Safe jumper cables?

Auto Pros recommend when jumpstarting you can mitigate the likelihood of a fried ECM/PCM, or other sensitive component by being sure the “doner” engine is off and its key removed prior to connecting cables, but whenever you use jumper cables voltage spikes can still occur and damage components. They say the safest way to jumpstart is with a battery pack. Even good quality Li-ion battery packs need periodic recharging and the last thing I need are few more pop-up task reminders to dig out a battery pack & put it on charge. So it’s likely just when I need it most, like when it’s averaged 0 degrees F for a week, a battery pack would be in need of a charge. Are there “safe” or “smart” jumper cables that would also help mitigate damage to electronics while doing a regular jump start?

I think the only issue is people reversing the polarity of the jumper cables. I don’t see how damage could occur otherwise. Does there need to be a safety mechanism for this simple, yet so difficult, thing?

Mine still have a good charge after a full year, so that’s honestly not much of a task to keep them topped off.

I bought one of the portable jummpers to rescue my daughter. Every 3 months or so I check the charge, and it has minimal charge time. My neighbors have borrowed it 4 or 5 times, and the recharge tim is 5 minutes at most. Going out of town, car will be parked in possible sub zero temps. Going to throw it in the car just in case.

The risk of electric damage to your vehicle or the one you are jumping with cables is just not worth the cost you might have . Vehicles with start/stop are more apt to suffer from jumping vehicle to vehicle .

If in doubt just get a jumper box and a roadside sevice.

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Yeah I’ve got a jump pack in the trunk. Never used it. Drag it out after a year or so and still got a good charge. When I called the tow truck for a jump maybe ten years ago, the wrecker showed up with a jump pack. That’s all I will use, but really I try to monitor my batteries to not need help. Still stuff happens.


Just bought a jump pack yesterday, so haven’t used it yet. Got it as much as for the air compressor as well as the USB ports.
Instructions stated initial charge time should be 40 hours, display showed full after three hours. I going for the 40 hours, instructions state pack will not overcharge.

I can think of three possibilities

  • If both engines are ever running at the same time the jump cables are connected, that could create a situation where one alternator is fighting with the other. For example, car 1’s alternator output is 14 volts, while car 2’s alternator output is 15 volts. Connecting 14 volts to 15 volts represents a short-circuit, high current situation, could damage alternator or wiring. This risk can be minimized by not starting the charging car’s engine.

  • The cables carrying the high current during jumping create a significant magnetic field. If they become briefly disconnected that magnetic field collapses, and all that collapsing energy induces a high voltage spike on the cables, which could damage either or both car’s electronics. This risk can be minimized by not wiggling the connections or otherwise creating an intermittent connection during the process.

  • Once the jumped car is running and jumper cables disconnected, jumped car’s alternator has a big job to keep car running while it charges the possibly nearly fully discharged battery back to full charge. Alternators are designed to top off a slightly discharged battery, not to recharge a completely discharged battery.

These sorts of problem didn’t cause much trouble in most pre mid-70 car designs, but once cars became rolling computers, imo, safest to use a battery charger at no more than 2 amps, overnight, engine off.

I can only think of one. A transient spike caused by disconnecting the jumper cables while the engine on the jumpee is running, which can happen if the battery on the jumpee has gone bad and is open circuit, and is no longer connected to the battery on the jumper vehicle to absorb the transients.

I always use a heavy gauge (4 gauge 16’ I think) jumper cables to hook up to battery’s

pos to good battery and then dead battery, neg to good battery and then dead battery…
after both vehicles are running remove neg from jumped battery 1st and then pos and then neg from good battery then pos from good battery…

Always unhook neg 1st before pos, but always hook up pos before neg, that goes for battery cables also, as neg is less likely to cause a spark than pos is… Plus if you are tightening a pos cable terminal (neg unhooked) and your wrench hits metal it doesn’t hurt anything…

i have never had a issue using those rules… I don’t have a lot of experience with stop/start battery’s so this may or may not apply to them…

As a side note depending on how dead the battery is I will let the running vehicle put a small charge in the dead battery for a little bit, if the vehicle is cranking over slowly then a short charge should do, but if it is so dead that the key won’t come out of the lock cylinder then you might need to let run for 15-20 minutes before trying to jump start… Don’t keep cranking as that
might possibly damage something, but a quick crank and start should be OK…

Also make sure ALL cable ends are tight (absolutely no movement from terminal end to battery) on BOTH vehicles…

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Also remember some Makes Alternators will go into a fail safe mode (stop charging even if good) and not charge if battery voltage is below X amount…

I agree that with new cars and their electronics, I am nervous about jumping any car. Someone got me a battery pack but I think it is a cheap one and has never charged to full and not been able to jump any cars.
Can you guys pots the link to a reasonably priced battery pack that holds charge.