Everything about e-bike batteries

Instructions, how to understand them and how to care for them so that they serve long.

A battery pack is a technical equipment for storing energy again, usually electrical. A battery is a secondary cell that needs to be recharged first, and only then can it be used as a power source. In e-bike it is the most expensive and at the same time one of the most important components.

Today about 90% of e-bike with lithium-ion (lithium-ion) cells. These are 18 mm high rollers, 65 mm high (so you will also encounter the 18650 mark), assembled in parallel and in series to provide the required voltage and capacity. With Li-Pol now they are a little smaller because they are formed by flat bushings and their shape adaptation is slightly lower (yes, these batteries are in all mobile phones). Li-iron-phosphate (LiFePO4) batteries are used mainly in electric skiing because they are about 50% heavier.

Initially, lead-acid (or gel) batteries were used for their extreme weight (often more than 8 kg), and for sulphuric acid content they are hardly used anymore. The same is true of nickel-metal batteries (NiMh), where, in turn, the problem with the memory effect (the battery for a full charge of the battery must be fully discharged), high stress resistance (remember how long the flash of the camera, which runs on NiMh batteries ... as well as its energy density - that is, how much energy it can absorb per kilogram of weight-approximately 3 times lower than modern lithium-ion cells.

These are the energy density parameters, or capacity and maximum load. This is what you should be interested in when choosing e-bike along with the battery life. 

článek baterie elektrokola 18650
The capacity is determined by the cells used. Now we often encounter a lithium-ion cell with a capacity of 3200 mAh. If we thus connect 10 series and 5 in parallel (referred to as 10S5P), we get a capacity of 16000 miliampérhodin, or 16 a (Ampérhodin) battery. In order to get the resulting battery capacity in watt-hours (Wh), we still have to multiply this capacity by the cell voltage - i.e. 36V - and we will get the received 576 Wh. Today, this is basically the standard battery capacity we find in many modern e-bikes.

But the voltage of the cells varies between 4.2 V and 2.5 V (see below).)  If one of the values is exceeded, irreversible damage occurs. To prevent this from happening, each battery in the e-bike must be equipped with an electronic protection system called BMS (Battery Management System). Never "squeeze out the maximum" from the battery - some cheaper e-bikes are not set up in the BMS mode too precisely and thus there may be one long trip of e-bike "to the end", it will also be the last one.

   © BASF 2011

Battery life and cycles

But how much will you drive on e-bike?

Once 15 kilometers to work and back, the second time you go on a long trip. In lunch you charge at 30-50% and go on. This is possible because lithium-ion batteries do not have the bustle of other technologies-so-called memory effect. Well-known manufacturers of battery cells (for example, Panasonic, Samsung, Sony, LG), if more cycles are specified, so write about 500. But other manufacturers who probably use the worst - unmarked types of batteries, without shame gain 1000 and more cycles of charging. The simple and real answer is based on simple mathematics

Let's say that your battery capacity 400Wh on a single charge will get you 40 miles. And this battery will realistically work for 500 full cycles. It is a total of 20,000 miles - so after three years, every day, in summer, in winter, even you can travel nearly 20 km. Is it a lot or a little? 

Recently, we in the environmen.cz was a customer who bought a e-bike in 2008. He bragged that moves annually around 3000 km and on the original - 8 years old - the battery slips off just 13 km away - that he said but for his needs is enough, so a new battery still doesn't need!

NabíječkaIt should be noted that the battery will degrade even if not used. Thus, buying a backup battery that you use only occasionally is not likely to pay for itself. What, in turn, should be monitored is the charging current. Its value is indicated on the charger in Amperes (A) and indicates how quickly you charge the battery with this charger. If you only charge your e-bike overnight, you probably don't care, because even with the weakest charger, the battery will be fully charged in the morning. The difference is when you plan to travel 120 miles all day long to take the charger into your backpack. There will already be a big difference here, whether you need to fill your lunch stop with 2A (most cheap e-bikes) or 4A (Bosch charger) or even 5A (Agogs turbo charger).

Be careful, not every battery can be charged so fast, it must be adapted to the electronics of the battery!

How not to ruin the battery

The e-bike battery does not need any special maintenance. But there are several proven ways to destroy it.

First, pay attention to the battery's on/off system. Famous manufacturers use the so-called "sleep mode" in their batteries. You activate the battery mainly by pressing a button or activating it on the control panel. Once you turn off the e-bike, the battery will sleep on its own after a few hours - so the power from the BMS circuits will turn off. If you are moving on, you need to press the button again to activate the battery.

In our market, however, often face the battery systems either with a stand or the key. After stopping the wheel, then you forgot to turn the key to position " off, and even more frequently forget to turn off the rocker switch on the battery (this is in addition, they are often skillfully hidden and it is not clear when in distress, and when it is in the off position). And With the Electronics of the battery BMS still flowing through the miliampery. If the electric bike to leave on over night, nothing is likely to happen, but if you leave the battery cost a lot missing, so, after several weeks, occurs under the influence of self-discharge to deep discharge the battery below the safe 3V per article and is waiting for you, probably, investment of several thousand dollars in new.

And similar it is with the charger – after charging, we recommend that you disconnect. The idea that if I leave the pedelec to charge for 4 months, everything will be OK is sadly mistaken.

Storing the battery over the winter is very simple. Basically, you just need a battery charge to 50% and store in a cool place. Is better battery stored outside the e-bike, to avoid unwanted activation of the over contacts.

Battery second hand

Every day on auction sites and markets appear several used electric bikes for sale at suspiciously favorable terms. We believe that at least half of them will have a problem with the battery capacity and therefore are the owners of the visor to get rid of. But as well as the second in the head, or into the battery you don't see and on a hit-and-declared XX km roll out the most is not the time.  Council is – if you opt for a used pedelec, always insist on a protocol of a fresh measure of the battery capacity. For accurate measurement of the battery and produce the chart we have service electric bikes special device, which renders the status of the battery in the load  according to its exact capacity. Buy e-bike with less than 80% capacity is not recommended.

The development of battery technology for electric bikes.

You've probably read an article about the revolutionary discovery of American, Chinese or even Czech scientists on the battery field in recent years. But over the next few years, there will be no major upheaval, and the price of batteries will not drop by 50% in 3 years.




Our tips for extending the life of your electric cooler battery 
Greatebike.eu recommends a few tips for proper care of the lithium battery.


Tip 1 - Try not to discharge the battery below 20%. Deep discharge makes the battery too difficult to access, reducing its capacity in the future. Charging the lithium battery starts with the oxidation process, which has a negative effect on battery capacity as well as battery life.  If the e-bike is switched off (e.g. in winter), it is recommended that the battery be fully charged at least once every 90 days.    

Tip 2 - Do not charge the battery immediately after rolling away. The battery should cool down before charging. If we start charging a heated battery, it will not be able to cool down at all, and its degradation will be much faster during charging.   

Tip 3: Do not charge the battery fully. If this is not necessary, do not charge the battery. When charging the battery above 80% of its capacity (voltage around 40V), the internal resistance of the battery grows, the battery heats up more and thus significantly accelerates the degradation of the negative electrodes. The creator of this degradation is the significant chemical instability of the charged article. It has been shown that charging the battery to 41 V instead of 42 V (i.e. about 90%) will prolong its lifetime by 2x or more.
Tip 4 - Avoid extreme temperatures. High heat or cold winters affect performance and shorten battery life. Never store the battery outside where it will be exposed to prolonged temperatures below 0ºC. Similarly, we do not recommend storing the battery at temperatures above 30ºC.  When using the battery, avoid long parking under direct sunlight.  

Tip 5: Charge the battery with a low current preference. A high charging current causes the battery to heat up more and therefore degrade faster.