In cold weather, the power of the battery drops, and sometimes you have to to use jumper cables to get the car started.
It’s a classic horrible moment–You’re late for work, it’s freezing cold, and you need a few extra amps.
So why do you have to call a neighbor or stand helplessly in the parking lot looking for somebody willing to let you hook your jumper cables onto his car?
Why can’t they make a car with two batteries, sitting side by side under the hood? (that’s a bonnet for you linguistically challenged Brits)
I’m guessing that the batteries could be wired together, both in series and parallel, and a convenient switch next to the radio could be used to get the extra amps when you need them. Or maybe even a very simple computer circuit could measure the strength of the current, and when necessary, automatically open a switch to draw some extra power from the second battery. I assume that the alternater generates enough power to re-charge both batteries once the car gets moving .
I am totally, completely and absolutely ignorant of how electricity works , but from what I remember of my junior high school science class 30 years ago, It seems like this idea would work. It could be a good selling point for cars in cold climates; But I assume that if it was workable, then somebody would have marketed it already.
So why am I wrong?
(Not that I’m worried now–I havent lived in a snowy climate for years, and have sworn that I will never scrape ice from my windshield again. God made snow for ski vacations, not for driving to work!)
I think Rolls-Royce used to design cars with two batteries. One solely for turning over the engine, the other for radio, lights etc I don’t know if the new BMW RR has this feature tho.
There is really no reason aside from cost and space for the second battery. It’s not uncommon in recreational vehicles and apparently on RRs as in Pushkin’s example.
The batteries would of course be wired in parallel, not series as that would add the voltage of the two batteries together. Of course it would be simpler and cheaper in the long run to just use a bigger battery with more cold cranking amps.
Is it possible, sure. Practical no. Here is Rick’s sure fire never fail method to make a million dollars in the car business. Save $1 dollar per car and build 1,000,000 of them. An extra battery, cables and your computer circuit would probably add say $50 to the cost of the car. Spending the extra $50 to build said car will not improve the salability of the car in most locations (why would a guy in LA want a second battery?), increase the weight of the car (lower fuel mileage) increase the cost of repair (gotta replace 2 batteries) and probably drive up the company’s warranty costs. One final problem is have you looked under the hood of a modern car lately? Just where are you going to put the extra battery? Real estate is getting real scarce.
So if we leave one battery out the car company saves 50/ car and now only has to build 20,000 cars to make a million
So why isnt it offered?( at least as an option, if not standard equipment.) Cost and space arent real problems–It wouldnt add much to the price of the car–maybe $50 or 100, and most cars have room under the hood. And it would be a good selling point in cold climates. I know I would have bought it, and lots of people would like the idea of “guaranteed” easy starts
Because most car batteries work just fine. If your battery is dying, it won’t be able to start your car in the cold, replace the battery.
For a while there were batteries offered that were actually two batteries in one, with a switch so you could use the backup if the primary failed. They never caught on and as far as I know are off the market now. The reason was increased complexity, higher cost, very little benefit. In extreme cold temps the smaller backup battery wouldn’t start the car, and 99.9% of the time it was never used.
You can buy heavy duty batteries for your car which will work better in cold situations. I have a friend who used to carry a marine battery in the back of his Subaru in very cold weather (freshly charged, of course) and had to occasionally give himself a jump start. But the real solution is to test your battery regularly and replace it with a new, good one before it fails.
When I lived in Anchorage, Alaska, I used an electric block heater in the engine of my car. I always kept it plugged in when the car was not in use, and the car never failed to start in the mornings on those long cold winter nights. It is a better solution to car starting than having two expensive batteries.
Yes, but how much did it cost you anually to run this heater? A quick Google tells me these units run between 600 and 1,000 watts. If electricity costs you 20 cents per kilowatt-hour and you have a 1 kW heater and you run it 12 hours a day, six months a year, it’ll cost you almost $450 a year to run it. You could buy a a few batteries for that.
True, but I lived in Military Quarters and cost was nil for me. I never even gave it a thought. I used to run it about 15 hours a day and on weekends perhaps 24 hours a day. And, in Alaska, more than 6 months of each year.
Er, pardon an ignorant question, but if the cold saps the ability of one battery to start the car, would not the cold sap the ability of a second battery in identical conditions as well?
Yes, but the theory is that the combined capacity of two cold batteries is often enough to make up for loss, at least enough to start the car. For example, if the temperature is such that each battery now has just half its original capacity, then two will just equal one good battery. In practice it’s more complex than this, but you get the idea.
Apparently, you have never been in the military. I gave 21 years of my life to the United States Air Force to help defend my country. So what is your problem?
I have none, and nor should you. The emoticon at the end of my post was meant to let people not to take my post seriously. There’s no need to get your knickers in a bunch.
Lots of people do this to their own vehicles (generally trucks, RVs or off-road vehicles). You can get kits with the cables, switches etc.
An advantage of this over one bigger battery is that you can disconnect one battery during normal operation, connecting it only often enogh to keep it charged up. Then you never have to worry about running the main battery down by leaving the lights or radio on, using an electric winch, etc.
most auto supply stores sell gadgets like this: a portable battery that you can charge from a wall outlet and carry in your car if you think you might need it. some brands are better made than others, but a good one will do everything a second battery would do without the drawbacks.
