How large does my battery need to be?
Understanding Battery Capability
Except you might have an eBike stolen from a museum, we’ll assume that your battery kind is lithium ion. These themselves are available varied sorts, nonetheless, the important thing data when selecting a battery is the voltage and capability, measured in amp hours (usually written ‘Ah’)
The amp hours measurement tells you what number of amps a battery will ship for one hour. So for instance, a 15ah battery gives you 15amps for one hour, or 7.5amps for two hours, or 5 amps for 3 hours. Hopefully you might be getting the thought!
When understanding how lengthy the battery will energy your motor it’s useful to transform the voltage and amp hour determine to watt hours. This can let you know what number of watts it’ll provide for an hour. It’s simply calculated by multiplying the volts and amp hours collectively.
For instance, a 15Ah, 48v battery would ship 15 x 48 = 720W hours (usually written 720Wh). Or a 17.5Ah 36V battery would ship 17.5 x 36 = 630Wh.
You then have to keep in mind that you need to by no means fully empty a chargeable battery. In the event you do, your battery life will undergo. As such, all units that use batteries are designed to chop out earlier than the battery is totally discharged. How a lot you’ll be able to discharge them will depend on the kind of battery. Lead Acid batteries of the sort that energy caravans or begin your automobile shouldn’t be discharged by greater than 50%. The excellent news is that lithium ion batteries might be discharged by 80%, in order that solely 20% of their capability is left.
Understanding Battery Capability
The ultimate complication is climate. All batteries unfastened capability within the chilly. At 0 levels, the lead acid battery in your automobile looses half of it’s capability – this is likely one of the causes vehicles might be more durable to begin in chilly climate. Lithium Ion batteries are likely to unfastened 10-20% – shall we say 15% on common.
With all of this data lets calculate the capability of a battery. Lets take our greatest promoting 48V 17.5Ah battery.
If we calculate 17.5Ah x 48V = 840watt hours. So the battery will in idea provide 840Watts for one hour.
Subsequent, lets take note of the 20% of capability we should not use. Taking 80% of the capability:
840WH x 80% = 720WH
Which means that our battery in the summertime can produce 720W for 1 hour.
Within the winter, if we drop this by 15% – we get 612Wh – so when its 0 levels exterior we’re solely going to get 612 watts for an hour.
How lengthy will this energy my motor?
As soon as you realize the watt hour measurement in your battery, bearing in mind the time of yr and making certain you solely use 80% of the capability, you could perceive the facility necessities of your motor.
All motors will include a most energy ranking. That is normally 250W (BBS01b 250W motor), 500W (the BBS02 500W motor), 750W (the BBS02B 750W motor) or 1250W (the BBSHD motor). Don’t neglect that is the utmost utilization of the motor. Except you at all times journey flat out you may be utilizing quite a bit lower than this.
The precise quantity of energy that you simply use will rely upon just a few different elements. Sometimes these are:
1. How briskly are you going to journey? At 8MPH a lot of the energy can be out of your pedalling and the motor will do little or no. At 30MPH most of effort can be your motor, which coupled with the additional wind resistance will use a great deal of energy.
2. How heavy are you and your bike? If you’re a bigger particular person, or in case you are utilizing a motor to maneuver a cargo bike (now we have carried out a number of ice cream bike conversions) they’ll use much more energy.
3. How hilly is it? There is no such thing as a getting away from the truth that each uphill will use extra energy!
4. Are you utilizing a lot throttle? Identical to your automobile, being heavy handed on the throttle will use extra energy.
5. What mode are you in? All eBikes will let you set a mode which can prohibit how a lot energy is used.
Understanding Battery Capability
Taking all this into consideration, we normally counsel that for a median bicycle owner, touring at a a medium pace of possibly 15MPH, with typical British rolling hill panorama, and never utilizing a lot throttle, then essentially the most they may use is round 50% of their motors said most use. So a 750W will in all probability use round 375W per hour. In fact, set your mode decrease, pedal extra, preserve off the throttle and get match, and you’ll simply drop that determine to solely 25%. Which means that a 750W will solely use 187W per hour.
So, if you realize that your 750W goes to make use of 375W per hour, and your battery is round 600W, then you’ll get round 1.5 hours of use out of your 48V 750W motor. If you’re heading alongside at 15MPH, you then’re going to journey 25 miles. Do a bit extra pedalling and you may be 187W use, which with the 48V 17.5Ah battery goes to energy you for over 3 hours. At 15MPH that is going to take you round 50 miles.