LifePo4.. Yes AGAIN!

[travellerw]

Originally Posted by arsenelupiga

i have pretty similar solution to you in mind, including 400 AH. However my motivation is to have energy for cloudy days, as we are modest users. Still throw away around 50% of energy on sunny day via solar, and we have sun plenty here.

Relying on 360 W panels to fill the whole thing. My charging voltage will be slightly lower, however definitely will have monitor for each battery, if not even BMS. So I wont have to worry about what to do with free energy.

Also will purchase LFP charger, to be able to correct voltages manually for each battery - running on generator.

From what i gathered so far, your solution looks robust and simple although for my taste too many powerful chargers.

Really.. You plan to charge to a voltage lower than 13.8V (or 3.45/cell)? I've only read of a few scenarios where people charged lower than 3.45V/cell. Do you have a reason for the lower voltage?

You say a monitor for each "battery". I'm thinking you mean each cell? The BMS I listed has a monitor for each cell, that are wired to a central board. It has the ability to do a LVD/HVD at either pack voltage or cell voltage.

I would love it you could post a link to an LFP charger! I'm not aware of any marine grade shore power LFP chargers. I'm also not aware of any solar LFP chargers that have individual cell connections! Please post a link if I'm wrong.. I would love to know.

[arsenelupiga]

Originally Posted by travellerw

Really.. You plan to charge to a voltage lower than 13.8V (or 3.45/cell)? I've only read of a few scenarios where people charged lower than 3.45V/cell. Do you have a reason for the lower voltage?

You say a monitor for each "battery". I'm thinking you mean each cell? The BMS I listed has a monitor for each cell, that are wired to a central board. It has the ability to do a LVD/HVD at either pack voltage or cell voltage.

I would love it you could post a link to an LFP charger! I'm not aware of any marine grade shore power LFP chargers. I'm also not aware of any solar LFP chargers that have individual cell connections! Please post a link if I'm wrong.. I would love to know.

i meant to say will charge less than to 100% Probably 3.50V. And yes, monitor each cell. And have this charger to charge fully first time and after that correct any imbalances:

https://www.ev-power.eu/Chargers-6V-...-1-cell-1.html

Will really go in action in 6 mths, for now just thinking thru.

this one interesting as well

https://www.ev-power.eu/Chargers-6V-...BMS-input.html

[downunder]

Originally Posted by arsenelupiga

i have pretty similar solution to you in mind, including 400 AH. However my motivation is to have energy for cloudy days, as we are modest users. Still throw away around 50% of energy on sunny day via solar, and we have sun plenty here.

Relying on 360 W panels to fill the whole thing. My charging voltage will be slightly lower, however definitely will have monitor for each battery, if not even BMS. So I wont have to worry about what to do with free energy.

Also will purchase LFP charger, to be able to correct voltages manually for each battery - running on generator.

From what i gathered so far, your solution looks robust and simple although for my taste too many powerful chargers.

I am surprised you are only relying on 360W of panels. I note it is relatively easy to fit 4x360W Sunpowers above the davits on a Lagoon 400 as others have done.

Worth considering if you are going to the expense of fitting 400ah LiFeO4.

[john61ct]

Originally Posted by travellerw

I'm not aware of any marine grade shore power LFP chargers.

You don't want a LFP-specific charger, all those marketed as such are way too high a voltage.

Sterling ProCharge Ultra and ProMariner Pronautic P are fully user adjustable, which is the key feature to look for.

Very common with solar.

Few chargers can set "just stop", so either set Float below 13.2V, or (better) use an adjustable VSR to cut of charging upstream, or (best) do that manually.

[arsenelupiga]

Originally Posted by downunder

I am surprised you are only relying on 360W of panels. I note it is relatively easy to fit 4x360W Sunpowers above the davits on a Lagoon 400 as others have done.

Worth considering if you are going to the expense of fitting 400ah LiFeO4.

well, i dont see it that expensive, thats the thing.

replacement gel batteries cost 2600 aud and mess with heavy installation, and will be due shortly, and I can get the whole 400ah LFP thing for under 4 k or so. So, extra 1400 aud is no that much.

Also cant see installing 4 x 360 due to aerodynamic, aesthetic reasons, max my wife will allow is 2 x 360, which will still be double power now if needed.

[evm1024]

This image of discharge of a 26650 LiFePO4 cell is quite instructive. The various curves show the voltage during discharge based on the charging voltage.

Charging to 14 v (3.5 vpc) gives 100% of the cells capacity while charging to 13.6 V (3.4 vpc) yields 96% of the cells capacity.

Of course different charging voltages will result in different charging times. And one should consider that. But, basically charging to 3.4 VPC yileds near 100% and charging to a voltage higher than that yields very little (or when charging to over 3.5 vpc nothing more.).

See: https://www.powerstream.com/lithium-...ge-voltage.htm

[downunder]

Originally Posted by arsenelupiga

well, i dont see it that expensive, thats the thing.

replacement gel batteries cost 2600 aud and mess with heavy installation, and will be due shortly, and I can get the whole 400ah LFP thing for under 4 k or so. So, extra 1400 aud is no that much.

Also cant see installing 4 x 360 due to aerodynamic, aesthetic reasons, max my wife will allow is 2 x 360, which will still be double power now if needed.

Here is just one example of a practical, asthetically done in my opinion.

https://www.youtube.com/watch?v=cMENm_7MenY

Ideal for liveabord situation as it takes electricity out of the equation.

But you may not be in that situation.

In the tropics the extra shade is a bonus.

[arsenelupiga]

Originally Posted by downunder

Here is just one example of a practical, asthetically done in my opinion.

Ideal for liveabord situation as it takes electricity out of the equation.

But you may not be in that situation.

In the tropics the extra shade is a bonus.

We live off 360W solar nicely. Going on longer trip, our preferences may change.

With only 400ah upgrade, I will be storing extra 50ah per day on sunny day. This i expect to allow for extra fridge if necessary and several days of overcast & more.

Next level is 720 w = 2 sunpower 360 w directly replacing 2 victron 180 w on davits. So this will double power.

I just cant imagine we would need more power than that. However, if we find it is necessary, what you propose would actually be next step.

[john61ct]

Nice thing about LFP, you actually capture lots more of the solar power without lead's trailing amps problem.

So 360W to 400+AH is plenty panelage, sunny days you'll be Full by early avo, make ice or heat water with the surplus.

[travellerw]

Originally Posted by arsenelupiga

i meant to say will charge less than to 100% Probably 3.50V. And yes, monitor each cell. And have this charger to charge fully first time and after that correct any imbalances:

https://www.ev-power.eu/Chargers-6V-...-1-cell-1.html

Will really go in action in 6 mths, for now just thinking thru.

this one interesting as well

https://www.ev-power.eu/Chargers-6V-...BMS-input.html

I know both of those chargers and that company well. They are a good company if you live in the EU. If you are outside of the EU, then their shipping prices can be a bit of a shocker.

I would also encourage you to do some more research. I'm pretty sure the experts here will agree that no matter what the literature says, that first charger you posted is not suitable for doing an initial "top balance" on a large AH bank.

First, I would not trust my new EXPENSIVE bank to a $30 charger. Just not worth it. You should be able to get a hold of a benchtop power supply to do that initial top charge. If you are in a big(ish) city, then its even possible to rent one.

Second, that charger has a max output of 5 amps. If we assume that your new 400ah bank will come %50 charged from the factory, then that leaves 800ah to put back in (each cell requires 200ah to be put back in). You would be looking at 160 hours to bring the bank to 3.65V (doesn't matter if you do it in parallel or single cell at a time). This would hold the cells at a voltage over 3.5V for an extended amount of time. Not a good way to start a new LFP battery pack IMHO.

A good benchtop power supply can put out 30A and run at %100 duty cycle no problem. This would allow your initial charge to only take 26-27 hours. Much more sane in my opinion.

The initial balancing of LFP banks is a endlessly debated topic. Top balance, bottom balance, there are fanboys on each side. Digging through the mud of the topic I have decided that both are valid methods and you should pick the one that best suits your use case. If you are a liveaboard with daily cyclic use, then bottom balancing makes more sense. If you are a weekend warrior that leaves the pack disconnected until just before you head out, then top balance is probably more appropriate.

[darylat8750]

Originally Posted by john61ct

Here's my "boilerplate" LFP summary, mostly from marine electrics discussion forums involving long-term users and professionals, with special thanks to Maine Sail (see below).

Any and all feedback is welcome, especially if more "canonical" information from the links cited conflict with my summary.

______
Systems: OceanPlanet (Lithionics), Victron, MasterVolt, Redarc (Oz specific?)

Bare cells: ​Winston/Voltronix, CALB, GBS, A123 & Sinopoly

Best to size your cells for two parallel strings for redundancy, unless you have a separate reserve/backup bank. Don't go past three, or you may see balancing issues that affect long-term longevity, maybe four in a pinch.

Note nearly **every** vendor, also those of ancillary hardware touted as "LFP ready", gives charging voltages **way too high** for longevity.

My (conspiracy) theory is that manufacturers would prefer their cells get burned out in under 10 years.

EV usage is very different from much gentler House bank cycling. Most EV people talking "lithium-ion" mean other chemistries not as safe as LFP, much shorter lifetimes, and with completely different setpoints and behaviors.

My charge settings for LFP: 3.45Vpc, which = 13.8V max for 4S "12V".

The point is to look at the SoC vs Voltage chart, and avoid the "shoulders" at both ends, stay in the smooth parts of the curve.

Either "just stop" charging when voltage is hit, or if you want another couple % SoC capacity, stop when trailing amps **at your spec'd voltage** hits endAmps of .02C, or 2A per 100AH.*

Note even at the "low" max charge voltage, letting the charge source continue to "push" even low currents long past the endAmps point is **over-charging, and will** greatly reduce lifecycles.

So if you can't then "just stop", set Float well below resting Full voltage, at say 13.1V, but that is a compromise, and *may* shorten life cycles.

With LFP, you don't need to fill up all the way at all, as far as the cells are concerned. In fact, it is bad for them to sit there more than a few minutes. Therefore only "fill up" if consumer loads are present, ready to start discharging, ideally right away.

Many sources claim there is a "memory effect" from keeping charge voltage and ending point exactly the same every time lower than manufacturer specs, that can apparently over time lead to apparent lower capacity. The recommended fix is to "go higher, into the shoulder" every so often, similar to "conditioning" a FLA bank monthly. To prevent the issue, vary your setpoints a bit, sometimes go a point or two higher or lower, vary Absorb time a bit etc. There is no consensus just how serious the problem is.

Store the bank as cool as possible and at 10-20% SoC, or maybe higher to compensate for self-discharge, if not getting topped up regularly (I would at least monthly).*

Letting the batts go "dead flat" = instant **permanent unrecoverable** damage.

Same with charging in below 32°F / 0°C freezing temps.

Persistent high temps also drastically shortens life.

Charging at 1C or even higher is no problem, as long as your wiring is that robust, vendors may spec lower out of legal caution.

Again, going above 14V won't add much AH capacity, but will shorten life cycles dramatically.

And of course, we're talking about gentle "partial C" House bank discharge rates, size appropriately and be careful feeding heavy loads like a winch or windlass.

Following these tips, letting the BMS do active balancing is unnecessary and potentially harmful, just look for LVD / OVD and temp protection. Multiple layers of protection are advised if it is a very expensive bank, so you don't rely on any one device to keep working.

Check cell-level voltage balance say monthly to start, then quarterly, finally every six months if there are no imbalance issues, but only if that seems safe to you.

This thread is long but informative
http://www.cruisersforum.com/forums/f14/...65069.html

, make sure to give both Maine Sail and Ocean Planet your close attention.

Also MS' summary notes here
https://marinehowto.com/lifepo4-batteries-on-boats/

**Everything** at that site is worth reading, very valuable. He also has great articles in Practical Sailor. His new site under development transitioning the pbase content is here

https://marinehowto.com/support, feel free to make a donation to help with those expenses.

Best of luck, and do please report back here!

I agree with most of your conclusions. I have a little trouble with this :
"Store the bank as cool as possible and at 10-20% SoC, or maybe higher to compensate for self-discharge, if not getting topped up regularly (I would at least monthly).*"

If there are zero loads they should self discharge very slowly and where you say "topped up" regularly I would substitute "bring up to 20 - 50% state of charge".

[arsenelupiga]

Originally Posted by travellerw

I know both of those chargers and that company well. They are a good company if you live in the EU. If you are outside of the EU, then their shipping prices can be a bit of a shocker.

I would also encourage you to do some more research. I'm pretty sure the experts here will agree that no matter what the literature says, that first charger you posted is not suitable for doing an initial "top balance" on a large AH bank.

First, I would not trust my new EXPENSIVE bank to a $30 charger. Just not worth it. You should be able to get a hold of a benchtop power supply to do that initial top charge. If you are in a big(ish) city, then its even possible to rent one.

Second, that charger has a max output of 5 amps. If we assume that your new 400ah bank will come %50 charged from the factory, then that leaves 800ah to put back in (each cell requires 200ah to be put back in). You would be looking at 160 hours to bring the bank to 3.65V (doesn't matter if you do it in parallel or single cell at a time). This would hold the cells at a voltage over 3.5V for an extended amount of time. Not a good way to start a new LFP battery pack IMHO.

A good benchtop power supply can put out 30A and run at %100 duty cycle no problem. This would allow your initial charge to only take 26-27 hours. Much more sane in my opinion.

The initial balancing of LFP banks is a endlessly debated topic. Top balance, bottom balance, there are fanboys on each side. Digging through the mud of the topic I have decided that both are valid methods and you should pick the one that best suits your use case. If you are a liveaboard with daily cyclic use, then bottom balancing makes more sense. If you are a weekend warrior that leaves the pack disconnected until just before you head out, then top balance is probably more appropriate.

you are absolutely correct, my mistake. I meant this one 3.6V /20A

https://www.ev-power.eu/Chargers-6V-...cell.html#tab1

This is 10 hours per battery. I may cycle charging so battery spends less time waiting on 3.6V for initial charge. And thinking of having reprogrammed charging solars to 14.00V, and shunt alarms at 14.20V. Also have monitoring of cells and more alarms there. Any imbalance maybe correct by the charger and no BMS. Once I am happy with process, decide if BMS is required.

[john61ct]

Originally Posted by darylat8750

I agree with most of your conclusions. I have a little trouble with this :
"Store the bank as cool as possible and at 10-20% SoC, or maybe higher to compensate for self-discharge, if not getting topped up regularly (I would at least monthly).*"

If there are zero loads they should self discharge very slowly and where you say "topped up" regularly I would substitute "bring up to 20 - 50% state of charge".

As long as not being loaded / cycled, SoC should remain low as you dare, given that going dead meaning destruction.

The charge input should only be enough to replace the self-discharge.

So if you check less frequently, safer to keep at higher SoC, but that will cost some longevity off the back end,

[travellerw]

Originally Posted by darylat8750

I agree with most of your conclusions. I have a little trouble with this :
"Store the bank as cool as possible and at 10-20% SoC, or maybe higher to compensate for self-discharge, if not getting topped up regularly (I would at least monthly).*"

If there are zero loads they should self discharge very slowly and where you say "topped up" regularly I would substitute "bring up to 20 - 50% state of charge".

At this point, we are kinda picking nits.... but.. The SOC I have seen suggested most for storage is 40-60%. Mainsail's article suggests no higher than %50-60.

[travellerw]

Originally Posted by arsenelupiga

you are absolutely correct, my mistake. I meant this one 3.6V /20A

https://www.ev-power.eu/Chargers-6V-...cell.html#tab1

This is 10 hours per battery. I may cycle charging so battery spends less time waiting on 3.6V for initial charge. And thinking of having reprogrammed charging solars to 14.00V, and shunt alarms at 14.20V. Also have monitoring of cells and more alarms there. Any imbalance maybe correct by the charger and no BMS. Once I am happy with process, decide if BMS is required.

Be careful.. Depending on how you implement this, you can actually shoot yourself in the foot. If the "monitoring" you implement puts a parasitic load on the individual cells, then that can lead to balance issues.

When you say "decide if BMS is required" I'm hoping you actually mean a true BMS and not pack protection. The term BMS get is used everywhere, but not really used correctly. A true BMS not only protects your pack, but actually controls the charging regime. A premium BMS would be a system where all the components share data about the system and battery bank. However most are not that sophicated and simply use relays to achieve the charging controls. A true DIY BMS is possible, but a pretty big undertaking.

Although I called the stuff I'm using a BMS, its not really a true BMS. Its really just pack protection for HV, LV or temperature events. The charging regime is not controlled by the BMS in any way. Our charging regime will be controlled by the solar controllers themselves (and me, on the very odd extended cloudy spells). Frankly, I would be surprised if we use the house charger once a year. With 900W of solar we are net positive on all but the rainiest days.