Author Topic: Battery safety - a practical lesson  (Read 1087 times)

Offline royfellows

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Battery safety - a practical lesson
« on: October 30, 2018, 11:51:25 am »
I have just had a lamp returned due to complete failure, I am not proud of this but there is an interesting lesson here.

What had happened was that some insulation had moved upon assembly and further movement had  caused the power input cable high side to short on the copper LED module.
A short circuit will cause the power bank management electronics to disconnect the power from the battery cells.

This if anything, clearly demonstrates the reliability of the Lithium Ion management safety.
What is interesting and worth noting is that only Li Ion has these sophisticated management electronics and that any battery type is a means of storing an electrical charge and if short circuited can cause fire and injury.

Almost all purpose built underground caplamps nowadays use Li Ion cells and can (hopefully!) be considered safe in this way, although I cannot in truth speak for other manufacturers.

Oldham lead acid batteries had a safety fuse but are now obsolete.

Bottom line - Li Ion by virtue of its sophisticated management electronics is inherently safer than other battery types.
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Online ChrisJC

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Re: Battery safety - a practical lesson
« Reply #1 on: October 30, 2018, 07:26:01 pm »
It is also true that normal NiMH cells have to be able to withstand a dead short without exploding. They can get hot and leak, but must not explode.
IEC62368 annex M. Trying to get anything with rechargeable batteries (and a built in charger) certified is a bloody nightmare!

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Offline royfellows

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Re: Battery safety - a practical lesson
« Reply #2 on: October 30, 2018, 09:53:21 pm »
With the puny voltages I would think that this is easily achieved.
 :lol:

Showing someone an 2070 a while back and describing the 2170 (if only I could get hold of them) they commented on how frightening it is for so much power to be contained in a single cell. About 15 watt hours in 2070.
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Offline Chocolate fireguard

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Re: Battery safety - a practical lesson
« Reply #3 on: October 31, 2018, 08:28:37 am »
With the puny voltages I would think that this is easily achieved.
 :lol:

Showing someone an 2070 a while back and describing the 2170 (if only I could get hold of them) they commented on how frightening it is for so much power to be contained in a single cell. About 15 watt hours in 2070.

I don't understand the point of the first part of that.

Also (sorry if this comes over as a bit picky but this is the Technical section after all): the watt hour is a unit of energy, not power.
1Wh is 3.6kJ.

Online Ian Ball

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Re: Battery safety - a practical lesson
« Reply #4 on: October 31, 2018, 11:51:01 am »

Bottom line - Li Ion by virtue of its sophisticated management electronics is inherently safer than other battery types.


I can't remember many exploding NiMHs, but I can think of LiIon explosions. 

Offline royfellows

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Re: Battery safety - a practical lesson
« Reply #5 on: October 31, 2018, 11:58:17 am »
With the puny voltages I would think that this is easily achieved.
 :lol:

Showing someone an 2070 a while back and describing the 2170 (if only I could get hold of them) they commented on how frightening it is for so much power to be contained in a single cell. About 15 watt hours in 2070.

I don't understand the point of the first part of that.

Also (sorry if this comes over as a bit picky but this is the Technical section after all): the watt hour is a unit of energy, not power.
1Wh is 3.6kJ.

It was someone else's comment not mine, but a short could be maintained for a longer period barring meltdown?

First part.
As a comparison I 'assume' a resistance of 1 ohm

AA cell is 1.5 V, so current would be 1.5 amps using Ohms Law.
It would be  wrong to assume the above or 1.5 X 1.5 =2.25 watts of energy being converted to heat due to the volts drop under load of the cell.

Li Ion cell at full charge is 4.2V and suffers less voltage drop under load.
Its just a thought, and a bit tong in cheek at that.
« Last Edit: October 31, 2018, 12:18:55 pm by royfellows »
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Offline royfellows

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Re: Battery safety - a practical lesson
« Reply #6 on: October 31, 2018, 12:01:03 pm »

Bottom line - Li Ion by virtue of its sophisticated management electronics is inherently safer than other battery types.


I can't remember many exploding NiMHs, but I can think of LiIon explosions.

I am genuinely interested and would like to know more.
I can see a charger, a possibly Chinese head torch?, and cells of type I cannot identify.
What happened?
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Online Ian Ball

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Re: Battery safety - a practical lesson
« Reply #7 on: October 31, 2018, 01:10:47 pm »
I'm sure there are other rail workers out there but this is from an HSQES Bulletin.  I don't know who wrote it, well actually I do, but I'm pretty sure they will have been given the text.
That's all there is I'm afraid.


« Last Edit: October 31, 2018, 01:34:07 pm by Ian Ball »

Offline royfellows

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Re: Battery safety - a practical lesson
« Reply #8 on: October 31, 2018, 01:31:23 pm »
Thanks for this.
It looks like I made a fairly accurate guess.

I suspect that the cells are of what I usually refer to as the "JunkFire" brands, examples Trustfire, Mailfire, Fandyfire, UltraFire etc, the bit they do get right is the "Fire" part.

Quality Li Ion cells as manufactured by Sanyo, Panasonic, and Tesla meet a very high standard and are of the Lithium Ion Phosphate type. There are several types of Li Ion cell, the phosphate is generally considered the best from safety point of view. Cheap Polymer, "Li Po" are to be avoided, in fact I would avoid Li Po full stop.

Protected cells have a positive conductor strip running down the length of the cell to the protection PCB in the base. This is insulated from the main cell body which is negative polarity by a thin strip of plastic. Obviously, physical damage can cause a short. What actually happened with that lot though, is pure speculation.
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Offline Fulk

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Re: Battery safety - a practical lesson
« Reply #9 on: November 01, 2018, 01:20:32 pm »
Hi Roy, do you happen to know if Fenix make their own cells or are they rebranded from another source (they're certainly not cheap!)?

Offline royfellows

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Re: Battery safety - a practical lesson
« Reply #10 on: November 01, 2018, 05:55:21 pm »
Hi Roy, do you happen to know if Fenix make their own cells or are they rebranded from another source (they're certainly not cheap!)?

I have no factual information but its unlikely they they manufacture their own, and as such they are likely to be OEM cells re branded with protection circuits installed. Sanyo and Panasonic are now the same company and tend to lead the market, they work in partnership with Tesla who as we all know also manufacture cells. There are still a lot of Chinese manufacturers, which I personally would not trust. The worst Chinese cells are those not actually 'manufactured' but recycled from overage battery packs for laptop computers etc.
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Offline Maj

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Re: Battery safety - a practical lesson
« Reply #11 on: November 01, 2018, 06:28:10 pm »
I decided I needed a couple of new 18650 batteries for my Fenix. After a lot of searching on the internet I found this site useful   http://www.torchythebatteryboy.com/p/18650-batteries-chargers.html  .
But in the end I purchased 2 x 18650 2600mAh with PCB from RS Components. £15.65 in free delivery, arrived within 24hrs of placing order.
 https://uk.rs-online.com/web/p/speciality-size-rechargeable-batteries/8801558/?sra=pstk
https://docs-emea.rs-online.com/webdocs/1585/0900766b81585472.pdf


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Offline crickleymal

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Re: Battery safety - a practical lesson
« Reply #12 on: November 01, 2018, 11:18:13 pm »
I'm sure there are other rail workers out there but this is from an HSQES Bulletin.  I don't know who wrote it, well actually I do, but I'm pretty sure they will have been given the text.
That's all there is I'm afraid.

How the heck are people supposed to tell the difference.  Some of those fake CENTRE marks are pretty much identical to the real ones.
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Offline Fulk

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Re: Battery safety - a practical lesson
« Reply #13 on: November 01, 2018, 11:30:00 pm »
Thank you, Roy.

Offline andrewmc

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Re: Battery safety - a practical lesson
« Reply #14 on: November 02, 2018, 07:33:06 am »
How the heck are people supposed to tell the difference.  Some of those fake CENTRE marks are pretty much identical to the real ones.

A crappy CE mark indicates that it is probably a dodgy item, but there is nothing to stop a dubious Chinese manufacturer from sticking a valid CE mark on anything they like (the European rules don't apply to them and they don't care about the copyright). It is the responsibly of the importer into the EU to verify that stuff a) has a valid CE mark and b) _complies with the relevant regulations_. Chinese manufacturers will ask you what certifications you want put on the items... :P

Offline royfellows

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Re: Battery safety - a practical lesson
« Reply #15 on: November 02, 2018, 05:19:13 pm »
A quick browse through the electrical items for sale at a certain recently closed down electronics store chain was very revealing.
Basically, the food chain is badly contaminated.
 :lol:
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