What exactly died on the dashboard? Sometimes it can be as simple as a protective diode. I saw things that survived even connection at wrong polarity and after replacement of the tantalum capacitors (which promptly failed short and protected the rest of the board) they worked again.
Given the irregularities in the car’s power lines, I’d expect such critical devices to be engineered to be a bit more robust.
I would not make that positive connection to the flat battery last. Connect both wires to the good battery (ensuring that the other ends of those wires are not touching each other or any contiguous metal surface that create a circuit), then connect to the positive terminal on the bad battery, and only then make the final connection to a good ground on or near the engine of the dead car.
One time I was eating at the Studio City Fatburger when a AAA tow-truck driver connected in the order you recommend right outside the window where I was eating. The dead battery had emitted some hydrogen gas, and the final connection to the positive terminal of the dead battery produced a spark, which resulted in the battery exploding in his face. He screamed like a bee-stung schoolboy, and was lucky he wasn’t blinded. If the last connection is going to make a spark, you want that last connection to be at the remote ground, not the battery terminal.
I think a lot of people (including me) hold on to ideas that were relevant for large, high-compression carbureted cast-iron engines with fairly high-resistance wiring that required a fair amount of cranking amps to spin over, plus alternators that typically only put out the 50 amps or so needed to run a carbureted V8 car with five light bulbs on the headlight circuit, a wimpy AM radio, and a half-assed heater blower. Today’s engines are typically smaller and much lighter, the starters are more efficient and require fewer amps, and the charging systems are much burlier in order to support multi-zone HVAC, satnav, DVD players, heated seats, electronic ignition and EFI and fully-automated drive-by-wire engine- and transmission-management, along with the seventy squintillion LED bulbs all over the place (which admittedly take less power to illuminate than a pair of Sylvania 1157 incandescent brake light bulbs). I wouldn’t be surprised if all those electronics were at risk from a surge by a donor car’s revved-up 160-amp alternator.
I would too. I wouldn’t expect electric or hybrid cars to be jumpable, of course, nor to be jump-donors in these situations. But I figured most car manufacturers still allowed for their conventional cars to be able to give and receive jump starts. If in doubt, check the owner’s manual.
There is a benign corollary to Murphy’s Law that holds that the best way to prevent an incident is to completely prepare for it.
You’re right, I had that backwards.
This is the way I was taught in high school auto shop and have followed this exact procedure for 25+ years now. However, I also leave the the good car running and rev the engine a few times when it’s completely unnecessary. I’ve found it good practice to start by clipping all the leads to a non-conductive surface on both cars like a hose or plastic fluid cap (so they don’t accidentally touch) then connect + to + terminals first, then - terminal on the good car and lastly - ground on the bad car.
I’m finding it much harder these days to find a good negative ground location in modern engine compartments - everything is plastic and what looks like metal is just harder plastic…and don’t get me started on weird battery locations (trunk, under backseat, etc)
I learned to connect the positives first, and the last connection is to the jumpee car’s grounding post or frame. It prevents the spark when the connection is made from being on or near the potentially-explosive battery gasses.
My car -02 volvo- has the battery in the back, but a pair of what I assumed were jump points under a cover near the fuse box under the hood. I know I’ve seen them on other cars as well. I’ve never used them, I’ll have to look in the manual some time.
I hope you dont feel as though my poor choice of words “more to the story” implies you did anything wrong.
What I was thinking when I said that is maybe the battery itself caused the problem? Or maybe the computer problem occured before you jumped the car? Or maybe your car model simply has a higher rate of computer problems than others? Just didnt want you thinking I was implicating you personally.
you can totally jump a prius - and in fact having to do so is more common than you might think. the 12V battery in a prius is tiny, and it’s very easy to run it down accidentally. this is why the 3rd gen prius actually shuts off the power after about 15 minutes in “ACC” mode. you really don’t want to be running the radio and headlights too long with the 12V battery as the only power source.
of course, when you jumpstart a prius, all you’re doing is providing enough current on the 12V rail to boot the computers. at some point along the line the main HV battery is brought online and thru regulators, it drives the car’s 12V rail. at that point the 12V battery will start to charge.
This is the correct answer as to why to hook ground away from the battery. The negative terminal is connected to the frame robustly because the frame is used as ground everywhere else. Electrically, it doesn’t matter where you connect. But if the battery has been off gassing, you don’t want to spark near it.
I am very surprised to read this. The standard for automotive electronics calls for them to withstand 28V and 60V surges. The only way you would get that by jump starting is if the cables were not connected properly to the battery terminals of the car doing the starting, which shouldn’t happen. With proper connection, the surge voltage won’t exceed 17V, and if that damages your electronics the car is not fit for purpose since you can get the same surge voltage from its own alternator.
Perhaps I should add that this car jump starter will not work under circumstances in which the main battery has enough capacity to run the car but not to start it. That’s because a puny 2AH lithium battery can’t start a car on its own; it depends on supplying enough charge to the main battery for it to be able to run the starter. Lithium batteries that can start cars are available but they are not cheap - to get a 600A CCA suitable for a small car you are looking at hundreds of dollars. Both times I have needed a jump start, it was because the main battery had lost CCA and the second car battery was needed actually to drive the starter.
On the other hand, the lithium battery needed for a Prius costs only a couple of hundred dollars because the Prius uses the hybrid battery to start the engine.
Sadly, that’s had, past tense. It’s all just re-runs now, and Tommy passed away in the middle of last year.
OH. That is sad, I didn’t know.
I listened to their broadcast for years, they were hilarious. Back when I owned a 72 pop top VW camper van, they were required listening for all VW owners. You needed something to listen to while waiting for your engine to cool down on the side of the road. 
i tend to think that all computer systems are persnickety
The main concern I have with not having the engine running is that if both batteries are marginal then you could end up spreading the charge so that neither one will start.
I suspect that the main way that modern cars are more fragile is in regards to accidentally reversing polarity. Older cars didn’t have so many solid state devices that can fry practically instantly when positive and negative are reversed on the jumpers. If they don’t handle a few volts over what their alternator can provide I would call that a design flaw but I am sure such flaws also exist.
I had a Stanley branded lithium ion charger similar to this. It lasted me only a couple of years requiring charges every couple of months before dying and being unable to hold a charge. I am thinking to make one out of alkaline batteries with a 10 year shelf life when I have the time, but for now jumper cables are my reliable backup.
Does it come with a defibrillation attachment?
Hah, I know how you feel. Used to drive an old Mitsubishi Magna(Or, fondly referred to, the Mitsubishi Magma, due to it’s little issue) that - for the life of us - we couldn’t solve an overheating problem on. Waiting by the side of the road was the only solution when it started boiling.
Currently, I drive what - to my American friends, at least - is an incredibly rare car. Rarer than Morgans in the US, Rarer than old GTRs, rarer than just about anything you’ll see. Carbecue world champ, a 1990 Nissan Vanette, which was recalled for an overheating problem. Not that it runs hot, like an old VW, but rather that they had a habit of catching fire and burning to the ground. Five recalls, before they recalled and crushed the lot - only a handful left in the US now.
I’ll let you in on a little secret- I still listen. There’s, what, 40 years of old episodes, and I’ve only listened to about 7 or 8 years worth so far. That means plenty of new materiel to me left in those re-runs. I’ve learned so, so much from those guys.
I don’t know about the current crop of ‘jumper-alternatives’, there seem to be enough of them that they must not be attracting too many lawsuits; but I don’t know if they are downright worth it; but I would say that the knowledge of how to do an ‘indirect jump’ from practically anything that puts out somewhere in the range of 12-17 volts is pretty handy.
A car needs reasonably heroic surge current capacity to start successfully, which is one of the reasons for using lead acid batteries(and one of the reasons why borderline batteries fail when things get cold); but they don’t actually require all that much power. This means that there are a great many sources that could never start an engine; but can, with varying degrees of speed, recharge a drained lead acid battery enough that it can then start the car.
Whether or not you prefer to buy a fancy prebuilt, or just have a homebrew tangle of wires; it sure beats trying to find another car and cooperative driver when none are to be had; and even fairly pitiful 12v wall warts, or quite modest collections of batteries, can do the job so long as you don’t demand that they supply the amps directly.
