I'm at about 3 ½ years using repurposed lithium modules on my boat.
Concerns? Sure---I had concerns from the get-go. But those concerns pretty quickly vanished for me as I have been a daily driver of a car powered by these same batteries now for 5 years. I couldn't rationalize investing in new batteries for my boat at the time. What I did rationalize was buying these batteries as spares for my car (THINK went bankrupt in 2012 and so the only quantity of batteries/modules out there for these cars are here in Portland). So I bought them and have been using them to power my boat---they'll probably never go into a car after this.
I've probably not given adequate thought to getting these modules wet, though for the most part, that's not a concern. Several THINK Enerdel packs have been flooded or otherwise ended up with water in the metal cases, water on the BMS circuit cards and the modules. There have been no stories about a THINK car burning up due to any issue or event with the battery pack---contrast that with Tesla which did see at least 3 of its cars go up in flames due to road projectile intrusion. The THINK Enerdel modules are steel-encased and all get bolted into a double-layer steel bottom to protect from road damage. Evidently water has gotten into some of these and caused issues, but never anything catastrophic---just cell replacement due to shorts.
So in my case, every 3kwh of energy storage is encased in a steel box and each box has 2 BMS boards that can manage the cells in its series 48v stack. I fuse each half-module with just 10amp fuses. That was my biggest concern: The risk of a cell short suddenly putting a high load on the entire pack and risking a meltdown. With 19 parallel low-impedance stacks feeding a shorted stack, a lot of heat could build up quickly and I could easily see a fire resulting. But that can't happen with a maximum of 10amps flowing into a stack with just a single cell pair shorted (i.e. just 10amps*4v ~ 40watts)---above 10amps, the fuse blows. I was then most concerned with the risk of "zippering" my fuses---e.g. pulling 200amps from the pack and having the nearest batteries delivering more than their share, blowing their 10amp fuses first, then the next, and on until their all blown. It doesn't take much testing to evaluate that risk. And I have 20 of these fuses---hmm…200amps should blow them all---maybe I ended up using 20amp fuses after all…?
Anyway, you're wise to ask the hard questions and be safe. The concerns for you and your boat are different that those for me and mine. My boat will not anytime soon be in salt water. Most of the pack is well out of any concerns for water getting in. Charging rates at the dock are so slow that there's near zero risk of any issue during charging as long as the voltage is kept below the limits.
Your mileage may vary-
-Myles
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com]
Sent: Saturday, May 13, 2017 8:17 AM
To: electricboats@yahoogroups.com
Subject: [Electric Boats] Lithium - Re-purposed auto battery packs
I have a question for the group. We have seen a growing number of Lithium auto batteries installed in boat and wonder if there is a concern on the part of this user community about the chemistry of these re-purposed Lithium batteries. Today, there is resistance in most marine Lithium battery manufacturers to move away from LiFePO4 battery chemistry. That may be changing. Engineering and the advantages of the lower costs of the more volatile Lithium chemistry may be overcoming their concern.
Are you as consumers concerted about safety of re-purposed batteries auto batteries?
Are you aware of the safety issues of the non LiFePO4 batteries?
Is the driving issue of costs overcoming your concerns?
Thanks
Mike
Electric Yachts of So Cal/Pacific
Posted by: "Myles Twete" <matwete@comcast.net>
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