Question about Auto batteries

current draw depends almost entirely on the load

then 13A flows thru the cables, presumably. Nothing else happens, cables have a fair amount of margin in their ratings. If you ran 130A through it it'd melt.

NT

There is no 'average' output current - the current depends on the load which will vary according to what electrics are in use. But of course with the engine running the alternator supplies all the current needed for pretty well all the time.

However, the other figure given with batteries is the capacity in amp/hours. Since this is measured over a constant time regardless of actual capacity means the current drawn during measurement will vary.

Same as with any other power source - if the cable is too small it will allow too much voltage drop at best and at worse burn out.

Yes. See above. You need to use cable rated at the maximum current you're going to draw.

--
*Is there another word for synonym?

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Motorcycle batteries are rated in Amp/HRS. A fully discharged 14A/H battery will take 14 hours to charge at one amp. Starter motor current is ~50amp. Obviously they can put out much greater current than their A/H rating. They're rated this way mostly to keep them from being over charged. A car battery is used for starting only so cranking current is all that's really needed. Theirs no good reason to short either type battery. A 10A rated cable means it's rated to carry 10A, not that 10A will flow when shorting across a battery.

If you want to now what happens, hold the ends of paper clip on to a fresh D-cell battery with your fingers.;0)

No, a 14 Amp hour rated battery will deliver 1 amp for 14 hours, to the rated discharge voltage. It will take more than 14 hours to recharge, because some of the current becomes head, instead of stored energy. Actually, the lower the discharge rate, the less of the stored energy is lost as heat.

For a motorcycle? Some cars don't use that much current to turn the engine over.

Yes, that is the CA/CCA rating, and it is for very short bursts during starting. Extended cranking, or a short circuit causes the battery to generate a lot of heat. That can either cause it to explode, or to melt the internal lead connections between the individual cells.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Rated at 10 amps for what application? it depends on if its wound on a transformer, in a bundle or conduit, the type of insulation, acceptable voltage drop and duty cycle, along with the temperature.

Worst case is when the insulation has a flash fire and hot copper is spattered everywhere. For that kind of current I would use #1 welding cable. The whole idea of jumper cables is to start the engine quickly. The battery is discharged, and you still need the full current the starter demands. That means that you need as low of a resistance connection between the two batteries. It also helps to let the dead battery be charged for a couple minutes before you try to start the engine. That allows the dead battery's terminal voltage to rise a bit, and reduce its demand while cranking.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Ah rating is only correct for a 20hr discharge. Faster discharge will give lower than proportional capacity.

Charge time depends entirely on charge rate.

Fiat 500? Trabant?

NT

They are rated with current output. Current is described in Amps. CCA is cold-cranking Amps. There is no "average" current. If you want to light a small 12v bulb with a battery, you'll get a few tenths of an amp output. If you want to crank an engine's starting motor, you'll get a few tens or hundred of amps, depending on the motor. The battery will supply a trickle or a flood of current depending on what you connect to it. That's true of all batteries and why you have to be careful what you connect to one.

If the cable is too small for the current you need to supply, it will probably get warm (or hot!) and the voltage will drop below 12 volts. It's always best to use a cable that's bigger than required for the job.

See answer #2.

You're welcome.

--
DaveC
me@bogusdomain.net
This is an invalid return address
Please reply in the news group

Well my car with a relatively small 2.3L 4 cylinder engine has a starter motor rated at 1.4KW, so well over 100A. I'm not sure if this is typical but the starter is powerful enough to move the car if I put it in gear and turn the key. I suspect larger engines typically have even more powerful starters.

battery

No. A typical car battery is 50A/H. Even a small car battery will be rated

300CCA. It's not the same rating. Problems can happen to the battery from it's over use but the biggest reason to not use it for long is to keep from burning up the starter.

The current needed depends on several things - notably how much friction in the engine which varies between cold and hot.

--
*Plagiarism saves time *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

I state that the CA/CCA is higher than the A/H rating, and you say that's not true. Interesting.

BTW, have you ever seen the damage done to a vehicle when a car battery explodes and sprays acid all over the engine compartment? I've seen several, here in Central Florida. One exploded while parked in the hot sun, and hadn't been used in over 8 hours.

A starter will be damaged faster by low voltage, or excessive voltage drop in the solenoid and all of the cables. I had to install #1 welding cable on the customized 389 8 cylinder engine in my '66 GTO that had over 220 pounds compression. When the engine was warm, it drew over 400 amps from the battery, but only for a second or so. If it didn't start you waited ten seconds to let everything cool. That rarely ever happened.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

I have never looked at the specs on the electrical system on a bike. Years ago any car starter that drew over 70 amps, no load was considered defective. That's why I asked.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

My car obviously had a battery explosion, or at least a severe boil-over at some point in its life. The paint is gone off the front bumper cover in a spatter pattern in front of the battery area, and the battery tray itself is nearly rusted out in spite of the rest of the car being rust-free.

Had one explode on a travel trailer once, too. The battery was in a plastic battery box on the front A-frame and had been on trickle charge for about three months. This was in the middle of winter. It threw shrapnel a foot or two on either side.

Hi...

I respectfully submit that CA/CCA have absolutely nothing in common with A/H. Apples and oranges.

Take care.

Ken

Froze up?

Please show me where I said that it did. I simply agreed that the CA/CCA was a higher current than the battery was normally used at.

The A/H rating is simply a way to state the amount of stored electrical energy that you can expect at a specified discharge current and temperature for that battery, when it is in good condition.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Probably. To say that the battery chargers in RV power converters are often poorly designed would be, perhaps, too kind.

My last car had pinholes in that corner of the hood The battery exploded when my Dad owned it. The '79 Dodge 1/2 Ton Limited Edition pickup truck I want to restore has damage. The previous owner was a hack mechanic and caused the battery to explode. The only real fix I've found is to braze the holes shut, then grind down both surfaces, if possible. In enclosed area there is rusty slag on the surface, but it doesn't cause any problems, and can't be seen. The ford ranger I'm driving now has damage, but i don't know what happened to it.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Oddly, the hood on mine is OK. This suggests one of two things:

- The battery explosion was the result of a collision, and the hood was replaced. I don't think it's that, because the cowl area near the battery is rusty, and any collision damage would have affected it, too.

- The battery explosion happened with the hood up. Jump-starting accident, maybe?

Another thing that puzzles me is the current battery has a tendency to weep liquid out of the cell covers. Normally I'd assume this was boilover due to overcharging, but the charging voltage is normal.