G751 Battery upgrade/rebuild

[aeolisio]

First off this is not a guide because the last thing i want is someone to start a fire or damage hardware or themselves because they couldnt follow simple directions.
I have rebuilt and upgraded quite a few laptop batteries over the years and even though none of our g751 batteries have failed i did upgrade 2 of the packs for longer use. You can find walkthroughs online but to make it simple the g751 battery uses 18650 cells at 3.7v and 2933 mah. After some fighting with the plastic case i replaced those cells with Panasonic 3600 mAh batteries. The upgraded total capacity on paper went from the stock battery of 5866mAh to 7200mAh and from 86Wh to 107Wh or a 24% increase. Real world heavy usage has added another 1.25-1.5+ hours for those users. As long as you install the batteries in the same series/parellel config you wont have any problems. Use this as a reference if you need to rebuild or upgrade your own battery and this will certainly void your warranty so attempt at your own risk.

[joshindaphils]

If you want to go down a rabbit hole on data regarding these cells go to flashlight forums hehe.

Currently it looks like highest legitimate capacity for 3.7v cells is 3600mAh. Anything above that is definitely false advertising and likely a fair amount under that capacity.

Would be interesting to see a comparison on stock cells vs. good 3600mAh cells.

[aeolisio]

You must be looking at old data panasonic put out 4000 mah in 2009. The 2933 cells in the oem g751 tested at 2600-2700 and the 3600s tested beteen 3400-3500. Neither matches advertised specs but thats still a substantial increase.
http://news.panasonic.com/press/news...n091225-3.html

[joshindaphils]

Currently it looks like highest legitimate capacity for 3.7v cells is 3600mAh.

Pretty sure my info is accurate and up to date, wasted an hour earlier looking into it all hehe. The 4200s you tested match my data as well

[aeolisio]

Thats because neither i or some random troll on a candle forum have run them to full discharge in a lab conditions. Its the same as your MPG when you buy a new car. Best case scenario is not real world but that doesnt mean that i couldnt get these closer to 4200 under the perfect conditions and that certainly doesnt remove panasonics claims of doing it in 2009.

[joshindaphils]

Thats because neither i or some random troll on a candle forum have run them to full discharge in a lab conditions. Its the same as your MPG when you buy a new car. Best case scenario is not real world but that doesnt mean that i couldnt get these closer to 4200 under the perfect conditions and that certainly doesnt remove panasonics claims of doing it in 2009.

Dear Aeoliso the devil is in the details the batteries you linked are 4.2v chemistries, while technically you can charge your 3.7v cells to a higher voltage you will seriously compromise the life of those cells (and is likely a mute issue in this application). I did bold and make red the 3.7v in my quote to try to drive this home.

The testing I've seen shows 3.7v cells pulling just under 3600mHa, and nothing higher. These numbers are at a good load as well. I fully understand the higher the load the shorter the effective mHa.

If you can link me a test of a battery having a 3.7v charge and yielding greater than 3600mHa I'll gladly say my post and data I read was wrong and out of date. Till then I am confident in what I read and in the accuracy of what I posted.

[aeolisio]

First off 3.7v is 4.2v charged on 18650 li ion cells.
Your right about 1 thing the devil is in the details you should have been more specific i await your edit . You said "If you can link me a test of a battery having a 3.7v charge and yielding greater than 3600mHa I'll gladly say my post and data I read was wrong and out of date. Till then I am confident in what I read and in the accuracy of what I posted."
http://budgetlightforum.com/node/4370
http://www.kaidomain.com/product/details.S003069

[joshindaphils]

Oh come on really... context is kinda critical here, you know very well we are talking about 18650 cells here.

I respect you enough not to hold your hand on the minutia, should I adjust my attitude here? hehe

EDIT: and you are being are playing all pedantic and give me test not on 3.7v chemistry... fail :P

[aeolisio]

Haha come on admit defeat nothing is implied. Ill settle for "aeolisio thank you for your wonderful battery contribution any improvement over stock battery is a win for all of us."

[Edweird]

I'll just add my 2 cents here.
Many model/fighting lightsaber builders like UltraSabers and Saberforge as well as others use only the Panasonic and Trustfire batteries with Panasonic apparently being the best of them all.

I don't know about Ultrafire vs Trustfire but I can confirm that Panasonic 18650 ones are very reliable - I've been using them for years for things like aforementioned lightsabers and flashlights. (The NCR18650B 3400MAh 3.7v ones.)

You can get 2 for $14 atm. I was actually quite surprised to see that kind of capacity at that voltage considering the size of the things.