Techniques to extend batteries in the cold

[scphantm]

Im running a 48v20ah ping. Problem is i live in Pennsylvania. This winter is very hard because i have to store and charge my bike in the mud room, where its only a small handful of degrees warmer outside. My range is down to about a third or quarter of what it normally is. Now i understand why, and i accept it, but more importantly, i know the dangers of charging below 40 degrees, you can and will lithium plate either the cathode or anode (can't remember which one) thus destroying the battery. There's nothing i can do about this battery, I'm stuck with no practical way to change the circumstances till spring. But if the battery survives till spring, I will likely replace it to get my range back.

The question is, are there any chemistry's out there yet that can withstand the cold?

I do plan on building a new battery box that will allow me to detach the pack and bring it inside to warm before charging, the problem is im on location for my job and my workshop is 4 hours away with no practical means to get the bike back there. Any of you have a creative solution for this problem?

 

[friendly1uk]

I'm not sure what lifepo4 ping use, but there are versions for low temperature.
Are you sure a 75% loss is expected? I use rc lipo and losses are nothing like that.
Can't you warm the batteries?

 

[kokopelli314]

To keep the cold from sagging my 60v and 48v Ping packs, I purchased 2 small AC electric heating pads and wrapped the batteries using Velcro strips that stick to the cloth wrap. When the packs start out cold, they can warm considerably under load but will continue to sag during discharge. When pre warmed the sag is much less and remains normal throughout the discharge cycle. Heating pads cost $20 each on sale. You could get used for much cheaper.

 

[amberwolf]

1--Insulate your battery box, and add a couple of thermometers with a sensor on a wire so you cna have the displays outside the battery box or even off the bike.

2--Add either battery warmers, available in your area for car batteries, or use small reptile habitat warming pads, available at reptile-carrying pet stores (petco, petsmart, etc) or online. These will run off the same ac plug your charger does.

3--instead of adding a battery warmer, get an electric blanket and a couple of thick fluffy comforters, and put the electric blanket over the whole bike, then the comforters over that. Plug in and set to whatever keeps the bike and battery at room temperature.

In either 2 or 3, just wait until the battery is at room temperature before you start the charging process, to avoid the potential issues with charging it cold, and leave the heating on to keep it at that temperature until you actually leave with the bike.


It doens't matter what chemistry you use, the technique will work fine.

 

[LockH]

Odd... Nobuddy here has mentioned yet a heater watt starts at 98.6 degrees Fahrenheit. Ya don't mention where your batt pack is mounted, but try taking a passenger? Ya know, ladies are good for cuddling in the cold, but have other uses too? Works just as well for guy pals? Just a thought... Heater operates on any food. Beer works too.

 

[silentflight]

I use a long cable to my headlight and keep the 3S3P 18650 LiMn pack in an inner chest pocket of my jacket. Extends the high power setting HID light time to LVC from 1 to 4 hours at 0 degrees. I also wear my CamelBak and its tubing inside my jacket. Everyone is happy, I like the light on the snow, the Niterider HID is finally kept cool in -20 headwind chill and the battery drifts along in 72 degree comfort.

Not likely to be a useful strategy for a 500 watt-hour pack!

My A123s perform better in the severe cold than my LiMn.

It seems like the higher C rating batteries would perform better when the cold slows down the chemical reactions.

 

[dogman dan]

Not true for lico IMO. My RC packs, when they get below 35F, they sag like hell and lose capacity just like the ping. I haven't tried the nanos, so I can't say about them. It's quite possible that within a certain chemistry, better higher quality cells will sag less in cold. The cheaper 20c lico sags when cold for sure. The lico seems to do better at 50f though, than the ping. I found ping performance dropped noticeably if below 80F.

For sure, you gotta heat the pack. Either build a reptile heater into the box, or carry a heat pad to wrap around it. Insulate too, even if it looks funky to ride around with a homemade tea cozy on the bike.

A heat pad from the drugstore will work. Balloonists use them on the propane tanks for cold weather flying. With insulation, the tanks will stay at 60-80F even when it's 5F out there, with the basket sitting exposed in the pickup truck bed. But they won't overheat either. Figure out what setting to use, by putting a remote thermometer in your battery box. Get that in the auto accessories section of Walmart or whatever, for ten bucks.

This problem is one of the reasons why I ALWAYS build batteries so they can easily be removed from the bike.

I'd just start working on modifying that box today.

 

[scphantm]

great ideas everyone, thanks. I was looking at the Electric Rider removable battery boxes and like them a lot. i just have to work out how to mount rails to a mundo frame, which shouldn't be horribly difficult. just weld up some pencil steel and bolt it on.

ill give this stuff a shot. Thanks

 

[dogman dan]

For rear rack carry, I've just bolted on a toolbox. It's lockable, sort of, and easy to lift the battery out to charge inside when it's really cold.

As part of the inner, protective box I always do for pouch packs, I add a nice carry handle to make toting the battery inside easy.

I'm planning some camping on the bike next week. Lows will be only in the high 20's F. But what to do? I"ll wake up, and my batteries will be close to freezing. My main battery will be in an insulated bag. The additional batteries will get some more insulation inside their saddlebags. Best I can do, is insulate so that when the battery does warm itself discharging, it will keep the warmth.

Likely, I won't start riding again in the AM, till it's 40F. But the batteries will tend to stay cold all morning. Lots of thermal mass once they get cold. I could sleep with one of the batteries in my bed, like you do to keep your water liquid. But sleeping with a big pile of cheap lico is not such a great idea.

If crazy cold, I could drop a pack in a ziplock, and dip it in hot water. I won't be camping in that kind of weather. I'm eyeballing a three day period of highs nearly 60F.

 

[melodious]

Likely, I won't start riding again in the AM, till it's 40F. But the batteries will tend to stay cold all morning. Lots of thermal mass once they get cold. I could sleep with one of the batteries in my bed, like you do to keep your water liquid. But sleeping with a big pile of cheap lico is not such a great idea.

I didn't think discharging a cold battery was as big a taboo as charging a cold battery

I thought a cold battery just gave a voltage sag & capacity loss which would spring back with rising temperatures

 

[melodious]

Was going to research more so I could answer my own questions and found some bits from the ohso popular battery university website.

The performance of all battery chemistries drops drastically at low temperatures. At –20°C (–4°F) most nickel-, lead- and lithium-based batteries stop functioning. Although NiCd can go down to –40°C (-40°F), the permissible discharge is only 0.2C (5-hour rate). Specially built Li- ion brings the operating temperature down to –40°C, but only on discharge and at a reduced discharge. With lead acid we have the danger of the electrolyte freezing, which can crack the enclosure. Lead acid freezes more easily with a low charge when the specific gravity of the electrolyte is more like water.

Some paragraphs say decreasing the amount of current you draw on arctic days is one way to prevent damage.

On the other side of the coin, in hot conditions (i.e. summer):

Batteries achieve optimum service life if used at 20°C (68°F) or slightly below, and nickel-based chemistries degrade rapidly when cycled at high ambient temperatures. If, for example, a battery operates at 30°C (86°F) instead of a more moderate room temperature, the cycle life is reduced by 20 percent. At 40°C (104°F), the loss jumps to a whopping 40 percent, and if charged and discharged at 45°C (113°F), the cycle life is only half of what can be expected if used at 20°C (68°F).

Not completely sold here as the info is rather dated compared to today's tech. Some places are well suited for lithium because they stay in the temperature sweet spot of 70 degrees F. San Francisco is one such place that stands out because of the temps and topography are well suited for such stuff. Just get rid of the lingering salty marine layer and your golden :lol: .

Anyways, this thread is making me think twice when the temp get's below roundabout 10 degrees F of leaving my batteries exposed for a prolonged period of time. They are semi insulated, and start the day off in room temps, so they get a buffer of warmth when I stop using them and place them in storage. How long this buffer lasts on arctic days like the ones we will get the next day or two is the question. Then again, we only get 1-3 days at the most of these temp events then the environment warms to mostly usable days. I think for where I am in the world, I'm over thinking this...

 

[friendly1uk]

Cooler bags might be of use.

I'm thinking cooler box with a 12v lamp and fan as a heater. Using a 12v wall thermostat to control it.
I would put my 25w soldering iron in one to estimate it's abilities. I reckon it would cook.


Edit: I found some interesting information about packaging used to deliver cold food: http://onlinelibrary.wiley.com/doi/10.1002/pts.773/abstract
It says

Thermalconductivity (W/m"C)

Glass 0.780
Polyethylene(PE) foam 0.076
Wood(dry) 0.120
Polyurethane(PU) foam 0.030
EPS 0.046
Air 0.026
Vacuum 0
Cardboard/corrugated 0.078


Polyurethane foam is the expanding stuff in a can that is often fire retardant. Stuff often used in modeling.

I imagine you could make a close fitting cardboard box for the pack. Then take the pack out. Place your now empty box inside another box, which is an inch bigger in all directions. Then fill the inch gap with foam. Once dry, slice in half, revealing a pack sized cavity.
I wouldn't heat anything without a thermostat, so such a clam-shell would be for housing an already warm pack for short durations.

I'm pretty sure cooler boxes are the same stuff. Just not cool.

edit: http://www.ebay.co.uk/itm/WAECO-TROPICOOL-TB15G-THERMOELECTIC-COOLBOX-15-LITRE-12V-ELECTRIC-CAR-VAN-FRIDGE/161085721459?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D286%26meid%3D3930428011361725058%26pid%3D100005%26prg%3D1048%26rk%3D3%26rkt%3D5%26sd%3D171129620520%26
That looks quite acceptable. The heat pump will just freeze up though at some point. Nice overpriced box though.

A mini fridge would do me.

 

[dogman dan]

Re back a few posts. No, discharging a cold battery is not taboo, except for the part where you may be riding in a place with 70 mile gaps between towns. So loss of capacity could be a big problem then. Out here in the west, 50 miles between towns is typical. 70 miles not unusual.

Best thing to put inside an insulated box or bag is the reptile heaters. They max out at about 80-90F. Safe for snakes is safe for plastic. They come in sizes just about the same as a bike battery, and are durable enough to put under the battery in the box.

Alternatively, the old school hot water bottle could do fine. Put it to bed with some hot water, and find it warmer in the am.

 

[LockH]

Alternatively, the old school hot water bottle could do fine. Put it to bed with some hot water, and find it warmer in the am.

HA HA. He said it, not me. (Used the "hot water bottle" euphemism for "gal pal". )

 

[r3volved]

Dogman, do you know of any good heating pads running off 12v?

 

[friendly1uk]

Here is a $15 12v thermostat rated at 10 Amps http://www.ebay.co.uk/itm/Fan-Heater-Car-Temperature-Controller-Thermostat-Regulator-10A-12V-20C-to-90C-/281083734883?pt=UK_Computing_Other_Computing_Networking&hash=item4171e56b63
That could use a number of heating element solutions. Pads, Lamps, Power resistors. Keeping at a nice 20c as reptile temps are not good for our battery life. Perhaps giving a 25% reduction.

tbh, I have not seen a reptile pad that is thermostatic. They track room temperature so need sizing correctly. We have to many external influences to get that right. I'm sure a thermostatic one is out there somewhere though.

Edit: I think the best I could do is this cooler box http://www.ebay.co.uk/itm/New-Holiday-Land-11-27-48-76-L-Litre-Large-Size-Cooler-Cool-Box-3x-Times-Longer-/121156984674?pt=UK_SportingGoods_Camping_Accessories&var=&hash=item1c3584df62
Pop in a lamp as a heater because it is very easy to change wattage, then keep some air gap around the cells. Using a fan to evenly distribute the heat.
I fear hot spots would occur with most other options. This could have effects on pack balance, tripping the bms or having hot cells driving current through colder one's. causing other effects I can't really get the information to back up.

 

[dogman dan]

I don't know any 12v heaters specifically, but likely the place to find one is in the clothing dept. Hunting socks, that sort of thing.

I was mostly thinking in terms of the original posters problem, cold porch the bike spends the night in. Gotta be really cold last few days. Anyway, I was thinking plug into the wall AC stuff. It might work on 12v, but weak compared to 110v.

By hot water bottle, I meant exactly that, If there was room in the battery box, you could have a bottle in there that you fill with hot water in the PM. Thus, heating the presumably now insulated battery enclosure.

 

[r3volved]

Ya that's my problem too
Outside locked up at work all day at -25.

I was thinking 3mm neoprene battery cover with heat pad or carbon tape woven in...a 9v would probably be plenty for just initial heat.

I know my buddy uses the large rolls and cuts into strips for his snakes. He has to run everything through a rheostat.

I saw a few postings elsewhere that mention cutting a 120v roll into 10ths and the temp sensors should work at 12v.

 

[Punx0r]

Low tech but, how about some microwavable heat packs?

Drape over the battery on the bike and cover with a heavy blanket. You could rewarm them at lunchtime. Could work if you don't have AC power outside to plug into.

In fact, same thing but with dogman's suggestion of hotwater bottles would probably be better. Water has high specific heat capacity so will store a lot of heat.

Still, -25*C is freaking cold. I admire anyone who tries to cycle in that other than once for a dare...

 

[friendly1uk]

It seems cooler boxes around 20L can hold a temperature 20-25c above atmospheric temperature with a power input of between 48w and 60w with 40w being the most common power consumption. My guess, a 40w peltier heat pump and a couple of fans.

My little 11L box from before has less surface area than a 20L box. I expect 30w might be needed for every 20c you want to lift box temperature.

Looking at the -51c thread, his box would want maybe 100w to achieve 10c inside it. The batteries and bms would lift that doing work, so a stat is my only answer to temperature regulation still. Say that bike stands in the cold for 9 hours, that is like 1Kwh

Perhaps someone can crunch some more sensible numbers.

More insulation could be the next answer. That paper I posted was using about 30mm of it, while a cooler-box is a beach toy with maybe half that. I believe 20mm more insulation would half the power requirement. That 11L box is like a bucket, there is a lot of room in there.

Commercially, I would need a bag round the batteries as a vapour seal, running a vent from this to the outside world. A bag lets heat pass freely, so shouldn't be an issue.

edit: That 1Kwh is 20Ah of 48v. If insulation could be doubled to make the power requirement 10Ah then that would be half a 20Ah pack to take sure the 10Ah left was all available. We have gained capacity and made the batteries survive. It's a cost effective project. Even at -51c

Edit2: Perhaps them 9 hours could be better spent. Just heating the pack for an hour, at 50w to cover losses, and another 100w to warm the contents. It's getting harder to calculate.

 

[Punx0r]

For comparison, the specific heat capacity of water is 4.18 J/g/K

So it holds 4180J (watt-seconds) per kg (approx 1 litre or 1 quart) per 1*C it's heated.

If it starts at 90*C in the bottle it will put out 4180/3600 * 90 = 105Wh by the time it reaches freezing point. After that it will still be "warm" compared to -25*C ambient.

From memory a hot water bottle holds about 1.5 litres.

 

[friendly1uk]

4kg of battery at -25 in a ready warmed cooler box, along with 1.5kg of water at 90c, might be around ideal charging temperature in 90mins. If you started charging at 60 mins with the charger in the box as another heat source, that might be just the ticket.

A beer fridge or small freezer would make good boxes too.


Edit: I would still put a lamp in there myself. It is what I have around. If you were doing this every day it would be much easier.

 

[r3volved]

Low tech but, how about some microwavable heat packs?

Drape over the battery on the bike and cover with a heavy blanket. You could rewarm them at lunchtime. Could work if you don't have AC power outside to plug into.

In fact, same thing but with dogman's suggestion of hotwater bottles would probably be better. Water has high specific heat capacity so will store a lot of heat.

Still, -25*C is freaking cold. I admire anyone who tries to cycle in that other than once for a dare...

Lol
The only think I'm not equipped for right now is transportation in cold and rain

Being outside isn't the problem for me. I'm more equipped for the cold this year, than ever before. I still walk 45 min at lunch to get my coffee and smoke

I need to build a sled for my dog to pull

 

[GiantEV]

I was keeping my battery pack in the garage up until a couple of months ago, when the temps got into the low teens here. Since then I have been keeping the pack in the house by the front door on the tiled floor, away from anything flammable. I plan to get some foam and create an insulated container that keeps the battery pack off the cold garage floor and retains the heat from the lamp that I will put in the box to keep the batteries warm. A friend of mine raises chickens and uses the lamp to keep them warm, so I figure if it's good enough for his chickens, it's good enough for my lipos.

By the way, I am running the nanotech and have been using them since last spring. They weren't too bad when it got down to the 30's F, but I go for evening rides and one night it was 15F. I kept the batteries indoors before I used them, and my battery case is insulated with foam, but I still noticed that the batteries had between a 30-50% drop in range. The sag was not enough to be noticeable in my riding, but my range was definitely decreased. I can definitely see a huge benefit from using some of the advice in this thread and others like it on this forum that I've read.