TM AK47 not firing with all batteries

[RostokMcSpoons]

This should be an easy question for someone to answer, I'm just a little bit surprised I'm needing to ask it:

My TM AK47S is refusing to fire when connected to my Titan 7.4v 3000mAH Li-Ion battery (fully charged)
But it will fire on an older Fconegy 8.4v 1700mAH NimH
And on a Turnigy 11.1v 1200mAH Nano Cell Li-Po

So is it just the lack of volts that's the problem?  I've been using the Titan in all the other guns without an issue.    

(All wired with Deans connectors)

 

[MagpieTactical]

Didn't you have similar issues in your other gun with this battery? 

 

[Adolf Hamster]

is there a mosfet involved?

 

[RostokMcSpoons]

Nope, I even took the chunky fuse holder out of the equation too. 
 

A mosfet seems like a likely addition now, I could run a small 11.1v in it, to make it a handy little beast.

Didn't you have similar issues in your other gun with this battery? 

I had a problem with the DE the first time round, yes.   It wouldn't charge and was showing weird stuff on the battery tester.  
Since the first successful charge it's been fine though.

Do you think I've just got a duff one?

 

[Adolf Hamster]

no mosfet and if as @MagpieTactical says this battery has suggested this battery has given issues in another gun then i'm inclined to blame that.

a checker can be very handy for situations like these, see not only the total output but also if perhaps a cell has decided to give up (some chargers have been known to fail on one charging circuit and kill a battery this way).

the only other explanation would be if it's been tinkered with and something like the shimming is tight, then it might not have the juice to spin on the 7.4, although it would also sound labored on the other batteries.

 

[RostokMcSpoons]

Cells are reading 8.22 total, 4.11 in each cell.

The gun sounds fine to me, with a healthy fire rate...

Yes it has been 'tinkered with', I just swapped out the nozzle.  And previously it had an upgraded spring, guide and gear set fitted.

It's shooting at 340fps with no hop, 0.20g BBs
 

 

[Skara]

Could be the phone mic but that doesn't sound healthy.

 

[Adolf Hamster]

Could be the phone mic but that doesn't sound healthy.

does kinda sound like she's stopping a bit quicker than she should.

Yes it has been 'tinkered with', I just swapped out the nozzle.  And previously it had an upgraded spring, guide and gear set fitted.

It's shooting at 340fps with no hop, 0.20g BBs

shims can be tricksy hobbitses, one drops free when opening up and will almost always drop such that it looks like it came from a different spot to where it was originally.

 

[RostokMcSpoons]

Could be the phone mic but that doesn't sound healthy.

It sounds ok to me, no screeching or grinding.  But all my guns sound different and I don't really know what to listen for, beyond 'unpleasant'

does kinda sound like she's stopping a bit quicker than she should.

shims can be tricksy hobbitses, one drops free when opening up and will almost always drop such that it looks like it came from a different spot to where it was originally.

Ah, that's something I'm not experienced enough to notice.

I was very careful when taking this apart to ensure the main spring stayed in place so it didn't upset the gears, and bugger with the shimming... but the bearings all fell out of the top half of the shell.
The shims had each stuck to their bearings, and as I'd cracked the shell open as gently as possible I tracked each bearing as it came out of place...   I checked in between the gears to ensure nothing had fallen.
So as far as I can tell nothing is in a different position or lost.

The site tech (who'd previously put it together) had checked the shimming and pronounced he was happy with it.

But this is making me think I need to open it up again and double-check the shimming, and be certain there's not a loose shim in there somewhere.

 

[Adolf Hamster]

Ah, that's something I'm not experienced enough to notice.

it's a tricky one, as all guns do tend to sound different naturally, depending on the gearing, the motor etc. can be very subtle.

But this is making me think I need to open it up again and double-check the shimming, and be certain there's not a loose shim in there somewhere.

loose isn't so much the problem as tight, which would drag on the motor.

that said, it doesn't sound like it'd be tight enough to halt a 7.4v.....

 

[Tactical Pith Helmet]

I had a problem with the DE the first time round, yes.   It wouldn't charge and was showing weird stuff on the battery tester.  
Since the first successful charge it's been fine though.

Do you think I've just got a duff one?

I've had this type of issue before with one of those crappy ASG chargers.  

 

[RostokMcSpoons]

Yeah I was looking at a Sky RC double channel charger to replace it

https://www.modelsport.co.uk/product/444856

Not that I've had any problems with it, after that initial weirdness tbh