I use a lot of cordless tools on a dailey basis 18v and 24v. most sit out in the cold trailer overnite , I know for a fact that the batteries run at a less rpm when cold ,and they dont charge untill they warm up. (the charger just blinks in a no charge mode) To day i drove several errands and i seem to get better milage the longer i drove and noticed more help from the batts once everything was warmed up.Does anyone notice this with there hihy or other vehicles. Also do the batts weaken when the sit a few daysin cold weather ?...joe

most batteries' efficiency goes down with colder temperatures [higher internal resistance, maybe .... slower chemical reactions...], so i don't think it should be very surprising. even flashlights are dimmer, and anyone who's tried to start a conventional car at minus degrees knows that not only is the oil thicker, but the batter itself doesn't have the "oomph" that it does when it warms up.

at college one year, a friend of mine couldn't get his car started. he ended up with somthing like four other cars "jumpered" onto his at once, and his still wouldn't start. i drove over, we hooked my battery to his, and i said, "ok, now get in my car and give me a dollar for gas." we sat, warm as toast in my car, charging and warming his battery, for nearly half an hour, until my ammeter showed that his battery was finally getting full. he jumped out, cranked his engine, and it fired right up. he paid me the dollar [back in the days of much cheaper gas, of course... ]

ps. the electrical equivalent of a "dead battery" is a short circuit, as most EE's know. you can't start a car with a dead battery until it charges up, even a little. you're better off just taking some time to charge the dead battery first, and in the long run, it's nicer to the battery, too.

+af
Northwest Raleigh, NC, USA
'04 Silver opt.BC/9; 24,000+ miles so far
http://www.plusaf.com/prius/prius.htm
http://www.plusaf.com/coast/coast1.htm
My Prius without the trailer:

My Prius with the trailer:

I am in Omaha, and I have only dealt with a cold battery once or twice. The battery wasn't the problem, but the engine warming was. It takes the engine awhile to warm up, especially if you want to use the heater; this destroys mileage.

I have a buddy in Canada who has a HiHy, and his comes with a block heater. I'm trying to get the local dealership to get it for me, but they have no knowledge of the part, much less how to install it. I think this would help out tremendously in the colder months. Besides, I fell empty driving around without a plug hanging out from the front of my car!

if the engine has a freeze-plug you can get to, there ought to be a standard block-heater that can be pressed into the hole after that plug is removed. (closed course, professional drivers only; do not try this at home.)

in my '04 prius, it takes about one mile in 40-degree weather before heat comes out of the dash outlets. but even with the heater set to 72 degrees, the fans are held off until there's warm air available. only then does the "heater" go into action. i love that! i love smart cars! (no, not the Smart Car... that's ugly.)

+af
Northwest Raleigh, NC, USA
'04 Silver opt.BC/9; 24,000+ miles so far
http://www.plusaf.com/prius/prius.htm
http://www.plusaf.com/coast/coast1.htm
My Prius without the trailer:

My Prius with the trailer:

The Smart Car isn't ugly- it's cute! I saw several in Germany a few years ago that were painted in interesting ways, and it was some of the coolest urban art I've ever seen- people moving around in these little boxes that don't look quite like cars in outrageous patterns or with, for instance, a gigantic but realistic long-lashed green eye painted on each side. It could almost have been a mascara ad or something, but it was just art. It was surreal!

Oh, sorry, lost track of my subject. On the subject of cold weather and batteries, I was poking around on google scholar and found this article, which seems to be exactly on point:

http://www.aes.nu/publications/2002-01-1975.pdf

The conclusion is that internal core heating, using resistance heating, is by far the best way to warm a hybrid battery in cold weather. It's a 2002 article, so surely it's been implemented by now. Anyway, if you wanted to read about the scientific details, here is some background for you, although I suppose it may not be up-to-date, as it doesn't involve the most recent hybrids.

aw, shucks, ma'am... i thought you were just picking on me....

as for the article... LOL... they got a grant to do that research, right?

ok, so you've got a hybrid or electric vehicle, and they're worried about the electric battery's efficiency at cold temperatures? so they're going to slap 115 amps of 60-Hz AC into a 13-amp-hour battery to heat it up so it can be "more efficient"???

here are two free, non-US-government-subsidized "from this planet" solutions: 1) if the battery can start the gas engine, start the gas engine and let it slap a bunch of watts onto the battery by charging it! just might warm it up a tad... and 2) just as several folks here have worried about the warmup time of the internal combustion engine in their hybrids, slap a block-heater on the engine and then put an electric heating pad under the batteries, too! keep 'em both warm overnight, jump in, hit the go button, and drive away!

c'mon... haven't there been enough hybrid drivers who turn off the AC so it doesn't drain electric power from the hybrid system and lower their hypermileage?! and these guys are talking about kilowatts of power for 3-6 minutes just to heat the battery so it's more "efficient"???

ivory tower, imnhsho... swatting a fly with a nuclear cannon.
c'mon..... if the problem is slow warmup before the heater puts out, put an engine-block heater in. if it's battery efficiency... hey, wait a minute... has ANYONE here gotten into their hybrid in ANY kind of weather and NOT had the gas engine (ICE) start up immediately when needed? if no, batteries are not part of the problem.



(kinda touchy, isn't he, LeahB...)??

+af
Northwest Raleigh, NC, USA
'04 Silver opt.BC/9; 24,000+ miles so far
http://www.plusaf.com/prius/prius.htm
http://www.plusaf.com/coast/coast1.htm
My Prius without the trailer:

My Prius with the trailer:

From a total cost perspective, I find it hard to believe that pre-heating an engine with an engine-block heater to save a few minutes of ICE warm-up could be more cost-effective than just letting good ol' ICE do the job. Electricity piped into your home is usually generated from the burning of fossil fuels, so you either have less energy for the same cost or the same amount of energy for higher costs. Either way, you're gonna pay more. You also have energy lost through heat diffusion throughout the engine as the engine-block heater heats up the oil.

You gotta pay the price somewhere.

It's like some of these guys that hacked up their hybrids by adding a bunch more batteries and charging them up in their garage. They get 100+ mpg, but I sure like to see their electricity bill!

i agree on all that about the "net energy costs" as well as the "pluggable "hybrids"", but i didn't want to open that can of worms again. ...

+af
Northwest Raleigh, NC, USA
'04 Silver opt.BC/9; 24,000+ miles so far
http://www.plusaf.com/prius/prius.htm
http://www.plusaf.com/coast/coast1.htm
My Prius without the trailer:

My Prius with the trailer:

Certainly it seems that the researchers in the article weren't trying for a real-world solution. Most basic research just gives us more questions to answer. I mostly posted the article to respond to the first poster's question: YES, researchers agree that the cold affects hybrid batteries and decreases their efficiency (which differs a bit from the advice above of randomhelloguy) and the industry knew this years ago so it's probably reflected in existing or upcoming technology.

With respect to everyone who has suggestions for fixes, we probably don't want the ultimate solution to be- buy the car, then open it up and change around bits of it to jerry-rig some other configuration. We want the cars to be built in such a way as to let the energy be used as efficiently as possible in the first place, right? In terms of energy conservation, of course it's a tradeoff between using energy generated from the ICE or from the battery to achieve better initial temperatures and performance, but in cold conditions, those two sources are not equal. External plug-in power sources aside, the inside of the car ought to be arranged so that it's most efficient, and that means addressing known weaknesses like this temperature problem in future incarnations of the technology. I'm not proposing any solutions, because that is outside the scope of my knowledge, but I thought I'd share the link in case any of you found it informative.