Batteries and New Battery Technologies

A friend of mine was working on making a boost controller to run the motor at double the supply voltage, using the motor inductance as the energy storage component. This was going to be more efficient than using a separate boost converter, probably not much less efficient than the standard buck controllers used with these motors. I'm not sure whether or not he ever got it working, I'll ask him and see.

The Prius uses a boost converter to double the battery voltage so that the motors run on about 550V, so it's a viable technique. You still have the big problem of high battery current though, which with lead acid batteries, in particular, results in lower usable capacity.

My personal view (based solely on my preference for keeping things simple!) would be to just build a higher voltage battery pack. Anything up to a couple of hundred volts or so is pretty straightforward to put together and the advantages from smaller gauge wiring, lower system current and improved system efficiency are worth the trouble, in my view.

Jeremy

 

Wouldn't a single huge cell with up converter (3V to 300V say) be simpler than all the multiple connections and individual cell sensors/monitors needed for a high voltage pack? Never a worry about a reversed or unbalanced cell requiring replacing the whole high voltage pack and wasting the remaining good cells which deliver at different temperatures and age at different rates. If the up converter was mounted directly on the 2 battery plate connectors, there would be no huge cables required to create losses. High currents shouldn't be a Peukert problem if the cell is sized proportionally larger. I don't know much about low voltage/high current chargers, so that might be a hangup due to efficiency losses....

Thanks,

Porta

 

That would require a technology which doesn't exist yet.
The problem is the inevitable fwd voltage drop in semiconductors. Even if a device or array of devices would exist, able to switch say 10.000 Amps with only 3 V control voltage and a Vfwd of .1 V, it would already dissipate 1000 Watts.

Upverter technology from a single cell is only used for applications requiring (almost) no current, like the light amplifier in a night scope, where several 1000's volts come from a penlight battery at 35% efficiency.

 

Thanks for that info, CDK. I still think this is simpler concept, though possibly not doable at the present time. We have some technologies on the horizon like high temperature conductivity and materials like graphene which might change the very poor efficiency. BTW, the largest 12 to 120 v upconverter I could find surfing was around 10 HP equivalent, so this would not be enough for big boats at the present....

Porta

 

Advancements in Water-based Processing for Large
Format Lithium Ion Cells

...a bit too technical for me, but I thought some folks in this forum subject might find it interesting

http://www.internationalbattery.com/pdf/InternationalBattery_ManufacturingWhitePaper.pdf

http://www.internationalbattery.com/technology.php

 

Brian, there is something wrong with both links you provided!

 

For some reason an extra http and // was appended - those two links should be fixed now.

 

Hi Brian,
That is a very interesting article. Although I personally still feel that the supercapicor is the ultimate solution. It will never materialize, you make it, you use it and maybe make it again after 30 years. Not a business proposition for governments, oil companies. Where do they get their taxes from in the future. I had a shock to learn that the LiPo4 batteries I have here, are absorbing moisture and loosing power.
Bert

 

I believe it has something to do with the way the link window displays. If you paste the address you want to put in where the curser is blinking it ends up putting an extra "http://" in front of the address you are pasting in. Its as if you need to make sure to overwrite that "http://" language that is already there on the address line.

It's kind of confusing, and maybe needs to be changed. I found myself doing this numerous times before I discovered the mistake....and obviously even after I knew of the problem, I inadvertantly made the mistake again.

On other forums I find that this "http://" is highlighted already when the link window appears, and thus when you paste the link address in, it avoids 'doubling up'

 

It is coming. Many forum members think that I am a total lunatic, just to hope, that super capacitors will materialize. I am pleased to see this link to an interesting article. I wish that more venture capital would be invested in this type of "battery"

http://www.dataweek.co.za/news.aspx?pklnewsid=38557

Not a bad idea to add it to your battery bank.
bert

 

The big issue with supercapacitors, and the one that makes them hard to use as a stand-alone power source for most electric vehicles, is that their terminal voltage drops in proportion to the charge used, as stored energy = 1/2 CV², where C is the capacitance and V is the terminal voltage.

This means that any circuit being driven by a charged supercapacitor bank has to be clever enough to adapt to the big change in supply voltage as power is used, unlike most modern batteries where the terminal voltage stays fairly constant right up until the fully discharged point.

It's not an insurmountable problem, but it does mean that system efficiency drops markedly as the supercapacitor discharges. For example, by the time the supercapacitor has used 75% of it's stored charge the terminal voltage will have dropped to 50% of the fully charged voltage, so for the same power being drawn by the load the current will have doubled and the system resistive power losses will have quadrupled. This is due to the basic physics surrounding the way capacitors store charge, not something that can be overcome with development, unfortunately.

All told this means that supercapacitor technology is probably never going to be a stand-alone energy storage medium for electric vehicles or boats, although as an adjunct to batteries, in order to cope with high peak load current or regeneration current, they may have a niche market.

Jeremy

 

Hi Jeremy, as I have shown before , it is not difficult to make a lower Voltage, let say 12 Volt, stable constant voltage supply out of a 300 Volt charged Capacitor. There are so many advantages (and lots of disadvantages) like no gasses, very fast charging, no explosion danger, very long life 100.000 + hours etc. The disadvantage is the lack of venture capital to explore this direction and the power of the oil companies to block it. But a sloping curve is for me not an obstacle.
Bert

 

Jeremy:

Best post I have seen which explains in simple terms the limits of super and ultra caps. I think the confusion lies when ads state the PEAK power per unit weight which is much higher than batteries, and can only be maintained for very short duration. There are also issues with fast self discharge for the cap systems I have seen. New materials like carbon aerogels have improved capacity for supercaps, but even with the lowest dielectric conceivable (vaccum?) they can't approach what batteries can do in capacity. Ditto for flywheels, fuel cells of various configurations including hydrogen, and some others which are just too heavy for ordinary transportation applications. Some of these may have applications in some stationary or niche uses, as you point out.


Porta

 

Powering a full keel sailoboat with electic power

I have never had an engine on any of my sailboats but now is the time. I own a 13,000 lb Bristol Channel Cutter that I would like to power with electric, Torqeedo, Minnkota, etc. using latest battery technology. I have transom room to bolt on a motor. With the high thrust that electric motors have, I thought I could get away from the standard 20hp gas outboard.
I have plenty of room for batteries. I mainly need power for cutting through waves when departing and returning to harbor since most will not allow sailing in. If it is calm out, I can scull her into a slip. How much power will I need? Thanks for you help.

 

Although I maybe sometimes a dreamer and hope we all are going to be wrong, I have to agree with you Porta.

I love to know what actual the weight/capacity ratio is for the best super cap, versus a Lithium battery. My gut feeling says, that the super cap will win. Any comment on this issue?
Bert