E-MotorWerks JuiceBox - an open source 15kW EVSE

[valerun]

Tadol - thank you for your comments! I believe we have come a long way from a few months ago but obviously have ways to go further, as well.

If you have specific suggestions on how we could make our product descriptions (http://www.emotorwerks.com/products/online-store/product/show/44-emw-juicebox-level-2-15kw-ev-charging-station-kit-or-assembled-unit) / assembly & user manual (https://docs.google.com/a/emotorwerks.com/document/d/127joe-QgHYRQVD4Zl2-oZO3A9gRjJZC4ReH_2jIM_x0/edit) clearer, I would really appreciate that! We constantly update those based on user feedback.

Thanks,
Valery

 

[Stan]

Valery,

I'm looking for a portable 240v EVSE with high current capability. The JuiceBox looks perfect except I'm puzzled about whether the relay is capable of 40A, steady state.

Referring to the specifications of the JQX-62F relay on your site:
http://emotorwerks.com/JuiceBox_Public/99%20-%20Supporting%20materials/JQX-62F%20Power%20Relay.pdf

Look at the graph in the absolute lower left of the spec sheet that is titled "Max. Operating Power". It appears that while the relay has contacts that are capable of 80a peak current according to the text in the spec, the maximum steady state power capability of the contacts are 28A at 250 VAC according to the graph.

Stan

 

[fooljoe]

If you're looking for suggestions, I'll second the idea to look into a different relay that clearly supports 40a continuous charging. Also to make the unit offer greater portability I'd switch from having both cord grips at the bottom to an inline configuration. Lastly, I've mentioned this before, but I really think you need to offer easy field adjustability for setting the amperage. The current method that requires taking the lid off and adjusting the trimpot just isn't cutting it.

 

[davewill]

... Lastly, I've mentioned this before, but I really think you need to offer easy field adjustability for setting the amperage. The current method that requires taking the lid off and adjusting the trimpot just isn't cutting it.

I would heartily agree. If I'm setting the output amperage, I want there to be no doubt about the setting. Variable pots are subject to vibration and temperature drift. I'd prefer either jumpers or a rotary switch. If you don't have the digital inputs to support these, you can use the rotary switch to switch in 4-10 different resistors and use the existing analog input.

 

[valerun]

Hi Guys - great questions.

I will take one at a time:

1. The contacts definitely can support 80A continuous. Relay power chart you reference (and other charts in datasheet such as lifetime, etc) is for operation under load. I.e. relay is rated for switching a 28A load at 240VAC (e.g., a 7kW heating element). In the EVSE, relay is never closed into an active load - the charger starts pulling power after the relay closes. Same on charge termination - the charger stops drawing power before relay is disconnected. The ONLY exception is GFI trip when relay is breaking circuit under load. But that is an emergency event and should happen very very rarely.
The current carrying capability has been tested multiple times at the limits of JuiceBox rating in different relay orientations. In fact, the hottest part of the relay is most often the coil itself and not the contacts.

2. Current setting is done via a digital remote in Premium Edition units. This setting will override trimpot value. If you are setting up for a fixed current output, you can also always fix that in the firmware, regardless of edition (I do understand that this is an involving procedure, though). In the future versions of JuiceBox Premium, you will be able to set current via a smartphone app, as well.

3. Inline glands - we thought about it and decided not to do this because it would make it much harder to mount the system on the wall. If you have any creative ideas for solving both of these problems at the same time, we will do it.

Thanks again for your suggestions!

Valery.

 

[fooljoe]

#1 FWIW I bought one of these relays because I thought about switching out the one I have in my current openEVSE. I tested it out at 40a and it got a little hot, but it didn't seem too worrisome. That said, for whatever reason there have been lots of posts from well-respected folks expressing doubts about it. So while I think it's fine to use it (and I may still put it in my openEVSE), I'd suggest that if you can find a good replacement to do it, just as a business decision if nothing else.

#2 I figured the premium edition could do this, but it would be nice if there was a simple add-on button / display you could add to the base edition for simple configuration tasks like changing the amperage and maybe displaying some other information. Obviously this is just my personal preference, but I like the look/shape of the base edition case better too.

#3 Perhaps you could just have two different case choices available. People looking for a portable unit could get the inline while those looking for wall mount could choose bottom-fed. Or you could have one case that has knockouts on either end, but I suppose that might affect waterproofing.

 

[valerun]

#1 FWIW I bought one of these relays because I thought about switching out the one I have in my current openEVSE. I tested it out at 40a and it got a little hot, but it didn't seem too worrisome. That said, for whatever reason there have been lots of posts from well-respected folks expressing doubts about it. So while I think it's fine to use it (and I may still put it in my openEVSE), I'd suggest that if you can find a good replacement to do it, just as a business decision if nothing else.

#2 I figured the premium edition could do this, but it would be nice if there was a simple add-on button / display you could add to the base edition for simple configuration tasks like changing the amperage and maybe displaying some other information. Obviously this is just my personal preference, but I like the look/shape of the base edition case better too.

#3 Perhaps you could just have two different case choices available. People looking for a portable unit could get the inline while those looking for wall mount could choose bottom-fed. Or you could have one case that has knockouts on either end, but I suppose that might affect waterproofing.

Thanks for your comments!

#2: you can add any part of the Premium functionality to a Base edition JuiceBox. The details are described in our manual at https://docs.google.com/a/emotorwerks.com/document/d/127joe-QgHYRQVD4Zl2-oZO3A9gRjJZC4ReH_2jIM_x0/edit#. It's not free but that's sort of the point behind having 2 versions...

#3: this is possible but actually is quite expensive - this means that we have to stock another set of enclosures, manage order flows for another product configuration, and manage supply chain for that new product. We would need to redesign the internal layout and train people on how to assemble not 2 but now 3 types of products. There are a lot of hidden costs in proliferation of options. So we have to figure out a way to satisfy all use cases with just 2 SKUs - Base and Premium. If I could, I would have 1 SKU but looks like it's not really possible. We are considering an inline design that would get rid of the box altogether. That would replace the current Base Edition but not anytime soon yet.

Finally, on #1: there will always be well-respected experts who will post their opinions without actually seeing or testing the part... To date, we have received only one report of heating above 70C on the relay conductors. This is from 500+ units in operation. Does your unit have silver contact surfaces (as the one in JuiceBox)? And of course we could always find an even beefier relay. But that would amount to unnecessary over-engineering and would force people to pay for capacity they will never need.

 

[Dsinned]

This is an interesting thread; many opinions both pro and con, so I thought I'd weigh in on the JuiceBox since I just took the plunge. :mrgreen:

First, the support I've received from EMW (mostly from owner Valery and his wife Julia) has been terrific. True, there were no phone calls, only emails, but I never had to wait longer than about 12 hours for a response. A product like this really does bring up a lot of questions prior, during and after the sale. Fortunately, I live close to EMW's manufacturing facility in San Carlos, so I have been there in person a couple of times, including yesterday to Will Call my order to waive shipping charges. I also was provided a special accommodation with respect to my JB order and its final assembly by EMW. This amounted to using my own, pre-existing J1772, 25' long cable in the assembly, because I felt the internal connections and routing of the power conductors was critical in the final assembly to get right the first time. This was accomplished at no extra charge. THANK YOU EMW!

My opinion of JuiceBox (fully optioned in basic enclosure) is absolutely stellar! I especially like the additional functionality in all the options; WiFi Internet access, LCD and remote operation via the four button key fob. These options truly make the JB shine even in the basic model enclosure.

The only "issue" I have with the design is with the actual size of the LCD. Although colorful (based on TFT technology), the viewable area is quite small. However, the text is quite sharp, when in close proximity to the front of the enclosure, but from 2 or 3 feet away, it is simply too small to make out any information or navigate thru the menus with the remote key fob. A much larger front panel viewable display would a welcome enhancement.

I plan to replace the metal front cover with plexiglass to see the LCD and all of the internal circuitry. I might add a miniature AC Voltage and Current display monitor as well. I was also pleased to find a BNC connector pass-thru port, cleverly designed for a screw on, swivel style, WiFi mast antenna connected to the top of the enclosure. This comes in handy for the "WPS" pairing to your WiFi router. Slick!

In addition to the WPS feature the other nifty feature via the menu driven user interface on the LCD, is the ability to remotely set the current limit of your J1772 charge port connection to the car, and a timer for scheduled charging operation. There is a lot of potential with WiFi and Internet access, and promise of cell phone apps. Most of these JB features simply do not exist on "brand name" EVSEs at more than double the price of a fully assembled JuiceBox.

All things considered, I consider a JuiceBox a big step up from the list price of $1500 for Toyota's "recommended" Leviton L2 EVSE. I have been using Leviton to charge my VOLT and RAV4 EVs for the last two years. No complaints. It worked and worked well. It was even possible, but not practical to use for portable charging applications. Most L2 EVSEs - even plug-ins - are meant for semi-permanent installation.

A JuiceBox Basic unit, on the other hand, can be effortlessly lifted from its "slip-in" wall mounting bracket in seconds and stowed in the truck of either my VOLT or RAV4 EV. In fact, it fits perfectly in the hidden (sunken) cargo area of a RAV4 without any difficulties at all. For enhanced "portability" I opted to get the hard to find, old style drier, adapter cord (NEMA 10-3P to 14-50R) as an extra cost option from EMW. This will come in handy on road trips to "fast charge" from a friend or family's drier outlet up to 15 or 30A respectively at 240V.

I HIGHLY RECOMMEND this highly versatile, low cost product, especially if "taking it with you" and charging from an available 240V outlet is important to fully appreciate driving electrically in the wild where public charging stations are few and far between!

 

[fooljoe]

Dsinned, now that you got your Juicebox what's the report on whether you can charge off your generator?

 

[Dsinned]

Last weekend "as a test" I had the generator charging my VOLT (via the JuiceBox) successfully. It definitely works and I did not have to use any resistors in a 120V "dummy" plug either. The only issue I uncovered with the generator was that about every 2 minutes it would appear to become overloaded and struggle to stay running; almost like it was running out of gas. However, each time this happened, after a few seconds of engine stumbling, it would eventually recover and resume charging all by itself. Of course, every time this happened, the VOLT would drop out of charging mode briefly, thus unloading the generator, which allowed it to recover automatically. After the third of fourth time this happened, I lowered the current limit on the JB to put the generator under a lighter load. When I reduced JB's current limiter to ~10A (while still sourcing at 240V), this problem went away.

Could it be the generator was beginning to overheat and has some sort of overload protection that behaves this way? There is nothing about that in the manual, so I think that is doubtful . . . The generator's circuit breaker (rated at 14.8A) never tripped, even though I was running close to its maximum allowable amperage (3300W / 225V = 14.67A). Besides, what seemed to be happening was the car's onboard charger was trying to pull significantly more current, thus pushing causing the generator's output to "sag" (like in a temporary brown out condition). This in turn, caused the VOLT to complain, and drop out of the charging mode. This pattern of abnormal of repeatable behavior kept reoccurring regularly about every two minutes.

I was measuring the output voltage and frequency of the generator before (and after) this problem occurred to determine how well it was regulating. The voltage was within specs at ~225 to 230V, but the frequency was down around 58hz (3420 rpm), while the output load was ~14.5A. With the load reduced down to ~10A, the frequency was closer to nominal (~60hz, or 3600rpm). The higher (or higher load condition) must of been too much for the generator, although the manufacturer's "rating" is 3500W continuous. At reduced load of ~2400W, there were no reoccurrence of these "brown out" events, and the generator's output voltage and frequency parameters were well within spec.

Of course, the end result of this phenomena was a slower charging rate of my VOLT at only about 2/3rd of the generator's maximum continuous power rating. So be it since I'd rather not burn out a $350 generator that is only meant to be used in an emergency to charge my RAV4 in between public charging locations.

Of course, I also tried charging my VOLT with the JB plugged in to a 240V wall outlet in my garage. This worked flawlessly at the full charging rate of the onboard charger (3.3kW). I did the same with my RAV4 EV and it also charged equally well up to its full power rating of 10kW.

It is possible I am using a defective generator, or maybe there was something strange going on in the VOLT's onboard charger, i.e. the J1772 pilot circuit between the car and the JB. I saw a similar problem on the generator when using either cars' OEM charge cords at 120V, when the output load on the generator exceeded 12A.

Do you still think this has something to do with the "grounding"?

 

[fooljoe]

Last weekend "as a test" I had the generator charging my VOLT (via the JuiceBox) successfully...

Replied in the generator thread.

 

[valerun]

The only issue I uncovered with the generator was that about every 2 minutes it would appear to become overloaded and struggle to stay running; almost like it was running out of gas.

Interesting. I wonder what kind of Power Factor VOLT's charger has. If the power factor is lower than 1.0, real power will be lower than apparent power. The generator will react to the apparent power level and might cut out earlier because of that. This is of course just a conjecture - perhaps this is just a testament to the overly 'optimistic' ratings of the generator...

 

[Dsinned]

Hi Valery. I hadn't thought of that. I just assumed the Volt's onboard charger's PF would be close to unity, but in actuality it must resemble any other AC to DC SMPS, with a typical PF of about 0.8. If same for the VOLT, then my generator was trying to operate at a higher output (apparent) power level, 225V * 14.5A * (1 / 0.8) = 4078VAR. My generator's continous output power rating is 3500 "watts" (assuming a unity PF). Peak power is spec'd at 4400W. This is misleading!

This is all beginning to make better sense now. Thanks! :mrgreen:

 

[valerun]

All - cross-posting from http://www.mynissanleaf.com/viewtopic.php?f=26&t=15444&p=379055#p379055 to avoid re-typing and re-inserting images etc - next rev of the JuiceBox PCB is in with a few tweaks and changes.

Check it out and let us know what you think!

Thanks,
Valery.

 

[Dsinned]

AWESOME!!!

My JB (ordered last month) already has the new antenna mast; a big improvement for the Basic unit.

Onboard temperature sensing and higher precision AC voltage and current sensing are welcome additions too!

Changing to a zero offset OPAMP and eliminating R26 should simplify calibration for users that do not have a good quality multimeter. (My JB was quite problematic with respect to proper AC voltage sensing, requiring R26 calibration in addition to a simple firmware mod to the "voltage sensitivity" algorithm. I'm sure glad I got the FTDI option!)

One suggestion to make future PCBs even better is provision for a set of four (2x2) standoff holes on the board to accomodate placement of the LCD opton (facing up). This would permit Basic JB owners to replace the metal cover plate with a clear sheet of plexiglass, for viewing the LCD mounted "inside" the enclosure. It would also permit Basic users to opt for the remote key fob option. I used an ~3/16" thick sheet, with no cutouts required in the enclosure, so it would maintain watertight integrity for outdoor use. I found an inexpensive 12 x 12" sheet of plexiglass on Amazon.com for this purpose which worked out quite well to showcase my fully optioned JuiceBox.

 

[Graphicsgirl]

Decided to order the JB. It was in our price range and it had higher capabilities. Juicebox Level 2 15kW 60A EV Home Charging Station (Base Edition) with Input Cable, J1772 32A 25ft Output Cable . Just to be sure what nema outlet do I need? Right now I have the 10 50 wired to a 50 amp breaker. I think I just need a new outlet possibly 14 50? Do I have to adjust anything or can I just plug in the evse and plug in to my rav4 ev?

 

[Dsinned]

Your Basic JuiceBox comes with a pre-wired, 6' long, AC power cord with a NEMA14-50P plug on the end. Therefore, you need a NEMA 14-50R (50A) outlet to plug it in to. Or, you can buy an AC Adapter from eMW to convert your existing outlet for use with your JuiceBox. (I am assuming what you meant by referring to a "10 50" outlet, is the type used by an old style electric dryer, which is actually a NEMA 10-30R (30A) outlet.

I believe your JuiceBox will be delivered "plug n play" provided you have the correct outlet or AC Adapter. Here's what the AC adapter looks like, available from eMW for $39, to convert an old style electric dryer outlet to what you need:

I also recommend you get from eMW, the JuiceBox Wall Mount "Holder" for $29. It will come in handy in your garage, so you have a place to put the JuiceBox on the wall. GOOD LUCK and CONGRATS on becoming a new JuiceBox owner!

 

[fromport]

Decided to order the JB. It was in our price range and it had higher capabilities. Juicebox Level 2 15kW 60A EV Home Charging Station (Base Edition) with Input Cable, J1772 32A 25ft Output Cable

Why ?

you have everything in place to charge at maximum capacity and because of a cheaper J1772 cable you now need to limit the charge speed ?

Pay the extra for the 50 amp J1772 cable!

You won't forgive yourself for the rest of the life of the car ;-)

 

[Dsinned]

Not to put too fine a point on this, but I tend to agree. If your existing outlet is actually a NEMA 10-30R, with a maximum rating of 30A, you will be limited to charging your RAV4 EV at 24A (80% of 30A). This means you would be charging at ~5.8kW, instead of the maximum allowed by the car itself (10kW). In practical terms, this means it will take around 8 hours to fully recharge vs. ~5 hours. However, if you do scheduled charging, between midnight to sunrise, when electric rates are lowest (on a "TOU" rate plan), and your battery is not fully depleted at the start, then a 240V/24A charging rate won't cause any significant issues.

Many of us have made this tradeoff because there is just no practical or economical way to charge from a 50A outlet at most residences without spending a bunch of money to upgrade your infrastructure wiring. Fortunately, I have a 40A protected outlet in my garage that is physically a NEMA 14-50R I wired in myself, so I can charge my RAV4 EV at 32A (80% of 40A). I never fully deplete my battery, so an overnight scheduled charge takes ~4 to 5 hours and I'm okay with that. 95% of the time, I do NOT need to charge any faster!

Having said that, I still suggest you upgrade your J1772 output cable to higher amperage (at least 40A). This is because your JB can be used as a "portable" EVSE on the road. Many, if not most RV Parks have NEMA 14-50R (50A) outlets. Thus, you can actually charge your RAV4 EV at 40A (9.6kW), i.e. 80% of 50A. This comes in handy whenever you're traveling some place near an RV Park and you need a relatively "fast" charge to get going again.

 

[Graphicsgirl]

Ok, I didn't realize that I didn't get the 50A cable. I may have to contact the company to upgrade that. As far as the outlet is concerned. It is actually an outlet for a kiln with a dedicated breaker etc. We just bought the correct outlet and are changing it for the JB. I would rather not use an adapter on a regular basis (just preference), but would for charging using a dryer outlet or ac or rv etc. etc. So I do need to purchase them for that.

Thank you so much for the info and the heads up on the cable!