eZee Battery Weight?

[Tiberius]

I seem to remember someone, possibly Flecc, saying the latest eZee Lithium batteries are lighter than the previous ones. Is this so, and is it a general trend in Lithium batteries or just a one off peculiarity?

For the record, I have two eZee lithium batteries and they weigh 4.6 kg and 4.5 kg. That makes their Wh/kg score worse than either my Ping LiFePo or my Headway LifePo packs, whereas I'd expect it to be the other way round.

Nick

 

[flecc]

Yes, it's the polymer batteries that are lighter Nick. The eZee one I tested was made by Phylion and is a standard rigid plate cell construction with the cells steel cased as previously, and that weighs 4.4 kilos as previously.

The alternative eZee have adopted now is a polymer one that has soft cell casings like the Panasonic one shown below, and it weighs only 3.3 kilos.

 

[Tiberius]

Thanks Tony,

That's a big reduction in weight, and it would put them ahead of the LiFePo. Even the pouch type LiFePo's.

Its probably worth pointing out that the pack case can make a difference. There's also the difference between theoretical and actual Wh from the battery pack. But in general you'd expect LiFePo to be a bit heavier on a theoretical (nominal) Wh basis, but possibly to work out better on an actual basis after a period of use.

Nick

 

[flecc]

I agree that one would expect the LiFePO4 batteries to be heavier Nick, but much of the weight of those older Li-ion manganese batteries was in the welded steel cell casings and their pressure release valves. I'm of the opinion that they were probably overkill resulting from the panic over the fires and explosions that the Li-ion cobalt types caused.

With more experience and the introduction of polymer construction, designers seem to be taking a calmer and more rational view of how to build them.

eZee still haven't changed the case construction for my battery and I think the polymer one is also still the same, unlike Panasonic and some others who now use thinwall casings. That said, the empty eZee case with base only weighs 650 grams, so I doubt that much saving can be made with the same slide attachment, locking method and blade connector base incorporated.
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[jerrysimon]

One of my other hobbies is electric model planes/helis. Lithium Poly cells have revolutionised the hobby in terms of electric flight, mainly becasue of their light weight.

The packs we use look just like this with soft cell cases that are then shrink wrapped together. One of the dangers as I understand is that if damaged they swell, pop and then release fumes that are highly combustable. Care has to be taken when charging though I think now intelligent chargers do a good job.

In this application for ebikes, I would have thought that a rigid case to contain them all was essential

Regards

Jerry

 

[flecc]

Care has to be taken when charging though I think now intelligent chargers do a good job.

In this application for ebikes, I would have thought that a rigid case to contain them all was essential

Regards

Jerry

I don't know what protection you have for the cells in those model applications Jerry, but in e-bikes the whole protection job is done by a BMS (battery management system) inside the batteries. The chargers aren't smart ones and don't need to be, since the BMS looks after all charge regulation cell by cell, plus the final charge cutout function. The BMS also includes low voltage cut-out protection for the cells. You'll see a typical internal setup on my Torq website here.
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[jerrysimon]

Ah now I understand. It hadn't accured to me that all the clever stuff is done by the BMS inside the rigid battery casings that you have with e-bikes

In the model areo world all the battery charging management is handled by the charger not the battery packs. As I said these need to be as light as possible, so no fancy BMS on board.

Regards

Jerry

 

[flecc]

Thanks Jerry, I had a feeling that would be the case but wasn't sure, since my involvement with the model world was many decades ago when electric flight wasn't an option. Lead-acid batteries don't take well to flight.
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