Batteires

[Phil_Black]

Hey !

My freind have 3 batteries that he was using in his remote controle car, and he want to give them to me for 20$. but theses batteries are 7.2 v 1300mah.

I got a Mp5 Sd5 stock, i wonder if they will put the same energy than a standar 8.4v 600 mah ?

Thanks

[[Avtomat]]

no, you will need a 8.4 Batt. I think i wold sound like a aeg running out of battery if you use the 7.2. I think the ROF would be lower too.

TM manual suggests 7.2v and for better go with the "HYPER COMMAND 8.4v"
IMHO, never go less then 8.4, but heck, if its stock, a 7.2 will do the job, just not as good. the higher mah will help a bit though.

[Phil_Black]

thanks !

Woud it be ok if i upgrade the batteries ? Like if i take 2 batteires and add a batterie fron the third one since it'is Sanyo bateries it woud take the Volts up to 8.4

If i'm right it's like 1.2v /Batteries so i need 7 batteries !

If some one coud tell me if it's rignt i woud now have 2 8.4v 1300mah batt.

Thank's !

[Whozat]

In theory, as long as the cells are the same (brand,size,type,etc) and you don't damage them while separating them and then resoldering them, the answer would be yes.

[yanhchan]

Wait It will work with a 7.2 thats odd.. so should i keep a 7.2 as a spare?

[Atomic_235]

You have a MP5 SD5, i suggest you to use a 8.4v batterie for lot of reason.
If you use a 7.2v, your ROF will be very bad...
The only Aeg (i think) that use a 7.2v batterie is the Academy L85 A1... :wink:

[PTE. Pyle]

a 7.2 v will work i use that as a back up in my m4 and have an 8.4 as my primary the only thing you will notice is that with the lower voltage the motor wont turn as fast thus a lowere rate of fire. you dont loose fps or anything and the gun will still fire. infact you should still get a ok rate of fire try it out and see if it works

[Phil_Black]

Great !

Thank's fro thoses answers ! I will make one 8.4 ans i will take one as a back up !

Phil_Black

[FieroGT]

Soldering to a battery is not as easy as it looks. Ontop of that, you can damage the cells by overheating them. I bet you could just go to an RC store or hobby store and pickup a brand new 8.4v 2000 mah pack for $50. And not have to worry about someones well abused RC batteries, or hack and slashing your own pack together.

[Sgt.Hartman]

o boy....
ok here is a bit of theories. You guys need it, its obvious.
In RC cars, the Mah will be a determinant factor of "how much time your car will keep running" but its just partially true in airsoft.
Why? Because RC cars have a device that is called "speed control". It wont allow the batteries to run always "full blast". That's why you can go at the speed you want with them. In airsoft guns, you don't have any device like that. It take the max it can(there is exeption if you have a totaly crazy batterie, it is explain later, keep on reading). That's why more the batterie is dying the slower the ROF will be.
So it is easy to calculate the power of a batterie:
Volt X amp = Watt.
Watt is the unity of power in electricity.
That does't mean though that a 4.8Volt 4200 mah will do the same job as a 8.4 Volt 2400mah. I will explain why in the next paragraph.
but in this case(stock gun), it wont be a problem.
now, you have a 7.2 V 1300ma
7,2 X 1300 = 9360ma, witch is a capacity of 9.4Amp
and then a 8.4 600ma
8.4 X 600 = 5040 ma witch is a capacity of 5 Amp.
1Amp = 1000Mah(milliamper)
Thoses batteries, when they are new(witch they are not) is far more powerfull then your 8.4
Here is why:
To make an image in your head, in hydrolic, the pressure(insite the system, not the work of a jack) is the equivalent to Voltage, and the debit is the Amperage.
The Watt would be the lbs/per square inch the hydrolic jack will lift.
The debit will give you the speed that the hydrolic jack will come off, but if you have no pressure, it wont lift anything. For example, the water in your aqueduc system have a high debit, but a low pressure. You can'T do a lot of work with that set up, due to the lack of pressure. But take that simoniz shit canadian tire sell, high pressure, low debit, you can remove the paint from your house with it. but that what you want out of this thing. So now that the difference between pressure(Volt) and debit(amp) is done, lets get back to electricity:

In electric motor, you need enough voltage to do the work, but you need a good amperage to gain speed. That's why high voltage doesn't necessary mean high ROF, but mean high capacity to do work(aka compress a upgraded spring).

Now for the limitation, if the batterie is able to give you let's say 15 amp(like a 9.6Volt 1500ma batteries) it is not sure that the motor will eat all that energies. If its a stock gun, the motor will get its maximum rpm and get stock to that speed(due to technical limitation, those motor are shit) it will take less amp when it will reach that rpm, but the motor can broke.
Easy way to prove that: remove your motor and put it directly on a batterie with a amper meter, the motor will blow after some time, overrunning, but you will see before that that the amp needed to keep it running will drop down a lot when it is reaching it's max rpm then when he is in acceleration.(you will see the amperage in acceleration by using the peak fonction because it will take like 1 second to be at max rpm) dont touch it with your finger then. Its the same thing for your car, when you do high way it cost less gaz becausethe motor have only to maintain its speed, not accelerate, brake, accelerate, brake, etc.

Now it will take more power when there is a "work charge" on it, let's say a stiffer spring in that case. That's the reason why we change that fuse when you do a important spring upgrade in a gun, unless if your gunsmith is a morron. Witch is not rare.

There is more scientific calcul to do to know how much Volt is the best for your gun with the upgrade you have, but i dont know them and they are really advance calcul and for god sake, i hate the " i think" way of sentence.

Questions?

[yanhchan]

wow...you could have just refered him to Unconventional Airsoft's explaination on battereies....it has beavers as an example...

[mcguyver]

i think a much simpler explanation is in order. in simple electric motor theory the ac/dc universal motors used in aeg's draw current from a battery in 2 ways. one is the simple resistive losses of the fine motor windings + the resistive losses of switches, wiring, conectors etc (very small). the other is the inductive losses of the motor windings as the motor rotates and phase reverses on the motor commutator. as speed varies (with higher or lower battery voltage), the frquency of this phase reversal also will vary. this can be calculated by the formula xl=2 x pi x frequency x inductance. basic math will tell you that as speed increases, frequency increases and inductive reactance increases. this means that the motor will draw less current at higher voltages and more current at lower voltages. this is really simple so don't get confused. basically what i'm saying is that voltages from 7.2 to 9.6 should be fine and remember mah rating means nothing when it comes to rof. this is a voltage issue. mah means "current delivery capacity" and simple math like volts x mah is garbage. batteries work on a geometric scale and you can't use that formula for any kind of accurate calculation. when an 8.4 v battery reaches about 5 volts it is totally depleted so those 5 volts that were used in your "volts x amps" calculations are just plain garbage. remember too that an electric motor draws alot of "inrush" current on start-up (which means everytime you pull the trigger) when there is no counter-emf generated by the motor to balance out the high starting current, so this will deplete your battery even faster. a higher mah capacity battery will help out in this regard.

[Drake]

Too much theory. Short experience-based answers:

- 7.2v will turn a stock AEG but it will suck, and will drain your batt faster.

- mAH does affect RoF slightly

- cell size affects RoF / battery life a lot, even on equally rated packs (small 8.4v 1200mah != large 8.4v 1200mah). don't know why, don't care why, thats just how it is

- you get what you pay for, and if you try to cheap your way out of batteries, it'll come back to bite you in the ass. this also applies to AEGs, GBBs, motor vehicles, home electronics, computer parts, girlfriends, air travel, hotel accomodations, and a whole slew of other things.

[Sgt.Hartman]

Originally Posted by mcguyver

i think a much simpler explanation is in order. in simple electric motor theory the ac/dc universal motors used in aeg's draw current from a battery in 2 ways. one is the simple resistive losses of the fine motor windings + the resistive losses of switches, wiring, conectors etc (very small). the other is the inductive losses of the motor windings as the motor rotates and phase reverses on the motor commutator. as speed varies (with higher or lower battery voltage), the frquency of this phase reversal also will vary. this can be calculated by the formula xl=2 x pi x frequency x inductance. basic math will tell you that as speed increases, frequency increases and inductive reactance increases. this means that the motor will draw less current at higher voltages and more current at lower voltages. this is really simple so don't get confused. basically what i'm saying is that voltages from 7.2 to 9.6 should be fine and remember mah rating means nothing when it comes to rof. this is a voltage issue. mah means "current delivery capacity" and simple math like volts x mah is garbage. batteries work on a geometric scale and you can't use that formula for any kind of accurate calculation. when an 8.4 v battery reaches about 5 volts it is totally depleted so those 5 volts that were used in your "volts x amps" calculations are just plain garbage. remember too that an electric motor draws alot of "inrush" current on start-up (which means everytime you pull the trigger) when there is no counter-emf generated by the motor to balance out the high starting current, so this will deplete your battery even faster. a higher mah capacity battery will help out in this regard.

it is smaller, simpler, i doubt... lol
anyway, that's what electricity is about, you know how it work, or you dont know how it work, it is a complete system that each part is connected to others.

Drake your right about it, ive forgot it, cell size and quality will changed the ROF.
anyway, im tired of this, if people want to understand, a monkey could understand it with the "so-user-friendly" explanation i gave.
even if my english suck.