Re: Converting my Amel 54 to lithium batteries: what I did, what I like and what I don't like (after one year of full time live aboard use)


Arno Luijten
 

Hi Scott,

Thanks for your extensive report on the Lithium conversion.
Reading your post I notice the same challenge as I've been anticipating when moving to Lithium. Basically you want the batteries to stick at 70-80% if you keep the boat on shore-power and avoid keeping the batteries at 100% for extended periods. When at anchor this is more easy as there is typically no permanent feed of power into the battery similar to shore power so the SOC will go up and down anyway. At the same time you want to avoid unnecessary cycles on the battery. There is no easy solution as ideally you want the chargers to stop charging at 80% unless there is a reason to go to 100% (i.e. start of a longer passage). At the same time you do need to feed the onboard systems even if your batteries should stop charging. Most battery chargers can also act as power-supply. So just isolating the batteries from the charger when the batteries reach 80% SOC would solve that problem. But how to handle the situation when the on-board systems require more power then the charger can supply and the "disconnect-from-shore-power" event without having a power-dip on all your on-board systems during the time it takes to re-connect the batteries. When at anchor ideally you need to anticipate when the renewable sources will no longer be able to support the on-board systems and the batteries need to brought back on-line. For the latter, as you rightfully say, you can determine the voltage the chargers need to produce to halt the charging process at 70-80% but there is no easy way to alter this voltage if you need to go to 100%. Ideally you should be able to simply activate a certain charging profile for all charging devices. I have not found a solution for this myself.
Balancing the batteries is another issue as this is typically performed at 100%SOC requiring the need to occasionally push the batteries to 100%SOC. There are systems that do continuously balancing but that required the usage of individual cells (https://www.ev-power.eu/).

So to me it seems the Marine industry had not yet made the full change to support Lithium batteries in the best way possible. The question is if you want to wait for that point if we will ever see it happen. By that time there may be another technology surpassing Lithium.

Arno Luijten
SV Luna,
A54-121

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