Why is jump start is not like regular start?

[Chapap]

the last couple people I jumped off looked like they had bad batteries, not just over-drained. That may be part of the reason.

Why is it that in this ^ condition, I had to let my truck sit and charge their battery for a bit? Even then it was a slow start. It seems like, with jumper cables installed, their car should act like it has my 1 year old battery in it. While hooked up, our batteries are wired in parallel, but it doesn’t seem like their bad battery should put such a drag on the system.

On top of that, I was curious on the last car and turned off my truck and started it back up. cranked perfectly. Just doesn’t make sense to me. I have 10’ long 4ga cables. That seems like an adequate size for jumping a sedan.

 

[rusty ol ranger]

Usually it has to do more with the quality of the connection then the batteries or charging systems. If im jumping one and its taking forever usually making sure the cables have good connection takes care of it.

 

[Curious Hound]

but it doesn’t seem like their bad battery should put such a drag on the system.

It does.

Each situation will be different. It depends on the age and condition of their battery and the condition of the electrical connections in the starting/charging system of their vehicle. Sometimes all they need is a little help. Sometimes it takes more time to charge their battery. Sometimes, even that doesn't work.

If there battery is fairly healthy, connecting your vehicle for the boost and then getting their car started and running for one of two minutes may seem to help and when shut off, it starts again immediately. But if left for a longer time, 15 minutes or more, that initial charge will dissipate and they will probably need help again. It is best to keep the car running for a while to get a decent charge back into their battery.

That's the short explanation. The long one goes into the chemistry and inner workings of the battery. Just trust me. It's magic. It does what it does. And it follows the laws of physics perfectly.

 

[Chapap]

Usually it has to do more with the quality of the connection then the batteries or charging systems. If im jumping one and its taking forever usually making sure the cables have good connection takes care of it.

Could be a big part of it. Thanks for reminding me. Going to stop by orileys to pick up a negative battery cable. I currently have a quick bolt on connector that has recently been tightened to the max because it keeps magically becoming rattley loose on the terminal.

 

[sgtsandman]

The gauge of the jumper cables makes a big difference too. At lot of the inexpensive cables on the market are made with wire that is much smaller than it should be. And the longer the jumper cable set is, the heavier the wire should be in the cables. I think my 20 footers are 4 gauge. 2 would be better but 4 works well enough.

 

[09fx4guy]

Connection is everything, connections can look clean, but can be dirty enough to impede performance. Cleaning battery terminals should be a yearly or every other year task.

I actually made my own jumper cables a couple of years ago using some leftover 2ga welding cable from my dual battery install. Sgtsandman is right about the differences in wire thickness. A friend of mine got a set of 2 gauge cables and decided to compare them to mine, and the difference was staggering. The insulation was significantly thicker on his, and only had the equivalent of 6 gauge wire, to mimic the thickness of 2 gauge.