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Ebike Battery Care Top Ten Q&A

1. I just got a new E-bike … how do I care for my battery?

Awesome – lithium-ion batteries are amazing and you will want to insure your pack is properly cared for. Your eBike comes with a battery charger, and most of the ebikes are shipped with the battery at approximately an 80% charge level. The level may be higher or lower, and you can power up and check your display for an exact reading. Once you plug in your charger, the LED light on the charger will be red, and when fully charged will turn green, indicating the battery is fully charged and ready for use. Unplug it and enjoy your ride.

We use the term “battery” here, but your ebike battery includes the case (pictured left), individual cells within the case (pictured below), a circuit board inside the case that manages the cells and communicates with the bike’s controller (cpu), an off/on switch, a connection plug for mating with the bike, a lock with key for removing the battery, and typically also a push button that will give an approximate read on the battery charge level (independent of your LCD dashboard, and not as accurate).

2. What is the best practice for charging my E-bike battery after my ride?

You may have heard, “top it off after each ride.” Most do this - they charge it fully after each ride. A high voltage cutoff (HVC) in the battery management system (BMS) will shut off power into the battery cells after the pack reaches a level considered 100% (approximately 42V for a 36V battery system or 54.5V for a 48V battery system). This practice provides roughly 400-500 cycles before there is a substantial degradation in the cell chemistry. Ebike battery packs are relatively economical and years down the road - an easy replacement – they range in price from $300. to $700. depending on your model. For most people, five years of charging twice a week is 500 charge cycles, and your battery is still alive and has a decent charge capacity, but your range may be reduced a bit (similar to year two on a cell phone).

3. What should the temperature be on the pack before charging it?

Observe the battery temperature by touching the pack, and charge your battery when it (battery) is not too cold or too hot. Ideally the room air temperature around your ebike, when idle, should be 50 – 80 degrees (normal room temperatures). Avoid storing your ebike where direct sunlight hits the battery and raises the pack’s resting temperature.

Let's say you just came back from a 50- mile ride and the battery pack is pretty warm (you may not be able to feel it by touching the plastic case, but it does get warm). Leave it for 30 minutes so it is back close to the room temperature.

4. Can I double the life of my battery pack?

Studies show you can double the cycle life of your battery by charging it only to 80%, rather than 100%. Here is an infographic - from Grin Tech, one of the innovators in the Li-ion space:

5. I want to maximize battery life ... how can I do it?

Be mindful of a couple parameters:

A. High temperature = is BAD for Li-ion cells. So, what is high temperature? Anything above 40'C or 105'F (trunk of a car on a hot summer day, or exposing the battery to direct sunlight in hot, sunny climates). Below freezing temperatures - those are not great either, so avoid temperature extremes.

B. Time (days or weeks) spent at high or low voltage = is definitely NOT the BEST for Li-ion cells. You charged it to 100% and you're going away on a a month’s vacation. This may not provide the longest lifespan for the pack. Conversely, avoid time spent at 0% charge level = really BAD. Although your BMS may report 0%, there is technically a little bit of voltage left, but after time passes, you may lose this little bit of charge and then not be able to recharge the cells at all – the lithium chemistry magic ends. In the electric automobile space, Tesla’s Elon Musk responds to this topic from a customer’s question, and he recommends charging to 80%:

In the desert SW area, where temperatures can get extremely hot in the summer, and where snow birds may depart the area and leave their bike stored away for months on end - beware. Avoid storing in a hot environment and leaving your ebike discharged for long periods of time when away at your summer retreat. Here is more on the topic ...

6. How should I store my E-bike battery?

It is best to store your battery at room temperatures (cool, less humid conditions) and again at a 50-80% charge level. Professor Jeff Dahn provides scientific insights regarding Li-on battery degradation - Prof. Dahn is the world's foremost expert when it comes to these batteries. He invented the NMC chemistry and heads the current Tesla battery research program in conjunction with a Canadian university, so Elon is tweeting insider information. Here is an excerpt from his scientific article on how the charge level and calendar life ageing and conditions affect Li-ion battery degradation.

“The storage initial state of charge – “SOC” level is one of the factors of battery ageing during its calendar life. According to our studies, a high SOC level (>80%), or a low one (<20%), engenders a huge potential disequilibrium on the electrode/electrolyte interface, and this accelerates chemical reactions. Through our experiments, we placed the battery under many conditions, including extreme SOC (>90% or <10%) quite often during each use session. Our studies show time spent at high charge, approaching 100% charge, is bad. If you leave your charger plugged in overnight, where the battery is consistently charged to 100%, expect ~500 cycles, instead of 800+ cycles. It's perfectly ok to charge your battery to 100%, but keeping the batteries at 100% for many days will shorten the battery capacity ...”

7. What kind of charger should I use?

Use the charger supplied with your ebike and plug into your 110 outlet. Your ebike charger will charge the battery at less than 8A (most ebike chargers run at 2A-4A), and won’t overheat the chemical compounds inside the cells. When fully charged, the LED light on the charger will turn green, and you can unplug it. Some use an outlet timer to run power to the charger for a set block of time (4-5 hours) without worrying about it. Today’s modern ebike chargers detect a full battery charge, and turn power flow to the battery off when full.

In the automobile world, a Tesla can be super-charged to 80% in less than 40 minutes, thus avoiding higher battery cell temperatures, but the car has very complex thermal management systems for the battery, the power control unit, and the engine. Since E-bike batteries do not have such cooling (or expense), it takes longer to charge at a lower power level, and avoid longer-term problems.

8. What is the battery warranty?

The battery warranty provided by the manufacturer is typically the same as the ebike. However, because it is easy to damage the battery with improper care or lack of proper maintenance, diagnostic tests can be ran on the battery and cells. When it is found that environmental conditions caused the premature failure, the warranty on the battery can be voided. In other words, take precautions regarding your battery, or be prepared to replace it. The most expensive component on your ebike is the battery pack.

9. Can I get a bigger battery for my ebike?

Most ebike models have an option for a larger battery, and typically a 40-70% longer range. Some models support an onboard second “live” battery. We suggest first determining your rider’s range – for most rider’s, the two hour ride time commonly provided with the standard battery is plenty of ride time for recreational riders. If you discover you are able to ride for longer periods, it is easy on most models to carry a 2nd battery pack on the rear rack in a pannier bag, and do a quick swap out on your ride.

10. Will there be longer range batteries in the future?

Yes - much research is occurring, and there is the promise of higher energy density per square inch and per pound, and new materials that may be used that are not as rare as lithium.

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