Re: [electricboats] Li-ion battery designer commentary

Excellent treatise, Kevin.  And no criticism here of the logic justifying using lead-acid batteries for displacement water craft propulsion based on the factors noted.  You could also add to the factors: Cycle Life.  A 2000-3000 charge cycle life is meaningless for most recreational boaters, let alone displacement craft that might only get used 1-2x/month.  In my case, this was a major factor in my early analysis for not considering lithium alternatives since most arguments for lithium vs lead are based on a 3-5x effective cycle improvement.  I mean, if, like me, you average only about 20-30 outings a year and assuming you only have to charge the pack 4x, that's just 4 cycles per year (what I typically do now).  It's hard to rationale paying more to improve cycle life when a perhaps 400 charge cycle life lead alternative would on paper last 100 years.

 

But that's not the whole picture with cycle life and lead.  Lead acid batteries usually die prematurely well before reaching the rated cycle life.  Often 10x sooner, especially and mostly in cases where cycle time is very extended---and that is particularly the case with marine pleasure displacement craft like mine.  My boat went thru 3 sets of lead acid deep cycle golf cart batteries all of which sulfated prematurely because I could not keep them maintained as they needed to be to realize anything close to a long cycle life.  Further, as this progression deepened, in each case, it was a guess and a worry how much capacity my pack actually had after being charged.  At some point you get really tired of this lack of dependability.  Not to mention the hassle to haul out a raft of lead each time and haul it off to the recycler.  Have you seen how nasty the recycle process is with lead?  I suppose in the States it might be environmentally sound but there are videos online of it being done in an open air shop in places in India and I wonder how eco-friendly the whole process really is.

 

Add to this the fact that there are a raft of ex-automotive EV battery packs out there with gobs of cycles and capacity left in them with cost/kwh that rivals or exceeds the cost for comparable lead-acid alternatives.  Saving those packs from the recycler or junk heap has eco value.  And so, some of us here (e.g. me) have gone to lithium thru this path, reusing ex-land EV batteries for our boat propulsion.  Result: Affordable and high performance packs with high dependability in terms of absolutely knowing how much capacity your pack has left.  Packs that otherwise might have been left to rot on the auto junk heap, packs that can sit in our displacement craft for months unattended with zero degradation, very much unlike lead.  Packs that will literally outlast our boats.  Replacing this pack in the future is no longer a necessity at all.  Hard to see the end-of-life recyclability as a big argument against lithium for low-cycle, displacement E-boat propulsion.

 

Thanks for the points you made.  You made them well. J

 

-Myles Twete, Portlandia

 

From: electricboats@groups.io [mailto:electricboats@groups.io] On Behalf Of Kevin Pemberton
Sent: Sunday, January 1, 2023 8:45 AM
To: electricboats@groups.io
Subject: Re: [electricboats] Li-ion battery designer commentary

 

Yah! If you're loading your racing boat up with lithium and your wanting to plane, energy to weight ratio is big. However when displacement hulls are the major players weight becomes less of a factor. 

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