Lithium-Polymer Batteries — Part 4

Free Image Hosting at www.ImageShack.usCome on now Thomas, sit down at the bar with me and have a sip of some li-poly kool-aid.  Let’s talk a bit about your doubts of the li-poly’s prowess.  What?  You still prefer your NiMH and NiCads?  Well, that’s just like preferring the horse drawn carriage over the steam engine!  James Watts would be turning over in his grave if he heard that!  Watts… watts… now there’s something I haven’t mentioned yet.  A watt is the measure of the rate of energy used.  Now we’ve look at the ability to put out current, and used that to determine what li-poly to buy. Let us take a look at wattage and see truly, how much space and weight can be saved by moving to a lower voltage li-poly and retaining the amount of work capable of being done.

Wattage

I’ve heard people say that a 7.4v 2200mAh li-poly battery can perform like a 9.6v NiMh / NiCad battery.  I’ve also heard the NiCad and NiMh crowd dispute that till they were blue in the face, passed out from lack of oxygen, and had their core body temp drop to below freezing as the hot air escaped them from as they collapsed from their soap box (not that us li-poly users aren’t guilty too).  The difference lies in the ignorance of wattage and work.  Since wattage is a method to measure work, we should be comparing these battery types by their ability to do work.  I mean, if you were in the market for a 4×4 truck for hauling your 50 foot yacht, you’d be interested in the truck’s ability to work, right?  Well, what’s that you say?  They don’t put a wattage measurement on the batteries. Well, that’s true, but it’s easy to figure out.

Wattage (Power) = Voltage x Current (in Amps)

Now let’s look at a large Intellect battery from Airsoft Atlanta (9.6v 3600mAh $56.99).  First we need to figure out the continuious discharge rate (most NiMH packs discharge 10-12C):

12C x 3.6Ah = 43.2A

Now we can calculate the work done (wattage)

Power (watts) = 9.6V x 43.2A

414.72 watts for the NiMh 9.6v 3600mAh battery

Now let us look at the lowly 7.4v battery from Elite (7.4v 2200mAh 30C $36).  First figure out the continuous discharge rate in Amps:

30C x 2.2Ah = 66A

Now the wattage of the li-poly:

Power (watts) = 7.4v x 66A

488.4 watts!!!!!!!!!!  That’s 73.68 more watts than the large Intellect 9.6v battery, and at a savings of $20.99!  Nearly half the price, and it has the ability to work harder even though it has a lower voltage.

Compensating

All this time, people have been increasing the voltage of their AEG’s as a means with which to increase it’s ability to do work. That was because the batteries lacked a high enough discharge rate and the only way we could compensate was with more voltage.  With li-poly batteries not only do we have the ability to put out a lot of current, but they work harder as well with less voltage.  That means fewer cells and lower costs!  So, switching to a li-poly could mean a cheaper power source in the end!

Density

I’ve mentioned in the past that you can put more punch in a smaller space with li-poly batteries.  Looking at the Intellect NiMH from the above example, we find that it takes up 11.21 cubic inches of space.  The li-poly on the other hand only takes up 3.19 cubic inches!  That’s 71% less space and 73.68 more watts!  We have more current, more wattage, and less space invested in the 7.4v li-poly than we do in the 9.6v NiMH battery.  Hum… starting to seem like a no brainier now isn’t it?

Wraping It All Up

So, how did you like that Kool-Aid?  Refreshing wasn’t it?  I thought so.  Let us reflect on what we’ve learned on this long voyage from Doomsday City to this little bar in the train station in Li-poly Euphoria.

  1. Li-poly batteries don’t kill AEG’s.  Poorly built AEGs just can’t run at 100%.
  2. Li-poly batteries are not as dangerous as a nuclear warhead under the control of a bi-polar woman with PMS
  3. Li-poly batteries do require some extra care, but not much more than a regular NiCad or NiMH.
  4. The terminolgy used to describe li-poly packs is easy to understand, and picking one out is no harder than picking out a NiMH or NiCad pack.
  5. Li-Poly packs will hold a charge much longer, and while unused discharge much less than a NiMH / NiCad pack.
  6. Li-Poly packs are able to fit more voltage and wattage in a smaller package and discharge  it at a much higher rate (current / amperage), than NiCad or NiMH packs, by far.
  7. In the end, Li-Poly packs can actually deliver a greater wattage / dollar than the NiMH or NiCad packs can!

Well, that about wraps it up folks.  There isn’t too much more to say about them as it pertains to airsoft.  I’m glad to have had the chance to bring this all out in the open, and hopefully convert some of you to the world of Li-poly euphoria!

2 responses

1 04 2010
kharn121

This is the best article I have seen on how easy lithium batteries are to use. Definitely convinced me to use em in my jg s-system, which has no room anyways hehe. Thanks for such a concise and informative article.

22 02 2012
David Pillers

Can’t seem to find the Elite batteries you have been discussing. Link?

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