Tesla Powerwall battery vs. inverter bank

Answer: We don't know...have no idea today.

It's too early to tell. I think first we have to observe it in use in the land world a while, then see how the price settles in and how the product functions. At that point you look at any complicating marine factors. Today it would be far more expensive than what most are using. I would anticipate that changing over time.

At this point there have been no deliveries of their Powerwall.

They remain a developmental company with some great concepts. Where any of them go long term will be very interesting to follow. Had they not dropped the Spider version of their car, we'd probably own one of those.

Tesla amazes me. First that they're still here. Second that they really grasp the entire picture and what is ultimately necessary. The fact there are now 425 Super Charging stations and you look at what they're adding the next two years. That has taken a huge commitment on their part.

With the currently available information: The price is interesting. - Not more, not less.

Very little is known about technical details other than capacity, price, color and the physical dimensions.
Just the basic facts would help a lot. Which chemistry is used? Which voltage? What is integrated. (An inverter is NOT integrated.)
Then you can go on and ask the more interesting stuff say: What does the 10 year warranty actually cover?

So, as with most product launches a lot of buzz but more questions than answers.

Btw, 10kWh translates roughly to:
12V system: 833Ah
24V system: 415Ah

Looking only at cell prices, a quick search shows that eight 400Ah LiFePo4 cells retail for ~$4400. Add money for a BMS, chargers, housing, etc...
So $3500 for 10kWh with 10 year warranty is certainly interesting.
But we don't know the chemistry. Tesla does not use LiFePo4, AFAIK they use LiNiCoAl02, in the model S. So the obvious and underhanded question is: Dreamliner anyone? (Those are are LiCoO2.) LiFePo4 is much safer, but not as high capacity, thus heavier. Not a problem in a boat, or stationary use.

Nigel Calder at IBEX 2014 in Tampa gave a great talk on DC systems. From this site you should be able to download the PDF of his presentation slides:

http://network.ibexshow.com/IBEX14/...e=Sessions.aspx&SessionID=189&SessionDateID=7

To compare "usable capacity" you need to compare 40kWh of lead acid to 10kWh of non-lead, because you can't discharge lead very much at all before you damage the batteries, while modern non-lead can be driven quite close to zero each cycle.

Also, the cost of charging the batteries is hugely different when using a generator. A non-lead battery bank can accept very high charge current, which means you properly load the generator (so its more efficient) and you can run the generator for dramatically less time. The costs are not just fuel, its the fact you don't need to run the generators 24x7, you can perhaps run a 30kWh generator for about 30 minutes every 12 hours to charge the 10kWh battery bank.

Its not trivially easy today, but its rapidly becoming easier.

This is almost true today: If you only want to charge with solar and dockside power (and weight of batteries is not important), then lead-acid is the way to go. If you charge using engine or generator, then modern batteries are much cheaper over even quite short time frames, but dramatically so over long term ownership.

When I recently (Oct 2014) did a trade study on electrical systems for a new build large ULDB sailing yacht, solar and lead was by far the way to go. Adding a generator was much more expensive than solar at construction time, and of course added a lot to ongoing maintenance and run costs. A generator plus modern batteries was a little lighter than the lead acid bank plus solar, but was much more expensive to buy, install, maintain, and operate. Of course, not many boats have the open space for a large solar array, but

The other risks are Lithium ION batteries can blow up if there is a major fault with the charger or etc. For remote control cars, they make special boxes to charge them in, in case they do and procedures regarding temperature and etc. I'm not sure about the safety situations for the larger ones.

This whole debate is something I have more than a passing interest in. I have a coastal property that I plan on retiring to. I am in the process of getting quotes for solar water heating and a fireplace fitted with a wetback on it to provide hot water for the hot water cylinder heating and the rest of the house.

I am very interested in getting the rest of the house off the mains even if it means switching to gas cooking.

This Tesla battery sounds very promising if it does what it says on the tin, only time will tell as the economic sense of what I am doing is obviously critical to it being successful or not and I see the first part ( Solar Hot Water) of what I am doing as a no brainer but am cautious about the next part and going fully solar power dependent.

I do have a genset now for the regular power outages so that might just be upgraded instead. As I don't want all the stuff in the freezer to go off in the even of a prolonged outage.

Considering that every single cell phone, laptop, tablet, etc has li-ion batteries, the risk of fire/explosion is quite low. Extremely low. Plus, it is far harder to make them ignite or explode than a tank of fuel.

As far as Tesla products go the underlying risks are basically the same. Tesla uses large amounts of 18650 cells from Panasonic in the cars, at 3.1 Ah each about 2000 of them per car.
The major difference is much better battery management and monitoring at the cell level. They are also not charged and discharged quite as fast as in RC use. (Which always seems to be as fast as possible.)

Just as AA batteries 18650 is a specification, not a particular product. They are used in laptops and powertools. Tesla went for these small cells because they are produced in huge quantities, which is not the case for larger cells. Thus using economics of scale and all of that.
One of the big question is if Tesla will go for another cell type now that they build them in their own factories.
Some of the more negative comments said that Tesla does not sell enough cars (=batteries) at the moment and now as their battery plant comes online has to get rid of the batteries at any price or their house of cards comes down. - Truth or BS? I have no idea.

That said, it looks like the powerwall is basically designed as quickcharger. Charge the powerwall slowly with the (bad) energy source you already have have in your garage, then dump all of it into the car when you need a fast charge.
As a second step it was opened a bit for other uses to sell more of them and maybe get access to a few renewable energy government incentives around the globe. How useful it is in other uses remains to be seen.



This is the link to Nigel Calders large battery bank presentation. The previous one was more about electrical systems design on a boat.

If one looks at the Palumbo shipyard solution for their hybrid yachts... that is the most practical solution.

As to batteries in general:

1. take more energy to charge than they give back.

2. have limited life

3. can cause fires or blow up

4. Cost wise really there is no savings when lifetime use is considered.

5. Add complication

If one has a very low baseline load that does not load a generator then a battery is a solution. Cost wise really there is no savings when lifetime use is considered.

I have several friends in the USA that have houses powered primarily by solar cells / battery with generator and electric grid back up. There are only two reasons for this one vanity and the other is the fear of lack of or loss of the electric grid supply and independence. If you are in an area with few thunderstorms it works but is expensive... if you are in an area with thunderstorms then it is much less reliable and much more expensive. If it is a vacation house it seems to work out because use is little... but often the owner shows up and has to call someone in to get it back working or it is a primary residence then I would guess the average down time is a few days a month and usually repair is needed at least every couple months.

As to K1W1 issues... it works but be prepared for lots of teething problems and many lightening rods spread around the property. A retired Naval Officer friend with naval engineering background has a very similar situation. Lots of care and maintenance required too but gives him something to keep busy.

Being still a big friend of the 2 Volt forg lifter type batteries for yachting purposes (still the most reliable and longest lasting batteries in the world), I must admit, that LiO batteries have evolved in the meantime and can be concidered save for cars, weekend houses, boating and aviation purposes, provided they handled correctly!

People knowing me, will be aware how much overcoming it cost me to say this in public (I personally hate Mastervolt ). We have tested several LiO batteries and battery management hardware in the company and on family boats, THE best LiFePo4, 24 volt battery for boating purposes on the market at the moment, are the Mastervolt Mastervolt MLI Ultra 24/5000, 180 Ah and its smaller sisters.


They are safe, reliable and long lasting and have great performance but there is a big a big BUT.

This battery and its smaller sisters need a good battery management system, that includes special charging, status and health monitoring and control and fully compatible users on the load side of the battery bank (thats why I hate this company, bloody marketing ). This battery only works properly in the long term with a genuine and complete Mastervolt electrical system with CAN bus network and all their Mastervolt black boxes.



And this batteries are quite expensive. They are the best as fare as energy density and amps to weight ratio is concerned but until now, they are the most expensive as far as $ per Amp is concerned. You can setup battery banks wit up tp 10 in seriell and large numbers in paralell and they can take high loads and charging rates.

The neighbour of our weekend house in the mountains has a setup with a 240 Volt DC system in his house made up out of this batteries, charged only with solar panels and a Fischer Panda high voltage, variable speed DC Diesel Generator. He is not using any electricity from the public network. The solar panels have additional water piping included under the silizium cells for producing hot water. This hot water is collected in a large and well insulated reservoir. The reservoir has 2 additional heat exchangers, one for the diesel generator cooling circuit and a second one for the heat exchanger behind the open fire place in the living room. This complex system makes all the electricity and hot water (central heating, tap water and for the indoor pool) for the complete house. He even sells the exess electricity to the public network. The diesel generator is only necessary as a backup and very seldom used. The only problem with the system, he has, is when using the open fire place in the summer time (for romantic purposes ) and the central heating switched off and the indoor pool empty, the heat exchanger heats up the hot water reservoir so quickly, that an overpressure valve opens and cooling water has to be introduced.

Very expensive setup but makes him fully independent and feel good.

Practically spoken, for a typical 50 to 60 ft boat with a 24 Volt DC system (both power and sail), a setup with two combined Charger / inverter like the above and 5 to 8 of those 24 volt batteries, you will only need a very small diesel generator with almost no running hours on a power boat and only may be 1 or 2 hours a day on a sail boat. A system like this will give you silence on the hook including cool down of the boat and electrical cooking plus entertainment for the everage overnight in the bay.

Just my 2 (Euro) cents

HTM09

Your friends mountain cabin sounds much like a couple people I know with similar set up and it works well. Is it cost effective no... vanity situation and I often think on this but I have little interest in a cabin in the mountains have grown up with that kind of thing... some of my best memories are from the vacations in the mountains as a kid.

Those that depend on these setups day to day suffer from the 'black box' issue. Fix and operation is solely dependent on expensive service that may not be available in some remote place as yachts are intended to go.

Back in my 10 m sailboat days... the battery with a small generator and also a small generator that the was deployed in the water did very well. But no air conditioning (not even considered) and the fridge worked off either electric or gas bottles. Those were fond memories too. I was always figuring on "free electricity from the wind" and tried many little generators set up that were water or wind powered... great pastime hobby. But that is roughing it now... and I am about to give up anyway...

Hi Karo,

His house is not remote at all. It is just one of those Zero Energy houses, as we call them. Below the line, his chalet deliveres more energy then it uses (over the year). Very expensive, it most likely never pays back but one may feel good not being harmfull to the enviroment by using almost no fossil fuel at home.

Btw. he has a bicycle with electrical motor and recuperation mode. When going downhill in the mountains, he recovers almost 60 % of the energy, he uses going uphill. Pretty amazing bike.

Transfering this ideas into boating, my approach, when "designing" my present sail boat, was not going automatically to a full generator boat with something larger than 100 ft.

Normally, larger sail boats are designed with large demands of electrical power, not only for hotel appliances and navigational instruments but also for powering hydraulic and electric motors, necessary for handling such a big sail boat. To produce this amoount of power, at least one genset is running all the time, if the boat is not connected to shore power. This is called a generator boat.

To run a 100 ft+ sailboat fully on battery power for longer periods is not possible in reality up to now. But I am a big friend of effiency and synergy.

When running on the main engine, a PTO / PTI DC generator / motor on the transmission produces enough electrical energy to run the boat without using the diesel gensets.

When sailing at sufficient wind and boat speed, the variable pitch prop is set to a blade position, that he is driven by the current and produces so much energy, that only the smallest genset has to run in order to produce enough electrical power for boat (but not during races ). On very long tacks (without Air conditioning), by means of this sailing generator, the boat can sail for several hours on this assisted battery mode.

When on the hook and boat has been cooled down, the boats hotel load can completely be provided by the large battery bank and inverters for one night. When the power demand is to high, one of the DC variable speed gensets starts automatically, charging the battery bank. If the power balance is still negative, the second DC Genset starts. Due to its variable speed setup, they are always running at optimum load.

If it is enough energy left in the battery bank, the boat can, due to its PTI motor and the variable pitch prop, leave the bay silently under battery power at a slow speed of 2 to 3 Kts. Outside the bay or harbour, the main engine or the generators are started and / or the sails go up.

With all gensets running, the boat can continously go in this diesel electric mode with the PTI motor at about 6 Kts until running out of fuel and it is (limited) dynamic positioning capable in this mode with the help of the electrical and retractable bow and stern thrusters.

With the main engine running and all gensets up plus overpitching the VPP, the PTI motor can act as a booster for the main engine.

The little positive side effect with this large and very heavy battery bank is, we are using it as ballast, as the batteries are located very low in boat and in the keel.

It is for sure not a Zero Energy boat but is has a significant lower footprint on the enviroment with its hybrid setup than a full generator boat. And that makes me feel good !

Will say, electrical mobility is catching up. Full electrical cars are comming for polution free urban driving, plug in hybrid cars (with diesel hybrid!) can go pollution free in towns and use their very low fuel consumption diesel engine when going long distance. Even electrical flying is comming. Serveral of my glider flying colleagues already have fully certified retractable electric motors on their planes. Several light aircrafts are under developement with electric motors and LiO batteries.

The light aircraft company Pipistrel in Slovenia has developed a basic trainer with electrical propulsion and quick exchange battery packs for flying training. It can go for an complete hour of traffic pattern work, then the battery pack is exchanged in 2 minutes and the next student / instructor pair is taking over.



Full electrical personal mobility will come. With the ever increasing energy density of modern batteries and advanced power management, this day will not be far away.

Remember, the solar aircraft is on its way around the world and a solar power boat has already circumnavigated the globe. And our member Norseman drives all over Florida with his electric duffy boat .

I will not pretend to be an expert in any degree, but I will relay that it may not be the chemistry used in the battery, but the actual engineering ("arrangement" if you will) of the battery that's key to its higher capacity. Or, there may be some breakthrough that Tesla is not willing to share as yet.

My chemistry instructor at the local junior college has a friend who in the 70s was messing around with solar cells. I forget what the efficiency of them was at the time, but there was a serious belief that they could not get any more efficient due some perceived physical barrier. But he was able to show otherwise, and now you see vastly more efficient solar cells used on a number of things.

When Tesla was local here in the Bay Area they tended to be like Intel, HP, Apple and and the other tech firms; not share too much with the outside world. That doesn't mean that what they have is real, but there may be some core concept that they think is workable enough for this showcasing.

Just my take.

Electric motor design has been very advanced for some time now.
It all comes down to energy density of batteries for storage (amp/hour per kilogram) and cost of these energy dense batteries per KG. It's not only the OP's view ,but Fact , fossil fuel has a higher energy density than current battery technology. But as every ones knows there is a lot of research and development in this field.

I think most people will be driving electric cars in the not so distant future (before fuel cells) and you will see hydrogen fuel cells first used in the commercial truck sector developed for fleets such as delivery & long haul trucking.

The now retired space shuttle ran on fuel cells that where developed in the 70's.

Siemens has developed an electric motor for light aircrafts up to 2000 kg max. takeoff weight, with 260 KW power and a weight of only 50 kg. Means a power to weight ration of more than 5 KW per kg of weight. Due to its low speed of only 2600 RPM, the motor can drive the propeller directly without an reduction gear. A new record as far as I know.

Now we just need the battery for this motor and electrical flying in a Cessna Staionair for example would be possible.

It would be great as the generator part of a marine genset.

~348 horsepower......... That's impressive, motor doesn't look much bigger than a alternator.

Correct me if I'm wrong, but aren't all rechargeable batteries prone to blowing up is overloaded?

Here're a couple of links to Tesla's Power Wall;

http://my.teslamotors.com/roadster/charging/high-power-wall-connector

http://my.teslamotors.com/it_IT/forum/forums/high-power-wall-connector

Gel batteries especially those 2 volt forg lifter batteries do not blow up or start a fire, if overcharged or discharged at a higher rate than specified. They just die chemically. The worst thing I have seen on one of them, was deformation and some melting of the PVC case. But the thing they really do not survive, is a very deep discharge and being left for longer periods in this state of deep discharge. And one bad 2 Volt battery pulls down the whole battery bank.

A LiO battery can take very high charging rates (up to its capacity, I am told) and quite deep discharging but if overcharged real badly due to a bad or wrong charger, they virtually explode and start burning. Due to this danger, I did not really believe in LiO batteries for cars, boats and aircraft up to now.

But those new LiFePo4, 24 Volt batteries are very advanced. They have there own intergrated health and status monitoring system which monitors and controls each individual cell within the battery. If one cell overheats or shows abnormal behaviour, it is disconnected from the circuit and the battery still works, just with lower capacity. But still, the complete electrical system needs advanced charging and discharging and an intergrated CAN bus network for monitoring and control.

The other big problem with those modern LiFePo4 batteries in my opinion are accidents. If the vehicle or vessel they are built in, catches fire, they become dangerous. I would not like to be one of the fire figthing crew members, attacking a bigger fire inside a vessel, where a big battery bank of those LiFePo4 type batteries is located.

I would rather watch this fire with my buddies in our rubber boat or from behind a big tree at a safe distance .

But the most dangerous type of batteries, I have come across in my life, were those high temperature natrium sulfur batteries, the big car producers were experimenting with some years ago. I really hope, they are history.

The back side of this modern technology electric motors and batteries are the chemistry inside and the matrerials they are made of.

Lithium and these Rare Earth Elements (REE) like Scandium or Lanthan and many others, which are needed for those permanent magnet motors, are the cause of crime, destabilization and crises in many third world countries. If the industrialized world gets more and more dependent on those critical recourses, more and more problems will arise.

Good old days, when electric motors were big and heavy and concisting of steel and cooper (and lasted for ever). And batteries were filled with led, sulfuric acid and distilled water, period. Now, your flash light has fuzzy logic and is computer contolled and the light bulb is called LED .

I think we should ask Geordi La Forge for one of his dilithium crystals.