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Apr 22, 2017, 09:46 AM
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Discussion

high voltage esc - whats the issue


Hi ,
I wander about the subject - what makes an esc , a high voltage esc ,
and why they cost 4 times as up to 6s "low voltage" esc ?
As I understand the mosfet "does not care" about the voltage , the high current is to worry , about am I wrong ?
So what remains is to fix the 5v voltage stabilizer that I can to supply from external 5v source as ubec.
Do you think it is possible to convert a regular 6s esc to high voltage esc ? What would be the maximum voltage ?

Is it worth to try to run 6s cheap opto esc on 7s ?

Thank you.


A little story . I wanted to find max lipo serial ability with low price .
I ended with 'Hobbyking™ SS Series 90-100A ESC (Opto)' which can handle 7s.
It was OK on first fly day on 7s , but a week later it puffed with smoke on the moment I connected the battery.
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Apr 22, 2017, 02:25 PM
Stuart
srnet's Avatar
Quote:
Originally Posted by danyra
A little story . I wanted to find max lipo serial ability with low price .
I ended with 'Hobbyking™ SS Series 90-100A ESC (Opto)' which can handle 7s.
It was OK on first fly day on 7s , but a week later it puffed with smoke on the moment I connected the battery.
So your ESC which 'which can handle 7s' went puff.

Do you think it might have been faulty ?
Apr 22, 2017, 03:27 PM
AndyKunz's Avatar
Quote:
Originally Posted by danyra
Hi ,
I wander about the subject - what makes an esc , a high voltage esc ,
and why they cost 4 times as up to 6s "low voltage" esc ?
As I understand the mosfet "does not care" about the voltage , the high current is to worry , about am I wrong ?
FETs most certainly DO care about the voltage. If it's too high, they break down and let the power flow even though the gate says it should be turned off.

So yes, higher-voltage FETs are going to be on it. And with the higher voltage usually comes a higher RDSon, which means you need to have more of them to keep the resistance (and heat) losses low.

Many will also be opto-isolated. That adds cost.

And they will have a higher input voltage regulator for their micro. Again, higher cost. And if it's linear, then you have to get rid of that heat - heatsink or bigger. Again, more cost.

Andy
Apr 22, 2017, 04:45 PM
Registered User
Thread OP
srnet
I dont know if it is faulty , it worked well for a long time with
5s and 6s . I opend it , visualy i see burn marks on two mosfets ( on outer layer ) .
So thist leads to the real question . Is this a non hv esc that claims to work on slightly higher voltage ?

Andy , i see , thank you.
I found 2 cheap escs that claim to work on 7s , thats 'Hobbyking™ SS Series 90-100A ESC (Opto)' and 'Red Brick 125A ESC Brushless
ESC'.
Do you think thay have "middle class semy high voltage" mosfets ,
I meen "better" then other cheap up to 6s esc's but not as real expensive hv escs ?
Or they use same mosfets as cheap up to 6s esc's and "hope for the best" ?

So , Is it worth to try to run 6s cheap opto esc on 7s ?

Thank you.
Last edited by danyra; Apr 22, 2017 at 04:48 PM. Reason: Add something
Apr 22, 2017, 06:15 PM
Registered User
High voltage low resistance FEts are expensive !
The max voltage also depends on the regulator too. Once you get beyond 5-6s the esc will need a switching regulator which brings up the price a little too. Unfortunately there are a lot of esc's right on the edge of comfort when it comes to voltage. What kind of MOSFET was in the esc that popped? We can check the datasheet and see what it can safely handle.

Edit: if the as 90-100a uses the same fets as the 200a version they use Nikos P0603BD. Rated for 30 volts. This esc should be rated for 20v max or MAYBE 6s. Especially if you use active braking 7s will make this pop only a matter of time. Plugging in the battery has a big voltage spike too easily exceededing it's rating.
Last edited by AlkaM; Apr 22, 2017 at 06:30 PM.
Apr 23, 2017, 10:35 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
Quote:
Originally Posted by danyra
... It was OK on first fly day on 7s , but a week later it puffed with smoke on the moment I connected the battery.
How high, or low, was the current you measured with this new setup?

Current is proportional to voltage squared, and proportional to Kv cubed.

Vriendelijke groeten Ron
Apr 23, 2017, 01:01 PM
Registered User
Thread OP
Ron ,

It puffed on the moment I connected the battery ,
It even didnt sound the arm beeps.
On the fly before I assume the current was about 50 amps.
7s fresh , 580 kv , 12x8 prop .

Is it a good practice to make first connetion through a resistor ?
what value ?

Thanks
Last edited by danyra; Apr 24, 2017 at 06:59 PM.
Apr 23, 2017, 01:05 PM
Registered User
Thread OP
Read all about it :
http://www.etotheipiplusone.net/?p=3096
What a pease of work , thank you Charles.
Very interesting issue is the swiching time .


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