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Comment by UnoriginalGuy | Hacker News Reader

I've seen these before. There are several companies working on similar products (and things like HUDs you can get off of eBay which show you OBD-II information).

The main problem with these (all of them!) is that the OBD II was never designed to be used like this. It will run the device 24/7 even when the car is turned off. So it will run down your battery in a similar way to leaving the cabin light on would do...

Nothing dramatic but if you're a "city driver" (i.e. no high-speed driving to recharge your battery) then you could get yourself into a situation where you need to be jump-started.

So as I said, great concept, however until the OBD-II port is "fixed" so it can be switched on and off I wouldn't get one for my car. Too high a chance that I wouldn't use my car for a weekend and then find it wouldn't start on Monday.

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We're paranoid about not running your car's battery down. When the ignition is off, we consume less than 1 mA. By itself, the Automatic Link would take 3-4 years to drain even a cheap battery.

I'm glad you replied to this criticism. I'm very excited about your product, and I'm hoping that you are planning on a third party API so folks can build apps for your customers..... maybe that was written somewhere and I missed it??

We'd love to build an API. It's on a long list of things we want to build. The Automatic Link supports OTA updates (through the phone). So, our users can expect improvements. In fact, we think of ourselves as a software company. We built a hardware device because that was the only way we could achieve the user experience we wanted to deliver.

That's a good number for IOD (ignition off draw). Radios, excluding screen aim to be sub-mA range.

Most other electronic components are sub-100uA

I think it's better to break this down, because this myth of 'running out of battery' is really exaggerated

Let's say your average battery has 40AH. That means it can provide 1A for 40h (or better, the product time(h) x current(A) = 40 for a charged battery) @ 12v

If your lamps consume 24W (I'm guessing), that's 2A, it means it would go from fully charget to nothing in 20h. But of course, your battery is usually not 100% and you need a certain battery capacity to start the engine.

Even if the consumption of this device is 1W while idle (which is really an exaggerated value), the device uses around 0.084A and the battery would take 480h to go from 100% to 0% (or about 20 days)

My guess is that an unpowered car uses more than that by itself, so this dongle is not an issue, unless you're leaving it unattended, you can unplug it but will probably run out of battery nonetheless.

> My guess is that an unpowered car uses more than that by itself

I don't think most car batteries are dead after twenty days of not driving, and, as you said, most batteries aren't always fully topped up.

I wouldn't call it a myth people have reported issues with similar port adapters, particularly bluetooth ones. If the issue doesn't apply here then great but in general people should pay attention.

My cheap chinese bluetooth obd2 device caused my battery to drain when I was ill for a week and didn't use my car over the christmas holidays. On the plus side now I know how to jump start it.

Thanks, this is good to know since I have one too. I'll have to start unplugging mine (also cheap and probably Chinese, though I got it on Amazon). But I've left it in for several months without issue, I guess maybe I just drive regularly enough that it's not an issue.

I'm not saying a cheap chinese adaptor won't drain your battery, but from what's shown I hope they thought of an energy saving system

It's possible to build it to not use excess energy.

Personal anecdote: Last year I would not use my car for long stretches (between 2 and 3 weeks), as I was traveling. 2 weeks is doable, 3 weeks I'll be certain to have a dead battery on arrival.

Car batteries don't die after sitting idle for three weeks, not in a normal car with a working battery.

At 1mA of current draw, this device is definitely not a problem. But the idea that an unpowered car uses enough power to drain the battery in less than a month is clearly ridiculous.

Weather is a factor, especially for those living in harsh winter climates. The first "C" in a battery's CCA rating is "Cold." i.e., how much current the battery can provide for 30 seconds of cranking continuously at 0F when brand new. That current rating drops significantly below zero Fahrenheit - http://www.pacificpowerbatteries.com/aboutbatts/car%20batter...

In a climate where 32F may be the highest temperature seen for months, a car sitting idle for two weeks can definitely be in danger of not starting due to the battery not being able to crank the engine after being cold-soaked at -20F all night.

Grew up in Wisconsin. Definitely an issue. I had an old Ford Aerostar that would only give you one chance to start if it was below -10F and if it started, you didn't dare let it stop for a while. :)

Well, when was the last time you left your car without powering it for a while?

If the battery is showing some age, and/or didn't go to 100%, less than a month is typical (depending on the accessories as well: alarm, stereo - some uses standby power, etc)

A few years ago, when I was traveling for about a month. Had no trouble starting the car afterwards.

An older battery surely won't do as well, but then it'll do even less well with an extra 1W draw hooked up. No matter how you slice it, a load that will drain a car battery in good condition in 20 days is a pretty big load.

The current budget for an unpowered car is on the order of 20mA, and they're specced to leave the factory such that they can be left in that state and started after a month.

If you switch the alarm on, that budget increases to something like 120mA, but you'll kill the car inside a fortnight.

Could you detect a drop in voltgage when the engine turns off and automatically turn off your device?

The ScangaugeII (similar use case) works is that it shuts off if engine RPM = 0 for >30sec.

At what voltage?

That's very good to hear, the reason why I didn't make talking to the obd port a regular hobby is because my wifi connector would eat the battery up in a few days.

Can't the dongle just kill its own connection to the OBDII port? i.e. appear inert to the car's hardware as if nothing is plugged in?

It could, but keep in mind many OBD-II ports are out of reach. The one shown in the marketing is real, but many are located on the passenger side or a lot deeper on the driver's side.

OBD-II might be a standard, but as I said it was designed to be used while the car is in a garage, never while it is being driven. So there is no "standard" for manufacturers to position it.

I think what he meant was, can't the device shut itself off in software to appear as though it is unplugged. Not having the user unplug it himself.

Oh I see what you mean.

I bet it could. But how would it ever turn its self back on? I mean if it is receiving OBD-II information then it knows when the car is running, but if it isn't (which it wouldn't be if it is "off") then it couldn't know to switch its self on.

Kind of a chick/egg problem.

They could put it in a low power sleep mode, and wake up once ever x seconds to check if the engine is on.

You could run something like this for months/years on a car battery.

Then you have a tradeoff: if you don't wake up frequently enough, you could conceivably drive for a good distance before noticing.

Something like every 5 to 10 seconds would work fine. The point is this is a solved problem for embedded hardware.

The company rep said in a previous reply that it consumes < 1 mA when the ignition is off, that's good enough.

If the device has its own battery power, it could probably use a transistor to just disconnect from the battery voltage completely and go into a low power mode where it just checks for ODB2 information periodically, or even just turns itself on when your phone is in range.

"Kind of a chick/egg problem."

The phrase you need to google for is "battery isolator". Unfortunately most are rated at like 40 amps for RVs and you want a 40 milliamp one. Many ham radio guys know all about little boxes that connect when the voltage rises above 13.7 volts and disconnect when the voltage applied drops below 13 volts or so. Traditionally you don't use a microprocessor for this, its a beefy FET and two resistors in a voltage divider and not much else. That can be kinda drifty and imprecise depending on resistor and FET tolerance.

Another way is the car squirts ODB-II "stuff" at the port when its on, so little more than a diode/cap/FET combined properly will more or less work.

The strangest way I ever saw relied on what amounts to "hearing" alternator whine over the DC bus. If the alternator isn't spinning while the engine's running, you've got issues. Any source of KHz range noise would activate them, including unfortunately high powered CB radios.

For cars sold in the EU, the position of the ODB-II port is mandated.

Do you have a source for that? Because from experience (being an EU driver) most cars I've dealt with have the port in a different location.

Some as wonderful as being literally right in the centre console, to being as horrible as under a mat in the passenger side.

I don't have a source, but I was also advised a couple of years ago that it is mandated to be under the dashboard on the driver side.

According to http://www.obdii.com/connector.html :

Where is the connector located?

The connector must be located within three feet of the driver and must not require any tools to be revealed. Look under the dash and behind ashtrays.

"never while it is being driven."

One reason to own a scan tool is to debug anti-lock brake sensors by driving around and noticing which wheel always reports zero... then replace that one sensor. This is far superior to random shotgun troubleshooting. Also while I had a thermostat problem I drove around quite awhile with my scan tool watching the thermostat misregulate my cooling system which is what led to failed readiness indicators because the engine never warmed up all the way only 99% of the way, etc etc. ODB-II is very old, like a college freshman, whereas this is a new iphone app. The equivalent for android, a program called Torque, is old. There are almost certainly HN posters younger than the standard ODB-II port. I bought a bluetooth ODB-II reader for my android/torque phone probably two years ago? It does apparently everything this new app does. My now antique orange physical scan tool appliance that cost me about $150 is about ten years old and obsolete, although it does still work. It is much tougher construction that my phone, which cost a lot more than $150...

One of the nicest Torque features is being able to reconfigure the gauge display. No point in being distracted by the oil pressure gauge when you're driving around if all you care about is a graph of the coolant temp vs time or peak coolant temp or whatever it was.

I wonder how Progressive solved that problem with their OBD II + Qualcomm MSM device.

The CAN[1] bus used in OBD is a broadcast protocol. So the dongle can just stop sending messages to appear inert to engine control unit.

[1] https://en.wikipedia.org/wiki/Controller_Area_Network

Drop an amp meter between the ground cable and your battery's negative terminal (after disconnecting that connection, of course), and you'll probably see and existing, full time current draw (while the vehicle is off and parked) in any modern vehicle well above what an odb dongle will use.

From this 2005? Toyota manual, 20mA average or less, up to 50mA is considered acceptable: http://home.4x4wire.com/deddleman/photos/elec_parasitic_load...

Oh really, I didn't realize this was the case. I have a cheap ODB2 reader and I use Torque to estimate my gas mileage, and I just leave it plugged in but in the settings it has an option to remind you to unplug it but I didn't know why. Now I know. I have to say though that I've left it plugged in for a good few months or so and haven't had any problems.

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