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49 votes
Accepted

Car battery at 10v, then shows 14,5v while car running after boost, then when car turns off, drops to 10v again within a minute

Nope. That pretty much sounds like a dead battery. It sounds as though one of the cells has a short in it, which is causing your rapid voltage decrease. There's no way to fix this other than battery ...
48 votes
Accepted

Why is my car equipped with a battery shutdown timer?

It is a turbo timer. The theory is that an engine with hot turbocharger shouldn't be immediately turned off. The turbocharger may be damaged because there will be no oil flow. The timer ensures that ...
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35 votes

Are car batteries meant to be disposable or are they re-chargeable?

Car batteries are not only rechargeable but are constantly being recharged by the alternator. Simply starting the car takes a lot of power reserves from the battery, then electrical systems such as ...
35 votes
Accepted

Why put copper in between battery contacts and clamps?

I think your guess will be correct. The clamp has probably been over-tightened in the past, has stretched and is no longer giving a good tight connection. The copper will have been added to act as a ...
  • 21.3k
33 votes

Is 15V too high for a standard car battery?

The 15V is not a real reading. It's an artifact of bubbles formed on the plates from overcharging, which have by themselves an anode and a cathode. This creates a false" voltage potential that ...
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29 votes
Accepted

Battery drops to 10.5 volts after charging

Yes, this is a bad battery. One of the cells has most likely shorted. Each cell is a little above 2vdc. A fully charged battery will usually be ~13vdc. If you lose one cell, it will drop it down ~2vdc,...
28 votes

Why is gas around a car battery only at risk of ignition from jumper cables?

This is going to get a bit technical but should still be understandable even if you slept through chemistry classes. When is hydrogen dangerous? Just as with the fuel-air mixture in an engine, ...
  • 2,827
28 votes

Why are these wires sticking out of battery terminal?

The main reason those would be sticking out of your battery post/terminal is because the terminal clamp has become too stretched. Someone put the copper wire in there to take up the slack of the clamp....
27 votes
Accepted

Car won't start after sitting for 2 years even with a jump. Is it a starter or alternator issue?

If the battery is completely dead, especially after sitting for two years, it most likely won't take a charge. Without the battery getting charged, you most likely don't have enough juice coming ...
25 votes
Accepted

Can one slightly charge a dead car battery with a portable battery jump kit?

As Miracle Max would say, there's two kinds of dead batteries, and there's a big difference between them. Mostly Dead This is the most common kind of dead battery. Let's say your battery is rated for ...
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24 votes

How slow ( not zero) can a car engine run without hurting engine and saving on fuel

You are right in the thinking of using less gas and that's exactly what the purpose was to have the start/stop feature. The main goal of doing it (at least here in the States) is for zero fuel ...
22 votes

Battery removal or just disconnect neg. terminal

I'd just disconnect the negative, personally. I'd also recommend having a look at some of the questions and answers on here about storing vehicles for a long time: Long-term-storage As these may ...
  • 28.6k
22 votes

Alternator dying so junk car?

A rounded bolt is not a reason to junk a car. The numbers you're quoting sound fine for an alternator; if it was below 12V, I'd be worried. If you're still concerned, take the car to a spares store ...
  • 8,602
22 votes
Accepted

Charging battery with battery charger vs jump starting and running the car

Got a 1998 Toyota Camry that has an empty battery and am wondering what the best course of action is. Why is it empty? Is it empty because the battery is old and dying and won't hold capacity? Or is ...
  • 14.2k
21 votes

What causes battery terminal corrosion?

Corrosion on the terminals is due to hydrogen gas being released from the acid in the battery. It mixes with other things in the atmosphere under the hood and produces the corrosion you see on the ...
21 votes
Accepted

I charged my car battery with no water in it

The battery is toast. Save yourself potential serious injury. Buy a new one. If the battery has been dead for eight months...it is pretty much a goner.
  • 3,872
21 votes
Accepted

Why do cars die after removing jumper cables?

It's because of a couple things: The battery is very dead and the alternator cannot put out enough power at idle RPMs to run the whole system and charge a battery. This leads to a lack of power which ...
  • 2,859
20 votes

When reconnecting a battery, why connect the positive first?

The reason I would connect the positive cable first (in a negatively-earthed car) is that while tightening the positive connector with a spanner (wrench), if I were to touch the body of the car with ...
  • 21.3k
20 votes
Accepted

How slow ( not zero) can a car engine run without hurting engine and saving on fuel

The oil problem You can run any engine speed you want as long as you keep the oil pressure up. Because of the impossibility of getting a roller bearing down a crankshaft, engine bearings are "...
19 votes

Can a weak battery destroy an alternator?

Your question is difficult to answer without you knowing the inner workings of an alternator. The basics. If you move a magnetic field near a coil of wire the electrons in the wire get excited and ...
  • 15.9k
18 votes
Accepted

Is charging my engine battery like this bad?

Use the jumper battery to start the engine, then disconnect it and leave the engine running (with no current drain such as lights, heater fan, radio, etc). The car should charge its own battery to 80% ...
  • 8,602
18 votes
Accepted

Can a car AC unit be run on just the car battery?

I can't give you numbers or calculations without some work, but I can tell you than energy is never free. Cars have an A/C compressor that is mechanically driven by the engine because this is the ...
  • 13.2k
18 votes
Accepted

Can I jump start one car with two other cars in parallel?

To answer your question, it will not cause any issues as long as the cables are connected correctly. If both donor cars are connected in parallel (negative to negative/positive to positive) to the ...
18 votes

What is more cost effective: re-charging a car battery or replacing it new when it dies?

The cost has been addressed, but there's an underlying question: is the battery dead (i.e. it cannot hold enough charge anymore to start the car), or has it just been discharged? If it's just been ...
  • 4,412
17 votes
Accepted

Lots of sparks and heat when jump starting a car

With the description you give, I'd say you connected them backwards with about a 99%+ assurance. Large amounts of sparks followed by heat are both VERY BAD SIGNS (as you soon figured out) and almost ...
17 votes
Accepted

When should I disconnect the battery to stay safe during repairs?

These are some general guidelines when working with electricity on vehicles: Always remove any jewelry, to include rings, necklaces, watches, etc. If one of these items should come in contact between ...
17 votes

Can I jump start one car with two other cars in parallel?

When you jump start a car, you are always putting the cars in a parallel circuit. Here's an illustration of parallel vs. series: Source Think of the bigger car's battery as the one on the left and ...
  • 5,225
17 votes
Accepted

Need advice for changing battery terminals

That the car now cranks and runs correctly tells us that the battery and the cables are conducting electricity acceptably. I see no need to cut and refasten either cable, especially (as you note) the (...
16 votes
Accepted

Does turning off the radio and other electronics in a car before shutting off the engine prevent battery drain?

This step is a carryover from days gone by and is not needed in modern vehicles. Batteries from 50 or 60+ years ago were not as powerful or reliable as modern ones. Older batteries had difficulty ...
  • 19.8k
16 votes

Will fitting a physically bigger battery reduce the working life of the alternator?

Great question! Taking a few minutes to think through this logically should come up with something. First of all, realise that a larger battery with a higher amperage (CCA) will not cause any ...
  • 5,225

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