Battery Design and Chemistry

[brucehawsker]

I wonder if anyone knows of a good and accurate review of the currently available and used, not reseach dreams, electric bike Li battery chemistries and technologies.

For example, there appears to be lot of erroneous material in electric bike marketing documentation about the batteries used, with terms which have specific technical meaning being bandied about without complete understanding. Also numbers regarding peak amapages seem unlikely or even downright dangerous.

I understand our batteries very well, but I would love to be able to point to a third party document which explains the pros and cons of the various competing technologies, especailly regarding Cathode construction oand the electrolyte and use of PEO.

Thank you in advance

Bruce

 

[Deleted member 4366]

Bruce, come on! Is anybody interested in what's inside a battery? That's for the designers and manufacurers. What we want to know is how many real joules (or wh) can it provide; how much does it weigh; how big is it; how many amps (max) can it supply; how long will it last. Most people are more interested in the colour than whether the CEO's put PEO in it. I agree with Eddio: It's starting to get boring now. We want reali (useful) info not smoke and mirrors.

Why don't you just send me a sample of the bike. I'll ride it to work and back a few times; take it down Ironbridge gorge on my weekend ride, and then I'll be able to to tell the world how fantastic it is.

 

[jbond]

Time for a battery FAQ. Pros and Cons of
- Whatever chemistry is used in the low priced Phylion ally cased batteries in typical commercial bikes.
- Ping style duct tape LiFePo
- A123
- RC style LiPo packs

And there appear to be some new chemistries coming with Li NMC.

We seem to be getting a rash of eBay LiFePo batteries as well that really aren't LiFePo at all.

There's some confusion here I'd love to see cleared up. That first one of the Phylion packs vs LiFePo, especially. The stats and specs don't seem to match Wikipedia's details about LiOn chemistries at all.

 

[jbond]

One thing that puzzles me. Ping's LiFePo batteries typically have a 2C rating. The A123 LiFePo cells are more like 20C. Is the difference due to the Cells (pouch vs Cylindrical) or the BMS and lack of it.

I think there might be a market for a packaged A123 based battery fitted with a BMS of about 4-5AHr. You'd get the light weight and small size for short journeys but still have something that was dead simple and protected to charge and use. And the High C rating would mean it could handle reasonable current loads. The ideal would be a setup so you could swap from a light, short range battery to a big, heavy long range battery using the same charger and with no other changes to the bike.

 

[NRG]

They have a 2~3C cut off protection inbuilt it seems so maybe a bit of both, the BMS protects the cells because they are not 20C types....maybe.

 

[tillson]

I wonder if anyone knows of a good and accurate review of the currently available and used, not reseach dreams, electric bike Li battery chemistries and technologies.

Generally, ebike batteries tend to be jaw droppingly expensive, have a life of just under 50% of that claimed by the manufacturer and come with, at best, a vague warranty. Anything else a diversion from theses important issues.

I hope this helps.

 

[flecc]

Generally, ebike batteries tend to be jaw droppingly expensive

Inevitable in a market for a small selling item which ages in storage and has to have it's import cost doubled before VAT is applied for the suppliers to survive long term in the tiny market. The market for A123 power tool batteries in comparison is worldwide, huge and consistent.

have a life of just under 50% of that claimed by the manufacturer

Unavoidable to a form of transport which is intrinsically unable to carry an adequately specified battery due to weight and size considerations and therefore unduly stresses them. The whole concept of an e-bike with battery technology as it stands is fundamantally flawed.

come with, at best, a vague warranty.

Best possible due to the above factor.

Conclusion? If we wish to use one despite the above, we have to accept the limitations.
.

 

[DefCat]

Can anyone comment on E3's product. Their battery is a 36V10Ah Li-Ion, with a claimed 2,000 charge cycle, therefore making it a pherosphosphate battery (the one's which go boom). Unsuitable for a road application in the UK unlike say a LiMn2O4 I think, but that's my personal opinion. Would less connections make any difference, and would a 1.5" tyre make that much difference against say a mid range schwalbe touring tyre? E3 seem to be promising the world but still look cheapy chinesey...

 

[brucehawsker]

My limited understanding of anyone else's batteries, it seems to me the candidates in the real world are:

Li-ion: Lithium Ion
Li-po: Lithium Polymer
Li-Mn-02: Lithium Manganese Dioxide

C: LiCoO2
A: Li (metallic) or Li-C intercalation
E: organic solvent + electrolyte LiPF6

C: LiPO4
A: Li (metalic)
E: Solid Polymer such as polyethyleneoxide PEO plus LiPF6

C: LiMn2O4 Manganese Spinel
A: Carbon (intercalation)
E: Solid Polymer such as polyethyleneoxide PEO plus LiPF6 or LiBoF4


Have I missed anything? Anyone care to comment on the relative attractiveness of the competing technologies?

 

[tillson]

Inevitable in a market for a small selling item which ages in storage and has to have it's import cost doubled before VAT is applied for the suppliers to survive long term in the tiny market. The market for A123 power tool batteries in comparison is worldwide, huge and consistent.



Unavoidable to a form of transport which is intrinsically unable to carry an adequately specified battery due to weight and size considerations and therefore unduly stresses them. The whole concept of an e-bike with battery technology as it stands is fundamantally flawed.



Best possible due to the above factor.


Conclusion? If we wish to use one despite the above, we have to accept the limitations.
.

I understand all of this, and on reflection, I can see, to some extent, how the batteries end up being so expensive. Unfortunately, the facts do remain. They are expensive and they don't last long.

Perhaps if the manufacturers weren't so, "enthusiastic" about their battery's performance, it would avoid customer disappointment. I don't suppose this will happen though, because if one company told it like it is, this would put them at a commercial disadvantage to the more, "enthusiastic" sellers.

An interesting point about the small capacity of the battery shortening its life due to the stress of general use. Perhaps if the new 18 Ah Kalkhoff battery was marketed and limited by the BMS to say, 10Ah, it would alleviate this stressing problem and allow it to perform closer to the promised specification. Again, unlikely to happen as a 10 Ah battery isn't as headline grabbing as an 18 Ah one.

 

[NRG]

You make a very good point there, the 18Ah battery could be setup as a 12Ah and the life would be extend by a large amount maybe past the 2000'cycle sometime quoted in specs but achievable in practice.

 

[flecc]

An interesting point about the small capacity of the battery shortening its life due to the stress of general use. Perhaps if the new 18 Ah Kalkhoff battery was marketed and limited by the BMS to say, 10Ah, it would alleviate this stressing problem and allow it to perform closer to the promised specification. Again, unlikely to happen as a 10 Ah battery isn't as headline grabbing as an 18 Ah one.

Unlikely as you say. Of course high discharge rates in smaller sizes which match demands are possible as witness the A123, but with those high rates and performance from a small, light battery comes short range. Ideally an adequate e-bike needs a LiFePO4 battery of at least 36 volts and 30 Ah with fairly high discharge rate ability for demands like hill climbing, together with software limitation of the charge limits to no nearer than 15% of charge/discharge extremes. A battery like that could be expected to last at least 5 years with usable range, in most territory for very much longer, and it need cost no more than present technology. The fly in the ointment is the impractical battery weight and size of course, which is where the latest mopeds and e-cars win out.
.

 

[Chief eZee Power]

battery capacity

eZeebike current arrangement has 37V14Ah and a built in option to connect another 14Ah with a flat pack on the rear carrier ( purpose built battery rear carrier ) or a soft bag. Total 37V 28Ah 1036Wh , it's not ideal, but it is the biggest there is in the market now, it is more than enough for any real heavy weight and range in electric bicycle applications. The less stress you put on any given battery, the better the life span, the bigger the capacity the less stress there is under any operating conditions.

Chief eZee Operator

 

[stevie]

Hello dear forum members,
I recently received my pro connect 11 (2011 model) and am generally very satisfied with the quality of workmanship and the handling of the bike. I have one issue that is troubling me a little: While pedaling, without the power on, I feel a little drag from the motor free wheel. It is much less than when the the motor is turned (I removed the chain to check this), but still more than I would expect from a free wheel. Can anyone help me in determining if this is normal? Or should the resistance be near to nil? Best wishes and Happy New Year to all, Stevie.

 

[flecc]

Hi Stevie. With the chain removed, do you mean the motor's small chain drive sprocket turns very freely clockwise, but there's drag when the chain is on?