Ebike charging for long Battery life
So, you want your battery to last a long time?…remember that most people will not ride their ebike 500 times in their lifetime. Maybe hard to believe, but 500 charges is the typical lifespan of a 18650-cell ebike battery. And, 500 charges will take nearly anyone a long time to get through. So our first advice is not to worry about it and ride it like you stole it. By the time your ebike battery is used up, there will probably be some amazing technology around and you will want to replace your old clunky battery anyway. Also, most people will damage their ebike battery from abuse (dropping etc) way before they use it up from natural wear and tear.
However it has been theorized that you can get up to double the life of your batteries expected life, by taking care when charging.
Simple Rule To Remember
Lithium batteries like to stay cool. If you want to make your battery last a long time do not let it get hot, either in discharge or when charging. How to tell if you battery is getting hot? just use the finger test and just put your finger on it. Warm is OK…Hot to the touch is bad and you are shortening the life of your battery when you get it hot.
Always Charge Slow When You Can
Ebike batteries prefer to be charged slowly…. The smaller the pack (in amp hours), the slower they like to be charged. If you are concerned with battery life don’t buy the highest amperage charger you can find….just stick with a low amperage (2-3 amps) charger, or go with an advanced smart charger which can charge slow or fast with the turn of a knob. It’s always good to charge slow unless you are in a rush. (read more on the benefits of slow charging here)
When to charge?
You do not have to charge your battery after every ride…. These are not old school lead acid packs that if you forget to charge you will shorten the life of your pack…. Lithium batteries only need to be charged when needed.
Where to charge?
All large lithium batteries are a potential fire risk and should be charged in a safe place, preferably outside or in the middle of a garage floor Other safe ways to charge an ebike lithium battery are in a fireproof bag, oven or barbecue grill. (read this article on safe charging) Do not attempt charging a battery you think is damaged.
Never charge a lithium battery unsupervised inside a house or building. Manufacturers are afraid to tell you to be cautious, because it makes them sound like they are afraid their battery might catch on fire. The two most important truths about ebike batteries are: Buy from a respected vendor (not Aliexpress, the Chinese ebay), and also…charge them with care and caution.
For instance, if you charge your ebike with the battery on the bike, and the ebike is in the garage…put a heat and smoke detector above the place where you park your ebike. Does that mean you don’t have confidence in the company that you bought your battery from? No matter who the vendor is, doing that means you are being smart.
80 90 100 percent Advanced Chargers
Consider buying a smart charger that will automatically charge your battery at 80, 90 or 100 percent, and only charge to 100 percent when you are planning long ride.
We know from research done by the auto industry that batteries live longer when not charged to 100 percent every time…but at the same time, you should charge your battery to 100 percent at least once in a while to ensure it’s “balance” charged.
Watch our video on the Luna charging station pictured above.
Balance Charging an Ebike Pack
Balance charging is a function that is controlled by more advanced BMS’s (read article on bms) . What it does is, when the battery has reached its peak charge, the cells will slowly be balanced so each parallel string of cells are at the same exact voltage….this not only extends the range of your pack, it also extends the life expectancy. Modern name brand 18650 cells are very good at staying in balance, but should be charged to 100 percent once in a while to ensure proper balance is kept.
Know your high voltage cut off limit
Always use a charger that is designed for you pack. If you use the wrong charger you not only risk the long life of your pack it can also become a fire hazard. Make sure the charger’s maximum voltage matches the maximum voltage of your pack. Here is an example of maximum charge voltage for 18650 battery packs. If you do not know what your batteries maximum voltage is find out…and write it on a label on the battery so you never forget.
Here is an example of maximum voltages for popular Luna Cycle 18650 packs
10S (36V pack) – 42V max voltage
13S (48V pack) – 54.4V max voltage
14S (52V pack) – 58.8V max voltage
Know your low voltage cut off limit
Knowing what your high voltage cut off, and knowing what your low voltage cut off is the clear way that you will start to understand your pack and how to maximize its life, and also how to maximize your range when you need it.
High voltage cut off:
Here is typical low voltage cut off of some popular 18650 packs. Low voltage cut off (LVC) will vary depending on which cells you are using and which BMS you have.
36V (10S) – 27.5 volts
48V (13S) – 36 volts
52V (14S) – 39 volts
Storage of your lithium battery pack
Do not store your lithium batteries either fully charged or fully discharged….but somewhere in the middle. If you have a smart charger, we recommend you charge to 80 percent and store there.
If you are storing for a long period of time (like the several months of winter), charge it to around 50 percent and keep it in a fire-safe place.
If you have to choose between storing your batteries empty or full…choose full to keep the battery from drifting down to a level that it cannot be safely charged. The BMS will shut down and you can ruin your battery if the battery drops below the low voltage cut off. The BMS is the battery management system that keeps your battery from overcharging or undercharging and monitors the safety and health of your pack. (read more about ebike bms)
Tools that can help you
Always have a handy multi meter around to monitor the health of your pack.
You can also invest in a wattmeter, a Cycle Analyst, or a batt-man which will also give you a fairly accurate voltage of your pack, and also give you a good idea of the capacity of your pack in amp hours as your battery ages.
It’s normal for a lithium battery to drop in both amp hours and max voltage as it ages.
Only buy ebike packs containing name brand and authentic 18650 cells
The last tip we will give you to maintain long life of your battery and the safety of it during charging is when you purchase your battery pack make sure that it is cells are made from a name brand Japanese or Korean company (Panasonic, Samsung, LG, or Sanyo) and that the cells are authentic.
At this writing China is not good at making their own battery cells, although they have proven they are good at re-wrapping Chinese cells to look like name brands on the outside, or re-label them as name brands that boast ridiculous impossible numbers (now in 2016, any 18650 over 3500-mAh is a fake).
Buy your ebike battery from a source you trust, and preferably a USA supplier. Of course I recommend Lunacycle.com for all your battery needs. (disclaimer, I am the owner of Luna Cycle).
Written by Eric, September 2016