Batteries you can't jump

We have a 2006 Mini Cooper that recently wouldn’t start. The dealer (100 miles away) said it might be the battery based on the age of the car. Having practically torn my first car apart - a 1954 Chrysler - and put it back together (succsssfully!), I grabbed by fully-charged, portable, charger and hooked it up. Nothing! Wouldn’t turn over. Just one “click,” then nothing. Undeterred, and not wanting to have to pay for a tow in my rural home town, I pulled my SUV into position and ran cables from it to the Mini. The previously slow-moving power windows in the Mini went up and down quickly again, but would it turn over? Hell no! The tow tuck took it the next morning and after our mechanic (not the dealer) had a look at it, he diagnosed the problem: dead (#@$%ing)battery! Now tell me, how is it that I can try jumping a battery two different ways and know I have a good contact because the power windows respond, and it won’t turn over when, in fact, it’s the battery? I want my '54 Chrysler back!

If your Mini’s battery is so deteriorated or has failed to where it will not take any charge, it is possible that your jumper cables, due to electrical resistance, are not thick enough to conduct the amperage needed to run the heavy current demand of your starter, yet will do so for a small motor such as what a power window has. Some current will flow if the solenoid pulls in and stays pulled in but may not be enough to turn over the starter motor.

Also, 12 volts is not a lot of voltage and may not break through corrosion that you may have on your connections so to counter this, wiggle the installed clamps a little to wear through any corrosion.

10 gauge wire is too small but will conduct current enough to charge a dead but otherwise good battery to make a starter work. Larger 8 gauge is better but may still not be thick enough. Beyond that, I don’t know the wire gauge size of a good quality jumper cable. 4 gauge? Maybe others can help.

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Whenever a battery is completely dead, boosting will not supply the starter with enough juice to turn over. Only hooking the booster cables DIRECTLY to the starter will work.

The starter is the highest power consumer in the vehicle.

What you should have done is shut off all the accessories in both vehicles, hooked up the booster cables to the batteries, leave your motor idling and wait 15 minutes or so to transfer some juice to the dead battery before attempting to crank the engine over.

The battery is only three years old so I doubt it’s due for replacement.

5 to 6 years is about the average lifespan, although I’ve had batteries for much longer periods.

Obviously there are reasons why batteries go dead. Have your charging system tested IN the vehicle. Bench testing sometimes misses bad grounds, etc.

Buy some REAL jumper cables made from 0 gauge welding cable. The ones made from 6 or 8 gauge wire can’t carry enough amps (200) to crank an engine…

When you go small, both with the battery and the engine, it is easier for the battery to go completely dead. With a larger engine and a larger battery, the battery will decline to where the car won’t start before it goes completely dead.

You need to get good at noticing when the car starts to crank slowly and get the battery tested before it completely dies.

I’m thinking you had a discharged jump pack or poor connection. Also, did you have good cables when you tried to jump it? “Wha Who” mentioned the jumper cable wire size. Did you use a set of $20 cables that came with safety triangles, a can of flat fix, and a 100-in-one flashlight? Those cables are made with tinsel (sometimes with wire as thin as 10 gauge). I learned my lesson with garbage cables when I tried to jump start a Lincoln with a Pinto. The insulated grips on the clamps melted and I burned my hand trying to remove the cables. If you have the junk cables, throw them out and buy some good 4 gauge cables (the lower the gauge, the thicker the cable).

By the way, when I want to be sure I have a good connection with my cables, I’ll turn on the headlights of the car with the dead battery and gently rock each jumper cable clamp. If I have a bad connection, the lights will flicker. After I’m sure the connections are good, I shut off the lights and try to start it.

Random jumper cable video: ( This cracks me up every time I watch it!


The Mini’s battery was so badly discharged that when you installed the jumper cables the donor car’s current went directly into the battery, leaving little to operate the dead Mini’s starter.

The solution is simple. Next time you’re in that situation, hook up your jumper cables and let the dead battery charge for a few minutes before even trying to start the dead car. This will charge the depleted battery enough that it won’t absorb all the current when you try to start the car.

And like Caddyman said, get a pair of VERY high quality cables if you’re going to be doing stuff like this. Welding cable makes good jumper cables. The $9.99 auto parts store specials are junk.

I’ve had this issue in a ford taurus 2003. Problem was that the battery had a bad cell. Not bad enough to drop the volts but bad enough that the battery ampacity was little more than enough to run the dashlights and door buzzer. Jumper cables do not need to carry more than 80 amps btw. Thats about all most starters can handle. The bad battery in circuit can prevent enough current flow though. After replacing the new starter when I first could not start I took the starter and the battery for testing at the local parts shop. Result? good starter and bad battery.

“Jumper cables do not need to carry more than 80 amps btw.”

That’s simply wrong. It may be true for very small engines, but starter current for larger engines can get as high as 600 amps.

“Jumper cables do not need to carry more than 80 amps btw”

I don’t know where you got that nonsense from, but it is dead wrong. The starters on both of my V8 cars take way more than that (about 300 to 500 Amps).

I want your 54 Chrysler too, 331 cube hemi and plush chair high seats!