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31

From an electrical perspective, it doesn't matter. However, a lead-acid battery that is charging or discharging rapidly will give off hydrogen, which is highly explosive. Since you generally make the ground connection last, there's a good chance that you'll get a spark, which is enough to ignite the hydrogen. So while it's unlikely that you'll have ...


25

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, hydrogen is combustible only when it's within a range of concentrations. We use what are called the Lower Explosive Limit (LEL) and the Upper Explosive Limit (UEL) ...


13

Chris makes a very good point regarding the hydrogen given off by the battery. There's also another reason, especially on older cars. Ground straps to the engine on most cars are notorious for corroding, so by hooking up the negative terminal to the engine you'll increase your chance of getting the maximum current flow when you're trying to crank the engine.


11

The biggest thing to look at for me is the gauge of the wire. The reason I bring this up is, the higher the gauge (numerically) the thinner the wire. Thinner wire will require your jump-start procedure to take more time, as it takes a while to charge the battery before you'll have enough juice to get it running. Thinner wire cannot pass enough amperage to ...


11

I am no expert in this topic, but I don't think a "cloud of gas" forms around the battery. Hydrogen gas is the lightest gas of them all (0.089 g/l) and won't pool up if leaked. It will simply rise as long as the bonnet is open because it is less dense than air, which is mostly much heavier nitrogen (1.25 g/l) and oxygen (1.4285 g/l). My guess is that the ...


10

Sounds to me like your starter motor is on the way out, as you are getting enough power, as a bump start is working, and sometimes you are able to start normally. This isn't that uncommon - they do take a lot of stress and load, and the internal friction can end up being too high for them to cope with. A temporary fix I have used in the past is to whack ...


10

The starter circuit should only draw whatever current it needs so the excess shouldn't cause any problem.


10

There are no special safety issues related to snow and ice. In general, voltages up to 48V are considered safe for the human body. You can touch both contacts of a 12V battery, even with wet fingers. (Did you never touch the terminals of a 9V battery with your tongue? This hurts a little, but that's all) A 12V car battery can deliver several 100 Ampere, ...


9

Your car thinks it is being stolen - jump starting a car looks a lot like hot-wiring a car to the computer. You need to do something that tells your car "it's OK, I own you". You can do this right after hooking up the cables, but before starting the engine, to minimize the annoyance to your neighbors. If you have a remote door key, lock and unlock the ...


9

I don't know the actual justification, but to me it makes sense to always attach positive first because it is easy to accidentally touch the lead to something else while installing. If the negative lead were already attached, then touching the positive lead to just about anything on the car that is metal would short out the battery.


9

The two biggest disadvantage of lead acid batteries compared to the newer types like Li Ion are that they are heavier, and that they contain liquid acid. Another possible issue is that they can produce hydrogen gas. On the other hand, they are very inexpensive, have a long life expectancy, have a very high tolerance for overcharging without being damaged, ...


9

No, you cannot. Well, you might be able to, but not in a feasible way in any likely manner. Electric Vehicles commonly have two separate electric circuits. One running at the normal 12V, which ties to all the common electronics that all other types of cars have. Light bulbs, radios, in many cases also a starter motor for the gasoline engine if it in fact ...


9

Since you have a battery which isn't that old (most batteries have about a five year life span), I'd suggest you put it on a charger and try to recharge it. This will allow the battery to come back to full charge without putting an undue stress on your alternator. You have to decide if the time spent in recharging the battery is worth your time. To me, ...


8

It sounds like you need a trickle charger or battery maintainer - this is a small charger than monitors the charge on the battery, and keeps it charged. Most modern cars have electronics that have a continuous drain on the battery - a trickle charger produces enough power to compensate for this drain, so that even if the car isn't driven for a few weeks the ...


8

You can get transient spikes from the other car while it's trying to start. Any battery or alternator issues that affect power quality will be transmitted to your car. The good news is that large 12v batteries make excellent buffers against power issues that might otherwise cause damage. However, it is still possible to suffer damage to your car from ...


8

I think you have an issue with the way you are thinking. You are describing the issue as if the batteries are hooked up in series. In that case, yes there'd be a huge back current going on. Both batteries would be made into a complete circuit and you'd have global thermal nuclear meltdown (or whatever the car battery equivalent would be). This is not the ...


7

Conventional lead acid batteries produce hydrogen gas as a byproduct of the charging process. This gas tends to collect in and around the battery. As you are aware making the final connection can generate a substantial spark. By making the frame connection the point where the spark occurs it is far enough from the hydrogen gas to avoid an explosion.


7

The amp count tells you the maximum amount of current that the equipment can supply. Eg. Your car needs 600 amps to start: The 1000 amp jumper can handle it. Your car needs 1200 amps: The 1000 amp jumper can't do it. You'll have to find a bigger one. Be aware that this does not apply to voltage. If you have a 6V battery and you connect it to a 12V ...


7

Lead sulfate crystals form on the battery plates as the battery discharges. As the battery becomes more discharged the crystals go from being soft and fluffy to much harder. Recharged in time, the lead sulfate is converted back into sulfuric acid and lead. A month is entirely too long for a battery to remain discharged. Reversing a serious sulfation ...


6

Any ground (earth) location will work. On my '06 Silverado, there are places to hook the jumpers which are away from the battery. You don't even hook the jumpers to the battery no matter which way you're going (whether jumping or being jumped). As long as you have a good ground location, you're golden. Given two vehicles with alternative connection points (...


6

Your description of connecting the two cars is correct. I want to emphasize making the last connection to the "bolt head" you mention. Any large piece of unpainted metal will do. The reason for this is to keep the resulting spark away from the battery. If they battery has been venting fumes, the spark can (although very unlikely) cause them to ignite and ...


6

I don't think you are likely to "put undue stress on the alternator." It is a myth in my opinion that alternators can't handle charging a battery, Alternators are literally motors run in reverse and are designed to handle a lot of current. The only issue with charging a batter is it will get a bit warmer than usual and that shouldn't effect it as long as it ...


6

Typically I've only seen three posts on the starter solenoid. The thickest one is for power from the battery. There is also a much small one which is for ignition switch (S). The last one is for a coil pack (R). Typically the starter solenoid is self grounded. When jumping you simply make a connection between the B and S. This activates the solenoid and ...


6

Fair warning, this is a guess. Vote appropriately... General accepted order: Dead + Good + Good - (directly to the terminal) Bad - (to a good engine ground, but not the terminal) Avoiding the last connection directly to the dead negative is to avoid sparks near the dead battery, but this also avoids sparks near both batteries since the good one is ...


5

The cranking amps required to start an engine are not the same as the cranking amp rating of a battery. I don't know the amps required to start your car's engine, but if it is less than 400 amps, then it will work. Higher cranking amps in a battery yields additional benefits. The battery can be used for more starts because less capacity is used on each ...


5

Those numbers are the max that they can supply. Your starter will "automatically" use as much as it needs up to the max. If the starter needs more than those units can supply, the jumper will only provide its max. If your battery is only partly dead, i.e. it won't start, but the interior lights come on, you can use a smaller jumper than if your battery ...


5

There are two power systems on all electric cars (fully electric and hybrids alike). This is in conjunction with the much higher voltage battery packs which normally power the electric motors. The reason for this extra power system is to power things like lights, electronics, and HVAC systems (to name a few). Most hybrid vehicles (and never a fully electric ...


5

In the circuit that contains your starter relay there is a fuse, typically it is a 30amp fuse. Here is an image a Yamaha R1 starter relay fuse Depending on your model of motorcycle you will need to: Discover the location of your relay fuse Remove a plastic cover for the relay Possibly, remove a plastic cover for the fuse. Remove and Replace old fuse ...


4

I'd like to preface my answer by saying that I think the OP has asked an interesting theoretical question that deserves a theoretical/hypothetical discussion. In no way should the following be taken as an indication that removing/installing batteries carries low risk of explosion. Take precautions when working around vehicle batteries. The risk of hydrogen ...


4

I can't think of any reason why you would damage the electronics in your car, unless you touched one of your jump leads somewhere you shouldn't and short something delicate or you connect the leads back to front. Connecting them back to front shouldn't damage electronics, as your car should have protection against this sort of thing, but it is the key thing ...



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