LiFePO4 at dock

[Barold]

Wondering for the sailors who have installed LiFePO4 housebanks on their boats. Do you leave your boat plugged into shorepower and the charger on (has float and absorbtion profiles but our batteries are pretty much back to full by the time we return to dock

With LA I always left the boat on shorepower with the charger on - should I change that behaviour now (since I understand LiFePO4 does not like staying at a high SOC?

My concern has always been about the bilge pump and ensuring it always has power but with a new bank it should be able to run for quite some time...

 

[Supervstech]

Left at dock for how long? Any solar?

 

[Barold]

Left for maybe a week at a time likely.

I have the solar but have not connected/installed yet. Need to take some deep breaths before drilling through my deck to run the cables.

But even with the solar - would I want the batteries topped all the time or set it to get it to say 60-70% then before heading out, flip on the 40A shorecharger to top off the batteries before leaving?

 

[Bob B]

It would not be necessary to leave at a low charge if only being gone for a week or so. Whether to leave it on while you are there depends on the charger and it's ability to go into a float charge level ... and what level the charger is trying to charge to.

 

[Fred S]

Assuming you have a bms, it should protect you from the (unlikely) worst-case scenario of over-discharge. If you have a charger for lifepo4 that, when you leave, you can set to "float" at 80%, that would be a good solution. 80% is probably about 13.0v (assuming your system is "12v"), but I would check with the battery manufacturer for their recommendation. Later, with solar hooked up, you can change the charge controller settings to output at the 80% voltage while you're away - no shore power needed. Some controllers make this easy by allowing you to save several charging profiles.

 

[Danny]

I have a on off switch to turn LiFePO4 off at the dock and I run my FLA battery at the dock and keep my LiFePO4 at at 50%-40% SOC with FLA charge on. When I get ready for a trip I charge the LiFeP04. See video time 8:05.

 

[ianganderton]

I was thinking a bit about this last night and came up with the info in this oost

Off Grid LifePo4 Battery storage/standby modes

I was thinking about options for storing batteries while they are not being used or when full storge is not required. E.g cabin uninhabited, campervan/RV in storage, a yacht is on its mooring My understanding is a LifePo4 battery prefers to 'live' around 80% for maximum life Batteries need...

diysolarforum.com

 

[Bob B]

The other concern you would have on a boat is a parasitic drain on the batteries if they are sitting without being on charge. If you have them off charge, it would be a good idea to also have a battery disconnect switch. Your BMS should also be a last ditch safety for a problem like that.

 

[Barold]

Thanks to everyone who replied. All great points - I have the solar but have not installed it yet but i should do so soon. The shorepower charger has float and an absorption setting that could be turned off (14.4V and 13.8V for the LiFePO4 charge profile. Interesting there is one that is called "SPE1 open type" that has a Float V of 13.2V and a absorption of 14.8V (which I would turn off and only use the 13.2V).

Coincidentally now that I have a clamp meter, i checked my shorepower cable for evidence of stray current. With everyone on the boat off (charger, AC outlets) the Klein clamp meter measured 0.04A to 0.07A of current going through the cable on DC (0A on AC) unplugging the shorepower cable could save my anodes (and more importantly my prop and propshaft).

 

[Dauntless]

I would not make a lot of changes based on a clamp meter reading of hundrediths of amps. I don't any clamp meter can be so accurate at that scale.

In any case, what is your float set to? I have mine set to 13.3 volts.

 

[Sails]

Thanks for the great vid.... Wow!
I am here looking to convert my sailboat to Lifepo4 too. My biggest concern is the BMS cutting out when motoring and destroying the altenator or the solar charge controller.
This forum has great info and says the solution is to have a LA battery in parallel, so if the BMS cuts out.... There is still a battery taking the amps.
Your solution is great. I am beginning to believe Lifepo4's are possible for an off grid sailboat.
Now its time to map out the system and see if its economicly wise. As you say... LA batts are cheap, readability available and if you use 30% capacity on a regular basis.... Have lots of back up amps in reserve for emergencys.

 

[Argosy]

@Sails there is also a alternator protection device availabe in the $70 range - can get from Battleborn. Eliminates size/weight/fill with water of LA battery in parallel.