A key issue regarding electric bicycles is, of course, the battery. In particular, the most important aspects to analyze are: autonomy, useful life, replacement cost.
When declaring the autonomy of electric bicycles, most manufacturers provide data that is not credible and in some cases even impossible. This practice is due to the fact that, declaring a few more kilometers of autonomy, facilitates the sale of bicycles.
Don’t be fooled: batteries are like fuel tanks. The larger the size, the greater the amount of energy they can contain and, consequently, the greater the autonomy of the bike. Determining the size of a battery is very simple, you only need to multiply the number of volts by the number of amps. For example, a 36V and 13Ah battery will have a size of 468 Wh, while a 48V and 17.5Ah battery will measure 840Wh. Almost double!
This reasoning cannot be questioned, it’s about physics. Outside of this formulation, however, we are faced with pure commercial speculation. If a seller wants to convince you that a 36V-13Ah battery reaches 100 km, keep in mind that, for the same reasons, 48V-17.5Ah batteries should reach almost 200 km.
To definitively avoid any kind of misunderstanding, there is a simple tool to determine the minimum battery autonomy, since maximum autonomy depends on the force applied by the driver when pedaling: the more you pedal, the less battery you consume!
Let’s see how to calculate how many Km an electric bicycle travels autonomously (without the aid of the pedals), on a totally flat route, without interruptions and with a driver weighing 70 Kg. The minimum range of a new and fully charged battery (with a 250w motor, at a maximum speed of 25 Km / h) it is calculated approximately with the following formula: autonomy, Km = Volts x Amper / 10 Example: a 36v-10Ah battery will have an autonomy of about 36 Km. 48v-17,5Ah battery will have an autonomy of about 80 Km. The minimum autonomy of a battery is calculated with greater precision by multiplying the volts by the amperes (volts x Ah). The result will show us the Watt / hour (Wh) of the battery, a result comparable to the tank capacity of a motorcycle. So we will know how much “electricity” can contain our battery. To calculate the autonomy you need to consider the electricity consumption of the bicycle. A bike with a 250w motor that can develop a maximum speed of 25 km / h, will consume 250W in an hour and will travel 25 km.
Therefore, the general formula is as follows: AutonomyKm = Volts x Amper x maximum speed / Motor power Examples:36v-13ah 250W 25 Km / h 36x13x25 / 250 = 46 km48v-17,5ah 250W 25 Km / h 48 × 17,5 × 25/250 = 84 km There is no data in case the route includes uphill stretches and it is strongly discouraged to tackle an uphill stretch without pedaling with a single watt motor !! If the path is not continuous, but involves stops and restarts, autonomy will decrease significantly. The driver’s weight is not very influential on the plains, while it becomes decisive in the event of climbs. Autonomy also depends on the age of the battery. In fact, this variable affects the level of energy that can be stored by the battery: the older the battery, the less the quantity of energy stored and consequently its autonomy.
USEFUL LIFE OF THE BATTERY
Batteries are subject to wear: with the passage of time, batteries are able to store less and less electricity (and will charge faster), with a consequent reduction in autonomy. This chemical process of wear starts from the moment of manufacture and increases with use. On the web, you may come across sites where there is talk of a more or less precise number of refills (from 500 to 1,000): this information is false, since it is obvious that using a battery 50 times a year does not mean that the battery lasts 10 or 20 years. Therefore, in the light of years of experience, we can say that, in normal and realistic situations, the batteries are to be replaced on average every 2 years. There will be customers who want to change the battery before the two year deadline and others who will keep it until the end of the second year. All batteries usually last more than two years, in fact in our stores we have changed batteries even for 3 or 4 years of life. So, when we say that the useful life of a battery is one / two years, we mean that, starting from this term, the first effects of age (decrease in autonomy) are noted. Drivers who use the accelerator intensively: accelerating rapidly (from zero to the top) and who, simultaneously, do not pedal strongly, cause considerable and rapid energy consumption which, in the long term, decreases the battery’s charging capacity. This type of use reduces the useful life of a battery on average to 12/18 months.
THE COST OF THE BATTERY
The cost of electric bicycle batteries may seem high but, in reality, when compared with other types of batteries (mobile phones, laptops, etc.), they are rather cheap: a lithium battery of an ebike can cost roughly 130 € / Kg, while those for laptops have an almost double cost and those for cellphones even up to 4 times as much. The price of Speedy eBike® batteries starts from € 499 (including VAT, 48v), approximately 50 cents. per day but.
It is important to know that batteries are discharged even if not used. A battery runs out in a period of time varying from 2 to 6 months (depending on the external temperature and the material). It is therefore necessary to avoid that the batteries remain totally discharged for a long time and for this reason we recommend our customers to recharge the battery (when not in use), at least once every 45 days.
BATTERY VOLTS = MOTOR POWER
The performance of an electric bicycle depends on the battery volts: despite the fact that the majority of the motors are 250w, those working with a voltage of 48 volts clearly have a higher power than those of 36 volts. This difference is found especially in the presence of climbs: bicycles with batteries of 36 volts are not recommended for use uphill.
To extend its useful life, we recommend that you avoid completely and frequently discharging the battery. For lithium batteries it is preferable to discharge and partially recharge rather than complete and intensive recharges. Recharging a partially charged lithium battery is not harmful, since this type of batteries are not subject to any “memory effect”. The short useful life of a battery is mainly due to the heat it is subjected to, rather than to the charging and discharging process. It is however advisable to make a full refill every 30-40 refills. This will ensure greater accuracy of the battery indicator. It is also recommended to keep lithium batteries at temperatures as moderate as possible, avoiding very high or very low temperatures and direct and prolonged exposure to sunlight. Furthermore, to extend its useful life, in the case of prolonged non-use, make sure that it has been 100% charged.