Li-ion or LiFePo

[carpetbagger]

thanks flecc,i hope to switch from leaded to unleaded fuel as soon as my battery packs in....but these warm temperatures keep giving it a new lease of life !....Maybe i should move to Spain and it would last forever

[Wooky]

Thanks flecc for that detailed explanation, the difference in weight between LiPo and Li-Ion is very noticeable on top of the chemistry side of things.

Terry

[torrent99]

Originally Posted by Wooky

Thanks flecc for that detailed explanation, the difference in weight between LiPo and Li-Ion is very noticeable on top of the chemistry side of things.

Terry

Terry you might want to read Flecc's post again...

Li-Ion refers to Lithium Ion ..... ALL the "lithium" batteries we talk about are Lithium Ion it's the way they work.

LiPo usually means Lithium Polymer i.e. the method of construction rather than the chemistry. Unless they are confusing it with LiFePO4.. (i.e. the newer Iron based ones)

Of course just to confuse things some people seem to refer to Cobalt & Manganese base cells as Li-Ion and talk about LiFePO4 as if it were something else!

Confusing eh?


Re Weight

For a given energy capacity:

LiFePO4 batteries are unfortunately currently the heaviest and largest.

Manganese are in the middle.

and Cobalt are the lightest and smallest.

[flecc]

Originally Posted by torrent99

Of course just to confuse things some people seem to refer to Cobalt & Manganese base cells as Li-Ion and talk about LiFePO4 as if it were something else!

I think that's how Terry is using Li-ion, it seems it's more or less become an e-bike convention to speak of li-ion manganese just as Li-ion.

With hindsight a much better way would have been to drop the "ion" in all cases and just use the principle chemical abbreviations thus:

Li-Co, Li-Mn, Li-CoMn, Li-Fe

adding poly where polymer construction applied.
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[Wooky]

My Head Hurts!

Terry

[Bigbee]

Originally Posted by torrent99

[b]

For a given energy capacity:

LiFePO4 batteries are unfortunately currently the heaviest and largest.

Manganese are in the middle.

and Cobalt are the lightest and smallest.

What are the approx weights of these three bateries please?

[flecc]

Originally Posted by Bigbee

What are the approx weights of these three bateries please?

Cobalt can be forgotten, they aren't available any more for safety reasons as I've indicated above. When they were available they were almost the same weight as the manganese versions. The three weights now are Li-ion manganese including compound types, either plate construction with rigid cells or polymer construction and LiFePO4,. Weights vary according to battery voltage and capacity and whether polymer or not, but to give a typical example of a 37 volt 10 Ah battery from eZee, the plate construction Li-ion manganese is 4.4 kilos, the polymer version is 3.3 kilos and an equivalent LiFePO4 would probably be about 5 kilos.

So the weight of LiFePO4 isn't a deal breaker, but more importantly they are usually a little bit bigger for a given capacity and discharge rate so won't fit into the same case.
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[RobinC]

The current Ping 36V 10Ah weighs in at 3.8Kg, adding a few 100 grams for a box makes it about 4Kg.
Unless folks are happy to replace the battery frequently maybe a fairer comparison would be size & weight for a given capacity after say 6 or 12 months use.

Robin

[Andy_82]

Originally Posted by flecc

It's all very confusing due to the abbreviated way batteries are referred to by the suppliers, none of the references complete and accurate.

The Lithium refers to the basic material and ion to the electricity handling method, and these are all lithium-ion

Terms like cobalt, manganese etc refer to the cathode material used, while polymer refers to a type of cell construction that avoids rigid plates.

Therefore a battery can be lithium-ion manganese polymer, each word referring to something different and not contradictory. Of course mouthfuls like this are too cumbersome, so the battery and bike manufacturers use the minimal combination they think most attractive in sales terms. li-polymer generally the current favourite.

Now the background. Originally lithium ion battery cells used rigid plates with a cobalt cathode and these performed really well for current delivery, but with time it was realised that slight manufacturing faults could cause fires to occur, and you may have seen or read of the sudden laptop fires that occurred. These also affected many e-bikes and in at least one case someone's house was burnt down as a result. Clearly something had to be done rapidly about the cobalt cathode which was the source of the trouble although not the direct cause.

There's about a dozen elements which are suitable for this cathode use in ascending order of suitability, with cobalt fairly high up the range, but the only suitable alternative which could be used with the technical knowledge available at the time was manganese which was very safe. Unfortunately it was lower down the range of suitability and couldn't deliver current as well, and led the well known battery failures on the more powerful bikes,

With time the chemistry and construction was improved, making them mostly just about good enough, but clearly more was needed, so some complex cathodes were created, basically a compound blend of the former cobalt with manganese and additional elements which was both safe and better at delivering current, and these are the expensive top grade cells of today that you see in batteries used by Wisper, eZee, Panasonic, BionX etc.

The polymer construction came in parallel with the developments in chemistry, and it's basically a particulate way of constructing the contents that allows soft cell casings and almost any shape of cell to be constructed. The attraction for e-bikes is that these are very much lighter than the former plate cells with rigid cases, which were often made of welded steel.

So going back to the terminology, we can now have this sort of battery:

Lithium-ion nickel manganese cobalt complex oxide powder polymer

with even more complex ones appearing, so I bet you're now pleased the manufacturers do abbreviate!

The latest development of LiFePO4 has the name lithium iron phosphate, note the word "iron" not ion, though these are also ion batteries. Iron is right at the top of suitable cathode materials, but for years it proved very difficult to find a way of using it. That's now been cracked with iron phosphate. Because iron is so suitable these promise to eventually be lifetime batteries, and they will already accept between 1000 and 3000 charges depending on the rates of discharge, in turn depending on the power of the motor used.

As yet the mass production of acceptably priced versions of these for our continuous high discharge use on powerful e-bikes has not been reliable enough, though they are used successfully in more intermittent applications like power tools. They should arrive for us eventually.

For the future there's developments of the anode material in hand. At present they all use carbon anodes which perform well so have not had much attention, but these will be improved upon. And of course there's always the possibility of a completely new type of battery appearing, though none of the other current advanced types are suitable for e-bike use.
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Hi Flecc,

This is all great stuff you are explaining to us. I was just wondering where the hell did you get all that knowledge as I can see you are very knowledgeable about all these electric bits. Are you a professor at Oxford or Cambridge Uni???

Anyway guys, all the biggest respect to Flecc, this forum wouldn't be the same without him.

[flecc]

Originally Posted by Andy_82

Hi Flecc,

This is all great stuff you are explaining to us. I was just wondering where the hell did you get all that knowledge as I can see you are very knowledgeable about all these electric bits. Are you a professor at Oxford or Cambridge Uni???

Anyway guys, all the biggest respect to Flecc, this forum wouldn't be the same without him.

Thanks Andy, very generous of you. No, I'm not a professor or anything remotely like that, in fact the most enjoyable part of my education for me was being expelled from school at 14 years old and getting out to work!

All my learning was subsequent to that and for the most part it's due to having an inquiring mind and very retentive memory, short and very long term. I often compare my brain to blotting paper, able to soak up large quantities of knowledge very rapidly! That, added to having previous trade experience and a long term interest in the subjects related to e-bikes is where the knowledge comes from, and I also supplement my memory with the fine details methodically filed away.
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