Batteries vs Cold ☃

[DrkAngel]

All forms of batteries seemed to be adversely affected by Cold! ☃

Very noticeable, especially on my various ebikes, was that, cold greatly reduced the rate of output, as well as the capacity of various types of batteries.

This degradation is common to both Li-ion, as well as SLA batteries. Based on complaints, from others, LiFePO4, Li-po, Nimh etc. seem to suffer similarly.

The "rate of output" is often designated as the "C" rating. For example a 30ah battery, capable of a 30 amp output, would have a rating of 1C, a high performance RC car battery, (Li-po), might be a 5ah 20C rated, thus capable of a 100amp output, of course it would empty, very quickly!

Sub freezing temperature might cut the C rating, as well as the overall capacity by 50%. 0 degrees Fahrenheit degrades considerably more!

In my experience, most of this degradation is due to the battery temperature, though the motor and drivetrain also contribute, somewhat.

My recommendation is that the battery should be kept warm.

Easiest would be the use of a water heater blanket, to maintain ambient heat.

Stage 2 would be the application of a thermostatically controlled heat tape, such as is used to prevent pipes from freezing. While charging, the heat tape might not engage, but will maintain temperature after charge completes. It might even be efficient to self heat battery if left for prolonged period in the cold, several hours?

Caution! Some batteries require active ventilation, (mainly to prevent over heating), be sure not to cover fans, ventilation grills, etc!

[DrkAngel]

My main transports are EZip "Trailz" electric assist bikes. They come stock with 10AH SLA batteries, which are very poor, to begin with, but suffer mightily when cold, and forced to push through snow, or slush.
Actual usable output is merely 6AH, but when cold, possibly only 3ah. Unfortunately, when pushed through a cold, geared, brush motor, actual output power might be less than 2AH. (The AH rating of SLA batteries is typically determined by a slow drain, over a 20 hr period, with a more typical 1 hr drain, output is approximately only 60% of "rated".)

Why even bother?

I bought my first about 3 years ago, when gas passed $4/gallon.
A complete electric vehicle for less than $400, which almost covered my, run around town, "errand", gas cost, for that summer!

$348 w/shipping included, available, right now from Amazon.com and Walmart.com!

Of course I had to upgrade capability and capacity! Speed was increased from OEM 15mph to, variously, 20, 22, 24, and 27mph, (motor alone speed), using various methods. "Motor only" range was about 8 miles, increased to, 40 miles @ 16mph, (30 miles @ 20 mph). Of course I upgraded pedal assist capability to allow much better range, and higher speed.

However, I digress.
My main point is that I built Li-ion battery packs, from used notebook batteries! EZip OEM batteries are 24v SLA batteries with a usable 6AH. I built 25.9v 31.2AH packs, as well as 37v 20.8AH. Approximately 5X the usable output, at about 60% of the weight. For the Winter, I place the packs in insulated, fabric "lunch bags" with cardboard inserts, allowing for insertion into the OEM battery racks. The bottom power contacts were impractical, so I converted to AC power cord connectors. So, battery is kept warm, and dry, by insulated bag. Removal to a warm location is a simple, unplug and lift, by built in lunch bag, handle. Bag is secured by a cable lock that happened to fit perfectly around rear rack, and over top of pack.

Yes, I do ride in Winter! Studded tires are essential. Visibility and proper attire, are important factors in being, "safe & warm".

This Winters project, will be, a Schwinn 3-wheeler conversion, to electric assist. Canopy and windshield are definite possibilities.

I am making progress towards an eCar!

Stories of my upgrades and adventures will be posted in the ebike section.

I will post notification here, when completed, (I have many pictures and articles posted on other sites, that use an incompatible format, proper translation might take some little work).

EZIP ENGINEERING 101

[Ypedal]

http://www.youtube.com/watch?v=PzoyfFuwDKE

[ET4041]

I ride my bike everyday to work so far this winter. It's been around -5C to -10C with some days down to -14C here in Toronto. This is before the wind chill. I just take the battery inside, let it sit for 1/2 hour to warm up, then charge. On the bike, the battery is in a Topeak rack bag with lots of padding so there is some insulation. My ride each way to work is about 18 km which takes about 30-40 minutes. The voltage is a little lower than in summer (maybe .5 to 1 volts lower on my 10 Ah, 50V Lifepo4 pack), and there might be slightly less capacity although I don't know for sure because I don't use more than 80% of capacity.

My colleagues probably think I am crazy for bicycling all winter, but it is quite addictive. Going through the snow just makes it more fun - especially the fresh powdery stuff. It would be a tough slog without my trusty hub motor - a BMC600W-T from Ilia. I haven't got any studded tires yet, but I have one on order (for the front). The biggest problem is probably the rusting of the chain and drivetrain as the bike cage at work is in a heated space.

[Lock]

Check out the specs on the Toshiba SCiB lithium-titanate cells:
http://www.toshiba.com/ind/data/tag_fil ... e_5383.pdf

80% capacity at minus 30 Celsius... not too shabby. Honda is using these in their new EV-neo scooter:
http://world.honda.com/news/2010/2101216EV-neo/

tks
LocK

[DrkAngel]

Link to some of my early EZip Reports:
https://endless-sphere.com/forums/v ... =3&t=23676

EZIP ENGINEERING 101

[ev_nred]

why not make some type of heater form the batteries or charge at low current while u park to keep them got

[wojtek]

Check out the specs on the Toshiba SCiB lithium-titanate cells:
http://www.toshiba.com/ind/data/tag_fil ... e_5383.pdf

80% capacity at minus 30 Celsius... not too shabby. Honda is using these in their new EV-neo scooter:
http://world.honda.com/news/2010/2101216EV-neo/

tks
LocK

the cell specs look impressive! 7000 cycles at speed charging above all!!!

But they are quite heavy comparing to Lipos.. 2.4V 4.2ah at 155g. That would make a 48v21ah cell weight 15.5kg!

[ev_nred]

I have an idea (this migth get ugly lol ) have an of u every seen one of those old heated blankets that plug in to the wall? well why not make a mini version of that and dump it in to a battery bock have a 3s battery connect to an inverter to provide the current for the 'blanket'
is this a stupid idea? Could it work?
thanks,
Jacob R

[Ypedal]

https://endless-sphere.com/forums/vi ... 93&start=0

[trappermike]

There's a good thread on this subject under Battery Technology.
Ni-Cd batteries survive cold temps. well without heat but not much appeal to mast folks.

[gge5]

From personal experience, cold cells definitely affect energy output. Normally my 24 x 40Ah Thundersky pack can get my motorcycle up above 60MPH, but last week it was 39 Fahrenheit and I couldn't push it faster than 47MPH. I was concerned it might be the new controller I put in last month, but yesterday it was sunny and it reached full speed.

[DrkAngel]

Over the Winter I have carefully measured voltages at lower temperatures, it seems the capacity is not affected so much as the "C" rating, the output "rate". Under drain, the battery seems empty, but after slight delay battery regains substantial voltage.

Li-ion 18650 notebook scavenged cells will sustain, a prolonged, 1C output at 70*, at 30* the output is closer to 1/2 C. Exceeding the "sustainable output" produces excess drain. This excess drain produces a voltage drop, which is perceived as a drained battery condition.

1C = drain rate equal to ah capacity (2600mah capable of 2.6amp sustained output)
* = degrees F

[Lock]

...capacity is not effected so much as the "C" rating...

Important distinction. Tks DK!

[DrkAngel]

Cold is back, I could tell, because I set my bike outside, this morning ...
Made a run to the post office a few hours later, and my EZip battery leds were dipping into the red?
On a fresh charge!
Usually I can cruise at 20 mph for 20 miles before I see any red, (Summer).
These LiPo hold up to the cold, (20F), worse than, my standard 18650 Li-ion packs!

Continuing my 2010 thread.
Stay tuned for some great items and clever ideas!

Found some nice 12V pack warmers!!!

[neptronix]

You've just discovered what the rest of the forum already knows.

Do you ever read this forum on your own, or do you pretend we don't exist until it's time to post?

[TylerDurden]

...do you pretend we don't exist until it's time to post?

That's a safe bet.

[DrkAngel]

Updating-continuing my 2010 thread!

Cold is back, I could tell, because I set my bike outside, this morning ...
Made a run to the post office a few hours later, and my EZip battery leds were dipping into the red?
On a fresh charge!
Usually I can cruise at 20 mph for 20 miles before I see any red, (Summer).
These LiPo hold up to the cold, (20F), worse than, my standard 18650 Li-ion packs!

As I mentioned previously, capacity is not as affected, as much as the C rate capability.
Voltage test, after 2 mile ride, was still near full ...

I will be reverting to my standard insulated lunch bags, might even experiment with pre-heating, or auxiliary pack heater.
Auxiliary pack heater, as opposed to self powered, from pack ... as a measurable drain vs performance increase.

Will probably handle bar mount my 6pack "Cool Cell" and give it a proper break-in, (37V 26ah - .96kWh).
Also tempted to drop in a couple heat packs, just pop em in a microwave for a bit, to keep my batts toasty.

[Joseph C.]

...do you pretend we don't exist until it's time to post?

That's a safe bet.

[DrkAngel]

Keep your battery packs warm.
Low wattage pads, in conjunction with insulation, should perk up your batteries, cold weather performance!

New Link>12v Flexible Adhesive Heatpads < $5/pair

Low wattage ... add as many as necessary!

Will run preliminary tests with separate power source, 3S Li-ion. To measure drain & performance increase.
Note: Should run nicely at 2S, or 1S, for less heat output! 4S, for more?

Ordered a few pairs, from China ...
But might take a couple weeks ... will post review, as soon as possible.

[DrkAngel]

Everyone knows that cold degrades your batteries performance.

Solutions?

Insulate your pack.
For Li-ion, LiPo, LiFePO4 etc, insulated lunch bags, 6pack coolers etc, provide nice thermal protection.
Pre-warm your pack.
or ... add heat packs, gelled preferred, liquid might not be recommended!

Found a nifty little item that might be the best-cheapest solution!

Inexpensive, thin, flexible, self adhesive, low wattage heating pads.

Keep your battery packs warm.
Low wattage pads, in conjunction with insulation, should perk up your batteries, cold weather performance!
12v Flexible Adhesive Heatpads, < $5/pair
Low wattage ... add as many as necessary!

Heat Pad s.JPG (16.65 KiB) Viewed 9884 times

Perfect for eBike battery packs!
Will run preliminary tests with separate power source, 3S Li-ion. To measure drain & performance increase.

Ordered a few pairs, from China ...
Thought about it some more, ordered a few more pairs!
But might take a couple weeks ... will post review, as soon as possible.

Use your better judgment with batteries that tend to heat up, SLA, NiMh, RC Lipo etc.

[lester12483]

In my experience if you keep the battery at room temperature then you use it in the cold the performance is not degraded much. However if keep a battery pack in the cold garage then try to use it you'll notice a big difference. It also depends on how long you're riding in the cold.

If you wrap your battery in a towel it will help for better performance in the cold.

[dogman dan]

Got a live thread in the battery section about this subject.

Those look ideal, chances are you could regulate the temp by changing the voltage. So if too hot at 12v, run on 8v? Could be great for that occasional need to ride a bike that has been parked out in the cold, while in class, shopping, etc.

If you can acess an ac plug, then the reptile heat pads are ideal. Flexible, small, waterproofed, won't get too hot, perfect.

[Ykick]

I add more battery capacity during winter cold.

[DrkAngel]

Rig up the heat pads to a nice little programmable thermostat, and keep your batts nice & warm.
LCD programmable 12V thermostat - $15.99 w/shipping

Note: "Current on Relay Contact AC 5/220" ... Relay Contact should work fine at 12V DC! - AC-DC any voltage - 5A/220V max!