Solar charge voltage of LiFePo4 for off-season

[Wandering1]

Originally Posted by sailingharry

For me, I don't "need" to know these things, and certainly won't pay the LTE modem fee to find it out. But I know I am, at my core, an unusually frugal person.

But boats are toys, and there isn't much about them that we "need" to do.

Wind is interesting. I have a weather station at my house, and it tells me rather useless stuff like wind speed and direction, and humidity, and solar intensity, and lots of interesting stuff. So it's fun to look at.

Bilge level is more than fun. If I were to have a monitoring system, and my boat were a distance away, I'd REALLY like to know if my bilge pump just cycled for the 5th time this hour.

Humidity is also more than fun. High humidity can be an indication of issues -- leaks, open hatches, etc.

Volts can be good to know -- I know people who have had shore power trip off and come back to the boat with a completely flat battery. Over on a solar forum, a fellow had his LFP batteries go way overvoltage and do damage (BMS failure of some sort) -- knowing volts would have helped him!

AIS is fun too. I often open Marine Traffic just to see what's going on out on the Bay.

The point is that if you already have all the sensors, and are either on shore power or have adequate solar, it's already there. If you either have already bought an always-on internet connection, or have linked to the marina wifi, it's free. Even if you only check it once a month, why not?

My boat isn't a toy. I live onboard for at least 9 months of the year.
Leaving solar connected up to lithium for extended period of time on an unattended boat seems crazy to me. Totally isolated lithium makes more sense in that situation.
Once I am off the boat for 3 months, I have no interest in the boat. We lifted it out of the water and store it. It gives the hull time to dry out and there are no risks of sinking.

[sailorboy1]

Originally Posted by Wandering1

There are some interesting technical studies around that suggest lifepo4 cells will last their longest kept at 30-50% charged. These are studies independent of the Manufacturer

Post a link to one. When I tried to find the best I could find was 1 that said it only made a 3% difference.

[sailingharry]

Originally Posted by Wandering1

My boat isn't a toy. I live onboard for at least 9 months of the year.
Leaving solar connected up to lithium for extended period of time on an unattended boat seems crazy to me. Totally isolated lithium makes more sense in that situation.
Once I am off the boat for 3 months, I have no interest in the boat. We lifted it out of the water and store it. It gives the hull time to dry out and there are no risks of sinking.

For the vast majority of us, our boat is a toy. Even those that live aboard full time, it's not usually an act of desperation -- it's a choice that reflects our love of the life. I've lived aboard for months at at time -- but when I do it isn't my sole residence -- I have and maintain a dirt home. So even when living aboard, it is for enjoyment, not necessity. So I have a wind meter (not necessary), newer sails (not necessary), a nicely polished and waxed hull (not necessary), a TV for movies (not necessary -- and normally stowed in a locker), and myriad other things that exist solely for my enjoyment.
But it may be that your boat is not a plaything, not something you have and keep for enjoyment. You asked "why would anyone do that" and I gave you an answer. It certainly doesn't sound like you would enjoy those things, but some do.
As far as "no risks of sinking" we have a friend who pulled his boat for 6 months. Someone broke in, stole a few things, and left the hatch open. The boat was a total loss, requiring haz-waste suits and masks to even get in to retrieve personal belongings.
Leaving lithium connected to solar full time during layup doesn't make sense, which was the point of the thread. There are alternatives, discussed up thread, that can keep power available for use, such as to allow the bilge pump to remain operable (if your mast is keel stepped, you will need that -- unless you have a garboard drain).

[Wandering1]

Haha, I have all the things you have and more. The point is, why do you need to keep batteries charging to run unnecessary gizmos whilst you aren't onboard. It just seems pointless to create a risk to expensive lithium batteries when a faulty charger or BMS could destroy them. Isolation of the batteries would creates no problems