PandaSoup

Hey, I didn't really know where to put this, sorry if this is incorrect. And a forewarning - I'm a noob.

I have a Traxxas Summit running off of 2 Traxxas Lipo 7600MAH 25C 7.4V 2Cell batteries.

On the "body" I have a Spektrum AR6210 receiver and a Kumba Cam video transmitter running off of a Venom 7.4V Lipo 1600MAH. This battery powers 4 Servos - 2 of them are Spektrum S6170's for the GoPro mount, and the other 2 for an arm, which are a Spektrum S6100 and a Spektrum S6040

I'd like to eliminate the Venom battery and and have everything running off of one of the Traxxas "chassis" batteries. Eventually including a battery eliminator for the GoPro, which is currently powered from its own battery.

I'm assuming I shouldn't just directly tap power from one of the Traxxas batteries? Too many amps for the Spektrum receiver to handle?

Do I need a separate BEC, and if so, any recommendations? Experiences? Is it possible to get the components I need from an electronics store?

I don't really know what I need or how to go about this. I do know that I need to have this thing running off of no more than the 2 chassis batteries. Even then, I'd like to eliminate those, but that's a different topic.

Thanks!

PandaSoup

I just measured the Amps from both the Traxxas and Venom batteries and they are both around 2.6A. The Traxxas only increases in Amps after the ESC (pretty "duh", dunno why I brain farted on that).

So if volts and amps are the same from either battery, my Spektrum receiver should be fine running off of one of the Traxxas batteries?????

Will it be an issue that I'm pulling current from one of the batteries if I tap into it?

ETA- Draw rate of all of the components outside of the chassis is a max of 7.4A

phmaximus

Ummm..... Ok so u have measured the idle current? But remember those currents considerably jump whe u drive of stall a servo...
But that's not really helpful anyway.

those batteries u are running can supply 380a continuos in parallel and 190a in series. So it every safe to say ur camera combined with the car will never exceed the limits of those batteries

the receiver is good for 9.6v so don't plug 2x 2s lipos in series into it. But parallel is fine

phmaximus

Important.... How are the two main batteries wired into the summit??
series or parallel?

phmaximus

Providing the 4 camera servos are all high voltage servos (can handle 2s lipo) there is nothing wrong with wiring the receiver directly to one or both of the batteries (dependant on how the batteries are connected)

this is might clear things up..... Amps don't push they suck. Ie. the battery is not going to push out amps, it's the servo.... The servo sucks the amps... And it will only suck as much as it needs..

so in short, the current draw through the receiver is determined by the servos not the battery. And if u are concerned that the all 4 servos are drawing to much current u can bypass the recover if needed

PandaSoup

The batteries are wired in series at the ESC. I think I only plan to tap into one battery before the ESC, unless that is an issue. Amps don't jump until after the ESC when running/they maintained about 2.6 idle and at full throttle.

I'm sort of worried that maybe draining one battery before the other would be a problem, but the ESC has an automatic shut off if either battery is low, so I don't really see why that would be an issue.


Thanks for the replies!

PandaSoup

So the plan would be to tap into one of those leads between the battery and the ESC, then connect it directly to the Spektrum Rx.

cumquat

personally, i'd just stick to the dedicated receiver pack. tapping into one battery and not the other is a bad idea. while you will most likely never max out the battery, you will be depleting one faster than the other which isnt the best idea. then you have to consider how the ESC will react to one input receiving less power. might be perfectly fine, might release the magic smoke. 50/50 odds are not ones you want to go all in on.

PandaSoup

Should I run battery taps from both batteries in parallel to power the receiver so that there is equal draw on the batts?

Sticking with the dedicated rx batt isn't really a long term option. If anything, I'd want only one batt on the chassis to power everything.

phmaximus

That will case a short.... Taping into both batteries

But powering accessories from on battery on dual battery setups is very common, epically when using a BEC.

here re is an example on how to do it


but... Doing it with that ESC....I don't think it's possible without knowing the internal wiring

PandaSoup

What is the harm in pulling from one batt more than the other?

cumquat

like i said, it could mean nothing or it could fry your esc. you have to remember that the radio will be pulling voltage too. which means the esc might try to compensate by either pulling more amps or pulling more front the other battery. i dont know what your esc will do.

phmaximus

Sorry m8, but that does not make any sence???

if u think it will case issues, for all means please explain

cumquat

all i'm saying is the esc might not like the voltage imbalance between packs. not sure why i didnt say that in the first place.

phmaximus

The voltage difference would be so minor and the batteries are wired in series so it wouldent matter anyway...

to to be honest I don't think the ESC could even detect that... As far as I know??