Hi guys!
It's been a while since I've needed to post here. Last time I posted I was talking about a thermistor circuit for my electric race bike. Well anyway, that bike has been put out to pasture and I have already started work on the next bike. I did pretty good, including winning two races at Winton raceway in 2011. I didn't race in 2012 because of a lack of time, and now I have stacks of time and no money. Oh well.
Now, about the new bike!
This bike will be running a very powerful synchronous AC motor and as such, needs lots of power from a big variable frequency drive. This drive in turn needs lots of volts to work the motor to it's full potential. And potential is the word of the day here.
The battery pack will be charged to a maximum of 700 V DC. It will settle to about 650 V during use, and it's considered spent at 590 V. Don't worry, there are multiple levels of isolation, both physical and electromechanical. But during use, I still need to know what the voltage of my pack is.
The instrument panel needs four critical diagnostics - AMPS, VOLTS, SPEED (or RPM) and AMP HOURS. Amp hours is a tough one, as most amp hour meters have voltage sensing built into them, and they are not rated to 700 V!
And here's the rub - I can't find a safe way to measure 700 V DC from the battery pack. Sure, I can run silicone wire inside a HV conduit up to the instrument panel of the bike, and mount a digital panel mounted voltmeter there, but the voltage sense leads are about 2.5 mm apart. That's just too close! Even if I fused it, 70 cm of wire would make an epic plasma ball if it shorted.
My question is, can I build a voltage divider into the pack and run say, 70.0 V or even 7.00 V up to the instrument panel, and somehow multiply this back up to read 700 V on the display? The decimal place is deliberate here, as I want 6.54 V to read 653 on the display. Most panel mounted meters have dividers built into them. Is there a way I can get around this?
I have a 75 mV shunt and I will be placing an ammeter on the instrument panel too. At least there's only one HV contact up there.
Any ideas?
It's been a while since I've needed to post here. Last time I posted I was talking about a thermistor circuit for my electric race bike. Well anyway, that bike has been put out to pasture and I have already started work on the next bike. I did pretty good, including winning two races at Winton raceway in 2011. I didn't race in 2012 because of a lack of time, and now I have stacks of time and no money. Oh well.
Now, about the new bike!
This bike will be running a very powerful synchronous AC motor and as such, needs lots of power from a big variable frequency drive. This drive in turn needs lots of volts to work the motor to it's full potential. And potential is the word of the day here.
The battery pack will be charged to a maximum of 700 V DC. It will settle to about 650 V during use, and it's considered spent at 590 V. Don't worry, there are multiple levels of isolation, both physical and electromechanical. But during use, I still need to know what the voltage of my pack is.
The instrument panel needs four critical diagnostics - AMPS, VOLTS, SPEED (or RPM) and AMP HOURS. Amp hours is a tough one, as most amp hour meters have voltage sensing built into them, and they are not rated to 700 V!
And here's the rub - I can't find a safe way to measure 700 V DC from the battery pack. Sure, I can run silicone wire inside a HV conduit up to the instrument panel of the bike, and mount a digital panel mounted voltmeter there, but the voltage sense leads are about 2.5 mm apart. That's just too close! Even if I fused it, 70 cm of wire would make an epic plasma ball if it shorted.
My question is, can I build a voltage divider into the pack and run say, 70.0 V or even 7.00 V up to the instrument panel, and somehow multiply this back up to read 700 V on the display? The decimal place is deliberate here, as I want 6.54 V to read 653 on the display. Most panel mounted meters have dividers built into them. Is there a way I can get around this?
I have a 75 mV shunt and I will be placing an ammeter on the instrument panel too. At least there's only one HV contact up there.
Any ideas?