casey_cole Posted April 21, 2006 Report Share Posted April 21, 2006 Well - I have an M4A1 carbine, so I can only use a mini battery with a basic maximum of 1100mAh. I want something bigger - and as AA cells are 1.2V just like A cells, would it possible to run my AEG off 7 AA cells in series? I would use some high mAh NiMh's like these, and I've made a nunchuck holder that fits in my hand grip: half at the top, hald at the bottom. (I'm going to tape the batteries in place and shrink wrap to prevent moisture getting in. The translucent gloop is from a hot glue gun to permanently seal the wires in place. I've been reliably informed that the thin wire should be able to take the current - but I didn't ask about the gun part as my electronics teacher is a non-airsofter) I've found a place where I can buy a connector (model shop), but before I buy that, and the most expensive part - the batteries - I want to know something: will this actually work well or not? I can't see any reason why it shouldn't - but if someone knows that AA's suck as AEG packs - then please tell me! I'm doing this mainly for higher mAh (double - hee hee!) and partly for cost - around £15 for 2400mAh instead of £30+ for 110mAh (or £45+ for 2400mAh in mini cells!) Thanks CC Link to post Share on other sites
doom6668 Posted April 21, 2006 Report Share Posted April 21, 2006 Well - I have an M4A1 carbine, so I can only use a mini battery with a basic maximum of 1100mAh. I want something bigger - and as AA cells are 1.2V just like A cells, would it possible to run my AEG off 7 AA cells in series? I would use some high mAh NiMh's like these, and I've made a nunchuck holder that fits in my hand grip: half at the top, hald at the bottom. (I'm going to tape the batteries in place and shrink wrap to prevent moisture getting in. The translucent gloop is from a hot glue gun to permanently seal the wires in place. I've been reliably informed that the thin wire should be able to take the current - but I didn't ask about the gun part as my electronics teacher is a non-airsofter) I've found a place where I can buy a connector (model shop), but before I buy that, and the most expensive part - the batteries - I want to know something: will this actually work well or not? I can't see any reason why it shouldn't - but if someone knows that AA's suck as AEG packs - then please tell me! I'm doing this mainly for higher mAh (double - hee hee!) and partly for cost - around £15 for 2400mAh instead of £30+ for 110mAh (or £45+ for 2400mAh in mini cells!) Thanks CC <{POST_SNAPBACK}> They work for me, but so far i've used them on 4 occasions so i can't comment on longevity. There have been no issues so far and my set up doesn't look half as tidy as yours, where did you get the nice holders from? I saved a fair bit, like yourself doing it this way and if there are no problems with charging/discharge over the next couple of months, say another 8-10 uses i'll be doing some more. nice job mate go for it. Link to post Share on other sites
casey_cole Posted April 21, 2006 Author Report Share Posted April 21, 2006 Ta for your info - it's first hand stuff like this that I want! I got the holders from my electronics departmen at school for a royal sum of £0.50 along with the heavy core wire, and some LX tape! I got a bit worried when testing with a multimeter - I put one contact on the end of each heavy wire - and switched to "connectivity". No signal. It took about 5 different 'meters before I realised that of course there was no circuit - there were no batteries to complete it! Dur! Thanks again. CC Link to post Share on other sites
staticzero Posted April 21, 2006 Report Share Posted April 21, 2006 Household AA cells don't really have the discharge characteristics needed to run AEGs reliably. They may work, but it's far from ideal, and is hardly worth the money. Just get a custom pack made with proper cells. You can get quality, powerful AA cells in at least 1650mAh. And it may be cheaper to have a proper pack built than go with your current plan. My CBP1650 double nuncuck pack cost US $24 from http://cheapbatterypacks.com and it performs great. I actually have two different configs made with these cells. If you want even better performance at the expense of some capacity you should get an Intellect IB1400 based mini battery. You'll get 1300mAh of run time above 1v per cell with the ability to fully satisfy any AEG's amperage demand. They're cheap too. Link to post Share on other sites
casey_cole Posted April 21, 2006 Author Report Share Posted April 21, 2006 Ah - but batteries are a LOT more expensive in the UK - like £40 ($80) for a 2000mAh mini... If it doesn't work - what have I lost though? Nothing - I need some good rechargeables anyway! CC Link to post Share on other sites
casey_cole Posted April 21, 2006 Author Report Share Posted April 21, 2006 Woohah! The forums are laggy. CC Link to post Share on other sites
staticzero Posted April 21, 2006 Report Share Posted April 21, 2006 Well, that's fair reasoning. Do also keep in mind that that the setup you have there is going to be pretty high resistance. All those connections, not soldered, iffy wire, you're going to degrade your performance even more with that setup. You might be better off forgoing the battery cages and just tape everything together really tightly with electrical tape. That'll reduce the number of connections reducing the resistance. Link to post Share on other sites
Tom Andrews Posted April 21, 2006 Report Share Posted April 21, 2006 I'd go along with Static Zero on this. Although your set up works, those joints are a bad idea if you want reliability. Each joint relies on springs and point contact. Every time you fire a burst, tiny sparks erode the contacts leading to corrosion and eventual failure. Try Bigboyz tToys, or one of the other battery suppliers as they should easily beat your £40 for one battery costs. Even if you haven't got it quite right this time you were on the right track and the experience is always useful. (Testing the circuit without batteries - tsk. ) Link to post Share on other sites
casey_cole Posted April 21, 2006 Author Report Share Posted April 21, 2006 They are soldered. I re-soldered all the factory stuff to make double sure too. If I have problems, I can rip out the crud wire - and whack some big stuff in instead. If you meant between the batterys and the cages - then, nope there's not much I can do about that. This isn't set in stone, mind, this is first try. If it doesn't work - I can just solder the batteries together (with a heat sink and a steady hand...) CC Link to post Share on other sites
Carson Posted April 21, 2006 Report Share Posted April 21, 2006 If you want cheap, high quailty and relaible batteries try here:http://www.vapextech.co.uk/ I got myself a 9.6v 3700mAh bat for £19.45 and its brilliant. Link to post Share on other sites
Argo Posted April 22, 2006 Report Share Posted April 22, 2006 http://cheapbatterypacks.com ship to the UK, and shipping doesn't break the bank. I ordered an IB1400 9.6v mini, and a custom IB1400 9.6v for my P90, and got both for under 50 quid, posted, including all of their low resistance upgrades. Link to post Share on other sites
AdamLazzara Posted April 22, 2006 Report Share Posted April 22, 2006 Here is a stupid shot in the dark... How about we all just get sponsorships from the major car and energy companies and run around with hydrogen fuel cell powered airsoft guns! Or better yet, we can get giant solar hats to wear! Imagine the new abilities of camoflauging a solar cell! ok. Basically I think it's a dumb idea. The battery packs will have alot of resistance, even if you resolder everything. The main problem is the connecters in the battery holders, and if you can't do anything about them it's all pretty much worthless. And good luck fitting that in anywhere. Doesnt look to small to me. Maybe you should just tape them together like StaticZero said. Or think about the reasons why companies make special battery packs for airsoft guns and other hobbies and why you dont just buy airsoft grade batteries at the local grocery store. I think there may be a reason behind that... Link to post Share on other sites
casey_cole Posted April 22, 2006 Author Report Share Posted April 22, 2006 In case you hadn't noticed - which you obviously hadn't - it's in a nunchuck formation so half goes above the barrel and half goes below... I didn't quite get the point of the first part iof your post... I've worked out a way to get rid of th resistance in the connections - put the batteries in, tape them in place, and then solder the ends ferociously. The answer to your last point is that there is no reason other then to make a bit of money and to save you a bit of time making your own pack. There is little to no difference between the batteries I got (btw. I found some (nominally) very high quality batteries at a special shop near where I live) and the batteries in your packs - except that you paid triple what I paid, and I had to pack mine up myself. CC Link to post Share on other sites
AdamLazzara Posted April 22, 2006 Report Share Posted April 22, 2006 I was simply being sarcastic in the first part about all the people around trying to create strange ways to power their guns. But I do not mean to discourage you from trying, just saying that it would be easier to buy a battery pack. But then again, as you said, it's harder to get them and they are more expensive in the UK. Link to post Share on other sites
Fragger56 Posted April 24, 2006 Report Share Posted April 24, 2006 IF you decide to do this, the battery holders are probably a bad idea, instead you should solder the batteries together in a pack, with a short wire run between each battery. this is how battery packs are made. also you will need to make sure you can get rechargeable AA batteries that are capable of supplying the large current that AEGs need, currently AFAIK sub C cells are the best for high current uses. and you can get rechargeable AA cells in the 2000+ mah range, so capacity shouldn't be a problem, but i dont think ive heard of AA batteries being good for discharging over 2-4 amps of current, and most AEGs i know of use closer to 10 or 20A of current espically if they are upgraded in any way. Link to post Share on other sites
doom6668 Posted April 24, 2006 Report Share Posted April 24, 2006 Hey Casey this is getting interesting (and informative), i will absorb all the info in these posts and keep experimenting. I can't argue with any of the points put forward by everbody but i can say that mine are functioning sufficiently well so far. But its all fun as far as i'm concerned, if you enjoy mucking about and experimenting with this stuff more power (geddit?) to you. cheers md. Link to post Share on other sites
Docv400 Posted April 24, 2006 Report Share Posted April 24, 2006 You know you could just buy the batteries with the little 'tabs' on each end that you can solder to, you know, like the ones battery packs are made up from... Good old Maplins... While you're in there, you could get some super flex high current wire too, although the stuff you have is fine, compared to the thin stuff that's in most AEGs Or just strap a large battery pack in a pouch to your gun? Link to post Share on other sites
doom6668 Posted April 24, 2006 Report Share Posted April 24, 2006 You know you could just buy the batteries with the little 'tabs' on each end that you can solder to, you know, like the ones battery packs are made up from... Good old Maplins... While you're in there, you could get some super flex high current wire too, although the stuff you have is fine, compared to the thin stuff that's in most AEGs Or just strap a large battery pack in a pouch to your gun? <{POST_SNAPBACK}> These are the right stuff true, but one thing to bear in mind (and i can speak from experience) by the time you have bought connecters, wire and shrink wrap, paid p&p and spent time manufacturing your packs, you save so little that most people will pay to get pre made packs and not bother with the hassle. All good experience however, and you won't know 'til you've tried. Link to post Share on other sites
Docv400 Posted April 24, 2006 Report Share Posted April 24, 2006 I agree Doom, but Casey's making a non-standard battery pack I believe, to specifically fit his particular gun. Link to post Share on other sites
casey_cole Posted April 24, 2006 Author Report Share Posted April 24, 2006 Well. I have tried the battery by sticking the contacts in the holes... as I'm still awaiting a connector (many thanks go to evoracer for sending me one freee!) The gun turned over...just. However, I don't know if this is because of the low current thingy mentioned above - or due to the batteries being basically uncharged. I should know by end of the week when the connector arrives and I've dis-charged and re-charged the battery and had another go. Thanks for all the support - and damnit, I didn;t know you could get batteries with tabs. Doom - the holder cost 50p. The wire was free, the batteries were £10 and it took me about 20 minutes (time which I would have spent doing nothing anyway). So - total cost = £10.50. Assuming it works, who's laughing? Me. If it doesn't - then I get some nice high capacity batteries for my digitial camera anyway (the little electronic git eats AA's for breakfast.) Well - that's what I'm telling myself... CC Link to post Share on other sites
casey_cole Posted April 27, 2006 Author Report Share Posted April 27, 2006 It worked! Not. The gun turned over gently once. Then nothing happens from then on. The gun is not broken - tested with my other battery (shot straight through a coke can I happened to have lying around. He he.) The pack has connectivity - tested with a mulitmeter. The pack has not suddenly discharged - also tested with a multimeter. Unfortunately, the mulitmeter only goes up to 250mA on the DC Amp's scale, so I can't tell what current it is giving out. Someone said that AEG's draw around 15A - if each AA gives out (say) 2A - is that cumulative over the whole pack? Like, Voltage = 1.2*7 = 8.4V Is it Current = 2*7 = 14A - which would be acceptable in my mind due to the increased mAh. If it is cumulative - then I haven't the faintest what's wrong with it. If it is not cumulative - then I guess the current is too low. If I = V/R V = 8.4 R = 0 ohms in battery, 30 ohms in gun. 8.4 / 30 = 0.28 Amps... However - the resitance in both batteries is 0 ohms (as I would expect) and the resistance in the gun is constant - so if one battery doesn't work, neither should the other with that logic! I've probably messed up somewhere. Can someone tell me what's wrong? Is it the current? CC Link to post Share on other sites
staticzero Posted April 28, 2006 Report Share Posted April 28, 2006 It's the current. As I believe I mentioned earlier, household cells cannot supply the peak or sustained amperage demand of a typical AEG. Their internal resistance is just too high. Link to post Share on other sites
Bigman Posted April 30, 2006 Report Share Posted April 30, 2006 A word on internal resistance. Each cell has its own internal resistance. Unless you can find specs on the particular cells you are using, you have to measure it to find out what it is. Think of a cell as a voltage source (ie something which provides as much current as you need while holding a fixed voltage) and a resistor in series (connected together in a line). Say that each cell is 1.5V, and we are trying to draw 1 amp through it and it has an internal resistance of 1ohm. The problem is, as you increase the amount of current you are drawing, the resistor is going to have a increasing voltage drop across it: From V=IR, R=1ohm & I=1amp V = 1 * 1 = 1 Volt So you will have a 1 Volt drop after your 1.5V voltage source. Overall effect? You get 0.5V out of your cell. Now if you increase the current draw to 1.5A, we get 0V output. If you relate that to AEGs, as the motor attempts to pull a whole hell of a lot of current, the voltage of the system will drop. As the voltage drops, the motor turns slower. Now if you plonk a whole load of cells in series with each other to get your 8.4V, each one has its own internal resistance, and we actually add in more resistance with the wire we use to connect them together as well as the connections themselves. Basically the lower resistance you can make your cells/battery/system, the better it will perform. To measure the internal resistance of the battery, you need to get yourself some resistors (make sure they can take the power you are gonna whack through them), a pencil, a calculator, a volt meter and a bit of graph paper. Put the resistor directly across the terminals of the battery, and measure the voltage across it. Write down the voltage and the resistor value in a table. Keep doing this for several resistors (the more spaced apart they are value-wise the better). Ideally you want to get some really low values like 10ohms and things and some high values like 10kohm. Bear in mind that at 10ohm, you are gonna draw 0.84A (8.4V/10ohm), which means the resistor is gonna have to dissapate 7W (P=IV, 0.84A * 8.4V), so you would need a pretty chunky resistor. Most resistors are only capable of dissapating 0.25W. Also watch out coz they will get hot. Once you have your results, calculate the current flowing for each result you took. V=IR, I=V/R. Now plot your results on a graph (voltage against current). Put the voltage across the bottom and current up the side. Draw a line of best fit through all your points (it should be roughly straight up until the point where the internal resistance becomes negleable I think). You have a choice of methods now, you can either find the gradient of the graph (if you know how, I'm not going to explain), and then do 1/gradient = internal resistance. Or you can find it via the threshold method: Draw your line of best fit all the way until it meets the voltage axis. Read off the value of voltage it gives you when current = 0 (ie the point it crosses). This is V(th). Now take any given point on the line, and write down the voltage V(o) and the current I(o) at that point. Insert into the following equation: V(th) - V(o) R(th) = ------------- I(o) So if V(th) = 2.03, V(o) = 1.5, I(o) = 11.2mA, then R(th) = 47.3ohm. Remember to get your units in SI (volts for voltage, amps for current - DON'T USE MILLIAMPS! If you record your results in milliamps, remember to divide them by 1000 to get your current in the correct units). Thats quite time consuming, but if you fancy it - now you know how Link to post Share on other sites
Bigman Posted April 30, 2006 Report Share Posted April 30, 2006 Oh just to clarify, you made some errors eariler. Someone said that AEG's draw around 15A - if each AA gives out (say) 2A - is that cumulative over the whole pack? Like, Voltage = 1.2*7 = 8.4V Is it Current = 2*7 = 14A - which would be acceptable in my mind due to the increased mAh. If it is cumulative - then I haven't the faintest what's wrong with it. If it is not cumulative - then I guess the current is too low. AA cells, or any cells for that matter, do not simply give out a current value. The internal workings of the battery will attempt to push out as much current as is required, and hold the voltage. They are limited by their internal resistance. Also current is not cumulative - if you stack a load of batteries in series like you are doing, you will not increase their current. Its not quite as simple as adding currents up because thats not what is going on. See internal resistance post. To increase your current (also capacity), you need to put the batteries in parallel. That means putting all the batteries side to side and connecting all the positives together and all the negatives together. You have the same voltage as you started with, but a much greater overall capacity and also an overall lower internal resistance (each cell has to provide less current than the overall current, so the internal resistances do not affect the overall battery the same). If you really wanted you can put a pile of batteries in parallel and then connect those up with more in series to get the voltage and currents you want. If I = V/R V = 8.4 R = 0 ohms in battery, 30 ohms in gun. 8.4 / 30 = 0.28 Amps... However - the resitance in both batteries is 0 ohms (as I would expect) and the resistance in the gun is constant - so if one battery doesn't work, neither should the other with that logic! Here - the resistance of the battery cannot be measured directly (again see internal resistance post). Also when you say the gun, I'm assuming you mean the motor and associated circuitry. Well unfortunately this cannot be measured directly either! The resistance you have measured is the resistance of the windings on the motor. When you put a voltage across the motor, the electromagnetics of it all mean that it will draw a whole hell of a lot of current (as much as it needs to turn in fact). The gear boxes etc inside your gun are pretty difficult to turn, so it can pull a lot. So basically it doesn't have a resistance. It is not a resistor - it is a mix of an inductor, resistor and solinoid (which is pretty much an inductor really). The way to measure the motor is to put an ammeter in line with the circuit and pull the trigger to get it to turn. The reading you get on the ammeter is the amount of current you need to work with. Note that you will need a really good source of electricity to do this (though a standard AEG battery will do the trick). Be warned - most ammeters only measure up to 10A, and it sounds like yours doesn't even do that, so you need to borrow a decent one off someone and probably buy some of the appropriate fuses for it because you might just blow them! Link to post Share on other sites
casey_cole Posted April 30, 2006 Author Report Share Posted April 30, 2006 Woah. I asked for it didn't I... So if - say - 4 AA's gave 15A when in parallel, and 7 AA's gave 8.4V when in series, if I connected 4 AA's together in parallel in place of each cell I currently have - it should work (assuming that those numbers are correct (which they aren't...)). Looks like it'll be a lot of money then. Well thanks for all your help guys - I need to buy another airsoft battery. Sorry for seeming like I didn't listen to you static - but I wanted to make sure that these wouldn't work before I s***canned the whole idea. Now - onto crazy scheme number 2: Power my gun solely using potatos! CC Link to post Share on other sites
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