# Battery technology



## david85 (Nov 12, 2007)

I wouldn't hold my breath on EEstor. They are too secretive for me to take seriously, but I do know of at least one EV builder that has invested some coin in the company (ZENN). Hypercapacitors also raise a the problem of voltage regutation, sice the voltage is relative to the DOD (not to mention safety conserns).

Balanced capacitators? never heard of them, what are they?

Betavoltiac energy, haven't heard of that either.

Solar power backup could definately play into the big picture, because they don't have to be very light, or compact but vast amounts of "sunlight" could be collected and stored for later use, after all, earth is solar powered!

Micro fuel cells are interesting as a low cost portable power backup option, but most fuel cells are not very efficient (30-60%) with more advanced ones using thermal recovery systems to save some losses, but this makes them more expencive. But fuel cells have been 15 years away from the market for the last 30 years, and I can't help but wonder how long it will take before they are in our reach.

Nuclear power through RTG-cells, not familiar with this, but nuclear power in general has always been controversial, and probably will be for a very long time. There is good potential for high energy generation, but nuclear will at the very least still be a security liability.

Better insulators could play a big role behind the scenes, and I suspect they already are. Gas turbine powerplants are close to 90% efficient in some cases, with about 30% coming from the turbines themselves and the waste heat used to run steam generators. It is in steam generation that insulators could make a good design even better.

Lithium Ferrous Phosphate batteries are one in a long list of recent battery chemistries that are aimed at solving the problems of more demanding portable devices as well as mobile propulsion (EVs). This paticular battery is safer that the lithium cobalt battery, and is not prone to exploding, it has a longer cycle life (up to 3000 cycles), and may have a longer shelf life (I can't be sure about shelf life yet, since this battery is only a few years old).

My bet is on lithium ion technology (there are many variants). Energy storage is the last great technalogical problem preventing mainstream electric powered transportation (political is annother story). But thanks to the information age, and a long list of high powered portable media devices, the profitability of a high performance battery is now assured, so there is a great deal of resources being poured into new batteries. Overall, batteries are going to get better, and cheaper, and since lithuim is light, and highly reactive, it will probably get the most attention.


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## david85 (Nov 12, 2007)

RevDon said:


> Hi I'm RevDon, and this is my first post to this group.  Allow me to do a little cross-pollination from one of my other groups: ....com. These guys are pioneering the use of the A123 cells that come in the DeWalt battery packs. They are disassembling them, building their own packs, battery management systems and chargers with some amazing results.  It would be entirely possible to take what they're doing and build upon it to make a system large enough to power an EV. While I am not an electrical engineer, (I am studying) the basic concepts are the same, the difference would be just how much power and amp hours you want. The DIY approach offers the most bang for the buck  and the most flexibility. So lets all get together and kick some Big-Auto butt and show them what we "Little Guys" are capable of!


RevDon, thanks for the heads up on that other forum, I am trying to keep an ear to the ground myself, as much as possible with EV tech. I started a thread here titled "building from the ground up", and I am trying to examine the possibility of kicking some big auto butt, please do stop by.


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## pandaran (Nov 13, 2007)

Oo, what's the expected life on these battery packs?

Edit: I went to check out the Battery Technology section on ....com. It's all still a bit over my head, but after watching Doc's video on disassembling a DeWalt battery pack, I think I'm capable of doing that. Just not really sure where to go from there. ^_^*

[Quote stolen from endless-sphere by Malcolm] I like idea of using the DeWalt pack "uncut" to power and control a small brushed motor. You could use a DeWalt flashlight base or even the base of a drill mounted on your bike as a quick connector. Then use single packs as you need – just switching to a fresh one as each runs out. Put as many single packs in a backpack as you need for the ride







[End Quote]

That makes it seem like they don't last very long, if you have to bring fresh cells to switch out on a bike ride.


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## RevDon (Nov 21, 2007)

pandaran said:


> Oo, what's the expected life on these battery packs?
> 
> Edit: I went to check out the Battery Technology section on ....com. It's all still a bit over my head, but after watching Doc's video on disassembling a DeWalt battery pack, I think I'm capable of doing that. Just not really sure where to go from there. ^_^*
> 
> ...


This would be true if the batteries were "uncut." Once you cut them, rebuild them to suit your needs, and use your own BMS / charger, then YOU have the control!


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## pandaran (Nov 13, 2007)

Please forgive my bad math skills. I did a little more poking around, and found a cool how-to on an R/C forum for turning A123s into a battery pack:

http://www.rcgroups.com/forums/showthread.php?t=599316

Then I did some calculating that may or not make any sense (I'm good at the latter in particular.)

Most EVs that I've looked at are 144v. These cells are 3.6v, so it should take 40 cells to reach that voltage. In that link, the author said they're 2300mAh.
2300mAh = 2.3Ah
144v x 2.3Ah = 331.2w
So, with enough cells to reach 144 volts you only get 1/3 of a kw?

Does that mean you only get 1/3 of a kwh? So is it just entirely infeasible for an EV car, or am I missing some important steps?


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## mattW (Sep 14, 2007)

You would be getting 2.3Ah per string but you can join them in parallel to boost the amps. 50 strings would give you 115Ah (~16.5kWh) but that would be 50x40=2000 cells. Thats a lot of space/soldering/money etc but you can work out whether you think it is worthwile.... I think parallel strings is the step you were missing.


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## david85 (Nov 12, 2007)

Has some one come up with a ballpark estimate on the cost of these batteries yet, in terms of wh/kg?


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## KiwiEV (Jul 26, 2007)

Am I the only one starting to lose track of which capacitor has more storage capacity? 
I'm not sure if these are in order but it seems like there are capacitors, super capacitors, mega capacitors, ultra capacitors and fanf*ckingtasticapacitors.

I think a little clarity from their marketing departments would go a long way!


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## pandaran (Nov 13, 2007)

mattW said:


> You would be getting 2.3Ah per string but you can join them in parallel to boost the amps. 50 strings would give you 115Ah (~16.5kWh) but that would be 50x40=2000 cells. Thats a lot of space/soldering/money etc but you can work out whether you think it is worthwile.... I think parallel strings is the step you were missing.


*lol* So much for finding a cheap way to get lithium batteries!
Thanks for the response, mattW. I'm slowly figuring out how all of these watts and amps and whatnot work. 

And david85, I don't know about per kg, but in the thread I linked the guy said he paid "an average of $8.94 per cell, including shipping and handling charges." $18,000 is a bit more than I can afford for batteries, especially if I'd have to solder the lot of them! *whew!* Makes me tired just thinking about it!


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## david85 (Nov 12, 2007)

KiwiEV said:


> Am I the only one starting to lose track of which capacitor has more storage capacity?
> I'm not sure if these are in order but it seems like there are capacitors, super capacitors, mega capacitors, ultra capacitors and fanf*ckingtasticapacitors.
> 
> I think a little clarity from their marketing departments would go a long way!


LMAO, you forgot *hypercapacitors* (EEstore aka, bridge company), I think I'll stick with good old fasioned chemical electric storage devices for now.

OK, I think I have the cost for the a123 battery per kwh. @ $8.94 per cell, and 2.3ah and 3.3v works out to ~$0.85/wh, not bad actually. So a 16.5kwh pack would cost around $14000.

Now if only a123 systems would sell high volume to private customers.........(volume discount maybe?)


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## pandaran (Nov 13, 2007)

Well, what made them so cheap is that they're buying DeWalt battery packs (for power drills, I'm assuming) on ebay and disassembling them. They're probably quite a bit more expensive if you buy the cells individually.


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## thartsell (Jul 24, 2010)

Having thought about this for years.... I keep thinking we're missing something basic... like carbon or sand or some other basic material around us.

If you look and Lithium and the filthy conditions in underdeveloped countries where it's mined... you come to an immediate conclusion that we're going to be at the mercy of some other undeveloped country with a tyrannical king or arab or something worse.

My money is on Bloom Energy or some derivation thereof... 
At least he can produce 25watt cells right now that are actually powering 
Google and other large corps...

The rest as stated above (solar for example) still 15 years away for the last 30 years etc. That being said, Battery technology has come a long way...
I'm glad to see that finally we're getting people cranked up on looking for solutions... I wish it was going to be in my lifetime.

So... what can we build DIY from basic materials?
If we can figure this out, we can save the planet and eliminate the grid.


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## Sunking (Aug 10, 2009)

thartsell said:


> My money is on Bloom Energy or some derivation thereof...
> At least he can produce 25watt cells right now that are actually powering
> Google and other large corps...


I wouldn't put one dime on Bloom. There is nothing new about Bloom technology. They take natural gas, crack the hydrogen off with steam, and use a regular fuel cell. Problem is it is less efficient than taking the same natural gas, burn it to make steam to turn a turbine to make electricity, and it produces no less CO2. The only way it makes any sense is for California where they have jacked up their electric rates so high, coupled with huge government subsidies, and cheap natural gas prices it is economical for them plus all the Green PR hype Google and E-Bay get to claim.


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## IamIan (Mar 29, 2009)

david85 said:


> Betavoltiac energy, haven't heard of that either.
> 
> Nuclear power through RTG-cells, not familiar with this, but nuclear power in general has always been controversial, and probably will be for a very long time. There is good potential for high energy generation, but nuclear will at the very least still be a security liability.


These are both types of energy conversion that convert a portion of the emissions given off by a radioactive material as it decays into electrical energy... usually with a Semi-conductive layer of material design for the specific radioactive fuel being used.

The energy density is super crazy high ... like beyond even ESSTOR claims ... and it has been proven ... and they have already been used for deep space probes by NASA.

They will never be good for vehicle power that isn't in space ... here on earth any mobile application it is a dead end ... unfortunately it is also not even something that can be scientifically fixed ... it is an inherent problem of this style of energy harvesting. 

The power density of these batteries is ... very very very low... how low?

This description of the RTGs used on Voyager might help:



> Power was provided to the spacecraft systems and instruments through the use of three radioisotope thermoelectric generators. The RTG's were assembled in tandem on a deployable boom hinged on an outrigger arrangement of struts attached to the basic structure. Each RTG unit, contained in a beryllium outer case, was 40.6 cm in diameter, 50.8 cm in length, and weighed 39 kg. The RTG's used a radioactive source (Plutonium-238 in the form of plutonium oxide, or PuO2, in this case) which, as it decayed, gave off heat. A bi-metallic thermoelectric device was used to convert the heat to electric power for the spacecraft. The total output of RTG's slowly decreases with time as the radioactive material is expended. Therefore, although the initial output of the RTG's on Voyager was approximately 470 W of 30 V DC power at launch, it had fallen off to approximately 335 W by the beginning of 1997 (about 19.5 years post-launch).


So initially ~470 W from ~39 kg ... or ~12 W / kg... that is all the peak power you have and it slowly drops with the half life of the radioactive fuel.

The energy density is still crazy high ... in the 19.5 years it took to drop to 335W ... so from that ~39 kg in 19.5 years they already got out about ~68,755,050 Wh ... or ~1,762,950 wh / kg over 19.5 years ... and it wasn't done yet ... It still has ~70% of its fuel remaining.

So they are great for deep space probes because the energy density is so crazy high ... but they are not much good for planet based vehicles because the power density is so crazy low.

- - - - - - - 

My bet for the future of batteries will be something like the Lithium Air batteries ... but those are several decades away at best ... might not see a buy-able unit for a EV for 50+ years... maybe longer.

Don't expect a sudden game changer ... battery tech that you can buy and use has shown to be pretty steady and slowly increasing.


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