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Thread: Change from Lead-Acid to Li-Ion batteries

  1. #1
    Join Date
    Sep 2017
    Location
    Boat: Croatia; Living in Tokyo during the months not on the boat
    Posts
    30

    Default Change from Lead-Acid to Li-Ion batteries

    The problem I have on board is the storage of electrical energy. Beside the alternators of the engines and a genset, I have 1kWp solar power and a wind turbine.

    I have 5x 100Ah lead-acid batteries for service purposes (engine batteries are separate), from which I can draw a max of 100Ah without damaging the batteries. When charging I have a the first a high and then a very low charging current to charge the batteries without damaging them.



    1. What is your experience with changing to Li-Ion batteries?
    2. Can solar panel controllers be replaced for Li-ion suitable ones?
    3. Is it necessary to also replace the inverter-charger unit?
    4. To which charging level can Li-Ion batteries be discharged to not damage them?
    5. What are charging currents and times to reach 90-95% recharging level?
    6. What kind of Li-ion battery maintenance is needed and how often per year?
    7. What are other experiences you made when changing to Li-ion batteries?
    8. What is your experience in using Li-ion batteries?
    9. What kind of experience did you make with other types of batteries and how much energy can be used without damaging the batteries?


    A lot of questions, I know. I appreciate your answers a lot.

  2. #2
    Join Date
    Jul 2009
    Location
    currently Columbia/Panama
    Posts
    355

    Default Re: Change from Lead-Acid to Li-Ion batteries

    The best place to start is here: https://marinehowto.com/lifepo4-batteries-on-boats/

    1. It has been the best modification we have done to the boat, and that is taking into account a lot of modifications including watermaker and washing machine.
    2. Yes, of course they can be replaced, but they may be fine as is. All charge sources simply need to be able to be user-adjustable for LFP voltages. If your solar controllers can be adjusted to, or have a charge profile of, 13.8-14.0V bulk charging, followed by 13.2-13.4V float, then they are good to go.
    3. Depends like #2. If yours has a user-adjustable or set charge profile like described, it will be fine.
    4. For real world application, most people only discharge their LFP bank to 20% SOC (80% discharged) before charging again. Technically, they can be brought to complete discharge regularly, but that would be with laboratory conditions.
    5. LFP will take high charge rates up to 1C (400A for a 400Ah bank), but few people have enough charging sources to provide that rate. Since LFP will take full current right up to being 100% SOC, and has almost no inefficiency, the time it takes to reach full charge will depend on how much charge you can throw at it. If you have a 100Ah battery at 50% SOC, and a 50A charger, then the battery will be full in 1hr.
    6. I've never done any maintenance on ours in over 3yrs of existence other than to check terminal connections occasionally.
    7. LFP doesn't experience much voltage sag under load, nor voltage drop over discharge. They sit at 13.1-13.3V throughout their discharge range, under all reasonable loads. Everything running off DC on the boat will love this. Your watermaker will be more efficient and produce more water, your MPPT solar will produce more power, and you can easily run AC appliances off the inverter without worry. We run our waterheater off the inverter, as well as our large AC-powered watermaker - the batteries don't even blink under 100A loads.

    Read the link I posted, then do some more research. Many people are going with popular "drop-in" battery systems that are not suitable for boats. They are finding this out the hard way, so there are some gotchas to avoid. Don't do your learning off youtube cruising boats - most of them don't know what they are doing. However, there are also good manufacturers of "drop-in" that provide proper systems. These are much more expensive. Finally, there is DIY, which is inexpensive, but one should fully understand what they are doing.

    Mark
    Mark Cole
    Manta 40 "Reach"
    www.svreach.com

  3. #3
    Join Date
    Sep 2017
    Location
    Boat: Croatia; Living in Tokyo during the months not on the boat
    Posts
    30

    Default Re: Change from Lead-Acid to Li-Ion batteries

    Hi Mark,

    Although very late thanks for your reply. I was just to busy with other matters and Covid19 destroyed my entire sailing year. Now I am tackling this topic again and I am grateful for your reply and the link you provided.

    My next step will be to contact the solar panel manufacturer to see if they have the right charge controllers. And I need to contact Victron to see if the Inverter-Charger can be used for LFP batteries.

    Regards,
    R
    Last edited by P435; 28th November 2020 at 11:05 AM. Reason: typo

  4. #4
    Join Date
    Jul 2009
    Location
    currently Columbia/Panama
    Posts
    355

    Default Re: Change from Lead-Acid to Li-Ion batteries

    We have a Victron Multiplus inverter/charger, so if that is what you have, it is good to go for lithium.

    Mark
    Mark Cole
    Manta 40 "Reach"
    www.svreach.com

  5. #5

    Default Re: Change from Lead-Acid to Li-Ion batteries

    colemj makes excellent points. FWIW, on our Maine Cat 30 , we replaced the single 8D 255 ah sealed LA battery with 2 170 ah Renogy LiFePO batteries. These new batteries have built in Battery Management Systems that make them, essentially, drop in batteries. To be on the safe side I replaced the old solar charger with a new 30 amp Renogy charger. We also replaced the 220W (55W x 4) solar panels with 350W (175W x 2) panels. So far it is great but we haven't really stressed the new system in any way. . . we use way less amps than what's available although I keep threatening to add an inverter for a small microwave, other small home appliances.

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