Batteries and New Battery Technologies

[Guest625101138]

Originally Posted by BertKu

Hi Rick, for me you are getting a 6 star rating. Well done and I hope that your lithium battery will not be a disappointment for the price you will be paying. The charging of a lithium battery is problematic. Have a look at the TI chip bq78L114. It is a smart battery management system and could be easy made by you to a full proper charger. Basically the IC is the core and the most difficult part of a charger. The rest is a matter of one weekend making a casing with cables.

By the way, the solarpanel industry is plunging down in price due to an oversupply in 2009. It is expected as from middle of 2010 to pick up again.
In view that you need 600 watt of solar panels, the industry is mumbling of only getting USA$ 2,50 - 2.75 per watt. This means for you some 1800 dollars from China or the Far east. Refer http://www.isuppli.com. It may be worthwile to consider this.
Bert

I will buy a small charger for the battery when I get it. The one I want for testing is 5Ah and 6 cells so around 22V. It costs USD76. The charger is about USD50. The charger monitors each cells during charging to ensure they are ballanced.

I have been working on using Sunpower 225W panels. They would have not been very good today. I will look forward to prices coming down because they are the most expensive bit.

I also have to build and test a turbine. I made one set of blades but I tried them out on a windy day and could not stop it as I was supporting the vertical shaft by hand and ended up smashing the tips into a bush so it did not clobber me.

Rick W

[BertKu]

Originally Posted by Rick Willoughby

I will buy a small charger for the battery when I get it. The one I want for testing is 5Ah and 6 cells so around 22V. It costs USD76. The charger is about USD50. The charger monitors each cells during charging to ensure they are ballanced.

Rick W

Hi Rick, That is what that Ic bq78PL114 does for you. Together with a number of bq76PL102 it monitors, charge and protect each cell to up 12 Li-Ion or Li-pol cells at the time. You can set it for Li-Ion and Li-polymer. I will see what they charge me here and if it is not too much, I will airmail it to Australia. The 50 Dollar can be better spent on additional batteries for you.
I have no idee whether you can put those batteries parrallel, I assume not. But at 3,8 Volt each cell you could loose a few millivolts by using a 2N3055 and connect the base via a small battery and resistor to the emittor. In that way you have a cheap 15 Ampere diode without too much loss as you saturate the base. You can then put 2 batteries parallel via the "diode".

Bert

[Guest625101138]

Originally Posted by BertKu

Hi Rick, That is what that Ic bq78PL114 does for you. Together with a number of bq76PL102 it monitors, charge and protect each cell to up 12 Li-Ion or Li-pol cells at the time. You can set it for Li-Ion and Li-polymer. I will see what they charge me here and if it is not too much, I will airmail it to Australia. The 50 Dollar can be better spent on additional batteries for you.
I have no idee whether you can put those batteries parrallel, I assume not. But at 3,8 Volt each cell you could loose a few millivolts by using a 2N3055 and connect the base via a small battery and resistor to the emittor. In that way you have a cheap 15 Ampere diode without too much loss as you saturate the base. You can then put 2 batteries parallel via the "diode".

Bert

Bert
I am interested in the IC but more for how it operates than actually building the circuit. Even if it does all the functions and only requires plugs it will take me a long time to set up.

The stuff I get from Hobbycity all just plugs together. It saves me time mucking about with soldering irons and finding the right plugs.

The full-scale boat I am working toward will most likely have 14 cells so a 12 cell unit would not do it for me.

This shows the Hobbycity charger:
http://www.hobbycity.com/hobbycity/s...idProduct=7373
You can see that there is a lot of functionality for the money.

I had to wire up the plug for the Kelly speed controller I purchased to suit the Mars motor and it caused me a lot of grief. Even with the finest tip iron I just do not have the fine motor control and eyesight to do this work and enjoy it.

There is another fellow BillyDoc doing a solar panel charge optimiser on the forum. This is stuff I am interested in but only with respect to operation. It would be very unlikely I would set out to build one.

Speaking of 2N3055s; about 35 years ago (actually 1975) I built an electric bike that used 20 x 2N3055s in parallel working in switch mode as the speed controller. The bike had 3 x 12V lead acid batteries and the motor was a small aircraft generator. I got it up to 35mph and thought it was fantastic - used to buzz down the street with only the clatter of chain and a slight whistle from the HF switching on the motor. The thing had built-in current limit so I did not destroy the transistors. So these days I marvel at what can be done with power mosfets and IGBTs. I am awed by the little controller I used on the boat yesterday. It weighs around 50 grams and can control up to 2kW.

Rick W

[BertKu]

Hi Rick,

Not a problem, I thought to do you a favour back. After my wife had seen your movie, braving the winter weather of australia, she immidiately grasped the potential of the combination, solar, wind and electrics. It made my life much easier to spend lots of bucks on experiments.

I personnaly would have gone the HiMH route for future cost reasons. You need to get more battery storage in anyway if you want to go higher in power. I have not been able to mess a NiMH battery up, but did with Li-pol.

Yes the 2N3055 were something robust. I still use them in the hunderds. They are cheap and the horsy people don't seem to blow them up. I charge small 6 Volt 4Ah drysealed lead acid batteries. The 2N3055 are merely used to drop the voltage from 14 to the regulated 7,2 Volt. In expensive and not easy blowable.

What is the reason that you do not use modern latest technology 36 Volt aircraft motors or generators? Are they too expensive or not easy avialable?

Bert

[Guest625101138]

Bert
I have not yet played with a lithium battery. I have had some involvement in lead battery manufacture and I know of some of the effort that went into getting these lighter and more reliable. I see that sort of development now going on with lithium but with much greater backing. It will only be a matter of time before the issues are resolved to a satisfactory level.

You can get 90Ah cells for USD180 so 4kWh of capacity will not be a killer for me.

As far as the motors go I got a deal on two PMSM Mars 3001 motors and 300A Kelly controllers so I am planning on using these in the full-scale boat. The model aircraft stuff is just fun to play with and very good bang for buck.

I have not looked outside the EV arena for other motors and generators. The Mars motors have very good reputation in light vehicle market. They are used in all sorts of commercial and light industrial applications as well the popular choice for powering things like bikes. There are a few manufacturers using them for outboards:
http://www.hobbycity.com/hobbycity/s...0_750Kv_/_600W

I am still at the tinkering stage so am open to ideas. Basically just testing and understanding the elements I need to bring together. The hull design was the hard part but I have good design tools for these now so I know I have the best possible underwater shape for my design conditions.

Rick W

[Fanie]

Hi Rick,

Again on your prop. A long prop like you are using could be 80% efficient in air, but not in water. Those props have a tendency to fly the outside diameter faster than the actual speed hence gaining on vacuum to fly off.

In water it is different. Water is not compressable so when your prop speed begins to get efficient for the outside the inside is going to begin working against it, causing drag.

I know small props are scarce and difficult to find, but you should experience a significant improvement in power and speed if you use the right type of prop.

[Fanie]

I have a 56lb thrust trolling motor on my power boat. 24 V and 2 x 105AH batteries I can run it almost for a day. On a slender hull like your I'm sure I can get it almost to plane. Keep in mind the prop wasn't designed for speed, but power. So I feel you propelling such a light load you should get much better performance if you get the right prop. Significantly more.

Easy test - when you start off you can measure the current drawn from your motor. When you accellerated the current drawed should become less as the setup becomes more efficient for the speed. So if your motor runs flat out the current to the motor should drop of when the boat is at speed. With the pop you have I'm almost sure the current is going to stay high and deplete your battery much faster.

[Guest625101138]

Originally Posted by Fanie

Hi Rick,

Again on your prop. A long prop like you are using could be 80% efficient in air, but not in water. Those props have a tendency to fly the outside diameter faster than the actual speed hence gaining on vacuum to fly off.

In water it is different. Water is not compressable so when your prop speed begins to get efficient for the outside the inside is going to begin working against it, causing drag.

I know small props are scarce and difficult to find, but you should experience a significant improvement in power and speed if you use the right type of prop.

Fanie
When you have to use a prop to cover 404km in a river race you learn what is efficient and what isn't. Remember I am only applying about 150W to this prop. The velocity ratio is about 1.03 so pressure ratio is accordingly very low.

There is no difference between air and water when it comes to a prop other than the size needed to get the thrust. The only reason you do not see more props like mine on boats is the need for draft to run such a prop in a higher power application.

If you look at Wageningen series of props you will see their high aspect blades get the highest efficiency - up around 90%. This is some Wageningen data I posted elsewhere:
http://www.boatdesign.net/forums/att...-picture-1.png
You will see the area ratio here is only 30%. I am using even smaller but I am operating at quite low Reynolds number compared to the Wageningen data so efficiency is lower. As the area ratio goes up the best efficiency comes down.

High aspect blades have low induced drag. This makes them more efficient. It is the same reason you see long narrow glider wings or long narrow foils on boats.

The 80% figure is based on calculations I have done for water.

I designed this prop:
http://www.boatdesign.net/gallery/sh...//ppuser/18624
It was used by Greg Kolodziejzyk to set the 24 hour distance record on water under man power.

If you want high efficiency in a any prop you go for long slender blades. Of course you need the room to swing them and they need to be strong enough to take the bending loads.

Rick W

[Fanie]

Ok, I see you didn't use an air prop. Now why didn't you say so in the first place.

http://www.recumbents.com/WISIL/hpb/prop/default.htm

[Guest625101138]

Originally Posted by Fanie

Ok, I see you didn't use an air prop. Now why didn't you say so in the first place.

http://www.recumbents.com/WISIL/hpb/prop/default.htm

Fanie
The prop I used yesterday is a commercially produced carbon fibre prop. It is made by Bolly in Australia. I bought one to compare with my home made ones. It is good for easily driven hulls. Not quite as good as I can make but better than any standard boat prop you can buy.

If you look down this list you will see it about half way down:
http://www.bolly.com.au/models/glasstwo.html
It is 15 X 25 - very high pitch to diameter ratio. This is a function of being such a large diameter on an easily driven hull. The ones I make are travelling about 30" every revolution. Slip is very low because they are acting on such a large area.

We are getting away from battery technology but I believe that the understanding of what drives efficiency will make current battery technology more viable for boats.

With 210Ah/24V lithium battery on a slender hull with good prop and motor you could cover something like 150nm in about 30 hours.

Rick W

[BertKu]

Originally Posted by Rick Willoughby

Bert
I have not yet played with a lithium battery. I have had some involvement in lead battery manufacture and I know of some of the effort that went into getting these lighter and more reliable. I see that sort of development now going on with lithium but with much greater backing. It will only be a matter of time before the issues are resolved to a satisfactory level.

You can get 90Ah cells for USD180 so 4kWh of capacity will not be a killer for me.

Rick W

Hi Rick,

Here an article on the Lithium charging management set of IC's.

!80 dollar seem to be reasonable, provided it is for 22 Volt.

I have to search for bigger motors. I will probably try Italy. This 600W is looking very good.
Bert

[Ad Hoc]

"...High aspect blades have low induced drag..."

Ive never heard of a propeller being described in terms of its aspect ratio. Mean width ratio, yes, but aspect ratio, never!

"...If you want high efficiency in a any prop you go for long slender blades.."

Having a large as area as possible on a prop is ideal, coupled with a low induced velocity, as per momentum theory to reduce the thrust load factor. However, in an attempt to have a lightly loaded blade, by increasing the mean width ratio, the increase in frictional drag of the blades tends to neutralise the attempt to obtain as large a blade area as possible.

Not convinced?...ask yourself how many props do you see that are long and slender on real boats?....these only work efficiently for aeroplanes owing to the vast different in viscous effects of air and liquid.

[Ad Hoc]

masalai
Don't understand what your point is?
Are you saying trial and error expts are better than actually understanding the mechanics behind what one is doing?
Are you also saying that no one else has seen the light because they are lazy, again, because there is no understanding of the mechanics involved?
Are you also saying that having a world record in a small thin-skinned model with a peddle and a seat and nothing else equates to being a naval architect and understanding the mechanics involved? Credit where credit is due, world record, can't take that dedication away. But I fail to see how that equates to being a naval architect and then able "prove a theory/definition" contrary to that which is in a text book?
If Lance Armstrong had a go, would that make him a competent naval architect to provide advice on technical matters such a lifting body and momentum theory?
I'm confused at the point you're trying to make.

He is, too. He just wanted to get something in about the USA.

Rick, that is one beautiful prop. Does the hub need to be that big?