Just shorted 12v battery, advice?

It doesn't sound like you hurt anything......other then yourself. This is why we always remove the ground (black) wire first.........if you had removed the ground wire first.....and your socket wrench touched the cars frame, it's would not have done anything.

 

Hi trs79,

Yep, this is why positive terminals on batteries have the platic cover, while the negative, which is connected to chasis are left bare, typically. The intent is for the negative terminal to be removed first, and any accidental drop of the wrench hits the insulated cover of the postive terminal, or the chasis.

Once the negative terminal is removed, one can then remove the insulated over on the positive terminal, and safely use a conducting wrench to remove its clamp.

So, what you should have done was remove the negative terminal on the battery, secured it so it could not accidently slide back on, and then did the work up front on the positive terminals underneath the insulating fuse box cover.

 

Hi trs79. There's a 150 amp fuse between the jump point and the battery. Since everything is still working then you didn't blow the fuse and there should be no damage done.

What happened is one of those events that is undesirable, and if repeated enough times probably would damage something, but for a one off occurrence if everything seems ok then it most probably is ok.

 

I agree, if your car still goes Ready, you didn't hurt anything. You are lucky!

 

Yes, there is a fuse, but if your car is still running you didn't blow it.

The voltage probably sagged enough to reset the microcontroller in the clock which is why you had to reset it.

 

Fuses function by amperage and time. You may have drawn more than 150 amps, but not for long enough to blow the fuse.

Tom

 

Exactly. You probably did more damage to your wrench and nerves than anything else.

Tom

 

Yes, a lot of people don't understand fuses. A 150A fuse typically won't blow even at 200A for a few minutes. But a 1000A for 5 seconds will probably do it.

The datasheet for the fuse will usually show the curves that indicate when a typical sample will open, but for custom parts like the one in the Prius, probably only Toyota has access to the datasheet.

When I was building my PHEV conversion, I researched the 125A fuse Toyota uses on the traction pack and was actually able to find data on it. Here's the summary:



Note that the fuse is the 125A model, and it looks like typically it will tolerate 200A for about a minute!

Since the fuse is a mechanical device that depends on heat to cause it to open, the trip points vary somewhat and are affected by ambient temperatures, and to a great extent by age. A fuse that has been stressed by overcurrent several times will generally get more "sensitive".

So if you ever come out to a dead car one day, I'd check that fuse! (it's built in to the positive battery terminal assembly located on the battery in the back.)

 

The comments about ambient temperature and age are why we use magnetic circuit breakers on boats. Marine environments are very harsh. Thermal circuit breakers often fail in the marine environment.

Tom

 

Tom, do you mean breakers vs. fuses? I would think that a fuse is more reliable than any type of circuit breaker in a marine environment. However, you cannot reset a fuse!

Thermal circuit breakers would in theory be a bit more reliable as they generally have a simpler design with less moving parts. Both have contacts, and contacts that are not sealed in a marine environment are the liability.

The reason magnetic circuit breakers are used over thermal, is like the difference between a fast fuse and a slow-blow. Magnetic will trip faster and not have the time constant a thermal type will. There is also a hybrid type that will trip fast past a certain threshold but will trip slowly when only overloaded slightly.

 

Yes, I clearly stated "circuit breakers". Marine circuit breakers are sealed, because of the risk of explosion. It is the temperature extremes that caused NEMA to specify magnetic, but fast trip times are a bonus.

We also use fuses, but circuit breakers double as switches on boats. Because of this they are designed for frequent operation. They are generally designed for both AC and DC operation.

The biggest fuse on our boat is a 500A one for the starter motor.

Tom

 

Fuses are also highly subject to something akin to metal fatigue. With repetitive current pulses that don't normally blow the fuse, the life expectancy is a very strong inverse function of the fraction of the current (actually the fusing energy) needed to trip it.

If you put the trip point somewhat close to some normal startup surge current, a fuse is going to fail prematurely. Perhaps this is one reason why magnetic breakers can be better.