[ILLusion]

Originally Posted by LUTNIT

NiCd's are better in the cold? This subject has never come up before in anything that I've read, I have no experience with it, and my R/C racing friend doesnt exactly race in the snow...

Are the chemicals in NiMH batteries retarded in the cold so their output drops or something? I always chose NiMH because the mAh capacity is almost always a lot larger and you dont have to worry about memory effect (even though I know its still there to a small degree and NiCd's can often be recovered from the memory effect.)

Like Scarecrow said, both chemical types begin to degrade in performance as the pack gets colder. However, you will notice the retardation sooner with Ni-MH types (around 5-10 degrees) whereas Ni-Cd can go a bit colder before you notice it (around 0 degrees). At -20, you might as well just leave your Ni-MH packs at home, unless you like playing with a ROF of 0.8 shots per second. ... and if your idea of a shoot-em-up day is being able to barely shoot off 3 lowcaps. I swapped to an external 8.4v 2400mAh Sanyo NiCd pack afterwards and ROF picked up, was still a bit slow but it still held up fairly well and lasted me the rest of the day.
(those numbers are based on my experience with an 8.4v GP cell 2500mAh A-cell pack in my P90.)

Originally Posted by LUTNIT

Yeah, thats what I was told by a couple different people, upgraded spring = shorter battery life because more force is required from the motor, same thing if theres extra friction.

Rate of fire is determined by voltage and current. mAh stands for mili-amp hours, how I understood this is if there is a 1000mAh charge that means the battery will last for 1 hour at a draw of 1000miliamps or 1000 hours at a draw of 1miliamp. Rate of fire is determined by both voltage and avaliable current, higher voltage = faster motor cycle and more current = faster motor cycle. I wont go into details as I'm sure I will get them wrong but that is essentially (I think...) what CDN_Stalker told me. Think of a taser, they have incredibly high voltage and next to no current, thats why they aernt nearly as fatal as jabbing a fork into a wall socket. The voltage is the amount of electricity but the current is how fast its moving (or maybe I got that backwards...)

Here is another way of looking at the issue:

Heavy upgrades also add stress to the motor - this stress also gets translated in to the battery. Any extra stress to the motor adds stress to the battery. Stresses can come from binding pistons, heavy springs, poor shimming jobs, high speed gears, etc etc. Higher torque gears will ease a lot of pressure off the motor and battery if running heavier upgrades. Personally, I always upgrade at least one torque level above standard ratio for any springs above 360fps.

Generally speaking, the main controller of rate of fire is voltage and current and the controller of how long you can shoot for is the capacity of the cell.
Larger cells (such as sub-C versus 2/3A [mini] cells) and even larger capacity similar cells (such as 4200mAh versus 2700mAh sub-C cells) have lower internal resistance within the cell. Basic physics tells us the relationship between V (voltage), I (current) and R (resistance). As resistance goes down, current is affected (since voltage stays the same) - and is why we notice a higher rate of fire with very large packs compared to smaller packs, even though voltage ratings are the same.
Even comparing a Sub-C 1700mAh pack to an A-cell 1700mAh pack, you will notice the sub-C pack has a higher ROF and seems to crank a spring with more gusto.

There are other factors that affect the rate of fire and how long the cell will last. For example, back to the 1700mAh Sub-C versus A-cell comparison again - a sub-C pack lasts longer than the A-cell. Why? Back to the internal resistance issue. The extra energy contained by the added resistance has to be released somehow. In the case of this chemical reaction, the extra energy is released as heat - wasted energy.
In a world of perfect atmospheric conditions, perfect cell production with 0% contamination and perfect cell mixtures and equality in a pack; yes... the rule of thumb of a 1000mAh charge lasting 1 hour at a draw of 1000mA or 1000 hours at a draw of 1mA. But that can only be used as a very general rule of thumb.



ALL of these reasons are why it's never recommended to jump to a high mAh pack when you have a low powered (stock) gun. I've seen pistons ripped to shreds in less than 10,000 rounds with 8.4v 2400mAh NiCad packs. Tokyo Marui's actual recommended pack for stock guns in sub-C form are 1300mAh!
Experienced tuners and shops do NOT recommend any higher than 1700mAh large packs for stock guns for this very reason! 4000+mAh packs lead to quick deaths for stock guns.

Higher capacity is NOT always better because in what I've just written above, higher capacity also means much more than just how long you can shoot for!

One way to balance it out if you MUST go to very high capacities on low powered guns is to drop the voltage level, which as the test in this thread proves, is still very effective for airsoft, even when running at 7.2V.
Depending on your size constraints, the stress to your motor and the size of your packs, your gun may be able to run at 6 volts? Who wants to give it a try?