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Old 01-21-2012, 01:25 PM
amynalbuq amynalbuq is offline
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Default using little aa lithiums for geo metro? why not?

I'd like to convert my geo metro hatchback. From what I've read while it is a light car it is not necessarily ideal since it can not hold as much battery weight. I've read that the tesla uses 6000 or so aa similar lithium batteries. Why can't I use 1000 -1500 or so little AA lithium batteries? A 50 mile range is plenty for me and 45 mph is also plenty fast. It looks like with the little batteries it would be easier to store and work with placement and securing the batteries.

Thoughts?

BTW. This would be a permanent car for me. I also intend to take the backseat out and use this as a commuter car/mini truck. Also intend to add a solar panel to the roof for some constant minimal charging. I live in super sunny New Mexico so a little goes a long way!

Thanks in advance. Amy N Albuquerque
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Old 01-21-2012, 02:11 PM
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Default Re: using little aa lithiums for geo metro? why not?

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Originally Posted by amynalbuq View Post
I'd like to convert my geo metro hatchback. From what I've read while it is a light car it is not necessarily ideal since it can not hold as much battery weight. I've read that the tesla uses 6000 or so aa similar lithium batteries. Why can't I use 1000 -1500 or so little AA lithium batteries? A 50 mile range is plenty for me and 45 mph is also plenty fast. It looks like with the little batteries it would be easier to store and work with placement and securing the batteries.

Thoughts?

BTW. This would be a permanent car for me. I also intend to take the backseat out and use this as a commuter car/mini truck. Also intend to add a solar panel to the roof for some constant minimal charging. I live in super sunny New Mexico so a little goes a long way!

Thanks in advance. Amy N Albuquerque
I believe cruisin on here built his pack using 18650 size cells, which is similar but slightly larger than an AA cell. If you get enough of the correct cells and get a CD welder to attach them then you are set.
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Old 01-21-2012, 07:24 PM
cruisin cruisin is offline
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Default Re: using little aa lithiums for geo metro? why not?

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Originally Posted by rwaudio View Post
I believe cruisin on here built his pack using 18650 size cells, which is similar but slightly larger than an AA cell. If you get enough of the correct cells and get a CD welder to attach them then you are set.
Using individual 18650 cells can be a nightmare if you want a decent ah rating and a resonable voltage. If one intends to do it anyway (not recommended) I would suggest you use the cells that have the attached tabs like I did, makes it a little easier.
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Old 01-21-2012, 07:12 PM
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Default Re: using little aa lithiums for geo metro? why not?

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Originally Posted by amynalbuq View Post
I'd like to convert my geo metro hatchback. From what I've read while it is a light car it is not necessarily ideal since it can not hold as much battery weight. I've read that the tesla uses 6000 or so aa similar lithium batteries. Why can't I use 1000 -1500 or so little AA lithium batteries?
this would be a nightmare to assemble and balance. you can EASILY get 50 mile max range into a Metro with a 120v (38 x 100ah) prismatic cells and end up at stock weight.... come visit my site linked below.

If you intend to regularly need 40+ miles or need longer highway miles, I would suggest a 144v x 100ah system which would fit without giving up any cargo space, OR you could go more if you really need more and are willing to give up cargo space.

forget the PV on the car, and put it on your house.

I am in santa fe if you want to some see a converted Metro/Swift in person.
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Old 01-22-2012, 01:20 AM
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Default Re: using little aa lithiums for geo metro? why not?

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Originally Posted by amynalbuq View Post
Why can't I use 1000 -1500 or so little AA lithium batteries?
I don't think that lithium cells come in AA size; perhaps you are thinking if Nickel Metal Hydride rechargeable cells, or 18650 size lithium (but not lithium iron phosphate) cells (as used in the Tesla, I believe).

Tesla have a lot of technology in their packs; it's not something you can easily replicate at home. Other OEMs license the technology from Tesla, rather than go through the cost of re-learning the technology from scratch.

Last edited by Coulomb; 01-22-2012 at 01:22 AM. Reason: clarified
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Old 01-22-2012, 07:14 AM
madmike8 madmike8 is offline
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Default Re: using little aa lithiums for geo metro? why not?

lithiums come in 14500 size which is approximately AA size.
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Old 01-22-2012, 10:46 PM
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Default Re: using little aa lithiums for geo metro? why not?

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lithiums come in 14500 size which is approximately AA size.
I stand corrected; thanks for pointing that out.

The prices I saw were a fair bit higher than the ~$1.15/Ah for larger prismatic LiFePO4.

Are they available at reasonable prices?

Are there higher discharge rate models available? (you really need at least 3C for EVs)

I suspect it will always be more economical to build a small number of larger cells. The Tesla pack however is a conspicuous exception.
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Old 01-23-2012, 08:27 AM
DJBecker DJBecker is offline
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Default Re: using little aa lithiums for geo metro? why not?

Tesla didn't have a choice. When they designed their prototype, the 18650 laptop cells were the only type they could buy.

Much of the early engineering went into figuring out how to connect, package, cool and monitor thousands of individual cells.

That's a whole bunch of extra work and packaging expense that you can avoid just by getting off-the-shelf large cells.

Imagine that you have 6000 hens and a vial of horse semen. You want to build a transportation product to sell by the end of the year. The answer is learn how to sew chicken harnesses, not to talk about how great a horse would be.

Now you have a choice of copying their chicken harness design, or buying a horse. A surprising number of people would say "they used chickens, so that must be the right choice".

Last edited by DJBecker; 01-23-2012 at 08:41 AM.
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Old 01-23-2012, 09:14 AM
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Default Re: using little aa lithiums for geo metro? why not?

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Originally Posted by DJBecker View Post
Imagine that you have 6000 hens and a vial of horse semen. You want to build a transportation product to sell by the end of the year. The answer is learn how to sew chicken harnesses, not to talk about how great a horse would be.

Now you have a choice of copying their chicken harness design, or buying a horse. A surprising number of people would say "they used chickens, so that must be the right choice".
I about spit my coffee out.....

great analogy.
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