Hmm…
I have no personal experience with anything but the Enerdel lithiums, both on my boat (2yrs+ now) and in my 2011 THINK (5+ yrs, 40k miles, no range degradations and NO BATTERY COOLING!).
Again, if the charge/discharge rate is low, the thermal concerns are made moot except for operating (charge/discharge) at high Temps, which was the primary issue with the Nissan Leafs---no forced air cooling of a battery pack for cars that sit (and charge) in the 100degF+ temperatures of Arizona were degrading the cells. An engineering goof. Probably would have the same issues for non-cooled THINK Enerdel packs if operated in Arizona. But we're talking boats here, not cars. We're talking packs in bilges or in compartments near the water line, not near 120degF pavement.
Matched cells: Yes…it's not just a good idea. But a good BMS will help correct for up to 5% difference or so, so it's important, but nothing new---heck, it's been a rule for DIY EV'ers for decades to match Lead Acid batteries by date codes and voltage as much as possible and to ensure that when series-charged they're all within 50mv or so of each other.
As for Big Battery == Low Cycling == Good, that's what we all here agree with, whether we use PbA, LiIon, Tesla or Leaf or whatever batteries. But we don't all have deep pockets…many of us start out cheap with only a small battery. Later we afford more and ultimately, with luck, we have a "Big Battery".
-MT
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com]
Sent: Monday, June 26, 2017 2:34 PM
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] Battery specific energy and power in relation to volume and density
I do not know about enerdel.
We do know that Leafs are crap, in longevity, and volts are crap, in longevity.
Typical loss is 15-30% in 3-6 years use.
This does NOT necessarily mean the cells are bad.
On those; ...
The temp / thermal conditioning is missing or poor, ...
chemistry is not so good, ...
cells are not balanced/equal (absolutley critical ! THIS is how tesla made their first batteries last, by sorting the cells), ..
and most important they are not shallow-cycled !!!
ANY of the critical-path factors in lion cells will massively degrade their lifetime.
C-rates, as You said,
balance,
chemistry,
temp conditioning,
cycling.
The Tsla Lesson is this.
Big Battery.
(= low cycling)
Thermal conditioning.
=> good.
(Optimal cells etc .. critical but less so).
No-one else in the world, so far, has demonstrated 1/3 the lifetime capacity of tesla packs.
This is NOT just because tsla was so brilliant, but because
1. they picked the cells for balance,
2. they used BIG batteries for low-cycling,
3. they used thermal conditioning.
At less than 1/5th C rate no commercial batteries last in any use I know of.
Lack of BMS/thermal.
Chemistry/shelf life/use life.
On 26/06/2017 21:16, 'Myles Twete' matwete@comcast.net [electricboats] wrote:
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.
--
-hanermo (cnc designs)
Posted by: "Myles Twete" <matwete@comcast.net>
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