Kev-
I'm afraid I'll never get this vendetta against high quality lithium-ion modules use on boats. This for modules that actually have passed all critical safety tests.
Enerdel's White Paper on Safety can be found here. It covers design decisions from chemistry to cells, modules and BMS.
Ø I do know they are car batteries, you stated they are for "2011 THINK City electric car", not designed for use on a boat. Even the site you linked to does not list boats under applications.
Enerdel makes batteries. THINK made cars. The THINK Enerdel modules were custom-configured (for THINK) steel module configurations that housed 2 Enerdel "Moxie" stacks.
I suppose CALB or similar LiFePo batteries are "designed for use on a boat" then? Do any Lithium or Ni* battery manufacturers design cells or batteries specifically "for use on a boat"? Doubtful. It's such a trivial part of their market it likely hasn't even occurred to them except perhaps very recently.
Ø I would be interested to hear if you contacted them to see if they are designed for your use on a boat?
Actually, yes, I have spoken with Enerdel (the mfr of these cells, modules and BMS) including an engineer and an application specialist. And yes, the ones I spoke with understood my application. Having said that, they would never make a claim that these are "designed for use on a boat"---that would be ridiculous given the miniscule market in 2009 for H2O-EV's. In cca 2009, their market/focus was cars and other land applications. In 2012, Enerdel (and THINK) went bankrupt and subsequent coming out of bankruptcy certainly didn't put marine applications on their radar as a business focus, let alone some directive to "certify or design these for marine use". Their focus was to develop options and models with focus on land uses, where the money still is.
Ø Did you keep all the components associated with the batteries?
Sure, when I purchased a complete pack of THINK Enerdel modules and removed them from the pack, I did "keep" all of the parts I removed. I do not "use" all of them.
Each of the q:10 THINK 3kwh Enerdel modules on my boat is 100% unmodified and includes 2 RLEC (Remote Lithium Energy Controller) cards on each. None of that is modified, nor have any cell interconnects been modified, altered or even accessed except in the one case where I found a weak cell pair and needed to remove the module, remove and disassemble the stack and replace the bad cell pair.
I DO use the 20 original RLEC (BMS) cards---and each of these I am able to communicate with thru dual CAN buses from an Arduino microcontroller running code that I wrote code for. When I occasionally do check and balance the cells, the BMS cards, along with the master controller is able to balance the 240 cell pairs onboard to within a standard deviation of 20mv or so across the entire pack.
Outside the battery modules, I use the same gauge cabling as original at the stack/module level. No, I am not using ALL the other hardware (e.g. high voltage contactors) as this is not a high voltage application.
Ø I would guess that there is a heating/cooling management system.
No, there is not---cells/modules for the 2011 THINK as with the 2011 Nissan LEAF were passively cooled. The internal resistance of a cell is so low that unless you're charging/discharging at the 1C+ level, heat buildup is not possible. Having said that, each cell pair has an aluminum conductive plate that brings heat out to the ends of the cells for either passive or active cooling. These cell stacks and the heat extraction technique are covered under Enerdel patents and they are designed such that forced air cooling is merely optional. Only a couple people I know worldwide have ever added forced-air cooling to a THINK Enerdel pack on a 2011 THINK City.
Lack of active cooling has been a problem on the 2011 Nissan LEAF packs---that is for those charging, midday over hot asphalt in places like Phoenix. I cannot conceive of any possible operational scenario whereby I would need any cooling at all for these cells on most boats.
Again, numbers matter: 20 stacks, in parallel, max. 200amps from battery to motor implies max. 10amps from a stack. These are 35amp-hour stacks, i.e. 0.3C max discharge rate is the absolute max stress they will see (and only for maybe 2 minutes)---typically I keep pack current under 80amps, i.e. 4amps per stack or about 0.11C. In what universe would that require anything but passive cooling? As for heating, I could if I really needed range in the winter, but winter usage for me is the maybe 2-3x per month 1 hour jaunt, using maybe 30amp-hours. I also am unlikely to charge the battery pack anytime between October and March.
Ø What is the end of life for these batteries? Is there a time when it is not safe to use them anymore?
EOL for these cells is not published, near as I can tell.
They are designed and certified as having 80% rated BOL capacity after 10years for an average DOD of 50%.
I suppose the same question applies for the guy who uses CALB or old ThunderSky LiFePo cells as well as ex-Volt, ex-Tesla, ex-Leaf, ex-etc. LiIon modules. I have pioneered the use of ex-EV modules on a boat perhaps, but I won't be the last.
Ø Did you test that your plastic top will melt and put out the fire? This does not seem like a realistic theory.
It's not theory, it's standards. You really need to educate yourself on UL-94V0 if this is of concern to you. 94V0 refers to the plastic not catching fire even if aligned vertically. Lesser quality plastics are rated to pass 94HB (horizontal burn).
No, I have not taken a $500 battery, intentionally submerged or shorted it to validate if the plastic lid will extinguish the fire. Have you validated that your wooden box holding your CALB batteries will contain a fire that is ignited from a loose inter-cell or corroded bar that overheats and ignites some wood dust there? I am thrilled you care so much for my boat's survival, but I'm frankly getting weary of this.
REMEMBER: The overheat scenario for lithium-ion requires either (1) overcharging a cell (likely also with significant current) or (2) a high current scenario. Beyond that, external shorts or high currents are required. None of these are the responsibility of the MFR of the battery or cells---it is up to the application designer/engineer to consider the failure modes and address them. BTW, I am an engineer (PE actually) and have done dozens of FMEAs over the decades.
Ø When the lithium has thermal runaway, it will produce Hydrogen gas and expand the melted plastic out of the top, then causing an explosion.
It's "IF", not "WHEN". Maybe that's the problem here—you think it is just a matter of time. I choose to prevent the bulk of the scenarios which might cause that.
Ø Your batteries may well be safe enough for you, but I would not have them on my boat. It is just not worth the risk.
Sure, I get it.
And on balance, I prefer 10 discrete, intact, paralleled and fused, nom. 42v dual-stacks over stringing together 12-14 large LiFePo cells. I don't see it as any more dangerous. But than I also have been involved in EV's since cca. 1991 and I have seen what happens when a wrench is dropped or something otherwise accidentally connects between to cells/batteries and dumps hundreds of amps of current. Sometimes plasma balls form or worse even with lead-acid and I'd say this will certainly happen with a string of LiFePo on a boat at some point. I understand that you want LiIon to be the bogeyman. Just realize that I am not stringing these together---I am using engineered, safety-tested cells, modules and BMS and charging/discharging that. I cannot drop a wrench on a cell and short it if I tried. And if I shorted the main pack? Each local fuse at each module would blow.
One can come up with many dangerous scenarios.
My boat is more likely to burn up from a nearby gas boat catching the marina on fire than my boat's batteries failing.
I have more risk with my propane heater than I do with the batteries—at least hydrogen rises…
-mt
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