Batteries

October 30, 2015 Posted by scriptadmin - No Comments

Voltage Explained

Voltage can be thought of as the pressure or strength of electric power. All things being equal (see AMPS below), the higher the voltage the better, because high voltages pass more efficiently through wires and motors. Very high voltages (100+ volts) can give you a nasty shock because they also travel through people rather well, but the sort of voltages found on electric bikes (12 – 36 volts) are quite safe. As a rule, a 12 volt system is fine for low-powered motors, but more powerful machines work better with 24 or 36 volts. Electric mopeds and motorcycles tend to use higher voltage – typically 48 or 60 volts.

AMPS explained?

Amps can be thought of as the volume or quantity of electric power. To aid this analogy, the flow of amps is called the current, as in the flow of a river. Unlike a river, though, the speed of the current is fixed – only the volume varies. The maximum flow of amps in a bike drive system can vary from 10 to 60 or more. A current of 60 amps requires thick wiring and quite substantial switchgear.

What batteries do we use?

At ByoCycles ltd we use Lithium-ion batteries supplied by Yoku and Samsung. Yoku provide our basic battery range and in the time we have been using them, since 2011, we have had fantastic success with reliability and performance. Samsung provide our upgraded batteries, these are lighter, more efficient and give improved power delivery whilst riding. These batteries also offer a greater capacity for improved range on one charge.

Battery prices

Battery Size Yoku 9ah 36V Yoku 10ah 36V Samsung 11ah 36v Samsung 13ah 36v
Chameleon Range £299.00 £449.00
Zest Range £275.00 £384.00
Ibex Range £299.00 £449.00

 

Voltage Explained

Voltage can be thought of as the pressure or strength of electric power. All things being equal (see AMPS below), the higher the voltage the better, because high voltages pass more efficiently through wires and motors. Very high voltages (100+ volts) can give you a nasty shock because they also travel through people rather well, but the sort of voltages found on electric bikes (12 – 36 volts) are quite safe. As a rule, a 12 volt system is fine for low-powered motors, but more powerful machines work better with 24 or 36 volts. Electric mopeds and motorcycles tend to use higher voltage – typically 48 or 60 volts.

AMPS explained

Amps can be thought of as the volume or quantity of electric power. To aid this analogy, the flow of amps is called the current, as in the flow of a river. Unlike a river, though, the speed of the current is fixed – only the volume varies. The maximum flow of amps in a bike drive system can vary from 10 to 60 or more. A current of 60 amps requires thick wiring and quite substantial switchgear.

How big a battery do I need?

The capacity of the battery is usually measured as the amount of current it can supply over time (defined as amp/hours). However, this is useless on its own, because you’ll need to know the voltage too. By multiplying the two figures together, we get watt/hours – a measure of the energy content of the battery. Unfortunately, it isn’t that simple… but you didn’t think it would be, did you? In practise, you’re unlikely to get results that match the stated capacity of a battery, because battery capacity varies according to the temperature, battery condition, and the rate that current is taken from it.

Lead/acid batteries are tested at the ’20-Hour’ rate. This is the number of amps that can be continuously drawn from the battery over a period of 20 hours. However, an electric bike will usually exhaust its battery in an hour or two, and at this higher load, the battery will be much less efficient. So the figures for lead/acid batteries tend to look optimistic. On the other hand, Nickel-Cadmium (NiCd) batteries are rated at a 1-Hour discharge rate, so although the stated capacity of a NiCd battery might only be half that of a lead/acid battery, performance on an electric bike will be much the same. Nickel-Metal Hydride batteries (NiMH) are measured at the 5-Hour rate, so their performance tends to be somewhere between the two.

The capacities of typical bike batteries vary from a 864 watt/hour giant (36 volts x 24 amp/hours) to the tiny 84 watt/hour pack on the early SRAM Sparc kit. It’s best to choose a package that will provide twice your normal daily mileage. It’s difficult to guess the mileage from the watt/hour capacity, because actual performance depends on the bike and motor efficiency, battery type, road conditions, and your weight and level of fitness.

Which Battery type is best?

95% of modern electric bikes come with Lithium-ion (Li-ion) batteries. These are more weight-efficient than the other types, and are supposed to have a longer life, but can do some odd things. Charging and discharging must be carefully controlled to prevent the cells going into terminal meltdown, so either the charger, the battery or both will be packed with electronics. Fires are now rare(!), but initial hopes that costs would tumble proved unfounded, and these batteries are currently very expensive. Cheaper ones abound, but their life can be very limited. Despite these problems, the Li-ion has become the default battery. Lithium-ion Polymer (usually called Li-pol) doesn’t really offer any performance advantage in terms of weight or range of Li-ion, but it’s safer and can be moulded into interesting shapes.