AGM MP40 Batteries

[odinfish]

I'd like to apologize upfront in case this topic has been covered but I haven't found much via the search option.

1.) My AGM MP40 came with an 8.4v 1100mAH. Can I upgrade this battery to increase it's efficiency without harming the gearbox or other internal parts?

2.) What is the consensus on how many batteries one should have in their loadout for roughly a 6 hour skirmish?

Mike

[2ndranger]

I too, have wondered on what battery and how many batteries to buy...I would also like to know what kind and how many batteries to use for a 2 day skirmish. Sorry this doesnt really help you out, Ive just been extremely curious myself.

Franz

[17 SS Allshaus]

I might be talking out of my ass here, but I believe I remember reading an article stating that you could use a battery up to 9.6V with the AGM on stock parts.

Like Franz said before, this might not help you out much. I'm hoping that the stock 8.4V battery that came with my gun as well will be adequate for the Anzio event on the 6th-7th.

[CharleyNovember]

How many batteries you will need depends on how much you lay on the trigger. I would stick with an 8.4 but have run my MP40 on a 9.6 with no ill effects short term.

[Jager.Drü]

I have a 7.4 lipo for mine, runs great but mine has a redone gearbox

If its stock, just use the 8.4v minis. One mini should last 6 hours, but back ups can't hurt.


For two days, I would carry at least 3 in a place where they can be kept warm if its cold or cooler if its real hot.

[2nd Bat]

I find that the Mah ratings on some level relates to the number of rounds you can get on a "Fully charged, it hasn't been sitting around for days" battery. In other words a 600 Mah battery will get you around 500 rounds. 1100 Mah around 900 rounds etc. Alot of course will depend on outside temeperature and how long your bursts are. I tend to do realistic short bursts so my batteries (and gearboxes) tend to last alot longer.

My 3000 Mah batteries last me on a three day op even when there is a lot of action. The higher voltage will speed up your motor and increase your rate of fire. It won't effect the guns power but it may impact your mech box durability. Especially if aggressive long bursts are used. Too low a voltage will usually fail to drive your motor or slow down the rate of fire. Potentially this could also be hard on your motor if right on the cusp of driving your gears.

Three batteries even the small ones should last you through a weekend event even if you do alot of aggressive shooting. Two is probably enough.

[odinfish]

So help me further understand this...I've seen the "mini" type 8.4v batteries available in various mAH: 1050, 1100, 1200, etc. Suppose I used a higher mAH 8.4v, would that be ok, if so, what amount, or should I just stick with what's recommended?

Thanks for all your responses,

Mike

[Jager.Drü]

Higher the Mah = longer lasting battery. It would be fine.

[summvideo]

The 8.4v 1100 mah battery that came with my MP40, doesn't seem to last very long. Has anyone had good results with the stock battery? I purchased a "smart charger" for it, but it still doesn't last as long as I'd hoped. Any recomendations would be appreciated, as I am new to the hobby.

[odinfish]

summvideo said:

The 8.4v 1100 mah battery that came with my MP40, doesn't seem to last very long. Has anyone had good results with the stock battery? I purchased a "smart charger" for it, but it still doesn't last as long as I'd hoped. Any recomendations would be appreciated, as I am new to the hobby.

Same here, with the same charger.

Mike

[Jager.Drü]

They are NiCad correct?
If you didn't discharge them all the way,took it off the charger early, or overcharged it, It won't charge for very long.
Best bet is you need a new one.

Thats the good thing about Lipoly batteries, you can charge it shoot it, leave for a few days throw it back on the charger and its fine. Downside is that they are expensive I pair 100 for a battery and charger. Its a little bigger than a mini, it fits in my MP40 snugly but it pulls my upgraded gearbox fine.

[odinfish]

The battery that came with mine is an Ni-MH and is "Hero" branded. I discharge my battery to the point when my gun stops working. Is there a better way to drain it further?

I definitely don't have a habit of half charging or taking the battery off charge early so that's not a problem. It may be that it's still relatively out of the box that it seems short-lived, or it may be that it's crap. I don't know enough to make a certain conclusion only what I can merely guess at.

Also, I'm not ruling out the fault with the smart charger either, although it was recommended by a few people from another forum. The directions for its use that came with it are in "Engrish" at best and sometimes cryptic imo.

Mike

[2nd Bat]

The NiHM batteries don't have the memory issues that the NiCad do. For NiCads you want to almost fully drain them before recahrging them but for NiHms it's really not an issue. There are some clip on dischargers that are a good idea for NiCad batteries. Batteries will also discharge from simple long term storage. The batteries that come "Free" with the chines guns are not typically very high quality so don't expect much from them.

My advice is by a back up that is a higher quality (NiHm or if you have deep pockets Li Poly) with as high a Mah rating as you can. Think of it as buying a larger fuel tank for your car. You won't have to stop and re-fill as often.

[odinfish]

Cool. Thanks for the clarification and info. Where can the Li Poly batteries be found? And who has the best deals for NiMH batteries around?

Mike

[Jager.Drü]

I bought my Lipoly off ebay. I'll try and find the store
There
stores.ebay.com/EnerlandLipo

[chill]

Hello guys.

Is there anybody here with M120 upgrade for mp40? What kind of battery do you use?

I put M120 spring, metal bushing, CA reinforced piston, cylinder, Systema silent head, decent tappet plate and nozzle. Problem that original battery (Hero NiMh 1100 mAh 8.4V) doesn't work with this configuration. I can hear it tries to cock the spring, but fails.

But it does work with Large type battery from my CA33 - Sanyo NiCd 8.4V 1700 mAh. And my CA33 has M130 upgrade. Assumption had been made that NiCd would benefit over NiMh because its ability to produce higher current at the given moment of time.
So I decided to go with a custom battery pack and ordered the battery that looks like this one:

It is made of 7 Sanyo NiCd 1.2V 1700mAh cells (KR-1700AU), so it's 8.4V battery. Alas, this one didn't work as well. Tries to cock and fails. After motor brushes cleaning it was able to fire 2 mags (about 100 rounds) only which is not enough of course.
BTW, I've been told that motor is not of any standard types (don't remember if it's shorter or longer a couple of millimeters) and not very good quality and probably consumes a lot of power.
What I would like to do:
1. Try to find custom 9.6 (preferably NiCd) battery, even if it's only 600 mAh (as I can see mAh is not an issue, the issue is probably very high current consumption, which can be handler by increased voltage) and check.
2. Try to fit a decent standard motor (that is expensive and not easy way)
3. Replace spring with 110 or 100 and see what 'll happen. Though don't want to do this on the permanent basis. Already spent more than USD200. If I had known that it's impossible to have M120 I wouldn't have bought all this stuff.
4. Go with LiPo? Very expensive and no guarantee it will work.

So, any practical examples about working AGM mp40 upgrades will be appreciated, as well as any advices and thoughts on this issue.

To Jager.Drü:
You sad you have 7.4 LiPo battery and it runs fine your upgraded box. Could you please tell me what's that upgrade exactly and how many mags or round it could shoot?

P.S. Sorry for my poor English

P.S.S. Just tested external 9.6V NiCd Sanyo made of 8 KR-1500AU cells, it lasted for about 200 rounds (4 mags) and died

[Jager.Drü]

4. Go with LiPo? Very expensive and no guarantee it will work.

What? True they are expensive but worth it.

I have the stock motor, metal bushings, stock TM gears, stock TM piston, piston head, new cylinder, M110/120 I dont remember.

My lipo runs my gun all day, this weekend I put over 20 mags through, and the battery still pulls the box fine. I just ran two mags through, right now, I charged the battery Friday night still good.

my lipo is a 7.5(2S1P) 2150mah, 20C continuous (30C Burst).

[chill]

Jager.Drü, thanks for reply.
This makes me think may be something wrong with the whole combination of upgrade parts I put inside the g-box... But it was approved and inspected by the two best upgrade specialists in the city..
Anyone else with working 120 upgrade?

[recoilrob]

I've got the Systema M-120, metal bushings, Area 1000 piston head, cylinder head, bearing spring guide, tappet plate and upgraded nozzle. Runs just fine with the stock battery and motor. Shoots over 375fps. Have at least 2000 rounds through it, and it will shoot three 50rnd mags as fast as I can load them and hold the trigger with the motor and battery just getting warm to the touch.

Sounds to me like you have something very wrong inside your gun. I used the stock gears and piston with no troubles. I'd pull it apart and check to see that the piston can travel far enough back to release properly (don't know if it is possible for it to hit the spring guide?). Are the piston teeth compatible with the gear teeth? Have read about some pistons needing the first couple of teeth removed so the gear releases properly. Changing the piston makes me wonder if the gear teeth are binding when they should release?

Also would check the shimming to make sure it is not too tight. Somebody did something wrong in there!

The stock motor and battery should pull the M120 with no troubles. More battery is NOT the solution (as you have found out) to the problem. The gear box needs to come back apart and the problem found.

[biged]

I used the stock gears and piston with no troubles. I'd pull it apart and check to see that the piston can travel far enough back to release properly (don't know if it is possible for it to hit the spring guide?).

A spring when fully compressed fits inside a piston. Every once in a while spring manufacturers have 1 too many coils in the spring. Add the space taken up by a bearing spring guide and a bearing piston head (both items add fps) and there MAY NOT be enough physical room left. Quick way to solve the problem is to swap out the spring guide with the stock one and test it again.

If the gearbox still does not work.

1. Check the motor height. Go up on the motor height a half turn. Fire the gun and listen to the pitch. It should be crisp pop. If the pitch increase (whining, screeching, or stops) reduce the motor height a half turn. You have to listen to it to find the "sweet spot."

2. Check the shimming by spinning the gears by hand. Remove everything inside the gearbox except for the wiring assembly, bushings, shims and gears. Close up the shell and put all the screws in. Reach inside through the cylinder hole and spin the gears with your finger or a pick. The gears should spin freely 2+ rotations.

The stock motor and battery should pull the M120 with no troubles. More battery is NOT the solution (as you have found out) to the problem. The gear box needs to come back apart and the problem found.

Yes and no. One way to eliminate the battery is to fully charge it then check the voltage with a voltmeter. It should read 1.2-1.4 volts higher than what the battery is rated.
Example: If you have a fully charged 8.4v battery it should read 9.4-9.7 volts when fully charged. If it only reads 9v or lower it's time to purchase a new battery.

///ed///

[chill]

Thank you guys, I'll try everything that has been advised here so fat, one by one to eliminate the problem.
Only one thing from Biged I didn't get - how do you mean "Go up on the motor height a half turn." and "reduce the motor height a half turn." I didn't get it at all. I cannot see how I can adjust something with motor or even it's position. Could you please elaborate? Thank you in advance.

[CharleyNovember]

There should be an adjustment screw at the back of the motor cage(thats the metal part that holds the motor onto the back of the mechbox. You turn it in (clockwise) to push the motor farther into the mechbox. This increases the amount the gear(pinion) on the motor and the gears in the box have contact with each other. I believe it is called mesh. Too far in and it binds because the gear teeth don't mesh against each other at the most efficient spot. Conversley if it is too far out you have the teeth just barely touching which will strip the teeth off or wear them down and shortly they will not mesh right. Gear lash.

[chill]

Again, thanks to everybody helping me to figure out the issue.
To allamericandan: thanks for the explanation, I got the idea. I found the hole at the back of the motor cage but in my mp40 there is no adjustment screw there, may it was lost during the series of assemblings/disassemblings. Detailed investigation showed that without that screw the motor is held by the spring in its most far position from the gear and there is a space only 1mm to push it towards the gear (if I could find the screw of course). Will it be worth of trying to find the screw and adjust motor position?

I have put everything original into the G-Box (except the spring guide and tappet plate - can't find original yet) and shot about 350 rounds with stock battery. Velocity was 99-101 m/s which is quite surprisingly. According to the numbers above in this topic I should have expected about 900 rounds, so either it's motor problem (not very good one or is not adjusted properly) or spring guide issue (described by biged - when the compressed spring cannot fit properly).
Just for the reference - does anybody have real life results (not general assumptions based on the other stock guns) on how many rounds should I expect from the stock mp40 G-box with the stock Hero 1100 NiMh battery?

[chill]

Just to let you know - I found the issue. Reinforced CA yellow piston + Systema Silend Head set were causing huge power consumption, even with stock spring or CA M90 spring. Most likely piston doesn't fit well into gbox. Troubleshooting took so long because of interference with sh*tty stock Hero battery, actually it died eventually.
Thanks everybody, your advices were very helpful.