Ebike Battery Safety: Storage and Charging at Home

Court

Administrator
Staff member
#1
Hi guys! I'm moving some content off of the main site and into the most relevant categories of the forum. This post was originally made on May 5th 2016:

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In recent years I’ve heard about a few incidents of electric bike shops burning down due to damaged batteries and chargers. These shops often perform maintenance/repair work on ebikes that have been subject to wear and this extends to their own fleet of rental bikes that might have been crashed etc. Their cost (in the event of an electric bicycle battery fire) is somewhat mitigated by insurance but it’s still dangerous and disruptive. Those same risks extend to home owners and while the number of bikes being stored is usually lower… and the condition of these bike higher, the risk is still present.

In my video reviews I often suggest that ebike owners store their batteries in a “cool dry location” to maximize the usable life of the cells and make charging convenient. In some cases this cold mean inside the house (either the entire bike or just the battery if it’s removable). So how can you charge these packs safely? What are some options for preventing electric bike fires? To help answer these questions I reached out to Edward Benjamin, Senior Managing Director of eCycleElectric LLC and Chairman of the Light Electric Vehicle Association for insight. Ed travels the globe doing consulting for large ebike firms, teaches ebike classes to shops (of which I have attended two myself!) and I consider him an expert but these tips are just that… the best information we have to help guide you towards making your own decision. Nothing can be truly guaranteed and some of the tips Ed shares below focus on what to do if a fire does break out.

Safe Storage and Charing of Electric Bike Batteries at Home

The very first thing I want to say is this: While it is true that lithium batteries, commonly used in ebikes today, can catch fire… it is VERY rare for them to do so, for several reasons. I suggest you are more likely to be injured by a falling coconut than to have a Lithium fire at home. Did you know that battery powered hand tools, laptops and even cell phones have burned down a number of homes and businesses? And yet to most people these products seem completely safe, even after being dropped or damaged they hold up well and never have an issue. Whether it’s some other portable electronic device or your electric bike, being alert and aware of how to treat the battery and what to do if there is a problem is advisable.

Being a “worst case scenario worry wart” myself, and a guy who is often working on batteries or evaluating bikes or batteries, I have given some thought to what can happen, and how to avoid letting it happen. I want to help you handle ebike batteries in a way that reduces risk as much as possible. And I want to repeat that while these steps are prudent and highly recommended, you, as an electric bicycle owner, have little to fear.

Switching gears briefly, if you are a bike mechanic, shop owner, or hobbyist that works on electric bikes (including conversion kits)… you may be handling batteries that have problems, have been damaged, or have a history that you simply do not know. And in some cases, as shown by the recent fires caused by cheap Lithium batteries installed in ‘hover boards’, new products from low cost producers can be risky. Perhaps that is why we now see fire-resistant bags specifically designed for hoverboards which may also be used to store your ebike battery. These bags are designed to safely extinguish a hoverboard fire by suffocating it (not allowing Oxygen to reach the fire) but I have not tested them and Lithium fires can still be very difficult to contain.

Lithium aside, even Lead acid batteries can be a fire risk… including the battery used to start most automobiles. The only battery fire I have experienced myself was when a wire dropped onto a lead acid battery, shorting it, becoming white hot and burning off the insulation, scaring me out of a years growth, and being ejected from the office onto the back deck in less than 10 seconds. This experience also gave my wife a lifetime supply of snarky comments about the “big bad battery expert who set fire to a ‘safe’ battery in his office!”

So without further ado here are some rules to follow to minimize your risk with batteries:
  1. Read the owners manual and any caution stickers, and follow their requirements for safe charging.
  2. Only charge your ebike batteries with the charger that was supplied originally with the bike or the battery. Create a process that includes clearly labeling chargers in your home or shop as to what goes with what. If you have chargers with the same connector but for different bikes (not uncommon), zip tie or stick-on a tag to those connectors that states what bike they are to be used with. Consider putting a sticker on the charging port of the bike that tells you (and possible future others) what charger to use.
  3. Charge only in a dry location. Rain, standing water, etc. is bad for chargers.
  4. Educate your family members, room mates and anyone who uses or borrows the bike on the safety rules and… which charger goes with which bike.
  5. I like to use a wall-plug timer when charging – mine was intended to just control lights in the house initially, and I set it so that there is no power to the outlet during the night, and limits the length of time that the outlet is “on” to only 8 hours during the day time. This saves energy, saves me from moments of forgetfulness, and makes me look pretty professional to visitors.
  6. Look over the place where you charge your bikes or batteries. If there was a fire… what would be nearby to add to the fire, or spread it? Charging next to your car means charging next to 15 gallons of gasoline which is much more dangerous than Lithium. Battery fires are hot, hard to extinguish, and generate toxic fumes and smoke. You are not going to be able to smother the fire, or pick up the burning battery and take it outside. So… choose a place that should a fire occur, damage will be minimized. I charge my bike on it’s kickstand, in the clear area of the garage a couple of meters from the wooden workbench, and a couple of meters from the car.
  7. Install a smoke detector over your charging area.
  8. Have a fire extinguisher located at the spot where you are going to be standing when you discover a fire. For example, hanging next tot he door from the house to the garage. Maybe a second one on the other side of the garage. Additionally, have a bucket that can be used to carry water to the fire – reasons explained below. Use a 5 lb. or larger ABC extinguisher, or a big CO2 extinguisher, or both.
  9. If you charge batteries off the bike, I suggest doing so on a metal rack that has wheels on the bottom (very inexpensive at hardware stores) whith the battery(s), and chargers on the rack. In the event of smoke, bad smell, or fire, you can shove it out the door quickly. Locate it closest to a doorway that you can use to eject the battery easily, quickly and without coming in contact with the burning material or breathing the fumes. Consider how you would get a bike out the door. I have a boat hook that could be used to drag just about anything outside, and it is ~2 meters long.
  10. In the event of a fire, evacuating the building is more important than fighting the fire. Calling the fire department (911) is essential. Keeping yourself safe and not breathing the fumes is more important than saving property. Even if the fire is safely moved outside, call 911, for these fires are tough to extinguish.
  11. If you can get the fire outside, onto a driveway or other pavement, then you can consider extinguishing it yourself. To extinguish a battery fire, review this video on YouTube
If you have experienced a battery fire or have other tips to add to this guide please share below in the comments. They are so rare that Ed has been compiling a list of case studies and is open to being contacted directly at ed@eCycleElectric.com
 
Last edited:

Court

Administrator
Staff member
#2
Following are some of the original comments that were made on that post:

CHRIS RANSOM
Wow!!! Thank U Curt!! I added a smoke detector to my shop after reading this and modified my charging station area, thanks to you and this smart article. Thanks again!!!! E-Bike Chris, Seattle WA

COURT
Awesome! I’m not really an expert at this stuff but I hear and see some good perspectives as I travel and am glad that sharing the topics has helped you :D appreciate your positive feedback and wish you luck with your shop!

GRANT JOHNSON
Can you charge a bike battery with a run of the mill 12v car converter with just the car idling? if so how much slower is it? thanks

COURT
Hi Grant! I think that depends on any accessories that the battery charger may offer. I think you’d be better off getting an inverter to connect to your car battery which can output 120 Volt AC. Look for a pure sine wave inverter… here’s a guide that may help. I used it to install an inverter in my own car :)

COLLEEN CARTER
I have an E-Bike with Lead batteries – I bought it NEW just before Fall, and never really used it, yet. I had to store it in my home. The batteries registered at full charge. Do I still need to charge it, and for how long at a time?It’s a TAOTAO 806 60V.

COURT
Hi Colleen! My experience with Sealed Lead Acid batteries is that they should be recharged monthly, even if you’re not using them. They tend to be more sensitive to cold weather and can get damaged if they fully discharge (even if you didn’t use it… the battery goes down on its own over time). I cannot say how long you’d need to charge it but probably at least 6 hours? Most of the time ebike chargers will have a light that goes from red to green when the pack is full, but otherwise I’d just try for six hours or so and then unplug it :)
 

JRA

Well-Known Member
#3
All the above relevant and want to add this I pulled from a battery makers site:

"If secondary cells or battery packs must be stored for a prolonged period, the state of charge should be checked regularly and provision should be made for recharging the cells before the cell voltage drops below the recommended minimum after which the cells suffer irreparable deterioration. (This is particularly true for battery packs which may have associated electronics which add to the self-discharge drain on the cells.)

Lithium ion battery chemistries prefer partial discharge, and since lithium ion chemistry does not have a "memory", you do not harm the battery pack with a partial discharge. If the voltage of a lithium ion cell drops below a certain level, it cannot be recovered. This is also part of the reason that you want to use fuel gauge technology on all battery packs so that you can actively measure capacity and extend the life of the battery pack.

Lithium ion batteries age, even if they are sitting on a shelf unused, and this capacity decrease is irreversible. So do not "avoid using" the battery with the thought that it will extend battery life for years. It won't. Also, if you are buying a new battery pack, you want to make sure it really is new. If it has been sitting on a shelf in the store for a year, it won't last very long. Manufacturing dates are important to review when it comes to lithium battery storage."


This is the problem with buying a used or older model year new bike (which you should ask for a warranty on) as the battery being arguably the most expensive component on an e bike should not be a gamble.
 

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