battery charging

[spurfan33]

just thought of something and figured i'd ask..
it may be a stupid question but i'll throw it out there anyway..
are there any rules that state that you should or shouldnt charge a battery right out of the device?
the reason i am asking is because i used to have some quite powerful radio controlled cars and they state that a discharged battery should be allowed to cool before recharging..
the batteries in those got a bit warm to the touch during the discharge.
i dont notice that the batteries that we use for vaping get very warm but i'm sure they do.
so would it be a better practice not to recharge immediately after discharge?

 

[Nermal]

I've never heard of this, but that doesn't mean it isn't true. Anyway, any answer will bump it to the top for a few minutes.

I have heard you should let them rest for maybe 30 minutes after they come off the charger

 

[Rat2chat2]

above me.

to ecf. Just a wonderful place with wonderful people. Good luck to ya and happy vaping.

 

[rurwin]

Generally speaking, we don't treat batteries as harshly as an RC car. Those will be run close to their rated maximum current from the start of the drive to its end. Whereas we only run the batteries for a few seconds and then rest them for much longer before the next puff. It stands to reason that our batteries would not get as warm.

But I have read that you should allow batteries to cool before and after charging. Lithium batteries fail by going into a condition called thermal runaway, where they get hotter and hotter until they burn or split. Once thermal runaway starts it doesn't need any external power. It might have started just at the end of the charge or discharge. When that process starts, the temperature of the outside is going to be lower than the temperature inside the battery, so even if the battery only seems slightly warm it doesn't mean that the insides are not dangerously hot. Waiting for the battery to cool down will ensure that there is no self-sustaining reaction going on inside.

Certainly I would be worried if my batteries were significantly warm in either case. Charging at close to the maximum specified current gets my AW IMRs up to maybe body temperature, so I try not to do that. I've never noticed any raised temperature when discharging them.

 

[spurfan33]

Thank you guys...

 

[Andrew LB]

Generally speaking, we don't treat batteries as harshly as an RC car. Those will be run close to their rated maximum current from the start of the drive to its end. Whereas we only run the batteries for a few seconds and then rest them for much longer before the next puff. It stands to reason that our batteries would not get as warm.

But I have read that you should allow batteries to cool before and after charging. Lithium batteries fail by going into a condition called thermal runaway, where they get hotter and hotter until they burn or split. Once thermal runaway starts it doesn't need any external power. It might have started just at the end of the charge or discharge. When that process starts, the temperature of the outside is going to be lower than the temperature inside the battery, so even if the battery only seems slightly warm it doesn't mean that the insides are not dangerously hot. Waiting for the battery to cool down will ensure that there is no self-sustaining reaction going on inside.

^^^ This!

Certainly I would be worried if my batteries were significantly warm in either case. Charging at close to the maximum specified current gets my AW IMRs up to maybe body temperature, so I try not to do that. I've never noticed any raised temperature when discharging them.[/QUOTE]

I have yet to see a vaporizer that draws power anywhere even remotely as fast as an RC car, which is able to drain a 7000mAh LiPo in like 15 minutes. Such an incredible discharge rate creates a lot of heat and due to the amount of stored energy such batteries are capable of holding combined with the inherit danger such a battery pack would pose if ruptured... you have to be extremely careful with RC car batteries. A few years back, the editor of European Car Magazine had the misfortune of crashing his RC airplane and ended up putting the pieces in his garage where the damaged battery ruptured due to heat, and when oxygen is introduced to those lithium cells... lets just say his garage was pretty much a loss.

here's an extreme example... World's Most Dangerous Battery! - YouTube

As for batteries for e-cigs... due to the cheap nature of chargers like the ones for ego-type batteries, I personally wouldn't plug one in and go to the store or leave it in all night.

Example: E Cig Fire Danger - YouTube

My guess is the battery had seen some abuse and was not brand new. It does make me re-think owning knock-off ego batteries and chargers though...

 

[Wheats]

Is there a general rule for charger mah to battery mah? I got a 420 mah 510 thread charger with my 1100 mah ego-c twist (by STAM). Can I charge a 180mah ego-t cig like battery on it? Is the general rule lower charger mah to higher battery mah?

 

[ImThatGuy]

Not a pro, but I highly doubt you would damage it. I think it will be fully charged in about 20 minutes...

 

[rurwin]

Is there a general rule for charger mah to battery mah? I got a 420 mah 510 thread charger with my 1100 mah ego-c twist (by STAM). Can I charge a 180mah ego-t cig like battery on it? Is the general rule lower charger mah to higher battery mah?

Yes there is.

Firstly, chargers do not have mah.

mA is milli-amps, which is a current and it is related to power. Like your house fuses have a rating in amps and the circuit with the lights on is probably 5 amps, with each bulb being maybe 100W and the circuit with the power sockets on is maybe twice or three times that and devices on that being maybe 2000W.

Batteries can only supply current for so long until they are empty. It's like measuring a water tank by saying it could supply three gallons per second for an hour. (Put like that it seems ridiculous, and it is but, unlike the gallon, nobody has ever heard of the coulomb, which would be the right unit to use.) So a 2000 mAh battery can supply 2000 milliamps for an hour. It could also supply 1000 milliamps for two hours and so on.

Now there's a twist. Every battery has a figure called C. The number is the same as the battery capacity, but the units are amps. So a battery with a capacity of 2600mAh has a C of 2600mA. It is important to understand this distinction, or you'll tie your head in knots. Capacity is in mAh, C is in mA, and they are different things but have the same numeric value.

The maximum charge and discharge rates for batteries are then often specified as multiples of C.
[quote="AW 18490 IMR]Nominal Voltage : 3.7V
Capacity : 1100mAh
Lowest Discharge Voltage : 2.50V
Standard Charge : CC/CV ( max. charging rate 1.5A )
Cycle Life : > 500 cycles
Max. continuous discharge rate : 8C
[/quote]
Here the maximum discharge rate will be 1100 mA x 8 = 8800 mA = 8.8A

You are generally safe charging a battery at up to C, so 1A for a 1100mAh battery, 0.5A for a 650mAh battery. As you can see above, if you check the actual specification sheet you may be able to use a higher current, but C is generally safe.

Now to answer your actual question... a 180mAh battery has a C of 180mA, and that is the maximum charge current you can assume to use. I'm not sure what your 420mah figure comes from, because it makes no sense. If it is 420mA, then that is above the 180mA you can safely use. I imagine it is 420mA because there is no ego-c battery below 420mAh, so you can use it on any ego-c battery.

So the answer is, yes there is such a rule, and no you can't use your charger on an ego-t battery.


[rant]
Always, always, always, pay attention to capitalisation when writing units.

"m" means milli and there are 1000 mA in 1A. But "M" means mega and 1MA would be a million amps.

"A" means amperes, abreviated to amps, and is a unit of electrical current. But "a" means "are", a unit of area equal to 100 square meters.

1ma is almost exactly a square foot.
1mah might be the capacity of a water tank capable of irrigating an area of one square foot for one hour.
[/rant]

 

[Wheats]

Ruwin,

I am still digesting your reply! Thanks for the attention to detail. I will have follow up questions.