FYI - some 'new' Fujitsu laptop batteries

Batteries and Chargers Rechargeable Batteries
81

When salvaging random laptop packs, I never keep cells that were below 3.0V

A wise man would probably toss these cells also, but they seem to be very nice cells and were never abused, overworked, etc. I’m going to keep a close eye on them, but my feeling is that they are OK.

82

But there's a difference in packs that are low because they're worn out, and new that have fallen from sitting on a shelf. And in a used pack if five are at 3.85v and one is 1.9v, then sure, there's something wrong with the one. If they're all the same, it's not likely that every single cell has suffered the exact same failure and just by coincidence happened to all end up at the same voltage.

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BTW, Fujitsu did not use any thermal sensors on the cells in these packs. Every other laptop pack I have opened had thermistors on the cells.

I measured the internal resistance of the cells and they were around 40 milli-ohms, which was the same as the new ones that I have.

84

Is that 40 mOhms for internal resistance, good, or bad? In general, what would be the ranges (good vs. bad)?

Thanks,
Jim

85

That’s good. Most new LiIon cells are in the 40-60 milliohm range. Typical laptop pulls may be 100 milli-ohms.

Some of the best IMR cells get down to 10 milli-ohms and can do 30 amps.

86

>>>>So, what IS the situation? Is it just that if a USED battery is low
>>>>>voltage (< 2.5V?) to toss it, but for a NEW battery that has low voltage,
>>>>>it’s ok to try to charge it/them?

That is correct. I believe the ONLY downside to batteries REPEATEDLY discharged below 2.5v is that sharp metallic crystals will form in the catalyst bag, ripping it, letting air in and causing a vent with flames situation. Nasa tests show that these cells can take a LOT of abuse, but do eventually seem to blow up.

Well, there is also the nondangerous aspect: That the cell will lose capacity and won’t be worth keeping. But that’s not a safety issue.

So it’s just about how lucky you feel. Take a chance that the battery has dropped below 2.5v 50 times and have it blow up after 20 more charges, embedding a tailcap in your skull with the force of a bullet (see the FBI report — it happens). Or maybe this is the first and only time this particular pack has dropped below 2.5v —— You and your skull will be fine.

Here’s the thing. It is my understanding that most laptop packs will refuse to charge in the dedicated pack charger if they drop below 2.5v. So the chances are, if you pull the pack from a recycle bin, the owner chucked it because it didn’t work. Once it dropped below 2.5v, he couldn’t charge the pack, let alone repeatedly charge the pack, so the chance of crystals forming seem to be about nil. Laptop packs are programmed so that they never (theoretically) drop below 2.5v. The only way that will happen is if the pack isn’t charged for a couple years. It drops below 2.5v because it hasn’t been charged in 2 years. Then it can’t be charged. Owner tosses it. And that’s where we step in. So if that is indeed the case, then (as I said before) there is little chance of crystals forming in any of these packs.

Like I said, it’s just how lucky you feel. I myself toss anything below about 2v. Just not worth the risk. But with these being new never-discharged packs, I’ll take a chance on 1.9 volts. Used packs showing 1 volt? Nah, toss it. Just not worth having a C8 tailcap dug out of my scrotum in the emergency room because I was trying to save a few bucks on an iffy battery. :wink:

87

Look again, it's taped to the backside of the circuit board. :p

88

Mine are supposedly coming tomorrow according to usps tracking. Can’t wait. Besides Samsung pinks and the older panasonic 2400 mah CGR18650D, those Panasonic grays are some of my favorite cells.

89

And these look like they’re actually about the rated 2900 mAh :)!!

I feel good that these (still hopefully) will turn out well for you all… was “sweating it” for awhile.

Congratulations ;)!!

Jim

90

Hi,

Thanks for that info. I’m glad I didn’t “toss” them then!!

And, FYI, I got another, different pack this week, a known-used one, and out of 9 batteries, 6 were < 1V, so I did toss those, and kept the other 3, which were all > 3.8V.

Jim

91

Hi,

Thanks for that info, and will keep that in mind.

BTW, so, is the low internal resistance the reason why the IMRs can source so much current?

Jim

92

Just noticed I forgot the link:

Sorry about that!

Jim

93

Basically yes…

94

I have the first one of these on the charger, it's taken 1793mAh so far and is only up to 4.01V. 8)

95

Wow.

That's just the first one, but if I don't start doing them more than one at a time, or at more than 1A, this is gonna take the next 3 weeks...

96

Great to hear the above reports. I finished charging 2 cells earlier. They took somewhere between 3 to 4 hours at 1 amp. I had them charging outside and don’t know the exact amount of time they took. My chargers use the proper cc/cv algorithm.

Tested tail current in a 4ish amp light. Reading was 3.75. That is better than all my new 18650’s, excluding my low resistance cells capable of 10 amps. The 10 amp cells have not been broken in yet either, but they read 3.8 amps in the same light. These cells are looking good.

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Slightly off-topic: What light do you have that is “4ish amp”? Just curious…

Jim

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P.S. I guess that this is one case where “oldies, but goodies” applies?

99

The light is a HD2010 with Nanjg 105c (using 12 amc7135’s) and XM-L2. Theoretically, it should draw 4.2 amps. I must have some resistance somewhere or the XM-L2 is bringing down the current.

EDIT: or maybe one of the 7135’s is fried.

100

This one pulls just shy of 5.8 amps.