famman47 Posted July 24, 2006 Report Share Posted July 24, 2006 Twenty pics, so two parts. Please wait for me to post part two before posting any replies. This was a very time consuming modification. I'm sure there are other ways to implement this concept other than how I did it, maybe easier. It seems like I had to remove and reinstall the gun's internal components dozens of times before I got everything right. I suspect there has been quite a bit of wear and tear on the parts for this reason. I started by ordering a custom battery pack from Cheapbatterypacks.com, according to Staticzero's ideas as posted in his topic titled "The Quest for a better TM MP7A1". I ordered the pack with two three-cell sub-units and one one-cell sub-unit, and twelve inch lengths of wire running between the subunits and between the sub-units and the mini-Tamiyama (sp?) connector. In performing the installation, I heavily modified the battery arrangement, so what you see in the pictures is far from being what Cheapbatterypacks sent me. In the preceding picture, you can see the small bracket that I crafted to suspend the single cell within the cavity that is found between the mechbox and switch assembly inside the MP7A1. This bracket was dremeled from a small bit of mild steel, less than 1 mm thick. It is coated with Plasti-dip spray-on rubber coating. It attaches to the switch assembly, as displayed in following pictures. Here you can see the modification to the wiring coming off the motor. No changes to the positive lead, but the negative lead is shortened and has a mini-Dean's connector soldered on (terminals bridged by solder.) The installation required removing some parts of the switch assembly to make room for the new wiring. The parts removed are shown above. Also removed is the fuse. A mini-Dean's connector is soldered on to the remaining fuse terminal (terminals of the Dean's are bridged with solder.) Don't miss the inset view. Another angle showing what's missing and what's been added. I found no room for these two parts in the modified gun. The upper part is the ejection port (hop adjustment) cover. The lower part is the battery removal assist piece. End of part one. Please wait for me to post part two before adding replys. Link to post Share on other sites
famman47 Posted July 24, 2006 Author Report Share Posted July 24, 2006 Part Two Unfortunately, the ejection port cover arm, which connects to the charging handle extension piece, protrudes into the cavity in which the single battery cell must fit (green arrow shows offending section.) I decided to remove the piece completely, but in the future I may go back in and attempt to reinstall it with the arm reshaped a bit. Here's how the single-cell support bracket attaches to the switch assembly. The spray-on rubber coating is to electrically insulate the bracket from the copper plate lead running underneath. If the single-cell sub-unit is allowed to free float within the cavity inside the gun, it ends up getting in the way of the semi-auto cutoff lever actuator arm. With the battery cell attached to the bracket, a gap of one or two millimeters is maintained between the arm and the cell, and the arm can move freely. Here are the modified internals (no mods to the hop unit or barrel.) Here's how it all fits and plugs together. A bit of dremeling had to be done to the charging handle extension piece to allow a mini-Dean's connector to fit directly underneath. Internals installed, wiring ready to be connected. Wiring and connectors PACKED in. Mini-Tamiyama plug, ready for charging of battery. Parts fit back together (BARELY!) As expected, rate of fire is considerably better. Link to post Share on other sites
a global threat Posted July 24, 2006 Report Share Posted July 24, 2006 wow great guide for all MP7 ownders Link to post Share on other sites
casey_cole Posted July 24, 2006 Report Share Posted July 24, 2006 Woah. Why has no-one else replied to this yet? +1 CC Link to post Share on other sites
Hauk Posted July 24, 2006 Report Share Posted July 24, 2006 Excellent! A1 to that! Looks great. Nice informative guide. Hauk Link to post Share on other sites
famman47 Posted August 1, 2006 Author Report Share Posted August 1, 2006 Update: I have now also added a Nineball spring and the rate of fire is still much higher than it was with the stock battery. According to my chronograph, it is firing 17 shots per second. I'm not sure if it's actually this high--seems a bit over the top. An unanticipated complication that I've encountered is that I'm not completely sure if I got the charge states of the cells perfectly matched in the final battery configuration. They were probably at the same charge level when I got the battery, but in the process of modifying it, I accidently shorted out the single cell sub-unit at one point. I recharged it to the point that its voltage measured the same as the other cells, but it may still be off somewhat. I suspect that this may result in it either being over charged or discharged when the pack is used, and it's life may be shorter than the other cells. It may have also been damaged somewhat by having been shorted. The moral of the story is to be very careful not to short out your cells when putting together a battery pack. Link to post Share on other sites
Shard Posted August 1, 2006 Report Share Posted August 1, 2006 Kudos for going ahead with the idea and taking it all the way through mate. I cant say i would have the guts to do the same to my lil MP7, but then i dont have the skills to do it either i doubt anyway Hope it continues to work ok for a while, it would be a shame if it didnt being the amount of effort and time you put into getting it to work and all fit in there ! Link to post Share on other sites
famman47 Posted August 2, 2006 Author Report Share Posted August 2, 2006 Yes, the durability of the entire gun is in question now, what with both the stronger spring and 8.4 volt battery. Hopefully the motor and gears can take the added stress. If it turns out I cooked the single cell part of the battery, that won't be to difficult to replace. I just fully charged the battery and checked the voltage of both the complete battery and the single cell by itself. The battery in its entirety measured 9.82 volts, and the single cell sub-unit measured 1.402 volts, which is almost exactly one seventh that of the whole pack--exactly what I hoped it would be. If there was any difference, I would want the single cell to be slightly undercharged compared to the other cells. This would lessen the chances of it getting over-charged when I charge the pack. Since I usually only ever partially discharge a pack before recharging it, I wouldn't be worried about over- discharging the single cell. Link to post Share on other sites
ronburgundy__ Posted August 2, 2006 Report Share Posted August 2, 2006 I would suggest deans connectors, theyre much smaller Link to post Share on other sites
famman47 Posted August 2, 2006 Author Report Share Posted August 2, 2006 I would suggest deans connectors, theyre much smaller <{POST_SNAPBACK}> These were the smallest connectors I could find. The connectors that I'm used to thinking of as standard Deans are actually a bit bigger. I would be concerned about not having enough electrical contact area if I got much smaller than the ones I used. On the other hand, using even smaller connectors might leave enough room for a fuse in the wiring area (I'm going to try to fit a fuse in somewhere in the battery compartment in my setup.) Link to post Share on other sites
3vi1-D4n Posted August 2, 2006 Report Share Posted August 2, 2006 Whats the FPS with a Nineball spring? Link to post Share on other sites
ronburgundy__ Posted August 2, 2006 Report Share Posted August 2, 2006 These were the smallest connectors I could find. The connectors that I'm used to thinking of as standard Deans are actually a bit bigger. I would be concerned about not having enough electrical contact area if I got much smaller than the ones I used. On the other hand, using even smaller connectors might leave enough room for a fuse in the wiring area (I'm going to try to fit a fuse in somewhere in the battery compartment in my setup.) <{POST_SNAPBACK}> From what ive seen, a deans connector is wider than a small tamiya, but shorter. Link to post Share on other sites
famman47 Posted August 2, 2006 Author Report Share Posted August 2, 2006 From what ive seen, a deans connector is wider than a small tamiya, but shorter. <{POST_SNAPBACK}> Oh, your talking about the battery charging connector. I thought you were referring to the connectors in the switch assembly area of the gun. Yes, a standard Deans would have been smaller than the mini-Tamiyama (sp?) that I used. I find however that the Deans require a lot more force to connect and disconnect, and on top of that they are harder to grip with your fingers, which I suspect might increase my chances of accidently breaking one of the soldered battery connections in the process of plugging or unplugging for charging. So, since there was enough room for the mini-Tamiyama, thats what I used. Interestingly, the reason there is the extra room in the battery compartment for the connector is that the six-cell portion of the custom battery is actually a bit shorter than the stock battery due to the lack of the stock battery's connector piece. Also, with the battery assist toggle remove from the gun, the cells can slide a bit further into the compartment. These two factors result in there being just enough room for the connector with the muzzle assembly of the gun attached. Link to post Share on other sites
ronburgundy__ Posted August 2, 2006 Report Share Posted August 2, 2006 next step, 10.8v mp7!! Link to post Share on other sites
famman47 Posted August 2, 2006 Author Report Share Posted August 2, 2006 Whats the FPS with a Nineball spring? <{POST_SNAPBACK}> I'm getting about 292 fps or 89 mps with my upgrades. The odd shot hits the 300 fps mark. In addition to the Nineball spring, I also put in a Nineball spring guide, damper piston head, air-seal cylinder, metal bushings and tight-bore barrel (all Nineball.) The stock MP7a1 cylinder is unvented, so any increase in muzzle velocity due to the Nineball cylinder could only be attributed to it forming a slightly better seal with the cylinder head. All of the above parts probably weren't necessary to get the performance boost. If I had been short on funds at the time I ordered the parts I probably would have just gotten the spring, bushings and barrel. Link to post Share on other sites
Rapier Posted August 2, 2006 Report Share Posted August 2, 2006 Don't know if you are aware, but for those let technicly inclined there is an adapter out from nineball. You plug it in like a normal MP7 battery then run a wire out the side where you can plug in an 8.4v mini battery, presumably in a PEQ box or some such. http://www.airsoftextreme.com/store/index....5bfec6b714631b5 Link to post Share on other sites
famman47 Posted August 2, 2006 Author Report Share Posted August 2, 2006 next step, 10.8v mp7!! <{POST_SNAPBACK}> Yes, maybe when 1/3 AA cells are improved to the point of having about a 500 mah capacity, if that ever happens, we will be able to buy an eight cell battery that plugs in just like the stock battery. I'm already getting a sickening rate of fire with just seven cells though, and thats with the Nineball spring. Link to post Share on other sites
famman47 Posted August 2, 2006 Author Report Share Posted August 2, 2006 An alternative to the seven cell modification that might still give an increased rate of fire or the ability to drive the upgrade spring would be to rebuild the stock battery with the CBP750AA cells from Cheapbatterypacks.com. They appear to be in stock at the moment. I wonder if you could send CBP your stock battery and have it rebuilt with the 750 cells. Link to post Share on other sites
DukeNeverwinter Posted September 6, 2006 Report Share Posted September 6, 2006 I hate to dig up and old thread, but I was pondering batteries. I had to get some new batteries for a remote around the house. I found some aaa's that were 900mah. I got to thinking that they might just fit in the battery bay of the mp7. I have not taken the gun apart yet, but I believe you could fit 6 of them in the front, staggered a little if you remove the battery loading slide. Then what if you cut a slot in the top RIS mount so one battery could fit there. Seven batteries would do it. I may try this If I can find positive feed back on aaa nimh's. Link to post Share on other sites
mwaggs_jd Posted September 6, 2006 Report Share Posted September 6, 2006 This would seem to be the ideal place for the use of a LiPo battery pack. You should be able to fit an 11.1v 1320mah or even a 2100mah. Of course I would also expect you would have to upgrade all of the internals to handle the rate of fire. Link to post Share on other sites
Shard Posted September 6, 2006 Report Share Posted September 6, 2006 The problem there being currently no reinforced gear set or replacement motors are available. Break either one of those due to a lust for a silly rate of fire, and you have a lovely looking MP7 wallhanger because it wont be good for anything else Link to post Share on other sites
DukeNeverwinter Posted September 6, 2006 Report Share Posted September 6, 2006 WHich is why I am not going to go with a lipo at 11.1, I believe that it may spin the gears way to fast. Link to post Share on other sites
allizard Posted September 6, 2006 Report Share Posted September 6, 2006 There is 2 cell 7.4 lipo at 1200mah... I would like to see that fit in the gun. Link to post Share on other sites
meGrimlock Posted September 7, 2006 Report Share Posted September 7, 2006 is there any room for a cell in the trigger handle? Link to post Share on other sites
El_Greco Posted September 7, 2006 Report Share Posted September 7, 2006 I imagine that a two cell Lipo would work well, aren't the cells really small? Link to post Share on other sites
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