Do cold temps affect batteries?
 

As we all know, low temperatures are generally bad for batteries. Has anybody else noticed?
Today, I did a short ride @ 27degF. My headlight started to get drained @ 15 miles, where it usually last almost 25 to get drained.

You are answering your own question. Nothing to add except Yes.

One more, yes, if they are lithium-ion batteries, especially. Lithium is affected by cold temperature.

Depending on the type of batteries, yes there are limit of various sorts. Some you shouldn't charge until they get to a certain temperature if you were operating them in colder temps. And many batteries will deplete quicker as the temperatures go down.

Find the manual for your lights and anything else that uses a battery. In the spec's they probably list those temperatures.

Yes. And dynamo lights are not affected by temperature, as far as I have noticed.

Most people, when they try dynamo lights, ask themselves why they didn't try them sooner.

Yep.
cold causes battery life shrinkage.

I have a Cygolite Hotshot Pro tail light. I get three 20-miles rides out of one charge when it is warm, but only two in the cold.

Mark

You should not charge Li Ion batteries below freezing temperature. But I suspect your light warmed up pretty fast when you got it inside, so it was probably warm enough to charge once you started charging it.

I am surprised the light had roughly 60 percent performance (15/25 miles) at below freezing. I would have expected less than 50 percent.

If you have your phone on during that time and if your phone is not kept warm, if it was running apps and had the screen on, that battery drains fast too.

You can find this info from the manufacturer's web sites. For instance, on the data sheet for the Panasonic 18650 lithium ion battery, you can see that the capacity is reduced at -10C relative to room temperature...


https://cimg0.ibsrv.net/gimg/bikefor...302eb2ea46.jpg

Also note that the terminal voltage decreases with temperature too. If the light cuts off at a certain battery temperature, it will cut off quite a bit earlier in cold temperatures.

Steve in Peoria

I have integrated dynamo, lights, and lithium batteries integrated systems that run year-round, one of them a decade presumably now. They do fine, and that decade-old powers a horn that draws far more current than lights.

Maybe your batteries are just beating the odds. Or maybe they have an internal temperature probe that blocks them from charging when it is sub freezing. I am not a battery engineer, all I can do is relay what I have heard.

I called Peter White a few years back and asked if there was a problem using my B&M Luxos U (now discontinued) headlamp in sub freezing temperatures. If you are not aware, that dyno powered headlight has a pair of built in Li Ion batteries. He said he had never heard that about Li Ion batteries and sub freezing temperatures, so he suggested I would have no problem. But I chose to unplug my dynohub whenever I rode that bike in subfreezing temperatures anyway.

The battery manufacturers are pretty clear and consistent about how they want their lithium-ion batteries treated, and they publish their recommendations on their web sites. This is what Panasonic said when I last checked:


https://cimg9.ibsrv.net/gimg/bikefor...282dd9ceb5.jpg

For this discussion, the key points are that you shouldn't charge them below 10 degrees C, and shouldn't discharge them below -10C.
-10C is 14 degrees F, which is as cold as most(?) cyclists will ride, so it's probably not a big impediment.

For things like standlights, which will be getting charged when the bike is ridden in the cold, it's probably best to use a super capacitor instead of a lithium-ion battery. Interestingly, NiCad batteries are much more tolerant of charging in very cold temperatures, which is what I use in my home-built dynamo lights. Nicads are pretty nearly impossible to buy now, so I expect to switch to supercaps for any future work.

Steve in Peoria (where is it is currently below 0F)

Obviously, there are lithium batteries for cars, and these must tolerate low temperatures, so the technology is there. If you Google around, you can find low-T versions in 18650 such as here.

do they publish any sort of datasheet with performance data or charts?

Steve in Peoria

There are many more offers from the manufacturers than retailers, and it is easier to find any charts with the former, such as here. However, there are now new lithium titanate (LTO) batteries, with specs here, and available cheaply at AliExpress. I think I will swap my current batteries for these in the system of my own construction.

If you are knowledgeable on this sort of thing, do you have any thoughts on NiMH batteries for cold weather?

I use a lot of those for a variety of things. But rarely use them below freezing.

My niece bought a Tesla a few years ago, just before covid. My niece's hubby was telling me that they get very poor "mileage" in winter because there is an internal battery heater that keeps the battery warm in cold weather. He is talking about Portland OR to put "cold" weather into perspective. When I have been there in winter, it was in the 20s and 30s (F) for temps.

I have read that Tesla is switching to a heat pump instead of battery heaters, as it is more energy efficient for maintaining battery temperatures.

But, I do not have an EV, so I can't say any more on the topic. More than half of my miles are long distance trips of several hundred miles, the charging networks are not well enough established for me to consider an EV yet.

Here's the datasheet for the Panasonic AA NiMH.
and one for the Energizer AA NiMH.

For my use in standlights, NiMH doesn't look like a good choice because the manufacturers only provide specs for charging at or above 0C. They are a bit more particular than nicads in terms of continuous charging, but that's not hard to accommodate.

As for discharge characteristics, Panasonic does have specs for temperatures down to -10C. No graphs or info on how much the capacity is reduced, though.
Energizer only specs discharge down to 0C, so I don't know if they are being conservative or if their batteries are less suited for cold than Panasonic. The datasheet does include the admonition "NOTE: Operating at extreme temperatures will significantly impact battery cycle life".

Energizer does provide more generalized info on NiMH batteries in their NiMH Handbook.

In general, all batteries operate by the use of chemical reactions to generate electron flow. Chemical reactions occur slower in cold temperatures than in warm, so it's to be expected that performance will drop when things cool off. Super capacitors offer better performance in the cold (although I haven't checked the datasheet...), but have to be much, much larger to provide an equivalent amount of energy.

Steve in Peoria

Thanks.

FYI - I prefer rechargeable batteries, thus I am not considering buying Lithium AA or AAA batteries. But, my camera owners manual specifically says for cold weather use Lithium AA batteries. And suggests having a spare set that is in a warm pocket. So, if I needed to have working batteries in very cold weather, I would try those out. My camera uses Li Ion batteries, but has an optional adapter to use AA batteries.

I switched to dyno on my fatbike after I had 2 hotshot taillights die on my 7 mile commute. It was 5F though.
It's possible I left one on the bike all day, don't recall.

I used to have a Canon point & shoot camera that used two AAs. When I used nimh AA's, it would quickly shut down in cold weather. My newer Canon Powershot p&s uses a proprietary lithium battery and it seems to tolerate cold temperatures quite well. A typical scenario is when I'm out on XC skis....

https://live.staticflickr.com/65535/...38c693_c_d.jpg

I'm not sure if the lithium performs better than NiMH, or if the difference is due to the lithium having a nominal voltage of 3.7V versus the nominal 2.4V of the two AA NiMH of my earlier Canon. I suspect both used similar technology circuitry that had similar minimum voltage requirements.

I do like the idea of having a AA adapter for a camera! It would be nice to have a cheap alternate power source when needed. ...although... I imagine that the adapter costs about as much as a spare lithium battery?

Steve in Peoria

Rechargeable Lithium (Li Ion) cells don't really like cold weather. Ask any EV owner living in a cold climate.

Lithium "Primary" cells (non-rechargeable) are a great option in cold weather.

All the best

Barry

It was a night-to-day change in winter for my bike power circuit when I swapped 5 NiMH batteries for 2 LiPo, I think, and this was not due to the nominal voltage as lights were operating well enough even when undervolted by 1V or so. I was worried I would blow my circuitry at the nominal 7.4V as it was a drop-in swap. However, all went well. With NiMH, the winter standlight operation was worse than a capacitor backup. With LiPo I can go on for hours in winter w/o the dynamo and honk w/o lights dimming. I chose LiPo over Li-ion due to its flatter discharge curve in my memory.

Count me as one of those people. I think it was 2016 or so when I got my first Dynamo but I first looked at them back in 2011-2012 and said "nah too heavy, too this, too that". Silly me. Now with the Supernova M99 Pro DY light I have essentially a car headlight with high beam ability powered by my front wheel moving from my pedaling is there anything better? Granted the light isn't installed yet but soon will be

My spouse bought a 2023 Tesla in August of 2023. The cabin heater is a heat pump. The car heats and cools the battery automatically, and it will preheat the battery before we drive if we tell it we are going to drive it. I don't know if it uses the heat pump to warm the battery. It also cools or warms the battery when we charge, depending on the conditions.

So with extra machinery and software, you can use these batteries in cold weather, but all of that comes at a cost. It's not a cost that makes sense for a bicycle light.