DIY Open Source EV Charger

[Mesuge]

In case you would like to see some guidance in terms of software features for modern chargers, check these made by Piktronik, they are probably the best configurable LV (<1.2kW) chargers out there and quite expensive (obviously apart from Brusa -CH- but these are more into HV and uber expensive). The only criticism so far about Piktronik was minor about only linear type of temp. compensation settings availability.

KOP line of chargers:
PIKTRONIK

page #2 PC settings screenshot:
http://www.piktronik.com/index.php?download=43.pdf

[NiHaoMike]

high current inductors from copper tubing? - diyAudio
Looks like at 50kHz or above, you might be able to make the inductor using supplies available from Home Depot. Certainly something to consider for a high current charger.

[bones007]

In my opinion the active power factor correction is very valuable as it provides three things:

1- It allows much higher charging current from a standard 110V 15A circuit (fully utilizing the 15A available from the supply).

2- Your power meter measures the Volts*Amps not the watts. If the power factor of the charger is only 0.6 than 40% of the electricity you are paying for is not going into your batteries.

3- It creates a charger that can operate from a universal source (ie: 85-250VAC), so if a higher voltage (220VAC) power source is available just plug it in and it will work. The charging circuit could be designed to detect the value of the supply voltage and adjust the charging current to maximize usage of the AC line.



I found an interesting application note from International Rectifier explaining the use of their Active Power Factor Correction IC IR1150.

See:
http://www.irf.com/technical-info/appnotes/an-1077.pdf

Also, there is an interactive design page that can tell you the value of components required for the desired performance of the basic PFC circuit:



You can get to this design page by creating an account and logging into:
International Rectifier - Design Center
Look for the "Design a PFC Circuit" link.

[NiHaoMike]

No need for a boost converter followed by a buck converter. Do the reverse. Then the inductor can be shared.

And on the link I posted previously, there's a new idea:

For the EV charger, maybe some surplus microwave oven transformers can be used as inductors. The switching frequency would need to be reduced, perhaps to the point where cheap standard recovery rectifiers and SCRs can be used. The main disadvantage would be the weight. However, a charger with a power circuit consisting of one large SCR, one large rectifier, and a few microwave oven transformers acting as inductors would be very easy for the DIYer to build.

I remember reading that SCRs are less sensitive to overload than other types of semiconductors. A SCR can block reverse voltage so no need for a separate input rectifier as the SCR is the rectifier. The low operating frequency means the flyback diode can be a cheap standard recovery rectifier instead of a more expensive high speed rectifier. SCRs tend to be very cheap for the power rating. And old microwave oven transformers can be obtained for free with sufficient salvaging work. It won't be the most efficient charger but it would be cheap and easy to build.

[bones007]

Can you achieve a high power factor using a buck regulator followed by a boost regulator? I agree that boosting the voltage up to something like 350V only to drop it back down to 160 or so doesn't really make sense...however I haven't seen an example of a power factor correction circuit that is not a boost converter.

From my understanding of SCRs: they work by distorting the current waveform from sinusoidal into a sine wave with the first X degrees set to zero. If this is true, the result would be a charger with a low power factor (ie: paying for peak current and getting only a low RMS current into the battery pack).

[NiHaoMike]

If you leave the buck transistor on, it becomes a plain boost converter. If you leave the boost transistor off, it becomes a plain buck converter.
Use hysteresis current mode control with the buck operating on a slightly higher threshold than the boost.

As for the SCR-based charger, it may actually be cheaper to operate.
a quiz about AC power - diyAudio

Does the utility wattmeter register the DC component of the power used? (probably not) Someone will have to turn off everything in their house to measure the meter rotation speed with the diode in and out.
...
No!
...
Take the extreme example: If our diode-equipped soldering iron was one of 1000 in a large factory, all connected in the same way, the facility would be consuming a considerable current which could not be registered by the eddy-current motor driving a standard consumer meter, which responds only to the in-phase AC component).
To put it another way: as you say, high I/V phase angle decreases the work done by, in this case, the meter, but the unregistered power is still available for space-heating or whatever, free of charge.

[jackbauer]

hey guys just a quick question. Whats the status of this project at present? Is there a pcb/ schematic ready?

[jyanof]

Originally Posted by jackbauer

hey guys just a quick question. Whats the status of this project at present? Is there a pcb/ schematic ready?

Sorry, no pcb or schematic at the moment. I got sidetracked with all the motor controller progress and then I focused on building a DC inverter. But, the inverter seems to work, so once the details are worked out, the charger project will resume. All of the new parts are in - I just gotta take the time to make a new power board.

Paul's control board should work nicely with some modifications, if you were to go that route. Mine is very similar with an isolated gate drive system, hall effect current sensor, and an atmel micro. I didn't include the hardware overcurrent stuff since I was able to test the control algorithm at power levels that are actually test-able with basic equipment.

If you make progress of your own, I hope you share!

[apowers]

I am using a Bonn charger I put together from microwave and Digi-Key parts. I have
a 120 volt pack so when it gets to 144 volts I have a light dimmer I use to control
the volts while it finishes off the charge. Could Paul's control board be used to do
this? The power section of the controller could be scaled down, maybe 1 mosfet
to control the low side of the DC output.
Thanks
Alvin

[lhogberg]

I'm thinking of building my own dc motor controller and a switched battery charger for my future EV. The charger and motor controller both have

1. a large and expensive capacitor bank in parallell with the batteries
2. a large and expensive heat sink
3. a case

So to "upgrade" a motor controller to a combined charger/motor controller I would only need an inductor, a slightly larger heatsink and case, a MOSFET, a diode, a rectifier and some control electronics.

What do you think?