DIY Open Source EV Charger

[lhogberg]

Originally Posted by bones007

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.

Are you sure? I live in Sweden, our power meters measures both active and reactive power, households only pay for the active power, companies pay for active power and a _small_ amount for the reactive power as well.

And what do you actually mean by Volts*Amps? If you measure it continuous then you will only measure the active power. If you measure the rms of current and voltage and then multiply it you will have the apparent power.

see AC power - Wikipedia, the free encyclopedia

[bennelson]

Originally Posted by lhogberg

So to "upgrade" a motor controller to a combined charger/motor

It's a great concept.

The charger and controller are really both in the exact same place in the circuit with the batteries, so the cabling would be pretty simple.

Do you think there would be any safety issues with power going to the controller while charging? I have a big physical disconnect I unplug while charging/parking/showing off my EV so nobody can accidently turn on the car or make it move.

You only ever use the controller and charger one at a time, and on-board chargers are nicer to be able to pick up a charge when you can out in public.

The whole device would be a little more complicated. The other trouble might be that if your charger breaks, so does your controller! Kinda like the old combination TV/VCRs - I've seen a ton of those thrown out because the one part broke!

[lhogberg]

Originally Posted by bennelson

It's a great concept.

The charger and controller are really both in the exact same place in the circuit with the batteries, so the cabling would be pretty simple.

Yea I didn't think of that, that's another pro, you can use the same cables to battery.

Originally Posted by bennelson

Do you think there would be any safety issues with power going to the controller while charging? I have a big physical disconnect I unplug while charging/parking/showing off my EV so nobody can accidently turn on the car or make it move.

Of course the motor should be disconnected while not driving. I know that most people have a contactor to disconnect the whole controller from the battery pack. But I see no big drawback with putting that contactor after the controller instead. The drawback I can think of is that when you mount the controller in the car and connect the batteries to it, a great spark at the terminal will occour if you haven't precharged the capacitors.
So either you always prechage the capacitors when connecting the batteries, or you have an additional switch/contactor between the controller and the batteries.

Originally Posted by bennelson

You only ever use the controller and charger one at a time, and on-board chargers are nicer to be able to pick up a charge when you can out in public.

Exactly, you get an on-board charger without sacrificing a lot of space and weight.

Originally Posted by bennelson

The whole device would be a little more complicated. The other trouble might be that if your charger breaks, so does your controller! Kinda like the old combination TV/VCRs - I've seen a ton of those thrown out because the one part broke!

Haha, I know what you mean, but since they electrically only share the capacitor-bank it is not very likely that the melfunction of the charger would cause the controller to stop working (or vice versa). Of course if you also share some of the control electronics (i.e. the microcontroller), it's another thing. But you don't necessairly have to to that, and it doesn't give you much cost savings.
Also since I plan to build it myself, repairing it shouldn't be hard

[sawickm]

I think this is an excellent idea !

If you purchased a separate motor controller and battery charger the cost is double of what a combined dual mode controller would be. That cost savings would offset the continuous duty cycle of the dual mode controller. Adding a separate Charger PCB to the modular ReVolt (Controller PCB, Power PCB) would be great !

For safety, the dual mode controller firmware would disable the motor main contactors during charging mode. If you added BMS you would have everything in one package, just add batteries !!!

-Mark

[MPaulHolmes]

I think it's very doable too! It could be as simple as a switch that lets the controller know what it's supposed to do. Instead of contactor to motor closed, contactor to an inductor is closed. It could even be the same chip if you wanted. The code would actually be very similar. Instead of reading throttle, you would follow some sort of algorithm so that current into the batteries was what you wanted it to be. You might need a different current sensor, though. Maybe you could have 2 current sensors mounted to M-. One for 0-500amp, and one for 0-30amp or whatever.

[sawickm]

Originally Posted by MPaulHolmes

It could be as simple as a switch that lets the controller know what it's supposed to do.

You might be able to switch the controller into motor/charger modes automatically with voltage sensing when the vehicle is plugged into the utility power grid ???

[lhogberg]

Originally Posted by sawickm

You might be able to switch the controller into motor/charger modes automatically with voltage sensing when the vehicle is plugged into the utility power grid ???

Yea exactly what I had in mind, an SPDT AC contactor can disconnect the control voltage to the motor contactor when the grid voltage is applied.
And I think it's easiest to let the inductor always be connected, because when no AC voltage is applied, it goes nowhere...

[sawickm]

FYI:

This fourm is also talking about charging with an AC controller. The Australian Electric Vehicle Asn: Pack charging with an AC controller

-Mark

[apowers]

Paul that is what I was thinking about the throttle input . Let the throttle be a volt meter that does not go past 144 volts (in my case) and when amps drop to I think
4.6 hold for certain amount of time. 2 hrs. ? All batteries are a little different depending
on ah I think.
Alvin

I don't think I want mine all in one.

[adamj12b]

I hate to be a bearer of bad news, but using the controller as a charger as well is very dangerous.

In order to use the controller as a charger, you would need to rewire the battery from the battery side to the motor side, you would then need to apply some kind of DC power to the battery side of the controller. This would require some large contactors to be able to switch back and fourth.

The second problem is the controller does not measure voltage yet. You would need to add this to the controller to control the PWM output or you could go way over what would kill the batteries.

Also, when you start adding things to code, you increase the risk of bugs.

A better idea, I think, to keep things cheep would to use a power stage that is only 1/5 of the drive controller. This would be 2 MOSFET/diode pairs, capable of 50A. To this you would add a current sensor capable of more accurate low current measurement. As for the cap section, the whole cap section of a controller is $50. 4 caps would be enough for a charger.

I've built a power stage of just this size. All it needs to be a charger is some logic.

As for the heat sink, it is mounted of the heatsink for a P4 computer processor.

If people are interrested, I could probably get to working on making it I to a charger. I actually have the pwerfect inductor already.

-Adam