Battery Problem Today

[38super]

My Double Eagle M904g had it's first game today.

Started off with my 1100mah 11.1v 20 battery which ran perfectly.

Decided to swap to my 1100mah 7.4v 20c at lunchtime which is where the problem started

50-100 shots into the first game after lunch and the gun stopped! No reaction from the trigger I didn't hear any sound from the mosfet but it's very quiet.

Swapped back to the 11.1 and all fine except that the mosfet had lost it's programmed single/3 shot burst and defaulted to single/full-auto.

Carried on with the 11.1 until the late afternoon until (after around 2000 shots) that stopped too.

I hadn't expected the 11.1 to last the whole day so it was kind of expected to die but the 7.4 should have been fine.

I've used the 7.4 several times before but only with a handful of shots.

I'm going to get another 11.1 as the obvious solution but the gun has (and is meant to) work with 7.4's.

 

Just wondering if anyone can shed any light on this?

Both batteries are new Nuprols.

 

Thanks

Rob

[Skara]

Did you set the battery protection?

 

If you set it to 11.1v and run a 7.4v battery the mosfet will recognize it as depleted and shut the gun down.

[38super]

5 hours ago, Skara said:

Did you set the battery protection?

 

If you set it to 11.1v and run a 7.4v battery the mosfet will recognize it as depleted and shut the gun down.

 

As far as I can tell the low voltage setting is fixed at 6 volts but I don't have a manual to be sure.

I had charged the batteries a couple of days before and I'd used the 7.4 to chrono around 25-30 shots.

I wouldn't have expected the voltage of the 7.4 to drop that much over 100 or so shots.

Does the duration of the 11.1v 1100mah battery at about 1700-1800 shots seem about right?

 

 

 

[Skara]

4 hours ago, 38super said:

I wouldn't have expected the voltage of the 7.4 to drop that much over 100 or so shots.

It's a common issue with G&G mosfets, they have battery protection set from the factory for a 11.1v so whenever you plug a 7.4v in, it goes for about half a magazine and the mosfet shuts everything down. No idea if the DE's Titan clone behaves the same way, try and set the battery protection to 7.4v and see what happens.

 

4 hours ago, 38super said:

Does the duration of the 11.1v 1100mah battery at about 1700-1800 shots seem about right?

 

No clue, when I used 11.1s exclusively mine lasted a lot (talking 9/10 high caps level of a lot), mine are all 1200 mAh roughly, but I guess the guns weren't drawing a lot (standard ferrite motors, Ares shit EFCS and M90-ish springs)

Edited April 19, 2021 by Skara

[38super]

1 hour ago, Skara said:

It's a common issue with G&G mosfets, they have battery protection set from the factory for a 11.1v so whenever you plug a 7.4v in, it goes for about half a magazine and the mosfet shuts everything down. No idea if the DE's Titan clone behaves the same way, try and set the battery protection to 7.4v and see what happens.

 

 

As far as I can tell there is no option to set the battery voltage.

 

Found this:-

 

and 

I've also read that damage occurs to a LiPo at 2.5v/cell

 

So.....

 

Really bad to run a 3cell 11.1v LiPo down to 6 volts where the mosfet cuts out but how the heck are you supposed to feel vibrations from the mosfet with everything else going on?

It appears I shouldn't run an 11.1 down below 9volts. Certainly not to 6v.???

It would appear to be only really safe for 7.4's which don't seem to last.

I'm now wondering if I've done something that has massively ramped up the current draw.

I'd probably gone through about 15 midcaps by the time the 11.1 stopped working.

 

Anyone know how long a 7.4v LiPo could be expected to last? 

[ak2m4]

What kind of charger are you using?  Do you have one of those small battery voltage checkers?  

[38super]

42 minutes ago, ak2m4 said:

What kind of charger are you using?  Do you have one of those small battery voltage checkers?  

 

This. Probably 10 years old but was a decent one at the time for my RC helicopter.

Should I get a newer one?

 

I've got a multimeter kicking around somewhere. Would that do?

[ak2m4]

hey bud,  I don't know a huge amount about batteries but if someone you know has another charger it might be worth getting them to try a charge and then see how that pans out.  I use one of these mini voltage checkers, only tells you the voltage but it's handy to have and only costs a few quid.  A multimeter will work as well though.

[Skara]

Get two birds with one stone and buy a usb adapter from eBay.

It will still monitor the voltage but you can also use a battery to power your phone.

 

It saved my life last summer

linky link tomorrow because I can't be arsed right now

[38super]

Thanks for the info. I didn't know such things existed.

I'm tempted to see if it's possible to fit one on the gun to monitor the battery until I get used to it.

[38super]

Ok. I got hold of a voltage tester.

Here's the results from my 3 batteries.

1st - 11.1v Nuprol - a few weeks old

2nd - 7.4v Nuprol - as above

3rd - 7.4v WE - came with the gun so age unknown

All charged a couple of days ago.

 

https://drive.google.com/file/d/1OuesPFSrccG1qF5GG6GUcfNKx4wV6QFP/view?usp=sharing

 

The tester has an adjustable low voltage alarm so I'll find a way to leave it attached to the 11.1 when it's in the gun at least until I get an idea of how long it should last.

If that goes off by my ear I will definitely hear it. Just hope it doesn't happen when I'm sneaking up on someone.

 

 

Edited April 21, 2021 by 38super
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