Re: What to do with LiFePO4 batteries when the boat is layed up?


Sv Garulfo
 


Hi all,

With MV you can define events that are based on the SOC, at either predefined levels (60%, 80%, etc) or a user defined level called “battery full”, and can be used to trigger actions on other components on the network, for instance switching on/off the inverter, switching charging elements to float   (or off), etc. 

Hope that’ll help

Thomas 
GARULFO
A54-122
Tahiti 


On 17 Sep 2021, at 10:11, Scott SV Tengah <Scott.nguyen@...> wrote:

Joerg,

I would be surprised if the MV software doesn't allow you to stop charging at a certain SOC vs having to guess with voltage. I can implement that on my less well integrated Victron system. Again, ask Garulfo as I believe they said it was simple to do so.

With respect to ideal SOC for storage, Victron delivers their batteries around 50% SOC, so that might suggest something. There's literature out there on how to prolong lithium batteries, but it's generally for more sensitive / explosive cobalt based batteries, but the consensus is 50-60%, matching Victron's SOC at delivery.

And correct, I don't leave the boat on shore power, even when it's available. The solar is far more than enough during storage periods and I don't risk bad wiring at the marina eating up my zincs and then my through hulls. Note that I don't have an isolation transformer or even a galvanic isolator. Was considering installing it but I find we're rarely at marinas and even if we're at one and aboard, I often don't bother plugging in.

What I like about setting the inverter to run above 60% is that my solar is more than enough to put in more power than the dehumidifier can draw. That, in effect, causes the battery to fill to 100% every few days, at minimum, but even if it's taken to 100% by the time the sun sets, the dehumidifier will draw down the batteries overnight so they don't sit at full for very long. And even if it's drawn down to 60%, there's plenty of capacity remaining to run the bilge pump for a long time before the sun rises again.


--
Scott 
2007 A54 #69
SV Tengah
http://www.svtengah.com

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