JHZR2
Staff member
I was thinking about getting my brother a set of jumper cables for his burthday. Its a permanently useful thing that is prudent to have... He encountered a weak battery in his car for the first time this year, so cables shouldn't be needed for a while, but you never know. I was looking at US-made, fine copper, 2 - 1/0 type size, 12-16 feet.
Biggest and longest, right?
In my search, I noted more and more commentary that standard jumper cables are obsolete, if not dangerous to modern cars. The basis was that voltage regulators go unregulated, and there are so many computers in there, that things can and do get broken. Of course, generally after that was a plug for either smart cables or a jumper pack...
So it got me thinking.
1) computers, even body and accessory control computers are not a post 2000 issue, yet many articles blindly define the issue after ca 2000.
2) dont vendors reasonably check and harden their equipment for a range of voltages and scenarios? Perhaps even 24v sources being used to jump a 12v vehicle?
3) dont vendors still often give a jumping post (if the battery is located away from underhood), and some depiction of how to jump the car?
I guess you could blame it on car to car jumping, and say that jumper packs are ok. Of course, in case of a shorted battery, the alternator voltage regulator will still be going possibly haywire, trying to ratchet the voltage up while the battery is dissipating energy in the short. Some things Ive read indicated that the removal of cables will make multi-hundred volt surges that damage things. Ok maybe. But im not sold on it being the voltage regulators.
What everyone leaves out is inductance. L*dI/dt creates a voltage spike, and this is where longer and bigger fails... voltage drop is a consoderation, definitely. But the longer the cables, the more inductance (0.4uH/ft or so, regardless of AWG)... so a 20' set will have a lot more inductance than a 12' set.
I am not a fan of Li-ion booster packs because the heat of a car in summer does not jive with safe storage of batteries. I also dont like that they cannot provide some sustained low-rate charge versus some over-hyped amp/Joule rating that doesnt make sense for the size of the conductors. I find those small lead acid jump packs stupid too... carrry a small starter or even a cheapo tractor battery if thats the desired approach.
I am a fan of keeping an older, marginal battery, if not a newer, cheapest size battery on a float charger as a booster pack if need be. Of course it would be at home, while cables would notionally be in th car... Putting a lone battery in parallel creates no issue other than that the voltage of the vehicle could rapidly drop when booster cables are removed when jumping. But at least there is no other vehicle in the loop.
I think im going to stay a believer in old fashioned, heavy gauge jumpers, with big, copper clamps and high quality copper conductors. But, im going to be more of a believer in as short as practical, and as high a gauge as possible, since it adds no inductance but minimizes voltage drop.
Then, the connect both cars up turned off method is good as far as Im concerned. Yes its slower and you only have the voltage deltas of the batteries themselves (a few volts or less most likely). Just use the voltage deltas to flow charge to the weak battery, and start the bad car wih the two batteries jn parallel to reduce impedance and improve power. I may not ever try to jump a car with the donor engine running again, merely because the risk of inductive spikes is real if a high output alternator and a low source impedance battery allows for a good amount of current flow from battery to battery...
Interested to hear others' thoughts on jumping. Ill admit that im pretty lucky. The last time I killed a battery was 2003, bad diode in an alternator. I did have a shorted cell in a battery in around 2008, could barely jump the vehicle being fed from a tow truck... maintenance is key, to prevent the need to jump... but when the need arises...
Thoughts?
Biggest and longest, right?
In my search, I noted more and more commentary that standard jumper cables are obsolete, if not dangerous to modern cars. The basis was that voltage regulators go unregulated, and there are so many computers in there, that things can and do get broken. Of course, generally after that was a plug for either smart cables or a jumper pack...
So it got me thinking.
1) computers, even body and accessory control computers are not a post 2000 issue, yet many articles blindly define the issue after ca 2000.
2) dont vendors reasonably check and harden their equipment for a range of voltages and scenarios? Perhaps even 24v sources being used to jump a 12v vehicle?
3) dont vendors still often give a jumping post (if the battery is located away from underhood), and some depiction of how to jump the car?
I guess you could blame it on car to car jumping, and say that jumper packs are ok. Of course, in case of a shorted battery, the alternator voltage regulator will still be going possibly haywire, trying to ratchet the voltage up while the battery is dissipating energy in the short. Some things Ive read indicated that the removal of cables will make multi-hundred volt surges that damage things. Ok maybe. But im not sold on it being the voltage regulators.
What everyone leaves out is inductance. L*dI/dt creates a voltage spike, and this is where longer and bigger fails... voltage drop is a consoderation, definitely. But the longer the cables, the more inductance (0.4uH/ft or so, regardless of AWG)... so a 20' set will have a lot more inductance than a 12' set.
I am not a fan of Li-ion booster packs because the heat of a car in summer does not jive with safe storage of batteries. I also dont like that they cannot provide some sustained low-rate charge versus some over-hyped amp/Joule rating that doesnt make sense for the size of the conductors. I find those small lead acid jump packs stupid too... carrry a small starter or even a cheapo tractor battery if thats the desired approach.
I am a fan of keeping an older, marginal battery, if not a newer, cheapest size battery on a float charger as a booster pack if need be. Of course it would be at home, while cables would notionally be in th car... Putting a lone battery in parallel creates no issue other than that the voltage of the vehicle could rapidly drop when booster cables are removed when jumping. But at least there is no other vehicle in the loop.
I think im going to stay a believer in old fashioned, heavy gauge jumpers, with big, copper clamps and high quality copper conductors. But, im going to be more of a believer in as short as practical, and as high a gauge as possible, since it adds no inductance but minimizes voltage drop.
Then, the connect both cars up turned off method is good as far as Im concerned. Yes its slower and you only have the voltage deltas of the batteries themselves (a few volts or less most likely). Just use the voltage deltas to flow charge to the weak battery, and start the bad car wih the two batteries jn parallel to reduce impedance and improve power. I may not ever try to jump a car with the donor engine running again, merely because the risk of inductive spikes is real if a high output alternator and a low source impedance battery allows for a good amount of current flow from battery to battery...
Interested to hear others' thoughts on jumping. Ill admit that im pretty lucky. The last time I killed a battery was 2003, bad diode in an alternator. I did have a shorted cell in a battery in around 2008, could barely jump the vehicle being fed from a tow truck... maintenance is key, to prevent the need to jump... but when the need arises...
Thoughts?