intermittent electrical problem

[bryn]

hi all. i'm having an intermittent problem with my car electrics. when accelerating on full throttle, it does so for a second or two, then i lose all power to the throttle and steering. then after the car is left for a second, power comes back. it seems to be ok on part throttle though? my system is
hot bodies d4
acoms 2.4ghz radio gear inc kit servo.
mtronics viper speedo
vapextech (or something like that) cells
basic modelsport slow charger.

does anybody have any idea what it may be? it's driving me nuts.
cheers,
bryn

[autonm]

i had this issue a few weeks back - turned out the connectors on the lead from the ESC to the battery were to slack.

So every time I went round a corner fast or over a jump, they would pop-out then reseat themselves and away I went again.

I simply replaced the connectors.

May not be your problem but its something to go on

[RichB]

sounds like it could be that the supply from the ESC to the receiver/servo isn't powerful enough, so that the load of full throttle causes the voltage to the Rx do drop too low and the Rx to 'reset'. A large capacitor connected directly to the Rx may help with this issue, maybe worth a try.

[Si Coe]

Its what Rich said. I've had the same problems with my Acoms system. If the input voltage drops too low it loses its bind to the TX and starts hunting for it again. Since this can take a few seconds the car kind of stalls for that time.
I had this a lot in my Micro T where the tiny battery can't supply the 10200kV brushless. I swapped to an old 27mhz set and the probelm stopped. The voltage to the rx still drops, but at worst it results in a tiny glitch

[bryn]

thanks guys. i'll check the battery connections but how the hell do i solve the voltage drop problem? where should i stick a capacitor and how big is a large capacity capacitor? in english please

simon did you give the post office peeps a kick up the arse?

thanks all.

[JJ The Boat Wizzard]

I Had the same problem with my dx3r and my micro reciver i just bought a specktrum 'Voltage protector' for about a tenner i think and that sorted it! I see no reason for it not to work with the accoms 2.4 system as i is only a capacitor

Hope This Helps
John

[RichB]

Do you have decent connectors between battery and ESC i.e. not Tamiya-style plug and socket? These can have high resistance and cause voltage drop at high load. Better would be Deans or 4mm plug-sockets (aka corally).
A receiver capacitor looks something like this: http://www.horizonhobby.com/Products...ProdID=NOV5626 and plugs directly into the Rx.

[dissy]

sounds like a dodgy esc had the same problem with my rv11 not long before it melted (mtronics c**p)

[bryn]

thanks again guys. i do have the tamiya style connector on my car, so i may well order the capacitor jobbie and a load of the corrally connectors too. where from? modelsport or somewhere else?

i'll give these a go and hope that that cures the problem and it isn't an ECU problem. i don't think it is though as i also tried my old tekin 420r in there too and it stll did it.

cheers
bryn

[bryn]

this is my speedohttp://www.fusionhobbies.com/Mtronik...per_sprint.htm

i have spoken to modelsport and they seem to think it is unlikely to be a voltage drop issue and more likely that this speedo is on the limit. with my motor peak racing vantage 8x2.

what do you think? still voltage drop?

cheers,
bryn

[dibble34]

I run the acoms 2.4 with a 4.5 brushless in a D4 and use a powercap. Gotta be worth a try as they are only about £5. Cheaper then replacing your speedo....

having said that you are obviously at the limit of the speedo if the limit is 8 turn.

Do you have a slower motor you could try?

[JJ The Boat Wizzard]

It is highly unlikely to be the spedo been at its limit because if it was all the spedo would do is thermal and shut down the throttle, it would still power the servo and radio!

John

[Si Coe]

It can be the speedo at its limit.
Thats because at the limit its unable to supply both the BEC and the motor with sufficient current, and the BEC is losing out.
I had this at the weekend with my B4. I thought I was getting interference because at certain points I'd just lose control of the car, throttle and steering. But it couldn't be that as I was on 2.4ghz.
What it turned out was I was massively overgeared (fitted the wrong motor basically) and when I hit full throttle the current draw was such the reciever got no power and cut out.........

[Chequered Flag Racing]

Bryn

what turn motor are you running with the speedo?

[bryn]

thanks folks, i'm running a 8double motor and the speedo 'should' be capable of running an 8 turn motor. i am using tamiya style connectors and they do get warm/hot, should they get hot? so i have ordered some corally connectors and i'll try them, then if that doesn't work i'll try a powercap, would this plug into the battery plug of the receiver? hopefully it will work ok then.

i do have an old reedy 11 double motor i could try.

simon could i be overgeared? my car is not as quick as my old bosscat with the same speedo, motor and pinion? i'm not sure about my gear ratio though. i haven't done any calculations, just bung in what gear i had lying around

[RichB]

connectors shouldn't get hot, as that indicates that voltage is being dropped and power wasted. (If things get really hot and melt than that is called a fuse!). Good quality connectors in the power lines is always a good start, and will give you the best performance/efficiency anyway. A cap would plug into the battery input of your Rx as you say.
Does your ESC have a "current limit" setting? If so you could try that to limit the motor current, to see if that helps at all.

[Chequered Flag Racing]

BRYN

esc
which viper have you got?
best one on site advises 9t limit / bottom right
http://www.mtroniks.net/products.asp...ontrollers.htm=&

Tamiya Plugs
no good on 8t I'm afraid

Ratio / hot bodies d4
what pinion/spur are you using?
what's the final drive ratio for this car?

Motor
is it newly skimmed or burnt brushes & comm?

[bryn]

thanks again guys, i have a set of corally connecors on its way to replace the tamiya ones so that will eliminate that.

i am running a 19 turn pinion and a 80 tooth spur (not sure on everall ratio though).

my ECU is here http://www.fusionhobbies.com/Mtronik...per_sprint.htm
it 'should' be ok i guess but i have just noticed it is suitable for up to 4500mah cells and i have 4600's would this overload it and make it cut out?

i haven't got a comm lathe to skim the comm but it looks in good nick.

cheers all,
bryn

[Chequered Flag Racing]

Originally Posted by bryn

i am running a 19 turn pinion and a 80 tooth spur (not sure on everall ratio though).

it 'should' be ok i guess but i have just noticed it is suitable for up to 4500mah cells and i have 4600's would this overload it and make it cut out?

esc should be OK on the extra 100 mah

internal ratio, shame on you

Hi Bryn,
The Overall ratio guide is in the manual.

Basically.

(Spur/Pinion) x 2.4375 = Overall Ratio.

e.g.

(80/19) x 2.4375 = 10.26
(80/18) x 2.4375 = 10.83

These 2 ratios shouldn't be far off. Depends on the make of motor though. You batts will make a difference too.