DIY Home EV Charger • Hacker News Board

Re: DIY Home EV Charger

#161

Post by myself248 » Mon, Dec 04, 2023, 3:55 PM UTC

conk wrote: post #36

foobarian wrote: post #12

I'm disappointed at the anti-DIY sentiments here, it's this safety obsessed mentality that got us to where kids can't walk outside by themselves any longer. The box in that guy's build is outside and could probably burn to a crisp without hurting anything else. I suspect it would not hurt anything even inside a garage, other than making a lot of smoke and setting off smoke detectors.

Except this DIY project could kill someone if it malfunctions. There are several inadequate parts of this design that make it a safety risk beyond the fire risk.

Oh, please, do tell.

Re: DIY Home EV Charger

#162

Post by StillBored » Mon, Dec 04, 2023, 4:11 PM UTC

Animats wrote: post #11

1. Two words: strain relief. 2. If it's outdoors, at least spray the electronics with Fine-L-Kote or similar to keep water vapor out. 3. Those relays look undersized for the load. Look at Grainger for similar ratings. Do not buy power relays on eBay or Alibaba. Current ratings there tend to be wildly exaggerated. 4. Er, overcurrent protection? An approved circuit breaker?

I used significantly higher-rated omron relays in a project I did a few years back to switch a 2.5HP motor on/off a few times daily. This area shouldn't be skimped on; relay contact arcing isn't a joke.

This brings me to my second point: I don't see a cycle rating on those relays from the datasheet provided. Most relays are rated for ~1M cycles, some for ~10M or more, but beyond that solid-state relays start to be a thing. And so, I question if people are using mechanical relays to chop 50/60Hz AC power, which from my 30 seconds looking at the article/schematic appear to be what is happening here... That seems crazy to me, and I imagine it requires some exotic contacts in the relays to avoid failure in short order, which these relays don't appear to be. The data sheet mentions they are used for chargers/solar inverters/etc but that doesn't mean they are used at 50/60Hz cycling but likely just as a disconnect/power on function which cycles once per charge/day/etc.

Then again, I don't really want to be this guys neighbor since chopping an AC line with that much load is going to generate an insane amount of noise, and I don't see anything in the circuit designed to damp it either.

Re: DIY Home EV Charger

#163

Post by StillBored » Mon, Dec 04, 2023, 4:23 PM UTC

sokoloff wrote: post #14

Animats wrote: post #11

1. Two words: strain relief. 2. If it's outdoors, at least spray the electronics with Fine-L-Kote or similar to keep water vapor out. 3. Those relays look undersized for the load. Look at Grainger for similar ratings. Do not buy power relays on eBay or Alibaba. Current ratings there tend to be wildly exaggerated. 4. Er, overcurrent protection? An approved circuit breaker?

He says he installed a 50A OCPD, which is the same overcurrent protection an electrician would install and used relays from TE Connectivity (a respected brand) rated at 125% of the current the EVSE advertises as available. Both of those decisions seem perfectly sane/safe to me.

Are you an EE with a specialty in power electronics? Cause that seems insane to me, inductive loads will cause a voltage spike (flyback) when disconnected, which will exceed that easily. That is why there is generally a reverse diode across the contacts, which I didn't see in the diagram.

Granted the article notes it appears to be largely a resistive load, but I would want data sheets on the car/charging requirements, not measurements, to ensure this is true 100% of the time. Maybe the car has an AC compressor or a pump to cool the battery during charging, which draws directly from the charger when plugged in. You might not see that doing a few random measurements because it turns on only after some time or if someone is sitting in the car.

Re: DIY Home EV Charger

#164

Post by balls187 » Mon, Dec 04, 2023, 4:39 PM UTC

repiret wrote: post #106

balls187 wrote: post #33

Earlier quoted context omitted.

Don't work with a live panel.

I know a few electricians, and none of them would agree with you. There's some things that can't be done safely on a live panel, but there are some things that can.

It's very hard to imagine any electrician advising a DIY homeowner to install a 240v line on a live panel.

It's not difficult to do, which was GP's original point--though you need to take safety precautions (in addition to researching local code requirements).

Re: DIY Home EV Charger

#165

Post by dylan604 » Mon, Dec 04, 2023, 4:59 PM UTC

sokoloff wrote: post #157

dylan604 wrote: post #154

Earlier quoted context omitted.

A lot of people would "shop" at brick-n-mortar stores with a mobile comparing prices online. They would look at the physical item right then and there, but purchase from online. At least, that was the early days of online when people were still actually getting off their couches.

I think price comparison is totally valid, even across channels. But if the online price is the same as brick/mortar, it seems only fair to buy it from the brick/mortar store if they provided you some knowledge/service that the online places did not.

in the early days of online shopping, online didn't charge taxes && gave free shipping. so if you didn't need it right then, it could be at least 8.25% cheaper where I live

Re: DIY Home EV Charger

#166

Post by ferongr » Mon, Dec 04, 2023, 5:10 PM UTC

gambiting wrote: post #120

elihu wrote: post #61

Earlier quoted context omitted.

And yet the technical people need accurate names to call things so they can communicate without ambiguity. I think "charging station" is the least confusing term for the fixed infrastructure part. If regular people call those "chargers" in non-technical conversation, then I'm not going to lose sleep over it.

The thing that you use to provide your phone with electricity - do you call it an AC-DC converter, or do you call it a charger like nearly everyone on earth, even though the charger part is actually inside your phone?

That's a USB power supply.

Re: DIY Home EV Charger

#167

Post by amluto » Mon, Dec 04, 2023, 5:12 PM UTC

marcosdumay wrote: post #159

amluto wrote: post #153

Earlier quoted context omitted.

What’s wrong with metal tubing indoors? Outside is another matter. Those galvanized steel tubes don’t last very long underground, and the results are terrifying. And nothing in the code requires ground fault protection upstream of a 120V circuit running through a corroded steel tube underground.

They conduct electricity. Thus if you have a leak from one conductor somewhere in your house (that without ground fault protection goes undetected almost every case) and gets a different one from a different wire, you now have a constant-on heater passing through God knows where, ready to start fires. A single leak also gives you a minor risk of electrocution. But the fire hazard is the important one.

This is possible with nonmetallic conduit, too, as well as with NM-B. At least metallic conduit has a decent chance of containing the resulting mess inside the conduit.

The right solution is ground and arc fault protection, both of which are available, and one of which is increasingly required in the US.

Re: DIY Home EV Charger

#168

Post by ferongr » Mon, Dec 04, 2023, 5:19 PM UTC

StillBored wrote: post #163

sokoloff wrote: post #14

Earlier quoted context omitted.

He says he installed a 50A OCPD, which is the same overcurrent protection an electrician would install and used relays from TE Connectivity (a respected brand) rated at 125% of the current the EVSE advertises as available. Both of those decisions seem perfectly sane/safe to me.

Are you an EE with a specialty in power electronics? Cause that seems insane to me, inductive loads will cause a voltage spike (flyback) when disconnected, which will exceed that easily. That is why there is generally a reverse diode across the contacts, which I didn't see in the diagram. Granted the article notes it appears to be largely a resistive load, but I would want data sheets on the car/charging requirements…

>Maybe the car has an AC compressor or a pump to cool the battery during charging, which draws directly from the charger when plugged in

No it doesn't. A/C compressors in EVs are 3 phase AC powered by an inverter supplied by the traction battery.

The contactors in an EVSE open and close at practically zero current, the OBC ramps the current up or down accordingly. And as another sibling comment noted, the OBCs are PFC corrected and act as a largely resistive load.

Re: DIY Home EV Charger

#169

Post by mrb » Mon, Dec 04, 2023, 5:43 PM UTC

mrb wrote: post #94

"It costs about £900 in the UK to have an EV charger installed by an electrician" £900 is $1140. In southern California, it cost me $750 for top notch work and hardware, including: $400 to have an electrician install a 240V 50A outdoor outlet (NEMA 14-50), plus $350 for a good quality level 2 40A EVSE (this one: https://www.amazon.com/dp/B082LMVSLY ) that I installed myself as it simply plugs in the outlet and it's j…

Thank you for the dozen of you who responded. It's fascinating for me to see the large range of price points due to different regulations in different countries and also affected by different needs (eg. need to track kWh for subsdies).

Re: DIY Home EV Charger

#170

Post by MostlyStable » Mon, Dec 04, 2023, 5:49 PM UTC

myself248 wrote: post #116

MostlyStable wrote: post #6

Earlier quoted context omitted.

I would have liked to see a cost breakdown. If it's significantly cheaper than OpenEVSE (somewhwere between $500-$600 depending on which kit you get), then maybe some people would be willing to take the risk (it seems like there are some safety concerns with his design that I don't feel qualified to adjudicate). But without some kind of a cost difference, I'd probably stick with something like OpenEVS, which seems to…

OpenEVSE can be a codebase or a kit. If you want to source all your own parts, or maybe reuse significant parts of a non-open EVSE and just drop the processor into it or whatever, then it can be very cheap indeed. If you buy their branded kit, then full price applies. When OpenEVSE was new, I built one on perfboard, actually a very compact modular stack of perfboards, one layer per subsystem. Handed it off to my soft…

oh wow, thank you. I'm going to look into this. I have been extremely unhappy with JuiceBox's app/etc the entire time I've had it. If I can reflash it (and/or relatively easily replace the brains), that would dramatically improve my charging situation).

After reading this article, I had been considering getting one of their most basic kits that doesn't include the cables from the wall to the box or the box to the car (since I have both of those with my current EVSE), but if I can get the same functionality reusing even more of my current one, that would be ideal.