Another battery question

[ltrainer]

I have a question about batteries. When I bought my Grand at the time protected 18650 Ultrafire batteries were the recommend choice so I bought 3 of them. Later on the AW IMR 18650s became the recommendation.

I now use LR 1.5Ω (wow, I just made the ohm sigh for the first time ) 306 attys.

So here's my question based on some of the math about batteries that I have been reading.

The Ultrafire 18650 has a C rating of 1.5 amps. The atty and battery combination I am using has an amp draw of 2.46. (3.7/1.5=2.46) .....Does the Ultrafire deliver to the atty the 2.46 amps to the atty (even if it stresses the battery) or just the 1.5 amps? I want to get the full benefit of the LR attys and I am not sure that I am.

If the Ultrafire is delivering the amps that the atty requires for its full potential then I'll just keep using these til they start to go down hill as I have been happy with them. If they arent delivering the full amps needed then I'll have to order some AW IMRS.

Thanks and happy fathers day to all the dads.

 

[mlinky]

From the thread http://www.e-cigarette-forum.com/forum/ecf-library/129569-rechargeable-batteries.html:

Power rating for rechargeables

The critical factor for ecig mod use is the C rating (discharge current) in amps. The minimum possible value for safe and effective ecig use is 1 amp (= 1000mA) although ideally it needs to be higher. The ideal rating is 2 amps (2000mA) or better as an atomizer usually draws 1A to 2A.

Chart of C ratings vs size
1C or less for low-quality Li-FePo4
Assume 1C for generic Li-ion unless otherwise noted
1.5C for ultra/sure/trust/-fire Li-ion
2C for AW ICR (Li-ion)
3C for BDL 10440 IMR (Li-Mn)
5C for BDL 14500 IMR (Li-Mn)
8C for AW 14500 and 16340 IMR (Li-Mn)
10C for AW 18650 IMR (Li-Mn)
10C for AW Li-FePo4

Note:
Tenergy etc Li-FePo4 (small cells) - <0.55A (~1C - half an amp or less - not suitable for ecig use)

Max drain rate in amps is C in mAh / 1000 x C rating
Example: an AW IMR Li-Mn 14500 battery has a capacity of 600mAh. The C rating is 8C (it can supply 8 times the capacity). Therefore the max discharge current in amps is:
600 x 8 over 1000 (600 multiplied by 8 divided by 1000)
= 4800 / 1000
= 4.8 amps
This shows it has enough beef to safely and effectively run an atomizer - which some 14500's don't. In other words it is less likely to go into thermal runaway if there is an internal fault in the battery and is then used to power a device that draws a relatively high current such as an atomizer; and it will not suffer from excessive voltage drop when powering the atty.


Using your battery example, multiply the mAh of your Ultrafire times 1.5 and divide by 1000. That will give you the effective amps. It is probably over 2.46 amps, and, therefore OK.

That is why the battery choice is less critical in the 18650 size battery, which has higher mAh, than with the 14500 size battery.

 

[ltrainer]

Thanks Margie. That makes sense to me. I've read that before but really didnt understand it. Guess I'll be hanging on to these batteries until they go south.

 

[fsroq]

Thank you very much for explane it so well. I allways wanted to know how these trustfires are rated, so 1,5 C, and if they have around 800mA (rated 900 for the 14500) in the real world that would make then suitable for 1.2 Amps.

 

[mlinky]

Thank you very much for explane it so well. I allways wanted to know how these trustfires are rated, so 1,5 C, and if they have around 800mA (rated 900 for the 14500) in the real world that would make then suitable for 1.2 Amps.

Right! Which is why having the AW IMR's, rated 8C, is so critical in the 14500 size