Batteries and New Battery Technologies

Much depends on battery chemistry. NiCads are very rugged and need to be 100% discharged periodically to maintain high capacity. Some of the early satellites used nicads for because of ruggedness and long life and probably some are still in operation. Most other types last longer with shallow discharges and are are delicate about recharging protocol. The basic zinc air has been around for quite awhile and is considered a primary (not rechargable) type cell. It is more like filling your car with zinc instead of petrol, except you carry around the weight of the waste products until all the zinc is used up. Then you have to go to a special zinc fill station, where you take on more zinc fuel and drop off the waste products. The waste products are then converted back to zinc using electricity at a stationary location. There is no existing infrastructure for such a scheme, nor will it be easy, fast, or cheap to set up. True rechargable batteries can use the existing grid so it is easy, cheap but slow to recharge compared to fueling. Probably the best bet on the horizon is the lithium air battery which is being developed. That is because lithium is the 3rd lightest element (atomic weight = 7) and very reactive (EMF =3.0 V) which produces higher voltages per cell. http://www.udri.udayton.edu/News/2009/Pages/BatteryBreakthrough!.aspx (no liquid electrolyte) Contrast this to the zinc air rechargables where zinc EMF= 0.76V and atomic weight is 65. http://www.physorg.com/news176034001.html. The lightest hydrogen fuel cells (liquid electrolyte) suffer from the same disadvantages of infrastructure mentioned previously for zinc.

Hope this helps.

Porta

 

Hi Porta,

Group9 (EEMB) thread #920 is already producing large 10 - 20 Kwh Lithium batteries and I believe that an Insurance company like Alianz would not link their name to this product, if it is not safe enough. Wonder what they are using, apart of LiFePO4.
Bert

 

This might be the "nano" phosphate technology which is more rugged but still not comparable with nicads in ruggedness. Don't think they will hold up to cell reversal like quality nicads. The "nanos" are reputed to occupy more volume and be considerably heavier and more costly than lithium poly and lithium ion, but of course last longer. Valence technology has been producing some lithiums in larger sizes for some time, now and touting the safety as well. http://www.valence.com/sites/default/files/images/U-Charge XP datasheet Oct 2010.pdf No need to assemble anything or use diodes, can be used almost like normal sealed lead systems but they are heavier than the previously mentioned lithium poly and lithium ion. I think one of the new electric cars will use a modified lithium poly system which is supposed to be a little safer than the traditional polys....

P.

 

I came accross this latest technology, whereby the Photo Voltaic cells with the interconnections are printed on a glass substrate. 0.6 x 1 meter is quite a good size.

http://www.renewableenergyfocus.com/view/16528/fraunhofer-ise-unveils-largescale-dye-solar-cell/

I wonder how long it will take before somebody will print it on a suitable sailing sail surface. Or on a surface one could use on the shape of a roof/cabin
Bert

 

"Or on a surface one could use on the shape of a roof/cabin"

And with a no skid surface , strong enough to be walked on.

FF

 

I have a very old sovonics flex panel you could walk on, but probably slippery when wet. It had previously belonged to a rafting company that had it mounted on the side of an inflatable raft. It took an incredible amount of punishment including one small surface puncture that did not completely penetrate the covering and many abrasions in collisions with rocks. I used some vinyl dressing to clean up the sections that were somewhat opaque from abrasions, and it still generates near rated power.

Porta

 

Hi Porta, am I correct in saying that your sovonics flex panel consist of small pieces of solar cells and then bonded with wire, encapsulated in plastic? A printing manufacturing process will certainly be substancial cheaper in mass production. Can't wait for this technology to materialize in vast volumes.
bert

 

Hi, Bert. No the panel is one piece amorphous cells with a very minimum of wiring mounted on a very thin flexible stainless steel substrate which can be bent or even rolled into a tube. The cover is very tough vinyl or pvc that holds up to abrasions very well, and was demonstated to continue operating even when shot through with a bullet. Efficiency is low compared to the modern, newer cells in direct sunlight, but it is supposed to do better in ambient light.
I like the idea of the printing manufacturing process, but it has a great way to evolve before it matches the ruggedness of my old sovonics. The printing process cell uses a glass substrate as described and would be generally more fragile and not flexible or portable.

Porta

 

ETEK motors/ASMO

Perry, what does the ASMO 17kW motor cost?

I just bought an ETEK on eBay here in the US for $340, 10 HP at 48V. I'm thinking with up to four of these totalling about $1500 belted on the prop shaft switched in by solenoids, I don't even need an unreliable DC controller and get 40 HP/about 26kW continuous.

But I should consider the ASMO too.

Ray

 

Ray,

Check your PMs for my reply.

P

 

The Etek won't deliver 10hp in a boat, I'm afraid. Briggs and Stratton rated them at 2.7hp continuous, 12hp peak for 2 minutes. B&S ceased production of these motors around 5 years ago now, although there are a lot of cheap Chinese clones out there being falsely marketed as Etek motors, when they clearly aren't. In my personal experience, the Chinese clones don't perform as well as the original B&S Etek motors; the exception being the Mars Electric LLC motors, that are similar to the Etek in performance (although a lot heavier and a little less efficient).

Four Eteks are going to give you around 11hp continuous running on 48V. You can over-run them to around 72V to get more power (and rpm) but you can't over-run them by just loading up the motors on 48V and running them at a higher current, as the internal soldered joints will melt and solder will fly out of the motor (guess how I know this.........).

The Eteks were good motors at a fair price, but to be honest they were never as good as the Lynch motor (B&S licensed the Lynch design and incorporated it into the Etek). If you are after powerful PM DC motors then the Lynch motors (and their successors, the Agnimotor) are probably the best bet, although the Perm motors are a reasonable choice, too. Any of these should deliver around the power you're looking for OK.

Jeremy

 

I received a MANTA motor

Probably a Chinese knock off, but sure looks well made. This is an experiment, but I wish I came here for advice first...

The instructions and datasheet rated this clearly for 10 HP continuous. If that turns out to be false, then I'll send it back. Testing under load for watts=volts x amps will be easy enough to do for a few hours and I'll watch casing temperature. Will definitely get back here and post results. I have to admit I was suspicious of the marketing, but there are a number of people building EVs with these motors that encouraged me, yours is the first negative comment I've seen. Beloe are the specifications that sold me.

My original plan was to buy a couple of used legitimately 20 HP forklift truck motors. They are available anywhere, and you can get 'em on eBay for about $350 each. Heavy buggers but powerful. I'll probably go back that direction, but I was seduced by the idea of four of these neat little "ETEKs"!

Ray

Specifications:
7.91" diameter / 5.64" length
7/8" shaft with 3/16" keyway by 1.75" long (threaded center)
Torque constant: 1.14 in-lb/Amp (0.13 Nm/Amp)
12V to 48V (has been run up to 96V / 45 sec. max. / 25 hp)
72 RPM per volt input (3456rpm @ 48V / continuous duty)
A put-up and forget design! Expect decades of dependable service life.
Rain, ice and weather proof electronics.
New Lithium/Graphite brushes.
10 horsepower continuous duty at 48 volts.
Max motor currents: 330A for 2 minutes / 480A for 45 seconds.
10 horsepower max at 48 volts continuous duty!
14 horsepower max at 60 volts continuous duty with optional air cooling port.
19 horsepower max at 72 volts for 2 minutes only!
28 horsepower max at 96 volts for 45 seconds only!
Works for both CW or CCW rotations.
Epoxy/Lam rotor efficiency = 94% (Brushed motors convert more electricity into usable horsepower)
Weighs ONLY 22 lbs. !! / Dimensions - 8"X 9"X 9"
Can be used as a generator, makes power when turned (Requires 100 amp blocking diode)

 

Hi Bert,
I had a similar system on my previous boat, 6x 64W amorfous flexible panels made by Unisolar, glued on the roof top.
In full sun sometimes they would trip a 30AMP circuit breaker. I am not sure how much power that is, but it was sufficient for me.
They would start charging at sunrise and stop at sunset, would charge partly shaded etc. We'd walk and drop things on them; one got badly damaged when the mast fell on it !!! Ouch. The insurance paid for a new one, but I left the old one on as it was still outputting power !

Now I bought 10 x 68W from Sumai and I am going to install them on the roof of my new boat. I will post here a short report on their performance.

 

10hp at 48V, assuming an efficiency of 80% (which may be optimistic, my guess is efficiency will be down around 75% or less at this high a current) means running at a continuous current of 186A per motor. I can guarantee that if they are Etek motors (the constants look very similar) they will overheat when run at this sort of current for more than a few minutes. To be Eteks they have to be old stock from somewhere, which is a possibility. Most of the Chinese clones are heavier, less efficient and generally of poorer internal quality. The best of the clone Etek motors is probably the Mars (now Motenergy) ME0708. The spec is here: http://motenergy.com/me0708.html You can see that it's a bit heavier, with similar constants to the Etek, but only rated at 100A continuous, which is OK when it's well cooled. In a boat you will probably need to derate it a bit, because it will probably be a bit harder to get good cooling in an engine compartment. Motenergy seem to have taken the data sheets for the ME0708 off their new website, so I've attached it, as it's very similar to the Etek spec although has a higher continuous current rating. 100A at 48V for the ME0708 will give you about 4.8hp output (allowing for the 86% efficiency at this current, with a cold motor - efficiency will worsen as the motor heats up and resistive losses increase).

I've experience of running both the original Etek motors and the Mars Electric (now Motenergy) motors in vehicles. The Etek built a good reputation in the hobby EV market, so it was inevitable that the Chinese would cash in on this by making cheap clones.

Apart from the motor overheating at that sort of continuous current there is also the issue of efficiently delivering that much current from a battery pack. If you're using lead acid batteries then the Peukert factor at this high discharge current will mean that you get very low usable capacity, although lithium chemistry cells would not be as badly affected.

In general, if you want to get high power with an electric system it is much, much more efficient to go for higher voltages, as the resistive losses in the motor windings, wiring, batteries etc is proportional to the square of the current. If you double the system voltage for a given power, you halve the current and the losses will be a quarter of what they were. There are some safety issues with using higher voltages, but these can be managed and are no worse than those associated with installing a domestic power genset on board.

Jeremy

 

Jeremy:
What do you think about the potential for using power up converters? The best efficiency was near 90% sometime ago, when I posted on the topic, and may have advanced by now. Wonder if that efficiency can be maintained over large in/out voltage differentials. This would circumvent some of the considerable disadvantages of running so many individual battery cells in series. If they could make them small and cheap enough (and combined with BLDC commutation) so as to be contained within the motor itself, the safety issues could be more isolated and contained. Overall efficiency might reach say, 90% if the boost converter and motor could reach 95% or so....

Porta