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Battery insulation/warming?


InfiniteWheelie
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Has anyone attempted to insulate or use heating pads for winter riding? It gets very cold here in the winter (-10 to -20c). I am planning to buy a long range wheel (the commander) to go on multi hour rides. I want to be able to ride year round, but multiple hours at -10c or colder will wreak havoc on the battery.

The options I'm looking at are using aerogel insulation to wrap the batteries, or heating pads. I believe areogel is the best insulation you can get, but it would cost $200+ to wrap the batteries. I also don't know if it can insulate well enough for many hours well below freezing. It may be fine considering the batteries generate a little heat themselves while in use.

Heating pads may work but they would likely need to be custom or homemade. They would also likely need to be attached to the main battery pack since i doubt there's room for a separate battery to power it. I have no idea if that's possible when it comes to the electronics. I also wouldn't want to overheat the batteries so it would need some kind of balance in temperature.

If anyone has any experience or suggestions for this I'm all ears.

Edited by InfiniteWheelie
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3 minutes ago, InfiniteWheelie said:

aerogel insulation to wrap the batteries

You'll face a couple of challenges here I think... aerogel is fragile and has a very high volume. There isn't much if any room inside the shell to add thickness to the battery packs.

Active heating on the other hand, can be had in very very thin form factors. In a former life we printed heating elements onto thin polycarbonate to make flexible heaters. Temperature control is dirt simple, we used a simple on-off thermostat about the size of a paper match head.

But no, I've never tried to heat or insulate my wheel beyond having a roll.nz cover on it. And I've ridden for an hour or two at -18C without problem, started with the wheel at room temperature of course. I'm not sure I could do 'hours' of riding at those temperatures, but I'm cold blooded and the amount of schnapps necessary to keep me out for much longer than a couple of hours isn't conducive to riding on frozen surfaces.

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As far as i know aerogel is the best thermal insulator per volume. I can't speak to them being fragile or not, I guess being pressed by the weight of a battery may be a problem? I'm looking at sheets like these http://www.buyaerogel.com/product/thermal-wrap-8-mm/ 

I supposed a simple on off switch with thermostat would do the job. Do you think it's possible to hook heating pads up to the main battery?

Edited by InfiniteWheelie
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11 minutes ago, InfiniteWheelie said:

As far as i know aerogel is the best thermal insulator per volume. I can't speak to them being fragile or not, I guess being pressed by the weight of a battery may be a problem?

It is the best! You'll likely find the battery pack is stuck to the inner shell with double sticky tape and the outward facing surface is 'clamped' in place by the outer shell. Zero room. You really don't want the pack floating around inside the shell like a pea in a tin can because it'll suffer physical damage.

 

13 minutes ago, InfiniteWheelie said:

Do you think it's possible to hook heating pads up to the main battery?

All things are possible, but a 100V source is "lots" and you'd be wise to step down the voltage to something more reasonable (12V?) so that you can isolate a fault in your heaters from the actual batteries. If your heater shorts out, you don't want it to apply that short to your batteries or you'll have blown fuses and possibly a fire.

While the fur coat seems like a silly idea, it's a pretty good one! Putting clothing heaters into the coat would be pretty easy, and they have their own batteries.

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36 minutes ago, Tawpie said:

While the fur coat seems like a silly idea, it's a pretty good one! Putting clothing heaters into the coat would be pretty easy, and they have their own batteries.

This could actually be a good idea. It's the simplest way to do it, and could easily be taken off when it's warm out. I'll put some thought into that.

Edited by InfiniteWheelie
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1 hour ago, meepmeepmayer said:

Imagine a EUC with a little fur coat:wub:

A number of us have imagined EUC outerwear already I think ;)

Unfortunately for heating, the batteries are pressed directly against the plastic wall of the wheel opening, with air circulating constantly driven by tire motion. So exterior covers won't address this main path of heat transfer.

I like the "start with it warm" idea.
Batteries dissipate heat during use, so if it starts warm, and you keep riding, it will never cool all the way down to ambient.

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On 10/1/2021 at 2:37 PM, RagingGrandpa said:

Unfortunately for heating, the batteries are pressed directly against the plastic wall of the wheel opening, with air circulating constantly driven by tire motion. So exterior covers won't address this main path of heat transfer.

That's a good point. Perhaps there's enough room behind the battery to place a single layer of aerogel if you remove the double sided tape. I've notice on some ewheels that double sided tape looks more like foam and is pretty thick. Aerogel comes in various thicknesses from 3-10 mil or so, I'm sure there's one that would fit. Maybe you could also place insulation on the outside (beside the tire).

Another thing to think about, I wonder if you'd want to enclose the top section where the controller is located (like on the sherman). Maybe that would be better left exposed to the cold for cooling, perhaps with some insulation separating it from the batteries below.

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43 minutes ago, RagingGrandpa said:

A number of us have imagined EUC outerwear already I think ;)

Nonono. There's EUC bodyguards and self-made protectors, and then there is fashion. We need some proper EUC winter couture:efefe00999:

Edited by meepmeepmayer
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  • 4 weeks later...

I'm sold on the insulating jacket idea, but I don't think it's enough. As was pointed out, the back side of the batteries will still let in cold like crazy, and insulating alone may not be enough for long rides in very cold temperatures.

I like the idea of also using silicone heating pads. The wheel I'm getting is the Sherman, which I believe has thin yellow foam on both sides (or just the front?). Silicone pads seem to be just a few mm thick, and would give cushioning, meaning perhaps you could simply use them in place of the foam. The two ideas I'm floating are...

 

1. Silicone heating pads front and back sides of the battery.

2. Silicone heating pad up front, with Aerogel in the back to insulate. 

 

Assuming there's about 3 mil front and back (the approximate size of both Aerogel and pads), which arrangement do you think is better? Heating both sides sounds good in theory, but the back is going to be letting in cold like crazy, so perhaps its better to insulate than lose all that heat. The front will be insulated regardless from the jacket.

 

 

 

 

 

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Seeing as the heating and jacket may take a while to sort out (and I want to ride this winter), I think I'll first try wrapping the individual battery packs in aerogel, and test how well it works. I think there should be room for the aerogel insulation. They come in 3.5 and 5 mm thicknesses, depending on the spec you choose. 

It will cost close to $300, but if it passively keeps the batteries warm without any extra fuss of external jackets or heating pads, it will be worth the money. Once my Sherman arrives I'm going to measure how much space is in there before i order the insulation.

Edited by InfiniteWheelie
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I received my Sherman and looked inside the battery compartment...

The yellow foam is only on the front of the battery (not the back), and it measures about 3 mm. The back has a thin horizontal strip (about halfway up the battery) of white sticky foam about 1.5 mm thick (maybe slightly less). The bottom has the 3mm yellow foam, as does the outer side wall. The inner side wall (next to the trolley handle) has no foam, although there is a slight gap (maybe 1+ mm) when the battery is pushed against the opposite wall. The top has no foam either as there's just empty space above the battery.

It's a tight fit, but I think I should be able to fit the 3.5mm Aerogel insulation. The yellow foam is very dense, where I think the Aerogel may have some more give. Front to back it's only about 2.5mm too tight, and side to side about 2.5-3mm. And the inner side could be shaved down because it's actually a few pegs sticking out limiting the width.

I think I'm going to give it a try. I can order a 24x30 inch sheet for $140 plus tax and shipping, which would be just big enough to cover the whole surface of the batteries. Maybe I'll heat wrap the batteries once more to secure the insulation and cover and seams.

Edited by InfiniteWheelie
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I found another aerogel which is only 2 mm thick which should fit perfectly! It's thinner but with a significantly lower thermal conductivity, so it's ends up only slightly less insulating. But when you consider it won't be squeezed like the 3.5 mm stuff, it probably insulates just as well. Price is similar. It's called Pyrogel 2250.

By the way, does the Sherman have battery temperature sensing? If I'm going to insulate I need to see how well it's working. If the Sherman doesn't have a sensor already, does anyone have suggestions on how to rig one up?

Edited by InfiniteWheelie
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10 hours ago, InfiniteWheelie said:

does the Sherman [have] battery temperature sensing?

Nope.

10 hours ago, InfiniteWheelie said:

does anyone have suggestions on how to rig one up?

If you have a decent multimeter, it probably reads thermocouples too (perhaps with an adapter plug; or get a cheap standalone reader).
Just tape a few K-types against the sides of the pack (and beneath the pack along the plastic wall of the tire cavity) and leave the thermocouple wires dangling outside the panel. Come to a stop now and then, plug in, take measurements, unplug, continue...

Consider instrumenting both sides, but modifying only one side (adding insulation, heaters, etc). You'll be able to compare temperatures left-vs-right during identical operating conditions.

 

 

Edited by RagingGrandpa
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I don’t know what the silicone heating pads you mentioned are like or how they work, but there are very thin plastic heaters available for reptiles. Several different sizes available, wattage being around 10-30W, and they are designed to bring the room temperature up to about 40•C. So kinda perfect for this.

I think they work directly from a wall socket though, so rigging one up to a DC source may be quite a challenge.

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1 hour ago, mrelwood said:

I think they work directly from a wall socket though, so rigging one up to a DC source may be quite a challenge.

If one gets one for 120V AC one can nicely use it with 100V DC. That's  just 20% less. (AC values are normally given as the "effective" value (rms) which is the value of the equivalent DC voltage).

One would just have to look how and if the work with about empty batteries at ~80V.

 

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I'm going to use a temperature probe and just slide it inside the battery between the cells, I think it should fit. It's a small AAA powered Bluetooth model that connects to your phone. It can measure from -40 to 125c, log the temperature over time, and alert you when set temperatures are reached. I'll be buying at least 2, to compare the insulated vs uninsulated. I may end up buying 4 to monitor all the packs, but it's probably unnecessary

https://www.amazon.ca/gp/product/B08V1HGYMX/ref=ox_sc_act_title_1?smid=AYS1QP79X4N5R&psc=1

I'm going to start by wrapping the individual battery packs with the 2mm Pyrogel 2250 (the best and thickest insulation that can fit in that space). I'll measure the temperature as it continues getting colder outside. If that isn't enough I'll look at other options like insulating the outside, and/or some kind of heating.

Edited by InfiniteWheelie
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The insulation is on the way. I'll keep the thread updated with the results.

The temperature monitoring will be vital to ensure the battery doesn't overheat. Both when riding in warmer temperatures, and when charging. I'm going to charge the battery with the insulation on and monitor it. I'm guessing it won't be a problem but I'll check to make sure.

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  • 2 weeks later...

I received the insulation and four temperature probes. I'm now waiting on the heat shrink I bought to arrive (same type as used on the batteries), which will be a couple of weeks unfortunately. I'll be fully wrapping the batteries in insulation, then heat shrink wrapping over that. I hope it works well, I don't really know how it will turn out.

 

Edited by InfiniteWheelie
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I had a go at installing the installation. I managed to get both batteries on one side done. Wasn't easy and took a few hours. After much measuring, testing and pondering I settled on a size of 14.25" x 14.25" This allows you to wrap the insulation horizontally, then fold the top and bottom kind of like when wrapping a gift. The insulation is quite stiff, but just flexible enough to bend around decently. I used tape to hold the seams in place, then covered it with 220mm wide shrink wrap tubing, cut to 16 inches long. I used a heat gun set to 250c (wouldn't want it any hotter), and shrunk it on. I then trimmed the ends a bit, and around the wires. I also stuck a single temperature probe on the bottom of one pack. I really only need one, and that's all I have room for (I stuffed the module inside the controller compartment).

Let me tell you, there is literally ZERO room to spare in EVERY SINGLE dimension. It's a miracle I was able to push the packs back in place. That's after removing all the foam and tape. The side panel was actually lacking space, but I shoved it on and screwed it down anyway. Hopefully it doesn't explode or something. I'll be doing the other side soon, then hopefully taking it for some long rides to see how the temperature holds up.

Edited by InfiniteWheelie
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The insulation is fully installed, seemingly without any major problems in the end. The temperature probe is working too.

Funny enough this is my first wheel so I'm still learning how to ride. I've only taken it out a couple times and managed to ride across a grassy field, and can mount without a pole. I found it really hard to ride without pads to push against, so I paused practicing until my new pads arrived which I just installed. All this is to say, you'll have to wait a bit for results until I can learn to ride the thing! Although I could leave it outside for a few hours to get a rough idea. I'll have some results coming soon hopefully.

Edited by InfiniteWheelie
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I've taken a few days to learn to ride, and I'm competent enough at this point. I've gone for some multi hour rides while monitoring the temperatures and I can say it seems the insulation is doing a decent job. The battery starts at room temperature and drops off fairly fast, but the drop starts to slow more and more until it seems to settle into a pretty stable temperature, which is substantially above ambient. Overall it seems like a success so far, but I haven't tested below freezing yet (just single digits).

If people want data logs and more details I can provide that no problem, but I'll wait until it drops below freezing since that would be a better test. Keep in mind I didn't test the battery without insulation, but I bet it wouldn't last more than an hour before reaching close to ambient temperatures.

 

 

Edited by InfiniteWheelie
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