Battery Packs

[Dougie]

Forgive me if this sounds daft but can any battery pack be
fitted to any ebike ? Obviously the connections would vary (how easy are these to adapt) but providing same volts etc would this be okay

 

[Ian]

In theory batteries of the same voltage and type should be interchangable, although the chargers may not be. In practice it would be difficult as the shape, size and methods of fixing vary, and as you say connectors will differ, some manufacturers using standard types with others using specialised types. It's probably best avoided unless you have electrical knowledge.

 

[Baboonking]

Dougie,

If your happy doing the physical modifications to allow the packs to fit and to attach to your bike then yes. The electrical side is pretty easy, though there are other paramters than voltage that are important. For a technical intro to batteries see here Information about Battery Packs

 

[Leonardo]

Is it still true what it is written on A to B’s “Electric Bicycle Questions Answered” about the different measurement ratio of the different battery types?

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 bicycle 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 bicycle 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.

(They don't say anything about Litium)

Because a good technician told me that on the contrary all the “traction” batteries – independently from their chemistry – are measured at a 10-Hour rate and only the common ("non-traction") Lead/acid at the 20-Hour one.

 

[Ian]

Because a good technician told me that on the contrary all the “traction” batteries – independently from their chemistry – are measured at a 10-Hour rate and only the common ("non-traction") Lead/acid at the 20-Hour one.

That may be true, however the batteries used in most e-bikes are general purpose types rather than those specifically intended for traction purposes. In my experience the term traction battery is normally applied to a much larger battery capable of delivering much higher currents than required for an e-bke. All the quoted capacities I have seen on data sheets for NiMh batteries have been at 0.2C, in other words 1/5 of the battery capacity or the 5 hour rate, and for lead acid types the 20 hour rate.

Hope that clarifies things.

 

[Leonardo]

Thank you for your answer Ian. May be I have some terminological problems, since I don’t know very well the technical language (and may be not only the technical one!). Doesn’t need a pelelec battery to be capable of something like a 10C – may be 20C in the peak – discharge rate? And how do you call this kind of batteries, if it is not “traction”? It cannot be the same kind of battery which are used for normal cars or emergency lights etc., or am I wrong?

 

[flecc]

No, it's not the same as the lead acid battery in cars Leonardo, since the bike batteries use a paste electrolyte. These Sealed Lead Acid (SLA) batteries come in two types. The ones like those used on bikes which are chemically formulated for regular discharge and charge and have a life of typically of up to two years but often less, and a second type which is chemically designed for very long life and full time trickle charge. This second type is used for burglar alarm standby current in cases of main electricity failure, so are very rarely discharged.

The first type is similar to the car types as far as usage is concerned. It's of little importance whether they are nominally 10 or 20x rate, since we use them far outside those specifications, hence the short life and poor availability of the contained charge as A to B infer on their site.

Traction batteries are very large versions of the car type with liquid electrolyte and are designed for high discharge usage. In Britain they are used on various electric vehicles like milk delivery vehicles, small tractors for towing trailers in pedestrian areas, airport passenger vehicles and light trucks. A similar type are also used on the diesel/electric submarines for underwater propeller drive when the diesel engine cannot be run.
.

 

[Ian]

Thank you for your answer Ian. May be I have some terminological problems, since I don’t know very well the technical language (and may be not only the technical one!). Doesn’t need a pelelec battery to be capable of something like a 10C – may be 20C in the peak – discharge rate? And how do you call this kind of batteries, if it is not “traction”? It cannot be the same kind of battery which are used for normal cars or emergency lights etc., or am I wrong?

In answer to you your first question Leonardo, I think you are confusing the term "C" with amps or "A".

The term "C" refers to the batteries capacity which is measured in Amp-Hours (Ah), that means a battery with a capacity of 10 Ah (A typical capacity for an e-bike battery) can in theory deliver a current of 1 amp for 10 hours or 10 amps for 1 hour, although in reality the capacity is reduced as the current goes up.

A 36 volt e-bike/pedelec battery will typically need to deliver a maximum current in the order of 20 amps, which in the case of of a 10 Ah battery could be referred to as a discharge rate of 2C (The discharge current in amps is 2 times the batteries capacity in amp-hours, hence 2C),
Similarly if the same battery is charged at 2.5 amps that would be a charge rate of 0.25C

The maximum current referred to above is a short term peak such as may occur when climbing a steep hill, most of the time the battery will be delivering a much smaller current in the order of 5-6 amps (0.6C).

In actual fact the term "C" is mostly used on manufacturers data sheets, it is probably less confusing so simply measure charge/discharge rates in amps as we always used to.

The battery types used bicycles are similar types as used in emergency lighting, uninterruptible power supplies for computer equipment and a host of industrial back-up applications. Because the bicycle is such an efficient vehicle its power requirements are extremely low when compared to any other vehicle and a relatively small battery will suffice.

True traction batteries are used in larger electric vehicles such as electric and hybrid cars, milk floats, the driver-less vehicles seen in large factories, forklift trucks, mining locomotives etc. where current demands can run to hundreds or even thousands of amps. Our requirements are tiny by comparison.

I 've tried to make the above as easy to understand as possible, I just hope it makes sense.

Ian

 

[Leonardo]

Thank you very much Flecc and Ian for your patience. I was definitely confusing “C” and “Ah”. And there was also a terminological problem, since in Italy technicians use to call the pedelec batteries (the one chemically formulated for regular discharge and charge, and that need to be able of a 20Amps maximum discharge rate) with the name “batterie da trazione”, which sounds like “batteries for traction”: I see that it means something very different in English…

 

[Ian]

Leonardo,

I understand that electric bicycles have been popular in Italy for longer than here in England, therefore Italian battery suppliers probably supply replacement bicycle batteries as an extension to their range of traction batteries, in that case is would probably be correct to refer to them as “batterie da trazione”.

Here in England most battery suppliers do not yet supply batteries specifically for pedelecs and would be very puzzled if someone wanted to buy a traction battery for a bicycle

Ian.