Protected batteries vs IMR - safety

[rolygate]

GK,
You are most likely correct: the safest mod of all is probably, as you say, a Puck-style 4-batt boxmod with either 4x '1.5v' main street rechargeable AA cells for 4.8 - 5v or 3 cells and a dummy cell for 3.6 - 3.8v. Variable voltage as well :-)

As most know, rechargeable AAs are 1.2v in reality, not 1.5v.

But the question the battery section is supposed to address is: which batt in a standard mod is going to be the safest bet. The answer is, the one least likely to blow up in your face no matter what goes wrong. There is only one answer to that question, and for a nominal 3.7v mod it's an li-mn cell (IMR).

However we could add a section with your suggestion because you are exactly right, IMO.

[swedishfish]

GK,
You are most likely correct: the safest mod of all is probably, as you say, a Puck-style 4-batt boxmod with either 4x '1.5v' main street rechargeable AA cells for 4.8 - 5v or 3 cells and a dummy cell for 3.6 - 3.8v. Variable voltage as well :-)

As most know, rechargeable AAs are 1.2v in reality, not 1.5v.

But the question the battery section is supposed to address is: which batt in a standard mod is going to be the safest bet. The answer is, the one least likely to blow up in your face no matter what goes wrong. There is only one answer to that question, and for a nominal 3.7v mod it's an li-mn cell (IMR).

However we could add a section with your suggestion because you are exactly right, IMO.

I think I'm more confused now. So the safest battery for a 3.7v mod is protected? IMR?

[cement]

The safest mod to vape is a true pass thru , it takes the battery out of the equation!!!

[Goldenkobold]

The safest mod to vape is a true pass thru , it takes the battery out of the equation!!!

until you trip on the cord

[rolygate]

I think I'm more confused now. So the safest battery for a 3.7v mod is protected? IMR?

No, an Li-Mn (lithium manganese) cell is not protected - because it is a 'safe chemistry' battery: that is, one that vents gas slower when there is a fault. An AW IMR cell is a 3.7v Li-Mn battery.

AW also make an ICR cell, this is a protected Li-ion battery, much like the usual protected Trustfire etc, but believed to be of better quality. Pila is a similar make with a good rep.

The difference between these types of battery is very much like the principal way explosives are categorised:

- The amount of gas produced
- The speed of the gas generation

Just as an explosive that produces a lot of gas, fast, is called a 'high-explosive' because it is a lot more powerful than your plain vanilla gunpowder, a Li-ion cell produces a lot of gas, fast. In fact if you put it in a metal container with no vents it's a grenade. In contrast a Li-Mn cell when shorted out or faulty due to charging issues produces less gas, and slower - so it does not 'explode' in the same way a Li-ion cell can. This is why it's called 'safe chemistry' although these things are relative. If it was placed in a perfectly gas-tight enclosure it might well still explode, though it would be less violent than a Li-ion cell going off.

It will still vent with gas, and catch fire (especially if confined in an ignitable container) due to the heat created and the fact the gas is partly hydrogen - but there is less gas, produced slower, than with a faulty Li-ion cell venting.

If you put some gunpowder loose on the ground and ignite it, it goes up with a whoosh, but without an explosion. It needs to be confined in order that the relatively low amount of gas, produced 'slowly', will cause a bang (an explosion).

If you do the same with a high explosive, such as those used as a detonator, like mercuric fulminate, picric acid, or lead azide, they go with a bang even when unconstrained. This is because they produce a lot of gas, very fast. (I used to work with the stuff.)

This is the basic difference between Li-Mn and Li-ion. You will note that even gunpowder will cause an explosion if confined, and so will an Li-Mn cell most likely, if placed in a strong, gas-tight container - though anyone using a mod with no vent capability is taking an unnecessary risk - drill some holes in it. But an ounce of gunpowder going off is nothing to an ounce of mercuric fulminate going off...

[D4rk50ul]

I just did a bunch of research on this because my prior belief was put into question and I had to reconfirm. I'm sticking with IMR ("LMR") batteries for sure. I do think that having a proper fail safe built into your device is half the battle though. I know on the Reo that I use the spring will collapse on the bottom in the event of a short, find out what your mod's fail safe is and make sure its intact.

Like the above post said, I'd rather have a slow controlled gas off than a violent explosion. Also IMR batteries operating tolerances are much less likely to be pushed over the limits than a cobalt based lithium cell when used with a PV IMO. They can handle rapid discharge rates and high current spikes whereas it could trip the protection on a standard LiCo battery or if the protection fails potentially cause a huge hazard. I apply the same logic that works for PSU's when building a computer, or engine dynamics when building a car. The closer to the limits you push something, the more likely it is to fail. If you only push it to 50% of its potential it is going to be much safer and reliable.

Make sure you have a vented battery compartment on your device as its the #1 thing you can do for safety from a malfunctioning battery properly before it builds up and causes an explosion. Make sure you check them for excess heat and store them in cool dry areas. Test them for over charge/discharge regularly with a multimeter as this is the most common way to get a failure. Don't run them in series unless the cell is designed to handle it, regular cobalt based ones are usually not designed for this, only LMR (IMR) and LiFePO4. Use the proper charger for the cell, not all chargers are made to work with LiMn and LiFePO4 batteries and can overcharge them making it a hazard. Ideally we would use LiFePO4 batteries but they seem to only exist in the 3.2v variety for a single cell unless ran in a pack or in series, the 18650 is 3.2v @1200mah.

As far as I can tell the order of safety for batteries is this,

LiFePO4 Example
LiMn2O4 Example
LiCoO2 Protected Example
LiCoO2 Example *DO NOT USE THESE*

Thought this was cool I found it looking through hobby sites at battery comparisons, etc. Fireproof Battery Bag


Remember this is just my opinion and should NOT be used as fact or even a guideline. Do the research yourself and draw your own conclusions!

[rolygate]

Some good points there. The only thing I'd debate is the relative position in the 'safety scale' of Li-Mn and Li-FePo4 cells.

We had to debate this initially and came to the conclusion that, although Li-FePo4 cells may be even more stable than Li-Mn ones, for practical reasons Li-Mn batteries are safer in the usage profile that we employ. This is because Li-FePo4 cells have two negatives:

• Some Li-FePo4 cells are of extremely low quality and may be even less capable than some cheap Li-ion batteries. They can have a C rating of just 1C or less. This means an unsuspecting buyer could purchase them thinking they are good-quality batteries. The buyer needs to actively select 'real' Li-FePo4 batteries, which have a rating of 5C to 10C.
• Li-FePo4 cells need a special charger, or, the charger voltage switch needs to be re-set to the lower range, where applicable. This means that there will be occasions where things go wrong and the cell is overcharged. Overcharging is probably one of the main causes a battery fails. Since Li-FePo4 cells are commonly stacked, for 6 volts, this is not good.

So our conclusion was that, although theoretically a Li-FePo4 cell may be better, in practice a good Li-Mn (such as an AW IMR) is a better choice.

[SteelJan]

Some good points there. The only thing I'd debate is the relative position in the 'safety scale' of Li-Mn and Li-FePo4 cells.

We had to debate this initially and came to the conclusion that, although Li-FePo4 cells may be even more stable than Li-Mn ones, for practical reasons Li-Mn batteries are safer in the usage profile that we employ. This is because Li-FePo4 cells have two negatives:

• Some Li-FePo4 cells are of extremely low quality and may be even less capable than some cheap Li-ion batteries. They can have a C rating of just 1C or less. This means an unsuspecting buyer could purchase them thinking they are good-quality batteries. The buyer needs to actively select 'real' Li-FePo4 batteries, which have a rating of 5C to 10C.
• Li-FePo4 cells need a special charger, or, the charger voltage switch needs to be re-set to the lower range, where applicable. This means that there will be occasions where things go wrong and the cell is overcharged. Overcharging is probably one of the main causes a battery fails. Since Li-FePo4 cells are commonly stacked, for 6 volts, this is not good.

So our conclusion was that, although theoretically a Li-FePo4 cell may be better, in practice a good Li-Mn (such as an AW IMR) is a better choice.

I would add the caveat that IMR batteries can be a better choice if your mod has short circuit protection built in and was designed to handle the higher amperage of LR at the same time, meaning it's switches, buttons, wiring, etc is rated for the higher amperage.

We cannot simply say that IMR is the safest choice in every mod.

[Mudflap]

From batteryuniversity.com

What every battery user should know

A major concern arises if static electricity or a faulty charger has destroyed the battery's protection circuit. Such damage can permanently fuse the solid-state switches in an ON position without the user knowing. A battery with a faulty protection circuit may function normally but does not provide protection against abuse.

Don't put too much faith in your "protected" lithium cobalt batteries. Especially if they have some variation of xxxxFire on the label.

[Goldenkobold]

I have had two true device shorts in mods.

I had a mechanical mod short once due to damage on the outer tape of the battery (caused by the threading catching the tape I assume as it was a tight fit). The metal on metal on the tube wall closed the circuit and as soon as I installed the cartomizer it fired, this is one instance where I am very glad I was not using an IMR battery. The thought of my house catching on fire is no more appealing to me than an explosion in my face. It caused no damage to the protected battery or device...obviously the battery was tossed anyway as its torn wrapper made it less than safe...its possible the spring would have melted if I was using an IMR its also possible I wouldn't have noticed and it would have burnt my house down and started a raging inferno the likes of which we have not seen since the great fire in New Orleans in 1788. By now most of us who care have seen the Photo's of the IMR in the coat pocket that caught fire....imagining the left unattended on my work bench or dining room table with paper strewn around and you have a recipe for something worse than broken teeth (though honestly either of the two fit my definition of catastrophic failure).


The second was just me building a bad DIY mod and I let the led connection wonder too close to the wrong wire, this one was noticed right away, the LED came on briefly, and I doubt it mattered what I was using battery wise as I fixed it before assembling anything.

If someone was to ask me what the safest non stacked battery to use in an all metal mechanical mod that they purchased (as opposed to building around a Nimh block) I would not say an AW IMR but an AW protected Li-ion. However I think the built in protection on a Provari or similar units probably makes it a safe choice, but the MOD has to account for the lack of protection.