Great then explain (96-72) x .08 = 300 amps. How will the controller going to 
see 24 volts

Sent from my iPhone

> On Sep 14, 2017, at 4:54 PM, Cor van de Water via EV <> 
> wrote:
> Paul,
> It seems you have difficulty grasping some concepts presented here,
> you would do well by studying them further before commenting.
> Maybe you just read too casually or fast that you missed what was being 
> explained to you.
> You have the right to not believe what anyone says.
> Wise people listen to wise advise is all I want to offer.
> Cor.
> -----Original Message-----
> From: EV [] On Behalf Of paul dove via EV
> Sent: Thursday, September 14, 2017 11:10 AM
> To: Roger Stockton; Electric Vehicle Discussion List
> Cc: paul dove
> Subject: Re: [EVDL] Slow due to 96V pack?
> There is no voltage adjustment on input voltage in any motor controller I 
> ever used.
> The PWM only controls the output voltage by switching it on and off. The duty 
> cycle then sets the average voltage the motor sees.
> It may have a low voltage cutoff circuit but that just shuts down the output 
> in the event the battery falls below 72volts.... thus the controller would 
> not be working if the voltage was 96-72 = 24volts.
> And yes hooking batteries straight up you would have no control over the 
> current but I still don't believe lead acid would put out 1200 amps.
>      From: Roger Stockton <>
> To: Electric Vehicle Discussion List <>
> Cc: paul dove <>
> Sent: Thursday, September 14, 2017 12:19 PM
> Subject: RE: [EVDL] Slow due to 96V pack?
> paul dove wrote:
>> That made no sense to me but a DC motor controller takes the input 
>> voltage to power mosfets or igbts which switch the power on and off 
>> with a pwm signal to get the desired output to drive a motor. It has 
>> no knowledge of the battery impedance.
> The controller does not have, or need, knowledge the battery impedance; this 
> is simply Ohms Law at work.
> The controller PWMs the power from the battery, and the duty cycle of the PWM 
> can be varied to limit whatever parameter the controller logic cares about at 
> any given time: input voltage, input current, output voltage, or output 
> current.
> Since the battery has a finite, non-zero internal impedance, its terminal 
> voltage will sag as current is drawn from it.  If the motor controller 
> enforces a minimum input (battery) voltage (as does the controller in 
> question), then its logic will vary/limit the PWM duty cycle to prevent the 
> voltage at the input of the controller from falling below the target level.
> Since the controller logic will limit/vary the input current to prevent the 
> input voltage from falling below the threshold, then the maximum voltage 
> difference across the battery internal resistance is the open circuit battery 
> voltage minus the minimum input voltage limit of the controller: 96V - 72V = 
> 24V, in this example.
> The controller does not know what the internal impedance of the battery is, 
> but Ohms Law still applies to limit the maximum current from the battery to 
> *whatever* value results in 24V drop across the internal resistance: 24V / 
> 0.08 ohms = 300A in this example.
> *IF* the sophisticated controller were replaced with a simple contactor 
> controller, then if the contactor controller allowed the entire 96V battery 
> to be connected directly to a stalled motor (~0 ohms), the voltage drop 
> across the battery internal resistance would ~approach~ 96V - 0V = 96V, and 
> the peak current into the motor would approach 96V / 0.08 ohms = 1200A.
> Hope this helps,
> Roger.
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