LiFePo4 lithium batteries in an Egret

TXWahooTXWahoo Posts: 515 Officer
I'm going to replace the original Interstate Gp 27 lead acid batteries in the boat this month.  I presume my boat is wired like most other late model Egrets.

- one 12V for the outboard and accessories
- two 12V wired in parallel for the 24v trolling motor
- Powermania 3 bank charger
- two red Perko switches (don't know if they are selectors, isolators, etc)

I'm thinking of replacing them with Lithium Iron Phosphate (LiFePo4) batteries

- For the main battery, planning on one 12V 100Ah battery.  I'm sure there are no issues there.
- For the trolling motor, is it better to go with two 12v or one 24v battery?
- If I put a 24v battery there for the trolling motor, is it safe to use it to crank the motor if needed?  I believe Frank told me I can do this with my current trolling motor bank with no problem but this is a lot of money to spend to have an "ah ****" moment.
- 12v 50Ah lithiums are about $650 and a 12v 100 Ah is about $1050 so it saves $800 to use two 50 Ah.  With lithium having a 100% depth of discharge rating, wouldn't this yield the same power as my current two 100 Ah lead acid batteries that can't be discharged to less than 50%?

Replies

  • Saltwater JunkieSaltwater Junkie Posts: 1,086 Officer
    You need 12 volt batteries. Every thing on the boat is 12 volts. Except for the trolling motor. If you put 24 volts on any other piece of equipment you'll trip the breaker and or in line fuse. Hence you will most likely not be able to start the outboard motor.
  • FlatsBoyFlatsBoy Posts: 1,371 Officer
    Like we spoke about three separate Relion 12 volt 100 ah will be your best option with your setup and charger.
    Once you go to 24 volt or 36 volt all in one battery it changes charging and alternate starting.
  • TXWahooTXWahoo Posts: 515 Officer
    edited September 2018 #4
    Wow, it took Florida Sportsman over a week to post this thread.

    Phil, since the 36v trolling motor is more efficient and can work with 3 x 50Ah batteries vs the 2 x 100Ah for the 24V motor.. it appears 3 x $650 = $1950 is about the same price as 2 x 100Ah batteries.  Makes me wonder if I should upgrade from 24V to a 36v trolling motor before I buy batteries?


  • FlatsBoyFlatsBoy Posts: 1,371 Officer
    That is a tough call.
  • TXWahooTXWahoo Posts: 515 Officer
    Appears the Rhodan is much more energy efficent than Minn Kota or Motorguide.  I couldn't fund the 36v numbers but their 24v 80lb only draws 41 amps vs 56 for the MK.
  • trponhuntertrponhunter Posts: 248 Deckhand
    Just curious as to why you would want to spend this much money on batteries? I assume it is not weight, as the 189 is not a super skinny boat to begin with and I can't imagine the weight reduction would affect the draft at all. Not trying to be dis respectful, just wondering what the attraction is versus the cost. 
    *Previous - 2000 Egret 189 carbon w/ vmax 150 - twin rotating prop
    *Previous - 2008 Egret 189 carbon w/ ETEC 150
    *Previous 2010 Beavertail Vengence w/ETEC 90
    *Current - 2015 Beavertail BTV w/ Suzuki 90
  • TXWahooTXWahoo Posts: 515 Officer
    edited October 2018 #8
    The weight reduction would be about 100-120lbs depending on models but that is not the main selling point for me.  I have a Moccasin 210 not 189, so the weight difference is even less of an impact.  

    Maintaining consistent 13.6v+ all the way down to near zero depth of discharge, not damaging the battery's life cycle when taking it below 50% depth of discharge, and not reducing the capacity when I don't have the ability to recharge them after each trip are main advantages to me.  

    That being said, I went with Full River AGM due to cost.... hoping the price of LifePO4 will come down when these need replacing.  I still think the lithium make the most sense,,, just didn't want to spend the money right now.
  • FlatsBoyFlatsBoy Posts: 1,371 Officer
    Just curious as to why you would want to spend this much money on batteries? I assume it is not weight, as the 189 is not a super skinny boat to begin with and I can't imagine the weight reduction would affect the draft at all. Not trying to be dis respectful, just wondering what the attraction is versus the cost. 
    There is more to just the basic weight savings. With the weight savings it like running the boat with a 1/2 a tank of fuel when everyone else has a full tank. This will gain you efficiency in fuel burn at cruise and WOT along with added speed of about 2 mph. You also gain which is the biggest advantage having 100% power to your trolling motor all day and none denigrating like agm or lead acid which reduce power as they are used thought the day. They recharge quicker have a better warranty and last longer. I've been using mine for almost 4 years now without a issue. Yes they are a investment but have proven them selves to me to be worth it.
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