Crappy Ultrafire 18650

I thought I'd test the 14500 Ultrafires I've been using for my flashlights too (they seemed to be working fine so not really thought about it). Advertised as 2300mAh. None of the four I've got made 750mAh.

tttonyyy said:

I thought I'd test the 14500 Ultrafires I've been using for my flashlights too (they seemed to be working fine so not really thought about it). Advertised as 2300mAh. None of the four I've got made 750mAh.

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That will be about right, did you test capacity during charging or draining'? if draining what kind of current draw? if charging what king or input current ?

RYDorDIE278 said:

That will be about right, did you test capacity during charging or draining'? if draining what kind of current draw? if charging what king or input current ?

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Cells were fully charged to 4.20V, then mAh capacity measured with a constant 1A drain down to 3.0V. At 3.0V they continue to produce current which dwindles to nothing, this tail off current was also included in the mAh measurement.

With Samsung ICR18650s this produces the stated cell capacity to within a few percent, so I believe the test to be accurate enough, and I've checked charge and discharge voltages are accurately reported with a DVM.

What I don't like the idea of is if someone assumed they were the stated 2300mAh and charged at 1C (which would be 2.3A), really they would be charging at 3C which the cell might not be able to take. But I guess most cheap eBay chargers take a few hours to charge Lithium Ion cells, so are unlikely to exceed 1C (@750mAh), and in that way cheap cells and cheap chargers work together.

The new D4 is different than the I4 so when charging I would use 1&3, 2&4 on the I4 and 1&4, 2&3 on the D4 so 2 cells don't get the 750mA each plus with the D4 I believe you can actually select a lower mA charge for cells like these (or to use with smaller cells of course). The manuals tell you this stuff.
Actually labeled my chargers with label tape so it would make it easier to remember how the pairs went together.

I've had a good harvest from the laptop batteries



Two are down at 0.8V but sprung up to 3.2V with a wake up charge. But I can't say I'd be happy about using them since they've been down at 0.8V for a long time so plenty of time to dissolve copper ready to form shunts... but the rest look OK. Some tested at 2400mAh, some 1600mAh. It'll take a while to work through them.

Certainly there are far more than I'll ever use for lasers so I've purchased a few 18650 based flashlights too.

I recognize the Samsung (pink), Panasonic (turquoise) and Sanyo (red) cells . . .

Lose the low voltage cells (below2 VDC)
, and check out the rest . . .

Watch for any excess heating when charging . . . .

I have changed over to the Sanyo NCR18650BF cells for slightly better voltage output . . .

LarryDFW

What is the lowest acceptable open-circuit rest voltage for recharging?

This page says 2V or more:

Lithium Battery Failures



This page says "Do not recharge lithium-ion if a cell has stayed at or below 1.5V for more than a week."

http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

It seems that below 2v the copper anode dissolves into the electrolyte and which then re-plates throughout the cell when recharged, which can cause internal shorts (and subsequent thermal runaway). The dissolving is a factor of time (see http://www.electrochem.org/dl/ma/199/pdfs/0010.pdf), so a brief dip to 1.5v may be survivable if the cell is charged before too much copper can dissolve, but if a cell is stored for any time below 2v then recharging can lead to internal shorting.

Found some genuine Trustfire 16340s on eBay:

2 x TrustFire TF 16340 CR123A 16340 3.7v Li-ion Rechargeable Battery | eBay

Test showed 660mAh 4.2V-3.0V @ 500mA.

Cells came with a shrink wrap around each with a hologram on, which I've not seen on other (fake) cells purchased on eBay, of which I have a few now - all refunded.

Crappy Ultrafire? Is there another kind? See the link in my sig, assuming you haven't already!

UltraFire? UltraFAIL, more likely. The only way to win at this game is to not play. Get some LG's or Panasonics. Ultrafire will just make you feel ultra-shitty when it detonates in your face. Avoid.

I have gotten 4 ultrafires for various projects both laser and nonlaser related and had no trouble. i buy them via amazon though. can you get them shipped to the UK from amazon?

Marco Polo said:

See the link in my sig, assuming you haven't already!

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Hiya yes I saw that one, it even appears on the first page of google results for "fake ultrafires"

jaykhjr said:

I have gotten 4 ultrafires for various projects both laser and nonlaser related and had no trouble. i buy them via amazon though. can you get them shipped to the UK from amazon?

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I'm afraid to say I'm put off the brand for life. Sure the cells I've got work in flashlights but they're not the rated capacity by a long way.

I'm still working my way through the laptop battery harvest - the Panasonics have been the most consistent for mAh capacity between cells (all coming in around 2000mAh) and the Samsung ones the worst (1100mAh to 1900mAh - no two the same!). Perhaps they age badly or the pack they came from was abused in some way.

The ONLY cells that have been completely tested to UL1641 safety standards are:

Sanyo, Panasonic, LG, Samsung and a few other "name brands" . .

Do not buy any others for safe operation . .