Mosfet, motor and battery question

[SawBone]

Hi, it's my first time upgrading an AEG's electrical system and I have a question for you AEG gurus.

So I got a Gate NanoAB mosfet hooked to a lipo 7.4v 1600mah 20c, and a SHS high torque motor. I changed all the wiring and got deans connectors. This particular setup seems to be working fine after some testing. However, if I try using the stock battery, a 8.4v 1100mah, it fails to spin the motor (even when it's out of the gearbox). If I remove the mosfet, the 8.4v spins the motor just fine. Also, the stock JG motor will work normally with the mosfet and the 8.4 battery.

So either the mosfet or the high torque motor on their own pose no problem, but both together will cause the stock battery to stop working.

Is this behaviour normal? Does the mosfet impedes the stock battery's initial amp peak to the point it cant even overcome the neodymium magnets? I'm not too worried as my lipo works fine with the high torque motor + mosfet combo, but it would have been nice to have the 8.4v as a backup battery.

Thanks

[lurkingknight]

does that mosfet unit have voltage cutoff/monitoring? what gearbox as well?

the shs motor is a very power hungry beast. Though with no load it should still function unless there's a voltage cutoff issue. A low charged 8.4 can read pretty low voltage, probably even below what a 7.4v lipo's safety cutoff would be set at.

[ThunderCactus]

Keep in mind voltage drop as well.
The battery will do nothing but send wattage, but if the motor needs more amperage, you'll get deeper voltage spikes. If the mosfet has voltage cutoff, it might be reading those voltage drops as the battery being too low.

[lurkingknight]

it's odd though it's not a merf so it shouldn't have a cutoff. it's just the AB fet.

Something else is up with it maybe.

[SawBone]

Originally Posted by lurkingknight

does that mosfet unit have voltage cutoff/monitoring? what gearbox as well?

It doesn't have any voltage cutoff/monitoring as far as I know, it's a simple active braking fet. Unless reversing polarity to brake the motor counts as voltage cutoff?
It's a V3 gearbox (JG G36), completely stock except for metal bushings and a shim job.

I was under the assumption the 8.4 battery should be almost on full charge, as I haven't gamed it since I last charged it about a month ago. But I'll double check the voltage it gives tonight after work.

Thanks for the quick replies. :tup:

[Hectic]

the likely issue is its the stock battery, those nicad/nimh things kinda suck as it is, then u get one that has sat on a shelf for a cpl years and suddenly they cand even shoot more than a few hundred rounds before they die. Id say stick with the lipo, u should be able to play 2-3 games on one charge with that.

[KenTsui]

I'm going to take a stab in the dark here, since it's your first time upgrading. Are your old battery's polarity wired correctly?

[ThunderCactus]

Active braking doesnt reverse polarity, it just shorts both poles of the motor and "disconnects" the battery.

[SawBone]

Originally Posted by Hectic

the likely issue is its the stock battery, those nicad/nimh things kinda suck as it is, then u get one that has sat on a shelf for a cpl years and suddenly they cand even shoot more than a few hundred rounds before they die. Id say stick with the lipo, u should be able to play 2-3 games on one charge with that.

That would make sens. However, I tested the stock battery at a little over 9v, which seems about right for a charged 8.4. I can't test amperage though, as my multimeter won't go above 10 amps.

Originally Posted by KenTsui

I'm going to take a stab in the dark here, since it's your first time upgrading. Are your old battery's polarity wired correctly?

Yes, polarity is correctly wired. I tried inverting the motor's connectors just in case, but I got the same results.

Originally Posted by ThunderCactus

Active braking doesnt reverse polarity, it just shorts both poles of the motor and "disconnects" the battery.

Gotcha