UltraCapacitor Charging Voltage
UltraCapacitor Charging Voltage
(OP)
I am working with a hybrid car which charges a bank of ultracaps from regen braking.
I read an article which I believe was written by someone who is misinformed, but it had me thinking...
Just to clarify some theory about charging voltage,
Scenario
Max ultracap voltage= 14V
Current ultraCap Voltage= 10V
Motor BEMF Voltage = 20V
It is safe to charge the ultracaps with the 20V source until the caps are at 14V, correct?
Potentially, the greater the difference of voltage (potential) is related to how much current can be transmitted. V=IR
I read an article which I believe was written by someone who is misinformed, but it had me thinking...
Just to clarify some theory about charging voltage,
Scenario
Max ultracap voltage= 14V
Current ultraCap Voltage= 10V
Motor BEMF Voltage = 20V
It is safe to charge the ultracaps with the 20V source until the caps are at 14V, correct?
Potentially, the greater the difference of voltage (potential) is related to how much current can be transmitted. V=IR





RE: UltraCapacitor Charging Voltage
I guess things have changed some, but do read up on ESR before you get all lathered up about jamming a lot of charge into a supercap in a hurry.
Mike Halloran
Pembroke Pines, FL, USA
RE: UltraCapacitor Charging Voltage
However, that capacitor is power-rating limited to 171A, but your proposed condition would apply about 1000A to the capacitor.
TTFN

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RE: UltraCapacitor Charging Voltage
RE: UltraCapacitor Charging Voltage
If you're going to have a complex controller, why not include a DC-DC converter as part of the architecture?
Hopefully someone has confirmed that there's an environmental pay back point within the life of these systems. It'd be a shame if this complexity, expense and extra mass results in a larger cradle to grave environmental footprint (as is reportedly the case with the most famous hybrid).
RE: UltraCapacitor Charging Voltage
The real setup I am working with 12 2.7 2000F capacitors in series with ESR on each cell of .03mohm.
These caps can withstand 1700 amps plus for 1-2 sec. Its power rating of 170 amps is for continuous operation. In my case braking will be at most 400-500 amps at 1-2 second intervals.
The motor controller applies its pwm frequency by voltage, hence raising the voltage of the spinning motor for regeneration. Specifically its V * 1/PWM.
The question is, will the caps be safe if you charge with a higher voltage source (ex. 42v) than the packs rating(32.4V) as long as you stop charging when the caps hit an internal voltage limit. It seems that VE1BLL has confirmed my assumption. I'm in the process of talking with the manufacturer.
RE: UltraCapacitor Charging Voltage
RE: UltraCapacitor Charging Voltage
RE: UltraCapacitor Charging Voltage
RE: UltraCapacitor Charging Voltage
RE: UltraCapacitor Charging Voltage
Bill
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Jimmy Carter