What you need to know about Electric Bike batteries

 

Electric Bike Batteries

Simple question really, what do you need to know about electric bike batteries?

And the answer is simple too…not much.  However, you will find that bike specification sheets and more technical experts than me (not an expert on anything really) will give you long and quite confusing answers.

So here’s what you need to know.

  • An electric bike needs a battery
  • It affects the length of time your bike can assist you in cycling
  • Its power output is assisting the electric motor to spin and drive your bike forward
  • It will need recharging every 30-50 miles
  • They come in different cases and can be located on different parts of the bike
  • You can buy extra ones and replacement ones
  • You can usually take it off the bike to keep it safe or recharge it

What specification do you need?

Brand name

Like most things in life you’re probably more assured by a brand name, so a battery made by Samsung or Yamaha will give you confidence in it’s quality.  They don’t produce any more power than an unbranded battery but they may have a longer lifespan, think Duracell battery for example.  However, that’s not always the case.

Volts (V)

Usually next to the battery brand it will say something like 36V, which means 36 volts.  Electric bike batteries typically come in 24V, 36V, 48V, and 72V.  With 36v now the standard.  In the UK bikes that assist you above 25kmph are illegal so really you don’t need a battery more powerful than 36v.  However, if you have a higher spec mountain bike, or a cargo electric bike which pushes more weight then you might require a 48v or 72v battery.

So the more volts the faster and more powerful the flow of energy from the battery to the motor.

Amps (ah)

Amps are designated with an “ah” on the description, and it designates the volume of fuel you have readily available.  So a battery with 10ah, which is pretty standard, will have 10 amp hours of power to deliver.  Now how fast that 10ah gets used up depends on a lot of factors, mainly how much weight is being shifted, how efficient the motor is, how much pedal assistance you’re asking it to provide, and whether you’re climbing hills.  So when a company makes a claim that the 36V 10ah battery will provide 50 hours of pedal assistance that’s usually under good conditions.  If you were to add on a pannier with a picnic in it, and climb a few hills on the way to your picnic site using the pedal assistance at maximum you’d probably find you only get about 20 miles out of the battery.

You can get batteries with 15ah or 20ah volume which can be handy for people who travel longer distances, or an alternative is to buy a second battery and swap them around when drained.

A 36v 10ah battery should get you most places

Watts & Watt Hours (Wh)

Some electric bike specifications refer to Watt Hours (Wh), which is basically a measurement of the energy capacity of your battery.  It’s calculated by multiplying the Volts x Amps.  So a 36V battery with 10ah has 360 Watt Hours.  Each mile you travel can utilise between 5 and 30 Wh depending on several factors mentioned elsewhere in this post.  So really this figure isn’t much help!

Li-ion

Li-ion isn’t about the roaring noise the bike will make when you accelerate…sorry!  It’s Lithium-ion which is basically the chemical component filling the battery.  Li-ion batteries are preferred for rechargeable batteries because compared to alternatives such as NiMH and NiCd batteries, they retain the charge longer.   NiMH and NiCd batteries can lose anywhere from 1-5% of their charge per day, which means while your bikes sat there unused the battery charge is slowly eaking down.  Li-ion batteries also have a higher energy density than most other rechargeable batteries types which means that for their size and weight they can store more energy…important for electric bikes.  The disadvantage of Li-ion batteries is they are more expensive than other batteries and need a dedicated charger, which does increase the cost of electric bikes.  So while you may be able to buy a cheaper battery which isn’t Li-ion, be aware of the cons of that.

Locks

Some electric bikes have lockable battery cases which does make it harder for someone to steal them.  Worth thinking about if you lock your bike up in a public place.

Cost of recharging

If you want to know about the cost of recharging electric bike batteries please see my post on how much it costs to run an electric bike.

Why do they look different?

A question some people ask is why batteries look better on some electric bikes than others.  Basically what you’re seeing is the case the battery is in.  Some companies have managed to disguise the battery somewhat as a water bottle (see the Gtech eBike) or made it look more slimline and part of the bike (see the HaiBike Sduro Trekking).  All of this is aesthetic really, but is a big challenge for electric bike manufacturers as the sight of the battery is the major turn off for new buyers of electric bikes.  Really its the only thing that visually differentiates a standard bicycle from an ebike. Hopefully, we’ll see advancements in this in the future with less visible slim line or frame-concealed batteries.

Summary

I’m sure, and I hope some more technical people than I will correct any wrong terms I’ve used here.  I’m also positive there’s much more to be said about electric bike batteries.  But this article is for people making a decision on which electric bike to buy, possibly their first ebike purchase.  So all you need to know really is what is contained in the image above with the map background!  If you’re buying an electric bike and it has a standard 36V 10ah Li-ion battery then you should be pretty pleased with the results.

2 Comments:

  1. What battery does your electric bike have, and how many miles do you get out of each charge? Look forward to hearing from electric bike owners…

  2. Although the Ah rating of a battery is the most common, Wh discloses the energy available without further calculation. For instance a 36v 10Ah battery stores 50% more energy than a 24v 10Ah battery and therefore has potentially 50% greater range. As 36v seems to be becoming the standard this shouldn’t be much of an issue but buyers need to beware that 24v batteries need 50% greater Ah capacity to compete with 36v ones. Also losses in the wiring are much less with higher voltages so a 48v battery with the same Wh capacity as a 36v will be more efficient.

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