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[rayivers]

It's been one cold "spring" here in the NE US and the few rides I've gotten in this year weren't the best.  With only one 2.8 brick in use on my bike, cold temperatures have a big negative effect on apparent power / acceleration, with a lesser (but noticeable) reduction in range.

Today I tried heating my battery (again), using a small space heater blowing on the LH side of the battery and underneath it too.  I did this last week as well, but used less heat followed by riding conditions/traction that weren't good at all.  Today I heated the battery case up to around 84° F (53° outside) over several hours, and took it back to the same trail where traction was now perfect.

What a difference!  The sluggish performance I'd come to think of as the 'new normal' was gone, and the front end felt spring-loaded again.  It seemed faster today at the start of the last lap (53% SOC) than it had previously on the first lap with a cold battery.  Once I passed 50% SOC it dropped down a bit as usual, but still felt real peppy.  It seemed like the initial external heating was maintained by internal discharge heating, keeping the good times rolling on.

The difference on larger battery configurations will surely be less than this worst-case scenario, but if temps are below 60° or so and you're feeling sporty, you might want to try this sometime if possible.

Ray

[MrDude_1]

If you want to do that easier and safer, look at silicone mat heaters. They're silicone mats that have a heating element directly in them, along with the appropriate temp monitoring.
You can stick one directly to the bike, and it will keep it nice and warm.
Once installed, you can just plug it in.. maybe even on a timer.

Covering the battery area with neoprene (swimsuit material) or similar would also help keep the heat in once you start riding.

[Richard230]

Or you could wrap the battery in a small electric blanket.  You can get those things pretty cheap.

[rayivers]

Both great ideas - thanks!  I found a 4" x 12" 120V 240W silicone heater on eBay I could maybe stick to a thin piece of aluminum & slide under the rear battery across the frame rails, then pull out before riding.  Way easier than the space heater, and surely more effective too.

Ray

[brose]

I have been thinking about getting a silicone mat to heat my S battery after going through this cold winter. Are there any guides or tips for using a heating mat? Such as number of pads, placement, wattage? I would prefer something to plug in and forget while I am at work when it's cold out.

[Erasmo]

I have a small heat mat that fits between the battery and frame. Don't expect wonders but I've observed a delta T of about 4-5 degrees Celsius combined with a bike cover.   

[rayivers]

Are there any guides or tips for using a heating mat? Such as number of pads, placement, wattage?

I have absolutely no experience with heating mats, other than the type for laying damaged limbs on.   I can tell you my battery soaked up external heat like a sponge, and a 1500W space heater on max 2 feet away running for over 2 hours brought the casing temp (on that side only) up only about 30° or so, the other sides maybe 5-10°.  Since probably 2/3 of that heat ended up in the room & not the battery, I'd go with a minimum of 500W mat-heating power. I'll know better after I try out the 240W one, which will surely be insufficient (but at least fits).  Ideally you'd want multiple smaller-wattage mats all over the batter(ies), but that's not a real option with removable bricks (one 500W mat on the bottom of each brick might work well, though).  The mat's direct heat conduction should be a lot more effective than the spray-and-pray convection heat I used.  For large battery setups Richard's blanket setup should work well, but be careful not to ever fold heating surface against heating surface with these (duh).  The timer suggestion is also a great peace-of-mind option if you'll be heating unattended.

Ray

[BrianTRice@gmail.com]

This is why I was looking at making and selling an insulating battery neoprene wrap - the heating from an overnight charge was enough under a wrap to provide this effect, and then retain it well enough throughout the day.

I may yet revive the project in time for the next season of northern hemisphere cold weather.

[NEW2elec]

How does this stuff sound?

[BrianTRice@gmail.com]

How does this stuff sound?

These certainly seem intriguing.

Ref. http://www.dupont.com/products-and-services/electronic-electrical-materials/printed-electronics/products/self-limiting-heaters.html

They're probably not cheap or available via retail yet, are they? One concern would be whether these could be applied to a wrap so that it's removable from the battery. I might stiffen the wrap around the side panels if it can't take too much wear from flexing.

[NEW2elec]

They will "give" you some if you help fund their Twizy across Britain attempt.
Here he makes a cup of tea by painting it on a cup with a 3 amp 24 volt power supply.
I figured it could run off the Zero's 12 volt supply with double the amps with maybe just painting it on the monolith with a plastic (maybe graphics) wrap and some copper contact points going to an on off switch.
Maybe nothing worth trying but thought I'd pass it on to you poor cold weather riders.