one bit. Thanks for trying but I will have to reject your answer.

In that case the answer is obvious.  One (or more) of the system's components are out of spec.  Possible culprits are the battery itself, the charger unit, or the internal power management circuit.  If this computer is under warranty, make IBM fix it.  Is is possible that you bought these from an unauthorized source?  Perhaps these were known to have problems and were to have been refurbished before being sold???

What is the three character extension of the model number?  I will get in touch with my IBM rep. to see what he says?



One of them is 4YW
I do not have the other one with me at this moment.



This is straight from IBM:

TP755C/CS - Battery not charging on AC


A small number of 755C and 755CS systems may not charge the main battery during AC operation when using the following 35 Watt AC Adapters:

On affected 9545 755C 755CS systems, the charging circuit could interpret signal strength from a 35 watt AC Adapter as though it was a Car-Battery Adapter. This would only allow main battery charging while the system was off.

To determine if this is occurring, shut the system off and unplug and plug the 4-pin power connector at the back of the system - then turn the system on and check for charging. Do this multiple times. This action resets the charging circuitry, allowing the system to intermittently recognize the power supply as a 35 Watt Adapter and allow charging during operation.

If the system charges the battery during the test, a 40 Watt 4-pin AC Adapter should be used on the system.

If the system does not charge the battery during the test, follow normal problem determination to determine the cause of the failure.  

This was found at: http://www.pc.ibm.com/qtechinfo/RMIE-3ETE3M.html

Give this a try.


I am rejecting your answer so that I can accept the answer that has been submitted by "semontgomery".
His answer provided a great deal more detail and solution.
Thanks for trying!

Gee, my answer said that your power supply was not providing enough power to run the computer AND charge it.  You said: "Your explanation sounds logical but in this case is not correct. IBM not only told me how the unit should charge".  Now you are about to accept an anwser that says what I said just because it's a quote from IBM????  I'm sorry, but last time I checked, right is right, regardless of the source!


I now see that you have a valid complaint on the way I decided to score this question and your answer.
I will notify the customer service people and ask them to help me correct my decision and allow the points to go to you.
Thank you for providing the assistance you did.


After re-reading JHance's answer, I would say give him the points.  My explanation only expanded on what he was saying.

Often it is experts working together that lead to the solution of a problem. The clarification by semontgomery helped chinman solve the problem.

Post an answer to this question so chinman can grade this question.

Look for a question directed to you in this topic area.

Linda Gardner
Customer Service @ Experts Exchange
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