g&g cm16 lmg issues with both 11.1v and 7.4v nuprol batteries

[Panama]

Hi Folks

My son just recently bought this lmg and it works fine, he loves it and the role, but he has tried both the 7.4v and 11.1v nuprol batteries in it (which work fine in our other G&G predators) and finds that the gun just stops. If he switches from one battery to the other it will work for a while and then just stop again.

It's almost as if the mosfet is detecting that on full auto (not massively long bursts) it detects the draw dropping below a certain level and then just stops/cuts off.

Testing both batteries on small plug in lipo checkers seems to imply there is still plenty of charge left and they charge fine as well and appear healthy.

Could it be the batteries or the mosfet or a combination of both?

Any suggestions welcomed as it is really taking the shine off his new toy.

 

[Adolf Hamster]

It's almost as if the mosfet is detecting that on full auto (not massively long bursts) it detects the draw dropping below a certain level and then just stops/cuts off.

does appear that model does do cutoff, which would certainly be a prime suspect.

even assuming it's able to properly distinguish between a 7.4v and 11.1v and apply the correct shutoff voltage (ie that it's not shutting off on the 7.4v because it's using the 11.1v cutoff) then it can still be shutting off under load.

it's very normal for a battery to have a lower voltage when supplying a given load (ie firing) than what you'd read in a static test. how much lower depends on a variety of factors such as the capacity of the battery, it's C rating and overall quality as well as the draw requirements of the gun itself.

the predators may well have a less stringent (including nonexistent) cutoff, or a lower amp draw which would allow the gun to run even if that same battery sets off the lmg's cutoff.

 

[Panama]

So I just noticed the burst figures on the batteries, so maybe that is the issue specifically with the LMG where as the predators are able to handle them:

11.1v - Nuprol 1450 mAh 3s 30c - 30c 43A Cont. 60C 87A burst

7.4v - Nuprol 1450 mAh 2s 30c - 30c 43.5A Cont . 60C 87A Burst

 

[Lozart]

So I just noticed the burst figures on the batteries, so maybe that is the issue specifically with the LMG where as the predators are able to handle them:

11.1v - Nuprol 1450 mAh 3s 30c - 30c 43A Cont. 60C 87A burst

7.4v - Nuprol 1450 mAh 2s 30c - 30c 43.5A Cont . 60C 87A Burst

Just looked up what I run my M249 with and it's a 7.4V LiPo but it's 1300mAh 35C/70C rated at 45,5A cont/ 91A burst. It may just be those Nuprol batteries are a bit rubbish for something like the LMG. Personally I'd recommend upgrading both to Turnigy batteries and a decent balance charger.

 

[Speedbird_666]

Looks like the LMGs come with G&G's much maligned ETU.

(pic from Evike's review video)

View attachment 77280

Pull out the MOSFET, bin it, and plug in a Perun ETU++ instead. Just need to take the buffer tube off to fit it 'plug and play', no gearbox-opening shenanigans required.

Then enjoy all sorts of programming goodness.

 

[Panama]

Thanks folks I will look at both those options maybe starting with the Turnigy batteries if I can find some slim/short enough to fit in the stock G&G, well, stock. If you have any preferred UK based suppliers, then I am all ears?

The Perun is a simple enough change and we may go down that route if the Turnigy's give him the same sort of issue.

 

[EDcase]

I get my batteries either from HobbyKing or Vapex

 

[Lozart]

Thanks folks I will look at both those options maybe starting with the Turnigy batteries if I can find some slim/short enough to fit in the stock G&G, well, stock. If you have any preferred UK based suppliers, then I am all ears?

https://hobbyking.com/en_us/batteries-chargers.html?___store=en_us#q=airsoft&idx=hbk_live_magento_en_us_products&dFR[config][0]=2&dFR[config][1]=3&dFR[warehouses][0]=UK&dFR[warehouses_stock_data][0]=UK|1&dFR[warehouses_stock_data][1]=UK|2&dFR[warehouses_stock_data][2]=UK|3&dFR[warehouses_stock_data][3]=Global|1&dFR[warehouses_stock_data][4]=Global|2&dFR[warehouses_stock_data][5]=Global|3&dFR[warehouses_stock_data][6]=EU|1&dFR[warehouses_stock_data][7]=EU|2&dFR[warehouses_stock_data][8]=EU|3&hFR[categories.level0][0]=Batteries %2F Chargers %2F%2F%2F Batteries %2F%2F%2F Lipo&is_v=1

The single stick ones are what I use in my buffer tube guns, usually 7.4V 1450mAh or 2000mAh (ymmv)

Whenever you use Hobbyking, be aware of selecting the Warehouse to UK if you want stock in this country!

While you're there, get one of these: https://hobbyking.com/en_us/accuell-s60-ac-charger-uk-plug.html?queryID=d571cc9bb9fa58e265c1d986b7f01a76&objectID=45266&indexName=hbk_live_products_analytics

 

[Panama]

awesome, thank you.

I bought the Skyrc S65 after hearing how much you all loved the nuprol chargers that came with the guns when we got them ?