Re: [electricboats] Lifepo4 Batteries available and ready to ship from US

Just to close the loop on this part:

Here is a link to the spec sheet:

https://static1.squarespace.com/static/6050cbc3ab828124470dd6da/t/61200a5c5ad38c5553ca1034/1629489757267/48v200ahPowerwallSpec.pdf

���which has a little more info on the the way they reached that number:

��� After Normal charge���discharge @0.5C current to the end of discharge voltage. Repeat above process until discharge capacity reduce to 80% of initial value.���

On Aug 20, 2021, at 08:41, Dan Pfeiffer <dan@pfeiffer.net> wrote:

���

Yes, I agree with your reasoning.  I just wanted to know where the 6000 cycles to 80% figure came from.   I see Ryan is looking into that.  Thanks Ryan.  And I thought you had been using the Eve or Lishen cells?  No more?


I have about a 4 mile round trip to make from my dock out to open water and back.  So far I am using about 20% of my usable capacity each time I go.   I have a 13,400Wh battery and at about 80% DOD the usable capacity is about 11,000 Wh.  I am using about 2200 Wh each trip out and back.   At this rate for even 1000 full charge cycles I would be looking at 5000 trips out and back or every day for 14 years.   For my typical season I get out 60 to 80 days.   At 80 days the battery should last 62 years.  I expect other issues will shorten that significantly.  And better technology may supplant my battery long before it's end of life.   Hopefully I'll be around and sailing long enough to collect some data. 

I am working on collecting more and better data now that I have the shunt meter installed.  I am trying to get my wind and boat speed (in water) integrated into the data collection.  Headwinds make a significant difference on consumption.  Waves too of course.  I hope to have some figures on all that soon.

Boat Details
Pearson 10M
33' LOA, 28.3'LWL, 12,500lbs
ME1616 motor, Sevcon4
48V LiFePo4 280AH (from Eve cells)


Dan Pfeiffer

On 2021-08-20 10:12 am, Myles Twete wrote:

Reminder: We are talking about electric "boats" here.

 

Unless you are adding fast charge capability to your boat (and marinas!), the most you will be charging is 360 cycles per year.  It would require 10 years of daily use and recharge to reach 3600 cycles.

 

I would venture to guess that most folks won't recharge even weekly, or with even larger packs and less usage, monthly or quarterly.  So typically you're looking at between 8 and 20 charge cycles per year.  Even 1000 charge cycles requires 100 years of use!

Given that, and until we have waterways riddled with quick charge stations, it's ridiculous and a waste of bandwidth here to talk about charge cycle life for boat packs.

 

Just my opinion, but based on 8+ years experience now running with lithium and charging at maybe 6-10x per year.  My boat will sink and I will be long dead before my batteries' charge cycle life becomes a limiting factor.

 

-mt

 

From: electricboats@groups.io [mailto:electricboats@groups.io] On Behalf Of Dan Pfeiffer
Sent: Friday, August 20, 2021 7:47 AM
To: electricboats@groups.io
Subject: Re: [electricboats] Lifepo4 Batteries available and ready to ship from US

 

Ryan,

What cells are you using?  Where does the 6000 cycles to 80% figure come from?  It looks like about 3750 at 80% in the cycle life chart in this document for the EVE 280AH cells.  I would expect the 200AH cells to be similar? 

http://www.dcmax.com.tw/LF280(3.2V280Ah).pdf


Dan Pfeiffer

 

On 2021-08-20 9:34 am, Ryan Sweet wrote:

One more thing: I will warranty these stateside with spares, for five years. I fully expect them to last the lifetime of your boat (6000 cycles to 80% capacity), but nonetheless I am reserving spares for warranty issues just in case, and you would not have to wait for them to ship from China.