Hannu-
I agree with your points, however, for the purpose of non-high-power applications like MOST of our boats (i.e. avg current < C-rating of pack), your points about the advantages of Tesla's cylindrical cell configurations are rendered practically moot.
· With most of our boats here, we're typically talking 5-10hr cruise time at cruise speed and pack size ---i.e. we size our packs for a 1/10 to 1/5 C draw rate. There is no heat issue here regardless of the cooling.
· "Cylindrical cells leave some space, but this space is used for liquid cooling." --- Not really---take a look at the Tesla pack configuration. Yes, Tesla runs a serpentine rectangular coil thru its pack touching all the cells, but that coil makes zero use of the 25% space loss due to "1-pi/4" area loss with cylinders vs dense rectangular or pouch cells. In fact, utilization of space is even worse: Tesla requires EXTRA space to run those coolant coils along horizontal rows of batteries from the images I've seen. So from a volume usage standpoint, it's not very efficient. And as I mentioned, the coolant is pretty moot at our power rates (unless you're running a boat at 1C or higher) and only really of use perhaps to cool a cell that goes haywire.
· "Liquid cooling / thermal management extends lion battery life by a factor of 5-10" --- Again, at the low "C" rates for our usage here, there's no heat and therefore no advantage.
· "All-above indicate probable lifetimes of 15-30 years in normal relatively-heavy use." --- Okay, and the Enerdel pouch cells I use are rated for 2500 cycles to 80% --- that would be about 80 years or more based on my usage and extremely low power rates. J
It's always important to consider the Use-Case. Tesla's batteries are great as are Enerdel's, Nissan Leaf's and Chevy Volt's. They're all designed to handle regular safe usage at up to 1- and even 2-3C current rates especially if rated for fast charging---e.g. Tesla's. At less than 1/5thC rate, ANY OF THE CAR BATTERIES will work fine and last for years for the typical E-boat. The extra cooling and other "advantages" of the Tesla pack are effectively moot for most of us---I wouldn't even see an advantage if I used TESLA batteries to power my 2011 THINK which can burn thru 24kwh at 1.1C rate but doesn't allow fast charge.
-Myles
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com]
Sent: Monday, June 26, 2017 11:08 AM
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] Battery specific energy and power in relation to volume and density
I disagree with this ...
politely..
and the reason is non-obvious.
The cylindrical cells 18650-c with nmc chemistry, are the most energy dense solution available 2011 when they were designed/qualified/put into production.
They were also the cheapest ! by usable energy when purchased in high quantity.
What happens, is that the heat-problem I mentioned is actually the NR 1 ! issue in massive lion-power systems.
And the heat-problem is ALSO *critically* related to
1. VFD inverter drive efficiency,
2. contactor efficiency,
3. safety,
4. cost.
Cylindrical cells leave some space, but this space is used for liquid cooling.
This makes the battery safe, as it will not run-away due to any errors/failures of a cell, single shorts, etc.
Liquid cooling / thermal management extends lion battery life by a factor of 5-10.
Liquid cooling/thermal management is really cheap to do.
Today, based on 400-500-600 sets of data from volunteers, current Tesla batteries have been driven to 200.000 miles, with 96% capacity remaining, and of all batteries in the 500-something data set, averages are about 93-96% capacity remaining after 3-4 years, and a surprisingly lowered !!! rate of loss after about 2 years.
All-above indicate probable lifetimes of 15-30 years in normal relatively-heavy use.
Datapoint:
VFD effiiciency is never mentioned, but is critical in high-total-power systems.
The Tsla 300 kW peak inverter, has been re-designed over 12 times.
Datapoint:
A difference of 3% in efficiency lowers total system cost by a huge amount, from say 93% to 96%.
A siemens inverter, 300 kW, is == 60 kg in mass, 12.000$ in retail price/cost.
The tesla inverter is 20 kg, under 500$ in marginal cost (parts and labour, ex r&d and production line.)
Datapoint:
Original tesla contactors peak power was 1000 amps.
Current peak is 1600 amps.
Same motor, battery, newer VFDs.
For boats, we are actually not (too) interested in volumetric or gravimetric results, but in costs / capacity.
My observations are mostly on trends/technology capacity, re: exponential industries like lion batteries, BEV cars, etc.
I grew business(es), a lot, on exponential trends in the past, re PC/HDD/RAM/processor/Internet.
So when I see Tsla doing 380 Wh/kg, this means, automatically, battery costs / power have dropped/will drop, 40-60% retail within a very short time.
And this exponential drop is likely to continue.
I am not saying that Tsla will take the cake .. although they likely will, because the incumbents dropped the ball for the last 5 years, and are now in too-little - too-late.
Note:
Tsla used == 6 GWh of 24 GWh total global production in motion-app use (ex cellphones, laptops etc), 2016.
Tsla will use == 12 GWh in 2017 (wide variance, depending on Model 3 stuff).
== 30 GWh in 2018 (high confidence, even with near-zero energy business.).(Could easily be 50 GWh).
So by == 2018, year end, or YE2018, Tsla will use more lion battery power than all the other users combined, this year.
Including about 1 M electric bikes, scooters, etc. etc.
So within about 18-20 months, Tsla will be bigger than any single other customer with advanced lion batteries, by a factor of 10-50.
BYD china will use a lot of lion as well, but it is Lifepo4, much lower tech/energy density, older, not so relevant.
It would still be barely possible, in theory, for Big Auto to actually seriously compete with Tsla and Good Lion tech.
They would need to reserve 3-6B$ (that they have, no problem) and put that towards massive investments in
1. battery research, first,
2. talent,
3. massively efficient factories making dirt-cheap batteries.
Incumbents have never done so- historically.
Reverse chronological order Nokia, coal, Lucent, Alcatel, Micropolis, IBM, trains, coaches.
So far, the management boards and investment plans (public companies, so they need to account for a disappearing 6 B$ in their 10-K and P/L) have not materialised.
Just my POV.
2-3 years ago I predicted 1 or more of Big Auto (top 5-6) would die, go BK, in 2018, +/- 1 year.
My prediction stands.
Reason is money.
If any of the Big Auto companies start losing sales in their most-profitable segment, premium starter-sedan autos, they go BK in 5 days.
Audi A4 series, BMW 3-series, etc.
They make most of their money in this segment.
GM for example has 160 B in liabilities aka debt.
Their bond ratings need a 1 % y/y growth, historical average, for the market to retain faith, for a 40-year current payback period.
If bond ratings reduce .. as would happen with reduced sales ... bank covenants mean they must produce extra collateral.
Same / similar applies to all others..
The Q is not that say VW has 4-12 B in cash/assets available, it is that it needs 30-50B if the bond ratings fail, and they do not have 30B.
And the fixed-liabilities re_workers are 50B++, that cannot be reduced in the EU / germany by law.
Unlike the USA, technical BK does not release EU companies from pension liabilities, only closure/insolvency does that.
On 26/06/2017 18:52, 'Myles Twete' matwete@comcast.net [electricboats] wrote:
Anyway, it seems to me that with boats, we are more interested in better volumetric energy density than we are mass energy density. Cylindrical cells as Tesla uses may not be the best way to go for volumetric energy density---they leave a lot of space unused ( Ncells * Lcell * (1-pi/4) Dcell^2 ). Still, compared to the energy density of lead acid (volumetric or mass), it's pretty dang good… J
-MT
--
-hanermo (cnc designs)
Posted by: "Myles Twete" <matwete@comcast.net>
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