Is this bad? Or will re-charging them fix the problem?
The situation: I have 16 of them powering my laptop (18.5VDC input required, using my battery pack in lieu of the external switching power supply running on mains power). The pack lasts about 2 hours.
Lately, though, I noticed my battery pack cuts out early. I measured the voltage with my AMM, and the needle pegged NEGATIVE.
Is this bad? Must I throw the batteries away? Or will charging fix the problem?
Michael
In message , dated Sat, 12 Aug 2006, snipped-for-privacy@gmail.com writes
Yes. Several cells have failed and have been charged in reverse by the others.
Yes; they should be recycled.
No; it is likely to make matters worse, by causing further cells to fail.
-- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
You have opened the batery pack and have full access to any of the NI-Mh cell terminals ? If yes, charge seprately cell by cell, using a fast charging algorithm. Then discharge separately every cell using nominal load (the same current which is discharging the battery your laptop) and measure discharging time. You'll discover there are cells which have a long discharge time and cells with very short discharge time. Probably some cells does not charge almost at all. So, replace defective cells with new ones, charge the whole pack with small current (0.1*C to 0.4*C untill the C=1.2*I*t equation is true (I is the charging current, t is the charging time, C is the cell capacity measured in amperes*hours and written on every cell). In 80% from those situations, only one or two cells are deffective, or the laptop charging circuit is broken. In the other 20%, the battery pack is very old (more than 2-3years of usage) and need to be replaced.
greetings, Vasile
"John Woodgate"
** Failed ???No need for cell *failure* to ocurr for the polarity to go reverse during the discharge of a battery. When a cell is fully discharged, the internal impedance goes very high so it can easily take up a small reverse voltage.
While not desirable, it takes a lot more to kill a rechargeable cell than this.
** Rediculous nonsense !!The reverse voltage cells will recover normal polarity when charged as usual and there is NO bad effect on the cells that have not reversed.
The Wood Duck is quacked.
....... Phil
In message , dated Sun, 13 Aug 2006, Phil Allison writes
Phil, he's measuring the TOTAL voltage as negative, so there are more reverse-charged cells than good ones. Unless he can charge the cells individually, which means breaking open the pack, that situation is unrecoverable.
-- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
"John Woodgate"
** Failed ???No need for cell *failure* to occur for the polarity to go reverse during the discharge of a battery. When a cell is fully discharged, the internal impedance goes very high so it can easily take up a small reverse voltage.
While not desirable, it takes a lot more to kill a rechargeable cell than this.
** WRONG - that is simply quite impossible. ** Not possible in the scenario as described.The PC cuts out the battery load at a positive voltage.
The Wood Duck is more Quacked than I thought.
........ Phil
In message , dated Sun, 13 Aug 2006, Phil Allison writes
It's what he told us. If it's wrong, it's not my error.
-- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
"John Woodgate SNIPPING MANIAC "
** Failed ???No need for cell *failure* to occur for the polarity to go reverse during the discharge of a battery. When a cell is fully discharged, the internal impedance goes very high so it can easily take up a small reverse voltage.
While not desirable, it takes a lot more to kill a rechargeable cell than this.
** WRONG - that is simply quite impossible. ** Not possible in the scenario as described.The PC cuts out the battery load at a positive voltage.
The Wood Duck is more Quacked than I thought.
** The OP's heading say "cells" .The OP's text alone is ambiguous.
You failed to exclude the impossible.
That is a massive blunder.
** Believing impossible things is your error.Your claims about cell failure are in error.
Quack, quack, quack ......
........ Phil
Make sure your "AMM" test leads are connected properly. Put the red lead into the AMM's + (plus) hole. Put the black lead into the AMM's - (minus) hole. Set the AMM for 20 or more volts. Touch the red probe to the battery + terminal and touch the black probe to the battery - terminal.
Is "the needle pegged NEGATIVE"?
John
"John - KD5YI"
** It won't be - as that is simply impossible.The get whole pack reversal, you would have to charge it in reverse.
The OP may have one or two reversed cells - or else he is an utter idiot.
....... Phil
In message , dated Mon, 14 Aug 2006, Phil Allison writes
Go on. You just want me to call you Phyllis Alison again.
-- OOO - Own Opinions Only. Try
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
Oh, sorry, meant to say that 4 batteries out of the 16 had negative voltage. Sorry I didn't clarify this. (Whoa... if the *whole* battery pack came out as negative, that would be weird!)
I tried this: I put one bad one in a flashlight (in series with the "wrong" polarity with another good battery, to ensure the batteries drained), then charged. Curious, I took the bad one out, and it registered a positive voltage of about 0.3V.
So, is it fixed, or is it ruined forever?
thanks,
Michael
In message , dated Sun, 13 Aug 2006, snipped-for-privacy@gmail.com writes
It may be OK. Charge it slowly by itself, being careful to control the current to C/20 or so, and stop when it shows 1.2 V. It won't be fully charged, but if it holds that 1.2 V above 1 V overnight you stand a chance. Do that with each one that shows a negative voltage. Then charge the whole string.
-- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
Yeah. I just saw his most recent post. Sorry to bother.
Thanks, Phil.
John
Go ahead. It makes her day.
-- Service to my country? Been there, Done that, and I've got my DD214 to prove it. Member of DAV #85.
Michael A. Terrell Central Florida
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