Volt Charging

Alternative energy sources
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The usual. As I have two large solar PV systems here, and my lab assistant just put one in, and others are interested in things like this, here's where that stuff goes. This is mostly for things that work now, not "gee someday a fusor will do this" -- we know that, but it's not someday yet.
The hope is to save anyone embarking on this sort of thing a lot of wasted time and money, as at least I have been off the grid since 1980 and have had a lot of practice (and made mistakes you won't have to).

Volt Charging

Postby Doug Coulter » Thu Feb 23, 2012 9:14 pm

Well, I've been charging this off the medium-lame 120v cord they supply with the car. It works, and has two charge rates you can set - but you have to plug and unplug the car to make it respond to the button on the panel (lame). At least you can switch the AC into it on and off to get a sort of bang-bang control. But it's slow. Unless you cheat, the most you can force the car to hold a charge is 45% or so in mountain mode, which leaves about 55% to be provided by the house. With the 120v cord, this takes minimum of about 10 hours - longer than the sun is up, and around here, we don't burn a lotta KWH after dark.

The limit on 120v is set by the car electronics (more below). So I wanted to go to 240v, where the car will eat up to 3.3 kw. Two possible paths here - one is to just buy an EVSE cord and add the required logic, or buy the Voltec unit from SPX (a division of GM) and use that, lame as it also is. I did both because I wanted something quick now - and might be working up a hack for the Voltec unit so I needed one, and I also want a super tweaker standalone unit to use here long term (I'll sell one of these and keep the other).

I got the Voltec installed in about an hour - no big deal, just pulling some wire mainly, and hooked it to the new Xantrex XW 4024 inverter I bought to do this with, so my house inverter won't be stressed - this is most of one of these all by itself at max rate. The bonus is when not charging the car, I get 240v at 4kw average, or twice that peak, to run my lathe, welders, and fusor.

These units are kind of expensive. The GM Voltec is by far the cheapest at "only" $515 delivered - people tend to pay about $2k to have them installed, even with subsidies, as they just mark up a local electrician until the subsidy is gone, plus about another thousand bucks or so - it's not a not for profit outfit. You'd think you get a buncha fancy stuff for that 5 bills, but here's what you actually do get:
VoltecGuts.jpg
Guts of the Voltec unit.

In a big plastic box, you get this little circuit board that's mostly blank. Fuses, then a GFCI sensor, a little +/- 12v power supply to run a uP, and a couple relays to switch power out to the car. It comes with a long coiled (ugh) cord that puts way too much side-stress on the car connector for my taste as well.

It turns out, that's all you need, and even a uP is kind of overkill for this. Sure, since they have it, they check AC frequency and voltage and a bunch of other stuff and refuse to work if anythings not perfect, but so what - the car doesn't care, it's just a brute force rectify and switch into the batteries kind of thing at the other end. After all, they don't have to change the car for 208v (between two phases of 3 phase) or UK, at 50 hz and whatever - it's just a universal switcher in the car.

Now, there's a pretty simple protocol involved, that uses only one wire and a ground return, and this is where the factory units are lame, and mine will be much better. Basically, the "cord" emits a 1khz +/- 12v square wave with a 1k series impedance. The duty cycle high is what the car uses to decide how much power it can draw (within the car own limits). It works like this. The EVSE (glorified extension cord) makes this signal all the time. When you plug in the car, the car has a 2.7k load hardwired so the cord can tell there's a car there. This load is through a diode - it only affects the positive part of the wave swing. When the car is ready to accept charge, it switches more load across the pilot signal - net about 880 ohms - to drop the pilot positive peak to around 6v. At this point the cord goes into action and closes the relays that let line power go out to the car. The unit could vary the duty cycle to allow the car to adapt to varying amounts of power being available, in a situation like my solar system - but the factory ones don't have any way to do that. The unit could also switch the AC off when there's a need to conserve power for a bang-bang algorithm, but again, not the factory ones. I put a switch in the line to the 120v one so I could do this, but then had to defeat the car alarm going off for "charge cable theft". It still beeps once when power is restored. Not a problem here, but some places people whine about the fan and pump noises the car makes when charging, so you know they're going ballistic about a horn.

My home solar stuff uses a CAN Bus to talk to itself, and be controlled by. Xantrex makes a very lame "gateway" to the ethernet for the system, but the one I have is also very lame, and also broken in various ways as far as a I can tell, and does not allow ethernet to control the solar stuff - like I said, lame.

Thus are all slick projects born. As mentioned above, I bought one of these expensive cords, raw, to implement my own system for this:

EVSECords.jpg
Better cord from TusconEV, also expensive, but lookie that fat, straight wire!


Got this nice orange one from http://www.tucsonev.com/

This uses straight wire (which I prefer) and this one's number 8 stuff - not number 12, so less losses at 15 amps. It's longer than the Voltec/SPX unit and obviously much better made. The only difference is it lacks the built in led flashlight on the end, but has a connector cap to keep mud out (important here). There is an open EVSE project out there that uses an arduino to control this, but I like PICs, and theirs also doesn't have the desired/required features (though I could probably add them if I wanted to bother to learn the ins and outs of yet another UP). Here's their page - I've asked them a few questions, and they've helped with answers. I plan to publish this there and here as well - the more open source ways there are, the better. http://code.google.com/p/open-evse/

Today, I ordered a CAN bus development board, and an easylynx ethernet/webserver board to make this project design off of. The idea is that this will tie into - and control doggone it - all the Xantrex stuff. It will be able to also see all the internals of the solar system so it can know when there's spare power. It will also control the car charger - it will be a versatile EVSE station. It will emit a web site on my network that I can use to control it all from my couch if I want to, or just watch it all happen. It will also allow me to log it all on a PC somewhere on the network to have some nice stats on what the entire mess is doing and has been doing. This is a little bit of overkill of course - the dev boards have way more capability than this actually requires...and here's the kicker - the total cost for both - with programmers and a spare ethernet board - was under $300 - and comes with source code for the CCS compiler I have already. If I just redo the layouts - this will cost perhaps $50 plus the fancy EV cord, tops, yet have much more capability than what you pay $500-$2000 for (yes, some other manufs - including Xantrex/Schneider, sell EV cables that cost that much, even though there's diddly squat in one). Mine will use NOS solid state 40 amp relays, far nicer and safer than the cheezy potter-brumfield ones in the official units - you wonder how long those will live running at 90% of their ratings... It will monitor AC, it's own temperature, the allowed and actual car draw, the system battery voltage and net amperes, you name it (anything the Xantrex stuff already measures plus whatever else I feel like adding).

There is a non official volt forum I've been posting on a lot lately. There are a few people there who are really drooling for this - they have solar systems too....so I'll have no trouble selling any spares, though I doubt I sell a lot of these - not many people have off grid solar systems AND a Volt (or leaf or tesla or...). But I was surprised that there are about 6 on that board who are interested and actively asking me when they can buy one. So off I go on this. I wanted more control over the solar system anyway, and Dave Knight found an old copy of the Xantrex protocol to work off, so I should be able to replace a few hundred bucks worth of manual system control panels along the way, inside this same project. This is going to be nice! CAN bus looks like fun, that is, since CCS provides drivers for PICs that have the hardware, and also for external chips, that handle all the ugly parts of a shared-wire protocol. All you have to do is figure out what you want to do at that point.

Here's the CCS stuff I got to work with. Looks like some fun is in store.
http://www.ezweblynx.com/product_info.p ... WEBLYNX_5K For the ethernet interface - and you get a spare one along with a programmer and code for the price.
And here's the can bus stuff - way overkill, two cpus and a couple expanders so it's a whole network by itself to play with. I plan to just grab the design for this project - any pic can do this with the interface chip - maybe even the ez web lynx one...but I wanted to make the learning curve as short as possible so as to get back to science here.
http://www.ccsinfo.com/product_info.php ... =CANbuskit
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Volt Charging

Postby Doug Coulter » Mon Mar 05, 2012 8:06 pm

I did a very simple hack yesterday just to get going on this, and it works well enough that I may keep it for awhile. The Xantrex charge controllers I have emit an AUX output that can be controlled by various things going on in the system - it's not as flexible as I'd like, but...it's there. And it will make 12 at 250ma "logic levels". So, I wired up some SSR's in series with the power to the Volt chargers, and implemented a "bang-bang" control system for it, as dirt simple as it gets. The one I chose for now might not even be the best, but in a couple days testing, it's not bad either.

It's simple - when the battery voltage gets up near the system "absorption" voltage - about 28.7v volts for a 24 v nominal pack - and stays there at least a minute, turn on the relays. When it goes below "float" (about 26.5v) and stays there for a least two minutes - turn off the Volt charger. Repeat as necessary. This scheme can only work if you get the car charged up before the end of the day, so the house batteries can then reach full charge - they are not there when this starts diverting power to the car, not hardly, but in fact, since the car charges pretty fast when there's plenty of power, this might be a good bet anyway. And it got the car charged on a very schizophrenic solar day - minutes to half hours of sun, followed by the same kinds of times of almost total darkness. At least this scheme can't wind up with totally dead house batteries at the end of a day - it will shut things down well in advance of seriously running them down, at least.

This should bet better when the panels currently sitting in my garden get up into the sky, but it's snowing again. Looks like I've finally gotten all of the 12 Schott 240w panels I've ordered - took three tries, as they've broken a few in shipping each time. There's another 1.8kw worth sitting against the garden wall since last fall, a terrible place for shadows from trees to the south, so getting those up into the sky will just about double to triple the power I've been used to getting. And the new inverter I got so the car wouldn't eat the whole capacity of the one I had - can run welders and fusors when the car's not charging, which is most of the time. I already have all that wired up, along with the generator backup stuff, finally.

The issue with the bang-bang is that it's just ugly. Yanking power from the charger crashes the car and the EVSE computer, which have to reboot every time power is restored (and of course, it all reports errors). I guess I don't mind the errors, since I know what caused them, and it was deliberate of course. But it just seems too brutal - I'd rather be adjusting the car drain smoothly to account for the net current showing for the house batteries, and that's where I'm heading. It looks to me like doing it all in the EZWebLynx is possible, including the battery monitoring stuff, which will make for a simple system, and it'll be nice to monitor or control this stuff from the proper position - feet up, beer down, in front of the computer on the couch, instead of having to run up and down stairs and out in the driveway.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Volt Charging

Postby KarlNorway » Wed Jun 20, 2012 3:47 am

Im working on a small PCB for the chargeer control circiut using the openEVSE as a base but going for a simpler desing (tossing out the ground falt detection, and different power options.) Im going for the pic 18f4520 as main controller ( thinkning about adding USB for either sw update and/or advanced settings like timers)

But starting with the main EVSE control curciut. I will post schematics when I get home from work. I was planning to have everything inside the car plug but I think that wont work mainly cos heat from relays. I will make this unit and do some testing with the relay I have found (its rated @ 250V 25A with the coil running @ 5-10 V) to see how much heat the relay dissipates.

I must also add som LED's to give the user info on charge state and EVSE "setting" (i.e 10 or 16A supply).

Im hoping this will be a some what comeptitor to the open EVSE as I think they might make a lot of money on their boards.
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Re: Volt Charging

Postby KarlNorway » Wed Jun 20, 2012 5:02 am

I see that someone already have done what I plan to do. So no complete unit from me only PCB with SW and links to where you can buy the different parts neede

http://www.elbil.forum24.se/elbil-about ... asc-0.html

Its a sweedish EV forum but the guy that makes it posts in english as well.
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Re: Volt Charging

Postby Doug Coulter » Wed Jun 20, 2012 8:49 am

Well, rather than just duping what the open EVSE guys did - why not come up with some improved functionality and differentiate your design? While certainly a niche kind of thing, my own plans include tying this into my solar power system (which is already talking between its parts on a CAN bus), and my home network. The idea I have is to vary the power fed to the car based on the current solar system status - I don't want my house batteries to experience a lot of extra cycling from the car load, but use whatever is "spare" power the charge controllers would otherwise be dumping - use it or lose it. Further, being human, I can see things like weather reports, and use judgment to decide my current "strategy". I might see lousy weather on the way and want to give more priority to either the car, or the house batteries depending on my own plans for the next day 0 or few. And I don't want to have to go out in the driveway to do it - I want to be able to do it via some computer on my network. So, those are my own eventual plans for a design, not so much to make sales, but because that's what I want myself (which in the past, has often led to more sales than I expected).

Just sayin. I doubt those guys are going to get rich selling these things, and kind of doubt that's what they had in mind anyway, being an open source type myself. The truth is, at present, is that while commercial EVSE's are pretty overpriced, quite a lot of their input costs are those SAE 1772 car connectors. They're probably getting a better deal than we can in low quantities (several sources on ali baba look good - if you're buying a shipping container worth) - but we are paying at least $150 for those guys. So, cutting the price of the electronics - which were already cheap, is solving the wrong problem so to speak. Making them more capable at the same price might be more interesting, and more flexible. For example, no one right now sells a unit that works at both 120 and 240v - but it would be easy with a universal type low voltage power supply for the electronics part - the cars already handle that fine and auto-detect the input voltage (the onboard charger is a universal type itself).
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: Volt Charging

Postby KarlNorway » Wed Jun 20, 2012 3:26 pm

Point taken!

Well I can start by making a supply that

Doug Coulter wrote:Well, rather than just duping what the open EVSE guys did - why not come up with some improved functionality and differentiate your design? While certainly a niche kind of thing, my own plans include tying this into my solar power system (which is already talking between its parts on a CAN bus), and my home network.


Point taken!

I only borrowed the +/- 12V part for the PWM and I dont feel bad about that. When I was studying for my engineering degree the proferssors were saying that there are no need to reinvent things.

Well I can start by making a supply that lets the user choose between 10 and 16 A on the "fly" to see that I get the simplest things right. Then adding on "web" server to let the user choose and select the current at different times (maybe with some sort of timer functions, from 2am till 4am charge @ 16A and the drop till 12A for one hour then down to 6A). I see endless posibilities with this. Maybe tie in apps for android (iOS Blah) as well. (I have some experience with android dev).

Doug Coulter wrote: The truth is, at present, is that while commercial EVSE's are pretty overpriced, quite a lot of their input costs are those SAE 1772 car connectors. They're probably getting a better deal than we can in low quantities (several sources on ali baba look good - if you're buying a shipping container worth) - but we are paying at least $150 for those guys. So, cutting the price of the electronics - which were already cheap, is solving the wrong problem so to speak. Making them more capable at the same price might be more interesting, and more flexible. For example, no one right now sells a unit that works at both 120 and 240v - but it would be easy with a universal type low voltage power supply for the electronics part - the cars already handle that fine and auto-detect the input voltage (the onboard charger is a universal type itself).


I got a qoute from a supplier wich was $100 (+pp) for one that is rated @32A with 6 meters of cable. so thats not to expencive (first one sample then min order 20 psc) I dont think that is too bad, I wnet for 32A as I wanted to be able to give the next gen Leaf owners full charge capabilties (runer is that they will get 6,6 KW charger in 2013). Depending on the circiut breaker size of course.
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Re: Volt Charging

Postby KarlNorway » Mon Jul 02, 2012 2:39 am

This seems to be good

http://www.charge-amps.com/

i have registerd for one to my leaf
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