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The Error Guy
05-08-2012, 11:45 PM
I have a DV7 6015tx laptop. The battery is over a year old now, nearly 500 days according to BCheck. It is expriancing a moderate drop in performance and is struggling to retain charge for 45 mins +

As you can see in the pic the 4th cell appears to have died, probably resulting in this performance drop. Not sure if it's significant but the Terminal voltage is nearly 2000mv over its design... but that might be normal.

The full charge capacity is 5100mAh and the battery is retaining approx 3000mAh of charge.

4061


My question is, should I locate the faulty cell/s and replace them or even rebuild the whole pack or should I find a replacement on eBay. I don't know what cells it takes yet but I found a replacement battery for about 50 NZD. I'm guessing cell replacement would be cheaper (and more satisfying) but in your experience what would be the best path to take?


Cheers

TEG

Agent_24
06-08-2012, 12:14 AM
Rebuilding really only makes sense if 1) you save a lot of money or 2) you can't buy that particular battery pack any more.

Used\handled incorrectly, Lithium-based cells can be rather dangerous (Fire\explosion). If you know what you're doing then go for it if it saves you money.

However you may also get hassles with the management circuitry in the battery not recognising the new cells properly and no capacity increase actually being gained, so you'll need to know how to work out any such issues.

The Error Guy
06-08-2012, 10:41 AM
Ok, the plan atm is to price out the cells. If they are Fairly priced then I'll replace the faulty cell, problem solved? Move on, if not replace all cells.

If the replacement cells are going to be close to a replacement battery i'll just replace the whole lot. After having a LiPo explode on me I'm well aware of the dodgy things lithium cells can do, can't be too careful!

1101
06-08-2012, 12:07 PM
looks dead easy
http://batteries-company-com.over-blog.com/article-how-to-replace-battery-cells-inside-laptop-battery-73755528.html

linw
06-08-2012, 12:37 PM
It actually looks like the Terminal and Actual voltage labels are swapped.

Good luck with the job. Let's know how it goes if you decide to do it.

The Error Guy
06-08-2012, 01:36 PM
Just FYI for those randomly interested, current battery discharge goes along like this:

100% - 1hr 40 reported remaining, discharges normally (a % mark every 3-5 mins) for 20 mins then drops instantly to 55% 45~ mins remaining and discharges normally thereafter.

zqwerty
06-08-2012, 03:02 PM
Yes sounds like one cell has lost about half capacity, probably from leaking electrolyte.

Billy T
06-08-2012, 05:44 PM
Yes sounds like one cell has lost about half capacity, probably from leaking electrolyte.

Lithium cells rarely leak, most likely the internal impedance of that cell has risen due to chemical deterioration of the internal structure. It can't be meaured directly by an ordinary meter, but an ESR (equivalent series resistance) meter will usually identify it straight away. From my Libretto: .2 / .2 / 15 ohms (old battery cells) New: .08 /.08 / .08 ohms IRMC.

Cheers

Billy 8-{)

chrisjay
07-08-2012, 08:43 PM
Yes, replacement will be better, but you will face the performance problem

Billy T
09-08-2012, 01:14 PM
As you can see in the pic the 4th cell appears to have died, probably resulting in this performance drop. Not sure if it's significant but the Terminal voltage is nearly 2000mv over its design... but that might be normal. 4061

I must be going blind! I didn't notice that Cell 4 was reading 0mV! :blush:

That means it is a dead-short, which in turn explains why the remaining three cells are showing overvoltage. They are receiving the full charge voltage intended for 4 batteries, which is a 33% overcharge. This also explains the rapid drop off in terminal voltage/apparent charge, and subsequent levelling out.

It is possible that the fault lies in the battery management electronics in the battery pack itself, in which case installing new cells might not be a very good idea as fully charged new lithiums can get stroppy if faced with a direct short, and might well explode/catch fire in protest.

Cheers

Billy 8-{)