42V Car Batteries

Ah, yes. :-) I remember them as #6. 6 of them in series is a lot of zinc-carbon, so I still say it's at least plausible. :-)

Cheers! Rich

Littlefuse developed them (others were working on fuses, but no longer appear to be doing so, since interest appears to have fizzled). The fact there is no stock is just further evidence of lack of sufficient interest.

Too bad, there are a lot of EV manufacturers who would have been happy to make use of them.

OTOH for lower current ratings (say

Not at a reasonable cost/size AFAIK, unless you're willing to live with miserably low current interrupt capability.

Best regards, Spehro Pefhany

A well worn engine takes less juice to start. I lived in Montana and a fellow I knew had a Kaiser-Fraiser, an old beast of a car. The engine was very loose and it was the only one which would start after an overnight cold soak of -30 to -40F. It would go, blub, blub, blub and slowly speed up. Once it was cranking, it was used to jump start some other cars in the parking lot. The car batteries put out very little juice at those temps. I wonder how the new wonder-hybrids would do under those conditions?

Al

The Prius has an interesting feature: After you turn it off, there's a little whirring noise as a pump fills an insulated tank with hot engine coolant. When you start the car, and are running off the big NiMH battery, it presumably transfers the saved warm water back to the engine, to pre-warm the block. After a going a short way, the engine starts and finishes warming up to be ready for efficient use. I had good experience with it at 10 below freezing, but don't know beyond that. When it's cold, the control electronics keeps the battery close to full charge, and is very parsimonious with the battery, consequently the MPG performance drops badly.

You might need to define reasonable ;)

A definite point. Fortunately I can use a resistor to lower the fault current. More space and cost though. Part of that will be traded off against the absence of a fuse holder.

Unfortunately the only alternative appears to be standard cylindrical fuses. Then there's the task of educating the end users of the difference between AC and DC rated fuses.

It really is too bad the Littlefuse devices aren't generally available.

Robert

NiMH battery capacity drops very quickly below room temperature.

Best regards, Spehro Pefhany

At that time, the 60's, Sears sold a self start kit. The kit would monitor the engine coolant and when it went below a certain temperature, the car would start up and run until the engine would be warmed up and then shut down. It was not unusual to walk down the street and have a car start up next to you with no one in it.

I didn't have such a set up. I went to my car every 3 hours or so and started it up. Otherwise you was screwed. -40F makes for interesting driving. The shocks were stiff. Since the street were not plowed, you had to get your tires into the correct groove in the ice or else you might go around a corner you did not intend to go around; sorta like a trolley. The slight flattening of the tires also did not go away and you would thump, thump down the street.

Many parking spots at apt. buildings had outlets so you could plug the tank heater into it for overnight.

So I still haven't heard any good solutions to the loss of battery power under extreme conditions. I suppose if you have heaters you can plug in overnight, you are OK. But what do you do when you are in the boonies or park your car all day while at work and it's 30 below. Or is global warming going to take care of that?

Al

If it's a hybrid you don't need to have the battery to run the car; the gas mileage just decreases when the battery is cold. A lot of people mostly park in a garage at home and at work so the car never really gets cold. Sometimes the idiots don't even take coats with them.

A different battery technology might help-- but Li ion and NiMH both are essentially useless at a relatively balmy -20'C (~0'F).

Best regards, Spehro Pefhany

The country solution to the cold battery start is to throw a hessian wheat bag over the battery.

Andrew

On Nov 1, 5:01 am, Al wrote: ...

I've been told that putting a wrench across the cold battery terminals for a minute or two warms it up, but I've never tried it. I've used a Coleman stove (naptha) on a tobaggan slid under the car engine, that worked ok, takes about 1/2 hour at -30F. Others tell me hot coals from the fireplace work about the same way. Ken

The "12V battery" in a car is actually closer to 14V under charge.

In exactly the same proportions, a "36V battery" in a car is closer to

Just as 13.6/13.8/14 is a nominal design point for many current automobile electricals, the 42V is a nominal design point for the next- generation electricals.

The wide range of conditions and especially load dump conditions that occur in a car are very important to solid-state electronics... less important to things like filament light bulbs. But I bet by the time

A "12V battery" trying to start a cold engine on a cold morning in Duluth can have substantially less than 12V on its terminals while trying to turn over the engine :-(.

Tim.

I don't know about the battery, but that will certainly warm up the wrench. :-)

My brother used to do this with a pie tin of charcoal. :-)

Cheers! Rich

Well the theory is that the current flow warms up the battery because of it's internal resistance, I^2 R, the wrench itself is supposed to be a near 0 ohm connector. Ken

Yeah, another little trick is to put a tarp over the car to keep the breeze from blowing away the heat. It's a PITA, but better than being stranded, and whinning about it. LOL, I doubt the procedure is UL approved. Ken

I guess you'd have to work out where most of the voltage drop would occur to see where the power is going. Anyone care to measure the resistance of, say, a 12" adjustable wrench?

Best regards, Spehro Pefhany

Yeah, Ken, I understood instantly what was supposed to happen and, in theory, I'm sure it would. But that's a drastic measure. Probably not good for the battery, for the wrench, or for the poor sod who's standing there holding that wrench.

I don't think I'd want to be the first in my neighborhood to give this a try. It sounds really dangerous to me.

Tom

Yep, that situation would call for an extreme measure. And the battery's internal resistance, no matter how low, surely must be greater than the wrench, so I'm sure that would heat up the battery.

Years ago, when I was working in the telephone industry, one of our power guys was doing preventive maintenance on a 48 volt bank. 2100 amp hour, or something like that.

His wrench slipped and instantly welded itself to the bus bar. Fortunately, he wasn't alone. His partner grabbed a chunk of pipe and whanged that wrench off the bus bar before the whole plant went up with a bang. (Some really quick thinking there.)

I wasn't witness to the incident, but afterwards I saw the remains of the wrench.

I alway had respect for the battery and the raw 12 volt wiring when I was working on my cars, but I think after that incident, I think I developed a fear of high current / low resistance object combinations!

-----

On the original topic... back in the sixties, I was working on a project to develop a reference 3-phase motor design for future automotive applications on the next-generation electrical systems.

Oddly enough, we were designing for a 42 volt system!

It's amazing that after all these years, with all the changes in technology, that very same number has resurfaced.

Best,

Tom