New Battery Technologies

[commanda]

Having just invested in Thundersky Lithium batteries for my electric scooter, I wonder how many here are monitoring the emerging battery technologies, and have jaw-dropping moments every time they check current prices for Lead Acid batteries.

These type of batteries will require a whole new paradigm when it comes to dump load controllers, charge management, and low voltage disconnect circuitry.

My scooter batteries are 16 of the first product on this page (40 AHr):

http://www.thunder-sky.com/products_en.asp

A total of 2 KWHrs, for $1152 Australian dollars (and the price is dropping almost daily), on a par with VRLA AGM H2SO4 (SLA) from the scooter shop. That price doesn't include shipping from Mackay in Qld to me in Sydney. Nor does it include the per-cell BMS (battery management system) which I'm building myself, similar to this one:

http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=3345

(Caution, it's 31 pages long).

I know, right here and now, the wet cell (ala Trojan T-105) is still cheaper than the Thundersky's, but watching the trends, it's only a matter of time.

Amanda

[wdyasq]

Here in the US, one can still get the T-105 for about US$150, rated at 225AH and 6V. IF one figures total discharge that will be 1.325kWh and ~$133kWh. Of course the batteries won't live under that treatment so the actual cost per kWh will be 2-4 times that much. 3 X $133 is $400kWh for discussions purposes.

If LiFePO4 can handle total discharge, your figure of $1152 for 2kWh is not that far from "the old standard" - at $576kWh (LiFePO4). At 25% discharge, where Flooded Lead Acid batteries will live,on the T-105 would take it to $533kWh (FLA).

I think some research into any problems the newer technology may have are in order. With the smaller size and lighter weight of battery storage and "IF" the battery storage is safe inside a home, the cost of batteries, wire runs and storage MIGHT be cheaper with LiFePO4 now.

Ron

[JW]

Wasdaq-q,

 You see, im scared away, from this comparison,because, Im trying to figure 'AH' at 12v.

 Lets say, my battery has a storage capacity of '40' amphours[AH] at 12 volts.

It will run my 'television entertainment centre' for 80 minuites.

 Which I consider 'good' if the kid takes over the remote.(because, in switching the batts, I can send the little one to bed Im sure this cuts energy usage...

Now, if train 'a' heads to the station at '25mph' and train 'b' heads to the station at '75mph' AND,,, they both get there at the same time(thank god for magnetic braking), which one was farther away, train 'a' or 'b' ?

JW

[commanda]

Ron, you make 2 good points that I overlooked;

LiFePO4 can handle total discharge without degradation (it does require a per-cell low voltage disconnect to do it though).

No explosive gasses generated whilst charging. Also, unlike some earlier Lithium technologies, the newer LiFePO4 won't randomly turn into incendiary devices.

With their much lighter weight, hiding them in the roof cavity may be an option, whereas lead acid are too heavy to do this.

Amanda

[wdyasq]

"Now, if train 'a' heads to the station at '25mph' and train 'b' heads to the station at '75mph' AND,,, they both get there at the same time(thank god for magnetic braking), which one was farther away, train 'a' or 'b' ?"

Does it matter?

Actually, if you are going to any electrical work, Ohm's Law is one of the first things you need to learn. It will help you in wire sizing, fuse sizing, battery sizing, inverter sizing and wind turbine and solar panel guessing. You will learn why 100W of 12V soler panel only net you 60 Watts in your storage device and why the battery bank is still too small...  no matter what you do...

And to actually answer the train question, one would need to know, "At what time". The 25mph train may have started its' trip last week and the 75mph train at lunch.

Ron

[antw]

What about the number of cycles/useful life that each technology can handle?  I usually have to replace my cellphone because the battery won't hold a charge.

[independent]

LiFePo4 and Lipo (Lithium Polymer).

From memory, Lipo technologies is well known to have less than 400 life cycles of duty. The cells have a nominal voltage of around 3.7v. It has been up until now, however, had the best charge rates and discharge rates. However, it needs a very controlled charge rate and temperature or fire or worse explosions can result. This is the technology of cellphones and laptops.

Nicad has a great discharge rate and charge rate, relatively robust, and long cycle life--1000 cycles. A nominal voltage of 1.2v. The problems have been primarily toxicity of cadmium and capacity (less capacity than NiMH and Lipo).

NiMH have good capacity (less than Lipo), relatively non toxic, relatively robust, much more so than Lipo but less than Nicad--500 cycles. Also 1.2v

LSD (Low Self Discharge) NiMH, also sometimes call NiOOH. This version of the NiMH cell have less capacity than NiMH but have low self discharge, longer life than a plain NiMH cell around 1000 cycles. Also 1.2v nominal

LiFePo4 are the new technology. 3.3v nominal. A very robust technology. Much more robust the Lipo, even greater charge discharge rates than Lipo. Greater cycle life than all of the above technologies 1000-3000 cycle life (manufacturers vary in quality and also DoD (Depth of Discharge) does have an impact on the life cycle). Relatively non-toxic.

So, as you can see, there is a big difference to your cellphone battery with this new technology. There are currently quite large intellectual property battles going on with the new LiFePo4 technology. Personally, I'm waiting for the smoke to settle. While I wait I am happy with my eneloop LSD cells, they are great.

[Jeff]

Awesome! Especially in a small elec. vehicle like a scooter, the weight advantage makes a big difference! If I am ever able to get another scooter, I think I'll go this route also. Most small personal scooters are 24v with a 40-50 AH system. Their manufacturers claim an average of 25-30 miles/charge on them. Measurement-wise, it looks like I could place a 90AH array in about the same space. So...almost double the range would be great!

[JW]

Spoken as a true gentleman...

Now Ron,

Its harder than most will tend to realize, to get a reply from yourself umm, um.

"Does it matter?"

Well, yes Ron, it does.

If I have only 2, 6volt batterys, with an amphour rating of 255 they would have to be wired in series to get 12volts, so 'I' times 'V' equals 'P'. Yet there amphour capacity cannot increase higher than 255 wired in series at 12 volts.  

Why is there such a difference with top capacity, such as with a 12volt batt, like 125 amphour? There basically the same size and physical weight?

Further more, unless you give some basic consideration to series-parallel circuit law, the 6 volt batterys you speak of, only confuse the issue.

JW

 

[wdyasq]

JW,

To make things simple take your Voltage X Amperage and you will get Watts. In our 'amperage' figure there is a time, the hour, so our final figure is in Watt Hours.

12V X 255AH = 3060Wh or, converting to kWh, 3.06kWh at 100% discharge.

Now note if we had worked with 6V Batteries it would have been 6V X 255AH = 1530WH and we would have needed to multiply by the umber of batteries (2) and we end up at the same place.

The 'real' way to calculate power is a lot more interesting and involves a bit of higher math than we want to go into here. It also yields similar results. The power in the bank is the number of batteries X the capacity of each battery.

Don't forget, that is at 100% discharge. The figures need to be lowered for any practical application.

Ron

[commanda]

JW,

The point Ron is trying to explain. When discussing battery storage solutions in terms of how much bang for the buck, the most convenient figure to use is KWHrs. The nominal cell voltage, times the AHrs, times the number of cells, gives WattHours. For a given number of cells, you can wire them all in series, all in parallel, or some combination of series-parallel, to give the system voltage required. The available AHRs will then vary as an inverse function of the system voltage. More voltage, less AHrs, but always the same total KWHrs.

Comparing 2 systems in terms of AHrs alone is only valid if they are both the same system voltage.

Amanda

[JW]

Hi Amanda,

 I agree.

"When discussing battery storage solutions in terms of how much bang for the buck, the most convenient figure to use is KWHrs."

 Honestly, I do think, Ron is one of the smarter folks around here. Im beginning to consider KWHrs, but amphours is easier to figure for me somehow, perhaps I need one of those 'Kill A Watt' meters

"Comparing 2 systems in terms of AHrs alone is only valid if they are both the same system voltage."

 This is totally true, depending on the series or series parallel arrangement, it would be totally compensated for, looked at from that way. Like one would have to figure with a 48v system.

 I guess, I just want 4- 12volt batts to all be in parallel, yeilding 800amphours. I realize they'd have to be 8d in size, so the weight gains to be made, with litium ion, are at the achielles(sp?) heal, of cost?.

 I found this old WestingHouse patent for some silver/iron KOH electrolite batts, for some odd application, the thing is about 30 years old. The problem is the commodity, the price of silver. I say what the hell, batterys have a trade in value now based on the price of lead, what would be the difference, using silver for an anode? These type of batts have atleast 2 X the energy density storage capacity, of the best lith-ion batts have now. The percentage of silver lost to the diffusion mat, over a single life cycle is negligible, I believe that is 300 deep cycles.

JW