- do not charge the battery below 0C or 32F outside temperature
- do not discharge below -20C or -4F
- during storage, store the battery with 50% SOC (state of charge)
In many situations, especially when replacing a battery in an existing installation, the required voltage is determined by the controller and can not be easily changed. It should be remembered that the voltage determines the maximum speed at which the vehicle will move. If you know the voltage [V] and the rpm value of the motor, it is easy to calculate what speed the vehicle will reach for a given voltage.
The range of the battery depends of course on how much effort we will make while pedaling, how fast we travel and what is the area where we are.
|Driving type||Approximate energy consumption|
|Street (Minimum electric drive assistance – using electric drive only at hill, driving below ~ 30 kph)||6-8 Wh/km|
|Standard (~40 kph with pedaling, continuous assistance of the electric motor)||9-12 Wh/km|
|Race (without pedaling / with additional load / fast riding)||14-20 Wh/km|
Estimate the distance you have to travel, multiply it by the appropriate Wh / km from the table above and you will get the total minimum number of Wh needed to cover this distance. Then Wh which you have estimated, divide by the nominal voltage of the battery, and get an estimate of the minimum amp-hours that you will need from the battery to drive a certain distance.
One of the more frequently asked questions is: “Should I buy a 48V or 52V battery?” The amount of power we will need is a choice that everyone has to make on their own. Some are satisfied with lower voltage, others are looking for higher performance and so on.
The battery for e-bikes has constantly evolved from 24V to 36V, then 48V, and now the standard becomes 52V. Higher voltage allows for higher efficiency (the battery uses less electricity to produce the same power)
When this higher performance is combined with more battery capacity and the latest charging techniques, we can achieve a surprisingly high battery life while maintaining very good performance.
Most of the engines that are designed to work with 48V voltage, such as Bafang BBS02 (BBS02 and BBSHD engine controllers can be used with 39-60V), they also deal with 52V batteries (max 58.8V). There is no doubt that these engines work much closer to the end of this range. 52V battery gives great performance, while in 48V battery the voltage drops below about 44v, the bike starts to seem anemic.
Using the 14S battery (52V), the motor has access to 48V voltage for a longer time and gains more possibilities than is the case with an equivalent 13S battery (7.7-10% more wat hour compared to a 13S battery). 52V battery will also work at a lower temperature when using the same power, from a battery with lower voltage.
With a 52V battery, the bike will be noticeably faster and will have better acceleration. Additionally, it should be remembered that the more cells, the less voltage drop during unloading..
We had the opportunity to work for a long time to test the BBS02 and BBSHD engines with batteries both 52V and 48V produced by us. When driving with fully-charged 48V and 52V batteries, you can feel minimal differences in dynamics and maximum speed. Real differences appear from the moment batteries are discharged halfway, then the power drop is felt, and when the battery runs out to about 1/4 of the capacity, the difference seems even more noticeable. With a 52V battery, it never really happens, because the voltage never drops to such low values as with a 48V battery. To sum up, 52V batteries with BBSxx engines are still working with high efficiency until BMS does not cut the voltage.
What are the long-term consequences of reliability resulting from powering these devices with a 52V battery compared to a standard 48V battery?
Why would you like to use a more powerful battery than the one for which the controller was designed?
This is really a million-dollar question, and I think that these engines were actually designed from scratch to work with 52v packages. Bafang’s engineers probably wanted to make their engines run with more popular batteries available. Now that Bafang has updated his Mosfets in the controllers, the weak point in both BBS02 and BBSHD has become the gear – the main gear reducer. When BBSHD was connected to the 65A controller, the plastic gear was the first thing that got damaged. Fortunately, the cost of replacing this item is around 40$, and the replacement time is 1 hour.
What about the reliability of the engine when using it with a 52V battery? In the case of the BBSHD engine, we did not find any failures. As for the BBS02 units – gear failure most often occurred with fully-charged 52V batteries. We met with other failures, however, they resulted from other reasons, such as poorly matched gears, too heavy weight, etc.
The BBSHD engine operates without charge during a long continuous discharge of 30A with a 52V battery. The driver hidden in the engine has 12 mosfets instead of 9 (as in the case of BBS02 750W), and the whole has a solid cooling system on both the engine and the controller. Even during large and long driveways at full power, you can see that the engine is barely warming up, which in the case of the BBS02 engine is strongly felt.
It is now known that in most lithium batteries (with the exception of LiFePO4), the cell / pack life cycle can be drastically increased by not charging / maintaining the cells to 4.2 V, but instead charging to a lower voltage, eg 4.1V. In this way, manufacturers of electric cars can get 5-8-year warranty on batteries, which usually when charging up to 100% reach only ~ 500 cycles.
CHARGING AND DISCHARGING BATTERY UP TO 90% WE INCREASE ALMOST TWICE BATTERY LIFE !!!
Most chargers for electric vehicles do not have the option of setting the charging voltage and operate in one charging mode up to 4.2 V / link. As a result, it gives the maximum possible range of the battery but at the expense of reducing the life of the battery at each charge. In many cases, this means a battery replacement worth 2000 PLN every 1-2 years, when with proper maintenance you can extend the life of the battery to about 4-5 years !!! In fact, the further away from full charge, the closer to the long battery life.
Thanks to our charger it is very easy to choose the battery level for a given percentage of full capacity – you can set the charging to 90% and 100%. And so in the case of a 20Ah battery, regularly overcoming trips requiring less than 18Ah, we only need to charge the battery to 90% (up to 18 Ah). At the moment when we want to get a full range of batteries or allow BMS to balance cells, this is the only opportunity to take advantage of recharging up to 100% (many cheap BMS chips start balancing cells with maximum battery charge).
Partial charging and cell balancing
The only disadvantage of continuous partial load is that large parts of low-cost and low-quality BMS circuits start the balancing process at the closest maximum battery level. This means that when performing partial charging, the cells will not reach the maximum voltage, and BMS will not start the cell balancing procedure. Over time, the voltage levels on individual cells can go away and the battery will have less capacity. To avoid this, it’s enough to occasionally (once or twice a month) charge the battery up to 100% or use high-quality, tested, programmable BMS systems that can start the balancing procedure even at 50% battery charge !!!