Bad batteries

[redneck crawler]

I just fried the esc in my wraith and I'm not sure why. I'm going to be getting a hh brxl I want to know if old/bad batteries can mess up an esc (non are shorted) thanks

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[Charlie-III]

Hmmm....can't really think of a reason why a bad battery would hurt a ESC.:roll:

If the battery shorted, yes, it could damage things. If it was low on voltage (and the ESC LVC was not set) you would hurt the battery.

All I can think of is if you reversed the polarity of the pack into the ESC.

I would double check that."thumbsup"

 

[JohnRobHolmes]

A bad battery can cause excessive ripple voltage, which doesn't help an ESC function. If it went down too far it could cause a brownout under load and there is a chance the FET drivers could get confused and dead short something. Really, really, really slim chances on these though. Especially on a simple brushed controller.

 

[Charlie-III]

A bad battery can cause excessive ripple voltage, which doesn't help an ESC function. If it went down too far it could cause a brownout under load and there is a chance the FET drivers could get confused and dead short something. Really, really, really slim chances on these though. Especially on a simple brushed controller.

Hmmm....I can see bad batteries showing excessive ripple voltage (it shows the AC component of a charger), but not in an ESC. Then again, I can't say I ever looked at the ripple FROM a battery going TO an ESC.
I will have to go look.8)

Thanks JRH."thumbsup"

 

[JohnRobHolmes]

Ripple is normally snubbed by the caps, a proper setup will have near zero AC component. If you want to have some fun, take the caps off an ESC and load it down. Watch the voltage on the board closest to the power rails, ripple will increase as amperage increases. The slower the frequency of the controller, the larger the ripple peaks. The lower the motor inductance and resistance, the worse the ripple. The higher the resistance of battery, the worse the ripple as well.


Think about a pulse by pulse playbook of the system. ESC turns on. Amperage increases during inrush current, resistance of battery makes voltage sag. ESC turns off. Amperage is clamped and both phase a battery voltage increase to try and "save" the decaying amperage because of inductance. ESC turns on, etc..