diy solar

diy solar

Multiple Charging Profiles - storage vs use?

picklz

New Member
Joined
Aug 11, 2020
Messages
17
Greetings All,

I've been doing quite a lot of reading around Lithium (LiFePO4 specifically) as it relates to boats and marine use. I feel pretty comfortable with how the technology differs from Lead Acid, the gotchas, design requirements, etc but I am hoping someone can offer a little guidance on charging and storage of LiFePO4 banks.

I have a smaller sailboat (new to me) that currently has a 460AH house bank (4 x 6v Golf Cart Batteries), they are in serviceable condition but some of the wiring on the boat is, shall we say, questionable. The battery charger also went out on me so I'm looking at installing a new charger at minimum, but may do a partial or full refit of the electrical system while I'm at it. The boat currently has ~300w of solar, and I'm looking to expand that to around 500-600w, also have a 2500w generator we can run if/when needed.

Lithium is attractive as I could get more total capacity, and a LOT more usable capacity, in about 1/2 the space - and since 2 of the 4 current batteries are not in a great location that is extremely attractive. The boat is kept at a marina w/ shore power, the vast majority of the time we're taking her out for either a day, or a 2-3 day cruise. Looking at probably two 280AH 12v packs in parallel for 560AH of Lithium if I went that route.

So the big question I have is, my understanding is LiFePO4 does much better if stored at lower charge values (50-60%?) being the boat will be sitting at the dock w/ solar and shore power the vast majority of the time, are there any options out there that would allow for the 'normal' profile to charge the batteries to say 50 or 60%, but with the option to change to a 'going out' profile that would increase that to 90-100% ?

For what it's worth I'm leaning towards installing Victron equipment (MultiPlus, MPPT Solar Controllers, Smart Shunt, Cerbo GX, etc) and the boat will have network connectivity at the marina. I've poked around in the Victron documents a little and just haven't been able to confirm if there is the ability to create profiles like that or not. It would be nice to just bring up the web portal on my phone the day before we're going out and switch from "storage" to "use" vs having to modify all the charging parameters manually every time. Certainly I could just leave the bank at 60% (~330AH) all the time (unless I know in advance we're gonna go out for like a week long trip) and still have more usable AH capacity than what I have now, but easily being able to swap back and forth would be ideal.

I'm not married to Victron (yet) if there's another solution that would offer that kind of functionality.

Thanks in advance for any help!
Matt
 
I don't think my Victron has anything like that. I can define custom ones, but not stored and selectable.

I wouldn't worry about the 50-60% need for storage unless you're talking a LONG time - months.

It would essentially be changing your absorption to match your float at 13.6 for "storage" vs. 14.4V or so for cycling.
 
Thanks - I think the batteries would essentially be in the 75-100% charge range for weeks at minimum and possibly months in some cases, our trips that are 2-3+ days long will have a higher likelyhood of draining the bank down a bit further but day sailing likely wont. I guess even if its a fairly manual task once it's documented making those changes for our weekend or longer trips wouldn't be that big of a deal and we could just leave the bank in that 60% range normally.

Also I'm considering using a REC Active BMS for it's CAN integration to Victron equipment, I've sent them an email to see if they have (or could add) anything that would easily adjust what is being commanded of the Victron equipment.
 
I use a victron blue solar MPPT and change settings via bluetooth on iOS device. The victron app has an option for user defined preset, but only one (oh well). So a simple drop down menu is out.

Settings for myDIY LiFe pack:

Absorption 13.72V
Float 13.31V

I suggest simply changing the absorption voltage and settle upon a “storage absorption voltage” and an “active absorption voltage” posted on a piece of paper somewhere.
 
BTW a brain dead but more expensive solution is to have two chargers with different settings and switch them on and off manually based on if you are just arriving or about to leave
 
A while back I asked about multiple profiles, specifically for this exact use case. I have two BMS and two Victron solar charge controllers as well as a Victron BMV-712. Loading one profile for "In Use" and another for "In Storage" would sure be handy.
 
In the process of some unrelated research I came across the fact that you can run the Victron Venus / GX software on a raspberry pi which for my purposes might work out really well and save a heck of a lot of money in the process compared to buying a Cerbo GX and the Display.

Part of that package includes nodeRed integrated in if you choose the 'large' image. If setting the charge voltages in the Solar MPPT's and MultiPlus devices via NodeRed is supported then I might just have found a good way to easily swap between two different charge profiles.

Some details for anyone interested:
 
I wanted to update this thread, because I know some of these answers to be false.

It may be the case that the Victron controllers did not allow custom and selectable profiles at the time this thread was answered, but they do now. I have personally saved profiles for the same purpose Picklz was asking about, and the profiles are easily selectable via Bluetooth or GX.

I have not done it yet, but I intend to use a "storage" profile during the winter for my boat's 200Ah LiFePo4 trolling battery w/ overkill BMS, as well as during periods of non-use in the summer. If I can use this storage profile to keep the voltage of the battery from dropping too low vs. checking the voltage manually every month, it would be just one more thing I don't have to remember to do.

The process I intend to use would be to discharge the battery while fishing (assuming to 50% SOC or less), and then to just set the battery charger to "storage" until the night before I intend to use the boat again. At that time I would switch to the "use" profile to charge to 100% SOC.

My questions: I'm pretty sure I would want the float to be set at 13.1-13.2V for both the storage and use profiles. The absorption settings are less clear to me. For the "use" profile, I intend to set absorption to 14.2V since I'll have plenty of time to charge, but do want to charge to 100% for a good full day of fishing. For the "storage" profile, I'm thinking I'll have to guess and test the absorption setting to find something that works. I plan to start with 13.6V to see what happens. I would really like to hear comments about these profiles....
 
Last edited:
Back
Top