Comment by Someone1234 | Hacker News Reader

Comment by Someone1234 | Hacker News Reader

I've been saying for years that vehicles, in general, aren't keeping up with new electrical demands placed upon their 12 volt battery systems. Safety systems, LTE connections, HUDs, charging, even literal built in fridges and vacuums.

For example my 2016 vehicle, left undriven, will completely drain the battery after just two weeks thanks to a timed flush and an always on LTE connection. Plus it refuses to run the alternator on any road slower than 35 MpH, even if the battery is almost depleted. Even while idle at a traffic light, it would rather just waste the energy than charge the battery.

So this sounds fantastic, I'm just glad they're thinking about electrical power AT ALL.

> The generator system is completely separated from the rest of the vehicle's electrical system, adding a layer of safety and ensuring that any Pro Power system problems will not impact the drivability of the truck.

This is a double edge sword though. While obviously you don't want your tools draining your starter battery, it also means that any issue with your starter battery cannot be immediately resolved by the two additional 12-volts you already have (at least without tools to physically move them).

Essentially you could get left stranded, even while having a completely working 24-volt system. So while the goal is admirable, being able to jump the vehicle from 24-volt would have been a function I would have wanted.

Manufacturers have wanted to move to a 24V (or higher) system for at least a decade. They just haven't agreed on how to do it. Jump-starts work because everyone is on 12V, and while there are various solutions to that, there just hasn't been a convergence on a single solution yet.

With all the engineering needed to redesign the system, it could easily be configured in a way to prevent situations where there was not enough battery to start the motor. Battery guards are popular in boats [1]. Some systems already integrate reserve starter batteries that can only be discharged by the starter.

http://dan-marc.com/31-0000514200.html

Jump starts have always been a crappy approach IMO. I think a small hand-cranked generator into a decently-sized supercapacitor could be a much better way to kick over a motor. I feel like you could get a reasonable jump start with just a minute or so of cranking. Certainly faster than waiting for someone to find their jumper cables or drive out to assist you.

Keep in mind that this is already sort of a thing for cars with manual transmissions. In this case, the proposed supercapacitor is replaced by the kinetic energy you are pushing into the car.

According to a google an average car might take ~9000 joules to start. Also according to google, an average hand crank only puts out about 15 watts. So you might be cranking for at least 10 minutes.

If you could convert gravitational potential energy into charged battery energy at 50% efficiency, you would need to raise something weighing 2000 lbs to a height of 6'6". Your own car maybe? You could have tripod legs that deploy from the side of your car, allowing you to winch it up that amount, and then to start it you just drop the car.

If you drive a manual and park on a hill, you can apply this method pretty effectively.

You've really only got to fire one plug one time to start a car that's in a fundamentally startable condition. A battery that doesn't have enough juice to turn a starter motor (which requires a lot of amps) often still has more than enough to fire the plugs if you can turn the engine over some other way.

Several times in my life I've had to roll-start a (manual) car with some regularity[0]. You don't have to getting it going to even a brisk walking pace if it's a small (< 2 liter) four cylinder engine. If you clutch out and back in pretty quickly, it'll start if it'll fire. If the battery is too dead to run the ECU and/or plugs, you're pretty well dicked unless you can find somebody to jump you.

Now, neither of these applies to an F-150, since you can't get one with either a manual or a four-banger, but practical experience indicates that for at least some cars, it's got to take less than 9000 joules to start the engine.

In rough numbers, if you have a 1500 kg car moving 1 m/sec, you've only got 750 joules to work with. In all cases, I wasn't trying to do this in the dead of winter.

[0] On 2 different cars:

1) I left the headlights on two days in a row and discharged the battery pretty deeply. I got it back after a couple days of driving my short commute.

2) I had an intermittently bad connection between the battery lug and the wire running to the starter motor. I finally figured it out after it did it at night and I could see the sparks with the hood open. That was after 2 or 3 months of bump-starting the car at least once a week :-)

4-cyl engines are easy enough to start with a hand crank off the crankshaft. Standard starting procedure for a long time, really. My first car had one, and it was made in 1963.

Won't work on the hulking mammoth engines of a modern F-150, but maybe a step down ratio maybe 1:4 (and a bicycle) and it could work.

Or a small lithium battery to supply the necessary current which is already a thing you can buy on Amazon for $80 and will start any vehicle short of an excavator.

To agree with this some, the super-capacitor jump starters should definitely change the necessity of jump starting, as they provide more amps closer than 6' cables.

Unfortunately, education is lacking; my father is an example that kept jump starting even when he had a super capacitor jumper.

How do you find out if the alternator is working?

I would like to know if putting my Mazda in Park at a traffic light and revving the engine to 2000 rpm charges the battery. Same question for city driving in "sport" mode (2000 rpm at 30mph). I'm guessing it should work, but I could also just be wasting gas.

Measure the voltage at the 12V accessory socket. If the alternator is running it'll be somewhere in the 13.5 - 14V range. If it's just the battery, it'll be more like 12-12.5V.

I'm pretty sure that you can read this off the OBD-II port, too. Plenty of cheap readers that will work with your smart phone are available online.

There's a 12v pin in the OBD2 socket to power whatever OBD2 reader or Bluetooth dongle you have plugged into it so you can use that to read the system voltage for the vehicle.

Thanks, this sounds pretty easy.

For my and others' future reference, here's a random video of how to do this with an obd2 port, as suggested by a child comment: https://youtu.be/dDY2lMMrpLU This may or may not be more convenient than the accessory socket.

What vehicle is that? Just curious.

2016 Subaru Outback.

I upgraded the battery from factory to a larger capacity, hybrid deep cycle, and that has increased idle discharge time by a couple of additional weeks.

So a low quality OEM battery compounded the issue, but either way the electrical system leaves a lot to be desired.

Which battery did you get? Been looking for one.

It was just a Duralast Platinum from Autozone.

The guy there didn't even realize they sold a correctly sized one for Subaru Outbacks, because they're typically for e.g. larger pickups or similar.

For $50 more, you're getting a much nicer battery: AGM internal structure, higher reserve capacity, higher CCA, better durability, some deep cycle properties (i.e. it can get drained down lower without damage), and so on.

I mean it is 10 lbs heavier, while fitting into the same physical space, that's the AGM structure within the battery. The new battery has been great, but the alternator is still not kicking on until freeway driving.

That wouldn't work for me. I've driven at highway speeds twice in the last year.

Cripes, that would help explain why I had to jump my ‘16 Outback three times during early shelter-in-place orders after sitting for long periods with very little use. I just blamed it on a crappy OEM battery (which I suppose is partially to blame), but I didn’t know about the alternator situation.

> it refuses to run the alternator on any road slower than 35 MpH

I noticed this in my 2017 Subaru Outback when I went to jump my wife's car. The car was running, but the battery voltage was only sitting at 12.6v or so. I'm used to a battery putting out 14v or so when the vehicle is running. The extra voltage seems to help a lot when jumping another vehicle. I understand why they did it, but it seems odd. Perhaps it's why my battery died after 3 years, when most others I've had last close to 5.

This. There are some features I decided to turn off in my car or the battery would just die every time. 70 amp hour batteries used to be way more than enough, but cars today have unbelievable battery draw that manufacturers have not taken into account -- heck my parking brake of all things is power driven. All the battery draw leaves little for cranking up.

Seems like the tradeoff is mid-drive shutoffs due to the PP vs dead vehicle battery.

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