How to determine if you can have a bigger battery

[OGnapkin]

I am looking at a warbird right now but don't know if i can add a 5 or 6 cell battery to it instead of the stock 4S recommended without burning out the electronics. how can i figure out if it will be ok to run on 5 or 6 cell?

this is the plane i was talking about btw: https://www.motionrc.com/collections/warbirds/products/freewing-p-51d-old-crow-pnp#description-tab

 

[kdobson83]

From what I'm seeing, by searching for hobbyking 80a esc, which is what that plane has in it, it is 2-6s capable. Keep in mind tho, the higher the voltage, the faster the motor will turn, you may need to reduce prop size. Also, the more voltage you run, the more heat it will produce. Unless it has good airflow over the esc, this could increase the chances of brown outs. But to your question, yes, it looks to be 2-6s capable.

 

[OGnapkin]

so the ESC is capable of 6S, but can the motor handle it without burning out?

 

[quorneng]

Going to a 6 s from a 4 s with everything else the same will dramatically increase the full power current.
The 4250-580 motor has a maximum continuous current rating of 51 A. You really need to know how close to this figure it already is with the current prop and a 4s battery so get a Watt meter.
Only then will you be able to tell how close you are to the limit and can safely experiment with different props to keep the maximum current within the motor's specification.
Even if you keep within the motors limit it will be generating nearly 50% more watts on 6s so the flight endurance will reduce by the same degree if you keep the same weight battery and you use the extra power.
Using the 6s power and keeping the same endurance as the original 4s set up will need a 50% bigger heavier battery and this raises the question as to whether the plane can satisfactorily lift it.

 

[OGnapkin]

ok i understand, but how did you figure out the amps of the motor? @quorneng

 

[quorneng]

The motor type 4258-580kV was given in the link you attached in your first post. I then just Googled this and it found several sites that gave the full specification for this motor.
I really must emphasise the importance of using a Watt meter if you want to deviate from a plane's "ready to fly" specification. RC Watt meters are not that expensive - Just Google "RC watt meter" to get an idea of the likely costs. In your case a 100A version would be adequate although remember it has to have the same type of connectors on it as you have on your battery and plane. XT60?
Remember electric planes, particularly scale warbirds, already have to work everything pretty hard to simply fly so it does not take much of a change for something to get over loaded.
Whilst a motor can withstand say a 50% over load for a second or two "electronics" are much more sensitive and can be wrecked in just a few milliseconds beyond their rated maximums.
Perhaps it would be helpful if you explained what was wrong with the stock set up that made you consider going to a 5 or 6 s.

 

[Hai-Lee]

My concern is not if the higher voltage battery can be used, (I will leave that to others to advise), but I do question the experience level of the would be pilot. I know the plane and it is relatively heavy already in original trim. It does not like to land too slow and adding a heavier battery and a more powerful motor could lead to severe landing accidents and even wicked "P" factor/torque roll on take off.

If you are not fully experienced with fast landing and difficult to handle rocket ships then I would NOT recommend fitting a higher power system into the plane. Fly it in standard trim first and if it survives a dozen of so flights then you might consider the upgrade.

Just worried about someone wasting their money on what could be a seriously dangerous projectile.

Have fun!