DIY Open Source EV Charger

[DJBecker]

Originally Posted by adamj12b

Currently the revolt is basically a constant current power supply. The duty cycle is always changing to maintain a steady current output.

You forgot to add the caveat "with a suitably large inductor". I'm sure you know this, but not the casual reader.

Without output smoothing, the Cougar will have bad behavior with many batteries. LiFePO batteries, which look pretty much like capacitors in the time frames involved, will absorb huge current pulses in the first few microseconds putting the controller at risk. Most lead-acid batteries will heat rather efficiently charge.

The Cougar runs the PWM at about 8KHz or 16KHz, which requires a pretty big inductor. It could be much smaller with a frequency 4x-10x higher. And a smaller inductor might have lower resistive losses, which could offset the higher switching losses. Perhaps.

[flores]

Originally Posted by DJBecker

You forgot to add the caveat "with a suitably large inductor". I'm sure you know this, but not the casual reader.

I didn't. I'm fairly good with digital electronics, but this power electronics is fairly new to me.

Originally Posted by DJBecker

Without output smoothing, the Cougar will have bad behavior with many batteries. LiFePO batteries, which look pretty much like capacitors in the time frames involved, will absorb huge current pulses in the first few microseconds putting the controller at risk. Most lead-acid batteries will heat rather efficiently charge.

Dumb question: I thought that the capacitors smooth out the output voltage? How does an inductor help with this? And with inductor you mean a coil with a wire wrapped around/through it right?

Originally Posted by DJBecker

The Cougar runs the PWM at about 8KHz or 16KHz, which requires a pretty big inductor. It could be much smaller with a frequency 4x-10x higher. And a smaller inductor might have lower resistive losses, which could offset the higher switching losses. Perhaps.

How can I tell that i'm doing it right/have the right inductance? can this be measured? seen on a scope?

Thanks

[ElectricZX2]

I asked Paul about using cougar as a charger and I too forgot about an inductor. Otherwise I think it would be relatively easy to switch back and forth between contoller mode and charger mode. He wondered if the motor could be used as an inductor when in charging mode. Anyone know if this could work? I want to try to use cougar as a constant current source for charging my batteries...I don't care about the output voltage because I plan to just open a relay on the input when my pack gets to a certain voltage. Otherwise, what about just using the stator out of an old electric motor?

[mrshirls]

Originally Posted by ElectricZX2

I asked Paul about using cougar as a charger and I too forgot about an inductor. Otherwise I think it would be relatively easy to switch back and forth between contoller mode and charger mode. He wondered if the motor could be used as an inductor when in charging mode. Anyone know if this could work? I want to try to use cougar as a constant current source for charging my batteries...I don't care about the output voltage because I plan to just open a relay on the input when my pack gets to a certain voltage. Otherwise, what about just using the stator out of an old electric motor?

The motor can indeed be used as the inductor, but you risk patent infringement with Tesla. ( the car Co. not the guy )

[ElectricZX2]

Hm, better disable it if I ever want to sell the car for profit . Could you just wire the stator posts in series with the charger output? I'm assuming a 9" motor would be a large enough inductor...l.

[vei]

Hi, I haven't read the whole post but I was interested. I saw you were talking frenquency vs inducter size.

I wanted to say I'm in embedded by profession, so if you have specific needs I might be able to help. I have one of my toy with a 32 bit IC running 2 pwm at 5000hz.

Just saying it's no problem, and switching frequency is limited by the mosfet's turn off time.

I'm starting work on a 3ph open source drive for 3ph induction motors to prepare for my build. So I might as well think of the chargers now since the motor has useful coils in it.

Let me know if you are covered on the uC side

keep up the good work

[apowers]

I found this and had to have it because of it's size. It looks like a big inducter but I think it may be a transformer.

[KUSAW]

I belive its a transformer....

[KUSAW]

I have some of those kind of transformer (toroidal), but for audio amplifier, centre tapped step down..
thanks

[apowers]

Yes I think it is a transforner. I'm not sure I can use it for anything other than a boat anchor.
Alvin