Ebike battery storage

Snoop

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So as I’ve determined that I don’t want to be a winter rider (winters are very cold and snowy here), I’ve been in the process of winterizing my ebike. Gave it a good cleaning, decharged my battery to about 75%, etc.

I‘ve been thinking about the best way to store my battery during the winter months indoors. I know that the risk of fire/explosion is extremely remote if the battery is well cared for and a decent brand, but as we’ve seen too much on the news the past year or so…..stuff happens.

I‘ve found a few “fire proof” storage containers which vary from:

Quite cheap (~$25)



To the more expensive with charging option (~$150)



I was wondering of there are any opinions from forum members about what to look for with these containers? One concern I would have about the second box which allows in-box charging is whether the battery would be at risk of overheating during charge due to lack of ventilation. Is that concern valid?
 
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A lithium ion battery can burn at more than 3600 degrees f and doesn't need oxygen to burn. If it was me I would get a heavy steel box with a good lid and keep it away from combustible material. Otherwise I would go with your 1st choice. I keep mine in my garage still installed in the bike a few feet from any combustible material.
 
Background (or "why I have some credibility on this topic").
I've had a lifelong fascination with super high-powered flashlights (the kind that WILL set things on fire if you are careless), RC vehicles, and I'm an electronics technician. I've spent a lifetime working with and testing many kinds of battery powered systems right to the edge of failure (and okay, sometimes over that edge) so at this point I can claim a pretty fair knowledge of the care and feeding of batteries and battery systems.

If we start with the primary assumption that the battery pack is certified (UL, CSA, TUV, et-al) so that the 18650 cells that comprise the battery are of some decent quality along with the electronics in the battery (the Battery Control Module BCM) and the construction is robust (good connections and solid structure to handle vibrations and impacts) then that puts us in a very solid place with regards to battery safety.

Temperature: LiPo batteries will tolerate being DISCHARGED when very cold but CHARGING them below about 40F is bad practice and can damage the cells. You want to avoid actually freezing the battery as well.

Long Term Storage: The "ideal" for LTS is 50% evenly distributed amongst all the cells. In practice anything below about 75% seems to be okay and any capacity loss is minimal at that point. The trick is to avoid DISCHARGING too low (below 30%) and leaving it that way. LiPo self-discharges so an unused pack really should be checked monthly. HIGH HEAT and OVER-DISCHARGE are the real danger because cells can actually reverse polarity causing an internal runaway cycle to start which results in rapid overheating and fire.

Storage Location: Anything fireproof -but not sealed-, for example if you use some kind of ammo-can you need to drill a couple of vent holes to relieve pressure. Purpose made battery boxes or bags are popular but I've also seen RC people buy an appropriately sized charcoal grill with a closing lid and use that for storage.

Screen Shot 11-15-22 at 11.10 AM.PNG
 
I live in northeast Wisconsin, where temps in the double-digits below zero are common in the wintertime. I do not have a basement and the garage is not heated. What would you recommend for battery storage during winter?

Thanks!
 
Battery inside a smaller styrofoam cooler within a larger styrofoam cooler?
 
A lithium ion battery can burn at more than 3600 degrees f and doesn't need oxygen to burn.

I suspect there is not much that can withstand this kind of heat. Kind of makes we wonder if it is even worth the effort to put it in a box or bag, etc. Maybe it will buy a couple of minutes or temporarily contain flames but not much else. What am I missing?
 
I realize that anything could happen but....keep some perspective....most of these batteries never explode or catch fire. You probably have a much greater risk of getting hit by a car while crossing the street than your battery exploding......just sayin......
 
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I suspect there is not much that can withstand this kind of heat. Kind of makes we wonder if it is even worth the effort to put it in a box or bag, etc. Maybe it will buy a couple of minutes or temporarily contain flames but not much else. What am I missing?
18650 batteries only burn that hot very briefly (a few seconds) before the relevant components are consumed, most of the time the remaining burning elements (plastic and so forth) are what actually trigger everything else around the failed pack to burn.
 
Does anyone actually know of a lithium bike battery that caught fire while being stored? There have been problems with cell phones and one brand of laptop but that is all I can recall.

Considering that electric vehicles have massive battery packs and are often parked in garages this should be a major problem but it is actually quite rare. From one study:

"We're increasingly asked about the risk of an electric vehicle (EV) exploding, particularly in underground parking or roadways, such as tunnels. Our research identified & verified fourteen (14) EV explosion incidents since 2010 - that's from a global market of 10 million EVs in operation at the end of 2020."

People are much more at risk from floods, wildfires, gas main explosions, hurricanes, tornados, and snow storms.
 
The only time I saw a lipo battery in a RC airplane application... catch fire, was when it was left in a closed car out in the direct sun, on a 90 plus degree day. The only other time I have seen one go up in flames, is when I shot one that fully charged with a 22!
 
So as I’ve determined that I don’t want to be a winter rider (winters are very cold and snowy here), I’ve been in the process of winterizing my ebike. Gave it a good cleaning, decharged my battery to about 75%, etc.

I‘ve been thinking about the best way to store my battery during the winter months indoors. I know that the risk of fire/explosion is extremely remote if the battery is well cared for and a decent brand, but as we’ve seen too much on the news the past year or so…..stuff happens.

I‘ve found a few “fire proof” storage containers which vary from:

Quite cheap (~$25)



To the more expensive with charging option (~$150)



I was wondering of there are any opinions from forum members about what to look for with these containers? One concern I would have about the second box which allows in-box charging is whether the battery would be at risk of overheating during charge due to lack of ventilation. Is that concern valid?
I think best practice is to store at 60-70% and in warmer room for the battery.
 
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Did my one month battery charge check today, and surprisingly it hasn’t dropped much at all.

My Aventon battery charger has an indicator light which is red when the battery has a 0-33% charge, green with a 33-80% charge, and blue with 80-100%.

When I prepared the battery for winter storage, I charged it up until the light turned blue, figuring it would drop on its own soon after. A month later, it’s still blue.
 
Personally I would trust the lights on the charger. The recommended long term battery storage percentage is around 70%. I find the best way to test battery voltage is to use a multi meter and probe the contacts at the battery.

A 48 volt system charges to 54.6 on full charge. 70% is around 38.22 49.9 volts.
 
Did another (almost) monthly check on my battery today, and still holding strong “in the blue.”

15DE2B08-6F7A-4C7D-8634-C17C09FFC062.jpeg


I think I’ll take up HogDoc’s advice and put a voltmeter on it when I get a chance.

.
 
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