wiring in an extra battery

[Cap n pickles]

i was thinking running two batterys at once, I just wasn't sure if you need the same Mah, and battery power to do it right, i would just add it into the wiring so i dont have to add a dead end connector like posted above.

i have done a few events that last for like 2 maby even 3 days at a time, of course its not pure hell all the time, i just think it would be pretty sweet to just be able to open the dust cover, and plug in another battery, instead of digging around in my vest, for a battery and screw driver for the battery plate on the stock.

thanks everyone, this info should give me the balls to hook two batterys up at once Lmao..

Wire it to the stock.

Buy 2 of these.

http://www.hobbycity.com/hobbyking/stor ... oduct=6540

[Paladin101]

why not just wire them in parallel?

For it to work properly, both packs would have to have the same voltage and mAh and be equally charged/discharged.

Wrong. For a parallel system you only need the same voltage, not the same Mah. It basically starts to act as one big battery, using the lowest discharge rate in the system as the constant.

[DMitri]

To back up Paladin

The only instance where you probably wouldn't want to do this is with NiMH batteries, as the voltage drops rapidly at a certain depth of discharge.

I will add, however, that running batteries in parallel will increase the charge (amps) that the motor can draw from the power source, so for those of you who claim to have seen melted Tamiya connector, you may consider switching to deans if you're going to run this sort of setup.

[SLINKEY]

cool thanks norm and dmitri,
thats gunna help alot when i get around to doing this setup

[Paladin101]

DMitri is there a constant point or does it fluctuate? Curious what people that run a parallel in an RS are seeing as far as non lipo battery life.

[DMitri]

I don't have any actual experience running batteries in parallel for airsoft. From what I've read, the voltage should fluctuate less with a parallel setup.

Here's some data on NiMH cells though to go back on what I was saying.
http://www.candlepowerforums.com/vb/sho ... hp?t=79302

The first drop is at about 10% DOD.

Also, you can see that obviously, as the amps drawn from the batteries increase, the voltage decreases. If the charge can be drawn from twice as many packs, it seems logical that the voltage wouldn't fluctuate as much.

[Kama_kazi]

why not just wire them in parallel?

Because that makes sense.

http://www.batteryspace.com/connectorad ... eries.aspx

I agree with both

[Sparky D]

why not just wire them in parallel?

For it to work properly, both packs would have to have the same voltage and mAh and be equally charged/discharged.

Wrong. For a parallel system you only need the same voltage, not the same Mah. It basically starts to act as one big battery, using the lowest discharge rate in the system as the constant.

I didn't say it wouldn't work, just that it wouldn't work properly. Perhaps the word I should have used was efficiently.

Yes, in a parallel circuit, the discharge amps equals the discharge of the lowest pack.
My post was more to the thought of hooking up a 2500 mAh 8.4V pack with a 900 mAh 8.4V pack and expecting peak performance.

[DMitri]

Yes, in a parallel circuit, the discharge amps equals the discharge of the lowest pack.
My post was more to the thought of hooking up a 2500 mAh 8.4V pack with a 900 mAh 8.4V pack and expecting peak performance.

No on both counts. Available amps accumulate, and as a result you can expect your motor to draw them if needed.

The amps and capacity are accumulative in parallel. Remember, mAh is just a capacity rating, a 9.6V 3000mAh battery should be able to supply 9.6V @ 1A for 3 hours. If you have a 9.6V 1000 mAh battery and a 9.6V 3000mAh battery in parallel, your new "pack" will be able to handle twice the amps if the application needs to draw it, regardless of capacity. So assuming one battery can provide 1A, 2 can provide 2A.

So for 60 minutes you could run this pack at 9.6V @ 2A. Once the small battery is empty, the bigger one can then continue with 1A @ 9.6V for another 120 minutes. These are approximate of course, resistances apply, also they never actually get to 0 during use.

The thing to remember though, the motor will only draw 2 amps if it needs it. If the motor were only pulling 1A, since the smaller battery can handle that alone (as in, if it weren't in a parallel circuit), the mAh ratings accumulate. If the motor were to draw 2A though, both batteries would be discharging full-bore simultaneously, so while the mAh ratings still accumulate, you end up not having gained any shooting time because 60 minutes @ 2A and 120 minutes @ 1A is 3 hours, which is what the 3000mAh pack can do alone at full discharge.

Remember these numbers are also completely made up and just used for reference.

Also, that's if you you're discharging at max amperage. Below twice the max amperage of the weakest battery, the cells will drain in relation to overall capacity. So, assuming one battery is adequate, adding another will increase capacity, not performance, but it doesn't decrease it either. In the hypothetical scenario that one battery weren't enough, adding another in parallel could increase performance by increasing amperage at the cost of trigger time (not capacity, that still increases). Although that's extremely theoretical because we're only at max amperage for very short periods of time.

http://www.youtube.com/watch?v=3TWk4SRoCQo#t=5m