DIY Open Source EV Charger

[jyanof]

Originally Posted by vwdevotee

Any more progress to report? I'm looking forward to firing up my soldering iron, but don't know enough to do R&D.

ya, i've been tied up partly messing around with the DIY controller and mostly working on A/C. My gf isn't keen on the idle table-o-electronics chilling in the living room either.

I've received all the necessary parts to do this up again. Now that I'm confident in the design, I've worked a little on optimizing layout so it's smaller. The power board should fit on a 4x6 PCB. A new heatsink is cut down so it's 4x9. So, overall, should be 4x9x6, or so. I'm also trying mosfets and diodes in an iso247 package so we don't have to worry about isolating them from the heatsink. This should result in better heat transfer.


Hopefully I can get the new powerboard goin within a couple of weeks.

[jyanof]

Originally Posted by vwdevotee

I might also be wrong, but it's my understanding that after the bridge rectifier there is normally a filter capacitor which maintains the output voltage very near peak.

The peak voltage from 120AC is about 170V - I've noticed about 170VDC on the output side of the rectifier - my scope doesn't seem to be too accurate when 'zoomed out' that far, so it's probably a little less considering the diode voltage drop.

When a load is applied, the voltage on the DC side of the bridge looks like a saw tooth - it'll peak to 170VDC and drain as charge is drained from the filter caps.

So, true - if you had a large enough filter cap relative to your load, it should stay very near peak voltage. A smallish cap or a large load will make that saw tooth discharge slope very steep and your average voltage will be lower...

I've also heard that a 144V pack can be charged with a simple rectifier setup. However, that 170V peak is only for a short time every cycle, so I suspect the average current would be very low as the batteries charge. I suspect it'd take a long time to fully charge. Maybe the K&W limited battery voltage for this reason?

[mcmahon.craig]

Originally Posted by vwdevotee

I might also be wrong, but it's my understanding that after the bridge rectifier there is normally a filter capacitor which maintains the output voltage very near peak.

You win. Just checked my basic electronics textbook. Vl = Vs - 1.4V. I was apparently thinking of a regular full wave rectifier. Whoops.

Sorry for the interruption. Will look in book *first* next time.

[adamj12b]

Hi Joe,

I love the work you have been doing on the charger. I think it will be a great addition to the community. Please let me know if there is anything I can help you out with.

I will be building something like your charger to charge a bank of 45 TS 180Ah cells for my electric vette project.

I have been looking through all my machine stuff and electronics and realized the high dollar 400Hz servo packs (VFD's) that I have sitting around have all of the power components needed to build a large charger.

I went and doug out the one that I knew had something wrong with the logic board, and opened it up. Heres what I found:



There is 3 QM150DY-H IGBT modules, a 3 phase rectifier, 2 massive ripple caps, a 2 channel hall current sensor, and some other small stuff. All of this is mounted to a heat sink thats about 10" x 10" and 1 inch thick with a fan!!

The IGBT modules are rated to 150A and 600V!! I was thinking of paralleling all 3 with the buss bars that are already on them to create a 600V 450A IGBT. This would allow me to be able to charge my pack at 0.55C or 100A! That is about all the service could handle in a home, I have a friend that I visit at his shop, I would be able to plug into his 3 phase service and easily get 100A 3 phase power.

Here is the diagram for the IGBT:


My question is, where do you think is the best place way to hook this up? I was thinking C1 from the B- and C2 to supply ground. B1 or B1X would essentially be the gate.

Do you think these would work?
When will you be releasing the schematic for your design?

Keep up the good work.


-Adam

P.S. Here is the link to the rest of the pictures of the servo pack: EV Charger - a set on Flickr

[NiHaoMike]

Save the entire inverter to use as the EV motor inverter. Just needs some modifications.

[adamj12b]

Hey NiHaoMike,

I have 3 or 4 of this same model inverter, plus another 6 smaller ones.

-Adam

[NiHaoMike]

Parallel the power stages of the large ones and make a huge one that is especially good for an EV.

What smaller ones do you have?

[adamj12b]

The servo packs I have are all Yaskawa CACR-PR series. Im using them for the milling machine that I am building. They were salvaged from a friends machines that he was scraping. I dont really want to take the rest of them apart, as they all work fine. This one was repaired once, then it broke again, and put into storage, So I didnt feel bad taking it apart.

The others get really small real quick. Most of them are only rated up to 1 HP.

Plus, going my planed route with 45 TS 180's and a warp 11 will be under factory weight, but if I have to double the batteries, it will push it over. I would have to go down to 100Ah cells as well as I could not afford 45 180's.

-Adam

[jyanof]

Originally Posted by adamj12b

My question is, where do you think is the best place way to hook this up? I was thinking C1 from the B- and C2 to supply ground. B1 or B1X would essentially be the gate.

Do you think these would work?
When will you be releasing the schematic for your design?

I think they'll work great! Wow, just did a quick search and each of those modules are over 100 bucks at a surplus store - nice!

Connecting as you suggest would work as a low side switch (as all of my configurations have been). You'll have to add inductance to the output loop in order to limit the peak current every switching cycle. It might be a challenge to find an inductor that is of high enough value to limit current spikes at low amps (finishing taper charge) and can handle the high currents your module is capable of. Lead Acids don't mind (much) overcharging and current spikes, but not sure about lithiums. I haven't heard this aspect discussed much, though I don't know how much ripple current fancy chargers have. Might be something to check out - I'd hate for an expensive pack to be killed by high ripple current towards the end of charge.

I have some preliminary schematics, but they've long since changed - I'll have to update them and upload em.

[NiHaoMike]

If you have a lot of large wire, you can just make an air core inductor.