The Battery technology thread - How will EVs be powered?

[n_dawg]

Originally Posted by KarenRei

What are you referring to? Are you suggesting people lower the pack voltage to increase amps? How will that help you any?

Ahh, that kind-of makes sense.

I guess my question is this – are EV batteries usually limited by total energy or total power? I guess I've always assumed they're limited by total energy, when in reality it's a mixture of both (depending on chemistry, of course).

[IamIan]

90% + of all EVs are limited in total energy Wh ... this is why the range question always comes up... Total Power is generally not a failing of batteries... The Original T-Zero got very impressive results from old school Lead Acid batteries.... Capacitors have been around for a long time to solve any peak power issues.... the recurring / persistent issue is total energy or Wh.

This is not to say the power density doesn't matter at all... it does... especially during hard accelerations and such... but solutions for power have been around for EVs for a very long time... the solutions to energy storage ... not so much.

[n_dawg]

So wouldn't it be best to use a hybrid energy cell which was a mix of high-power and high-energy units, much like Aptera's supercap?

[jhm614]

Originally Posted by n_dawg

So wouldn't it be best to use a hybrid energy cell which was a mix of high-power and high-energy units, much like Aptera's supercap?

Is the Aptera still using a supercap? Weren't there some photos showing Maxwell's mounted on plywood in the original shop?

[DonC]

Originally Posted by speculawyer

These various high price Li-Ion numbers are discouraging. So I hope the info from this article remain true:

It's actually not too bad. While EnerDel quoted $500/kWh for the Th!nk packs, that is very low volume. The guess is that GM will get the packs for the Volt, which will have much higher volume, at around $300/kWh. Basically about $5K per 16 kWh pack or $10K for the two packs GM was originally budgeting for each car. This is consistent with the contract for the USABC.

In any case, GM says that the next gen battery pack will cost half as much and be half the size for the same number of kWh.

[speculawyer]

Originally Posted by DonC

It's actually not too bad. While EnerDel quoted $500/kWh for the Th!nk packs, that is very low volume. The guess is that GM will get the packs for the Volt, which will have much higher volume, at around $300/kWh. Basically about $5K per 16 kWh pack or $10K for the two packs GM was originally budgeting for each car. This is consistent with the contract for the USABC.

Wow, that is very encouraging.

Call me a conspiracy theorist, but I often wonder if Aptera and other EV makers are kinda dragging their feet a little bit (delaying launches) in order to wait for more Li-Ion factories to come online so they can pay less for the Li-Ion packs. Things should become a lot cheaper when there is a much bigger market for Li-Ions & EVs. The risk premium of investing in a Li-Ion factory will go down when there is a bigger market of buyers for big Li-Ion packs.

Damn . . . $300/Kwh . . . bring it on! Even the conversion market will pick up at price. I just hope it comes true. It is not encouraging when you see things like $10K for the 5Kwh Li-Ion pack for Prius plug-in conversions:
http://www.a123systems.com/hymotion/...range_extender

[DonC]

I'm not sure if anyone has mentioned this, but one of my major concerns about the Aptera 2e is the battery pack. Being able to deliver a battery pack which can be maintained over time is not child's play, and, in addition, many of the batteries that could be used in the packs are quite expensive. Plus a hundred mile range is too short. In the real world that range could easily go to 50 miles depending on terrain and the use of AC and heat.

This last week Chinese battery maker BYD announced it would sell its ferrous packs to car manufacturers in the US. I haven't seen much about this technology but the packs seem attractive. First revealed at the Detroit Auto Show, the batteries are similar to Li-ion, have a great range (BYD claimed 225 miles for its conventionally designed vehicle), and can be charged to 50% capacity in ten minutes (presumably with some sort of fast charger). They are also claimed to be considerably safer than Li-ion. The only drawback seems to be that they are heavier.

Most importantly -- and this is the big deal -- BYD claims the price should be half that of competing Li-ions.

These seem like they might work really well for the Aptera. BYD claimed the pack in its vehicle could provide enough power to drive it for 225 miles. It weighed only about 1300 pounds. You'd think a pack with half the size and weight would give the Apera about the same range, which is far more than the (too limiting) 100 mile range they're talking about now.

Here's the BYD press release from the Show: http://www.byd.com/press_kit_naias2009.pdf

[KarenRei]

I don't really care who they're from. I care that they pass longevity testing, which we know Valence is doing for Aptera. If BYD can manage that sort of build quality, then they're good in my book.

As for range, I seriously doubt Aptera is going to be putting a 650 pound pack in there. Too big, too heavy. But I wouldn't rule out the possibility of them offering options for more than 100 miles; we'll have to wait and see.

But yes, having a pack designed for rapid charging, whether or not Aptera includes a L3-charging port, would be a huge plus in my book for future upgradeability. 50% of 10kWh, which was how big the pack in the Mk1 was, would only need an input of 30kW. Now, in practice, it'll be a bit more than that due to losses, but still, not some incredible amount of power there. Even the Yazaki connector, if utilized at maximum, is, what, 17kW? And we know Aptera is working on integrating that (although we don't know whether they'll integrate it at full power capability)

[speculawyer]

Originally Posted by DonC

These seem like they might work really well for the Aptera. BYD claimed the pack in its vehicle could provide enough power to drive it for 225 miles.

There is quite a bit of skepticism about BYD's claims. Yeah, you can get really long range if you go to a really deep depth of charge. But you'll burn out those batteries pretty fast. I think this may be another example of an EV company over-promising.

[iwannaptera]

This link http://www.greentechmedia.com/articl...-cred-489.html

suggests that the BYD "ferrous" batteries are iron phosphate based. Sounds like it is another contender for aptera's lithium iron phosphate with pixie dust battery chemistry....