Storing a battery outside in winter - what kind of insulation?

[MaximilianMM]

I'm looking into installing an Asgard ebike metal shed outside my home for my ebike, and running power to it (it comes with built in plates for this).

I'm aware the advice is generally to store the battery inside, but I'm looking into if there's a good way to store it outside. I'd much prefer this from a fire safety point of view.

I already have a Bat Safe fireproof box. Even with this, I'd prefer to keep it outside. I'm in the UK, so it gets cold, occasionally sub zero but rarely.

Do you think with some additional insulation for the battery inside the the Bat Safe box (maybe a neoprene cover or something), it would be ok throughout the year? Cheers.

 

[docw009]

Most cells have a lower storage temperature limit of -20C. Does it get that cold in your part of the UK? If so, maybe a small oil filled heater set to come on at -10C will do the trick.

 

[orcasprout]

Hello Maximilian,

This is a pertinent thread, thanks for starting it. I'm a small eBike repair business working outta my garage. I NEED to address my battery situation pronto. I've got lots of customers batteries coming through.

I've considered installing a regular metal shed on the side of my property but then I'd need to pour a concrete foundation and that gets complicated quickly. (site prep, permits, etc).

I'm considering commissioning a metal box that would fit INSIDE a larger metal box (perhaps a "job" box type thing at construction sites).

It would have "flame arresting" material in between the two boxes. I recall someone in the NYC eBike fire thread used ammo cans packed with glassmat. I'm wondering if that can work for me at a larger scale.

Does the bike need to live outside or just the battery? I'm also considering a low level heater for this (yet to be specified) outside enclosure.

 

[nicobie]

A low powered heating pad on the battery can sometimes solve the problem.

 

[amberwolf]

If there's wall power available, then you can setup a temperature-controlled reptile heating pad inside the cabinet you will keep the battery in (either one that's directly controlled, or a basic pad powered from a controlling power strip like the Pymeter***).

***I have a couple of these, and they have been reliable for the >2 years I've been using them. Since each one has two outlets each independently controlled, you can modify the internal relay wiring to switch just one of the outlets (leaving the other disabled, or parallel them both if you keep the load below the relay ratings) so that you have *two* temperature probes each with their own independent settings for high and low limits, either of which will turn the outlet off if the limit is exceeded, both of which being within limits is required for the outlet to be on...this makes it a bit safer to leave unattended. Also, if the sensor fails, the outlet turns off and the strip beeps continuously until you deal with it.


Heating should only be needed for the battery itself, so if you can put it in any form of even mildly insulated enclosure, it will be far easier (and cheaper) to keep warm in a controlled way than trying to heat the entire shed or bike storage unit.

I recommend putting the heater in the battery enclosure so it keeps the enclosure air warm, and not directly on the battery itself, so that it will evenly warm the battery, rather than just the part it's in contact with.

I also recommend insulating the entire shed or bike storage unit at least a little bit. You can buy sheets of insulation at home improvement stores, or if you have more time than money you can use layers of styrofoam recovered from shipping box packing; this is commonly discarded at most big-box retailers for many items. Anywhere that sells live fish will also have a lot of discarded foam coolers the fish are shipped in--even if you only use the lids to make the process simpler you can insulate the whole thing in a matter of months or less from such free sources. (this is how I built my 3D printer enclosure:

 

[offGridDownUnder]

Consider viewing the various videos on Youtube about battery enclosures, and how they fail or don't. You don't want to just try what someone else tried, you want to try what someone else tried that worked.

 

[MaximilianMM]

Most cells have a lower storage temperature limit of -20C. Does it get that cold in your part of the UK? If so, maybe a small oil filled heater set to come on at -10C will do the trick.

Thanks. It averages about 2 degrees overnight in the coldest parts of winter. An oil heater is a good idea, although could get expensive.

 

[MaximilianMM]

Hello Maximilian,

This is a pertinent thread, thanks for starting it. I'm a small eBike repair business working outta my garage. I NEED to address my battery situation pronto. I've got lots of customers batteries coming through.

I've considered installing a regular metal shed on the side of my property but then I'd need to pour a concrete foundation and that gets complicated quickly. (site prep, permits, etc).

I'm considering commissioning a metal box that would fit INSIDE a larger metal box (perhaps a "job" box type thing at construction sites).

It would have "flame arresting" material in between the two boxes. I recall someone in the NYC eBike fire thread used ammo cans packed with glassmat. I'm wondering if that can work for me at a larger scale.

Does the bike need to live outside or just the battery? I'm also considering a low level heater for this (yet to be specified) outside enclosure.

A fireproof cabinet perhaps? I've seen those in bike shops.

My bike will be outside, and ideally the battery too.

 

[MaximilianMM]

If there's wall power available, then you can setup a temperature-controlled reptile heating pad inside the cabinet you will keep the battery in (either one that's directly controlled, or a basic pad powered from a controlling power strip like the Pymeter***).

***I have a couple of these, and they have been reliable for the >2 years I've been using them. Since each one has two outlets each independently controlled, you can modify the internal relay wiring to switch just one of the outlets (leaving the other disabled, or parallel them both if you keep the load below the relay ratings) so that you have *two* temperature probes each with their own independent settings for high and low limits, either of which will turn the outlet off if the limit is exceeded, both of which being within limits is required for the outlet to be on...this makes it a bit safer to leave unattended. Also, if the sensor fails, the outlet turns off and the strip beeps continuously until you deal with it.


Heating should only be needed for the battery itself, so if you can put it in any form of even mildly insulated enclosure, it will be far easier (and cheaper) to keep warm in a controlled way than trying to heat the entire shed or bike storage unit.

I recommend putting the heater in the battery enclosure so it keeps the enclosure air warm, and not directly on the battery itself, so that it will evenly warm the battery, rather than just the part it's in contact with.

I also recommend insulating the entire shed or bike storage unit at least a little bit. You can buy sheets of insulation at home improvement stores, or if you have more time than money you can use layers of styrofoam recovered from shipping box packing; this is commonly discarded at most big-box retailers for many items. Anywhere that sells live fish will also have a lot of discarded foam coolers the fish are shipped in--even if you only use the lids to make the process simpler you can insulate the whole thing in a matter of months or less from such free sources. (this is how I built my 3D printer enclosure:
View attachment 339888

Really good suggestions, thank you! I'll look into both of these.

I'm also thinking about condensation in the metal shed as well. The Asgards are designed to minimise this with some ventilation, which would obviously compromise insulation as well. Maybe an Oxford bike cover inside the shed.

 

[Comrade]

Thanks. It averages about 2 degrees overnight in the coldest parts of winter.

You will have some heat gain from the sun, and if there is some insulation in the box your inside temps will probably average much closer to 10c than 2c overnight, without any extra heating.

 

[harrisonpatm]

You will have some heat gain from the sun, and if there is some insulation in the box your inside temps will probably average much closer to 10c than 2c overnight, without any extra heating.

You're also probably not going to be using it as much, and especially as long as you don't charge it below zero (which from your description of your circumstances won't ever happen), I wouldn't worry about doing too much extra.

 

[A-DamW]

I'm considering commissioning a metal box that would fit INSIDE a larger metal box (perhaps a "job" box type thing at construction sites).

Just a thought, you may want to have individual isolated boxes for each battery, would be a bummer for one battery in a box of batteries to go up in flames and destroy all the other batteries...

 

[calab]

Cheap - Reptile heating pad
$$$$ - Battery heating pad

 

[docw009]

I really meant an oil filled electric radiator, I used to keep my garage above freezing with one when I worked on my cars in winter, Miserable times. I wouldn't want an open flame in a shed.

But if it's more like 2C, I wouldn't worry. I've got several batteries that are 7-8 years old, made with Samsung 30Q's that still have reasonable capacity, They were stored winters at temperatures that went down to -10C (attached garage) at mo particular voltage (50-90%).

 

[MaximilianMM]

I really meant an oil filled electric radiator, I used to keep my garage above freezing with one when I worked on my cars in winter, Miserable times. I wouldn't want an open flame in a shed.

But if it's more like 2C, I wouldn't worry. I've got several batteries that are 7-8 years old, made with Samsung 30Q's that still have reasonable capacity, They were stored winters at temperatures that went down to -10C (attached garage) at mo particular voltage (50-90%).

Ok, that's good to know, thanks.

 

[4πr^2]

Just beware that heating pads, oil heaters and generally any other electric heater or form of heat is going to have some fire or failure risk.

If you have a 1:1,000,000 chance of a battery spontaneously erupting in flames and a 1:1,000,000 chance of a space heater shorting out / catching fire - and put those two in a shed, now you have a 1:500,000 chance the shed will catch fire.

 

[nicobie]

Just beware that heating pads, oil heaters and generally any other electric heater or form of heat is going to have some fire or failure risk.

True enough. While I suggested using a heating pad. Personally I've never done it as I store my bike inside my shop and live in CA.

As usual take everything you read here with a grain of salt.