Drop in LiFePO4 batt

[dhays]

A 1/2/B should ideally be a "bank use" selector not a "charge directing" device...

This bit of advice from Rod has stuck with me for a long time. For years, Catalina setup their boats the the 1/2/B switch being a charge and bank director. It is my understanding that many other sailboat manufacturers did the same. This simple sentence from CMS (Maine Sail) explains it well.

 

[john61ct]

When proper equipment is available for 3-4 decades and boat assemblers and boat yards are too uninformed to do a correct installation, and "surveyors" too are ignorant of an improper wiring job, what is a boat owner to do?

Just keep on rebuilding their alts?

In many tech areas, it is common for a well-informed (even if self-taught) end user to become more of an expert than average (or even most) professional service providers.

A passionate and curious amateur will keep expanding their knowledge, while many working people just do the minimum to keep their job, aren't actually interested in the tech for its own sake.

Even the ability to judge whether or not a service provider is competent and then to exercise oversight over their work output takes a fair bit of work and knowledge.

 

[FlyWright]

A 1/2/B should ideally be a "bank use" selector not a "charge directing" device...

This bit of advice from Rod has stuck with me for a long time. ...This simple sentence from CMS (Maine Sail) explains it well.

This is how I recabled my boat 6 years ago. The 1/2/B controls loads only. Alternator charges flow directly through appropriately sized cable directly to their respective battery bank. I haven't needed to use the 1/2/B switches in years since they're only there for emergency disconnect or paralleling the banks due to a depleted bank.

Doing this also resulted in my Port and Stbd ammeter shunts being bypassed, rendering them inoperative. No matter to me since I was also installing a battery SOC monitor to provide all the info I need. I am still without start battery amps but, in my world, start battery voltage is sufficient. If the port alternator malfunctions, I'll know it from the voltage and can switch on the combiner to provide start battery charge from the house bank.

CMS, one question. My Balmar alternator is 120A regulated externally to 100A. My port alternator is standard-issue, internally regulated of about 55A. I have not fused my charge cables and will be correcting that soon. What size fuse do you recommend for this installation?

 

[psneeld]

In many tech areas, it is common for a well-informed (even if self-taught) end user to become more of an expert than average (or even most) professional service providers.

A passionate and curious amateur will keep expanding their knowledge, while many working people just do the minimum to keep their job, aren't actually interested in the tech for its own sake.

Even the ability to judge whether or not a service provider is competent and then to exercise oversight over their work output takes a fair bit of work and knowledge.

I found this when I worked for a marine electronics firm.

I was the "new guy" and expected to study up on the new technologies.

When I started saying we needed heavier gauge wire plus pieces and parts for inverters and different systems, the owners were holy cow, we never used anything near that much.

Scary but true.

Finding true pros like CMS these days is a treat...the thirst for knowledge and the best practice is a true blessing in an industry full of amatuers.

 

[CMS]

CMS, one question. My Balmar alternator is 120A regulated externally to 100A. My port alternator is standard-issue, internally regulated of about 55A. I have not fused my charge cables and will be correcting that soon. What size fuse do you recommend for this installation?

OCP (over current protection) for an alternator's B+ cable should be right around 150% of the alts output rating, or more. The fuse is there to protect the wire from the battery bank, not from the alternator.

With a well installed system, less than 3% voltage drop in the alt B+ & B- cables, ideally less than 2%, the wire will not be at max ampacity of the fuse at 150%..

An alternator is a current limited source, like solar, which means it can't fail in excess of it's max potential. Because the alternator is not our dangerous source we are protecting the wires from, the OCP is installed at the battery end of the circuit.

 

[FF]

On my own boat the system is very very simple.

The Alt output goes to the starter terminal .

The batts are 6 ft from the starter, under the salon sole..

The (2) 8D are wired to a 3 way selector , that is built into a stair , so unlikely that anyone would notice or tamper with it.

And of course it is wired to the field of the Leece Nevelle 135A truck alt.

The back of the Start rotary is used to supply a second rotary in the companionway , EZ to find.

This 2nd rotary only controls loads placed on either batt.

Turning it off just means the lights , water pump etc all stop, nothing more.

With a propane reefer and a propane range our DC loads are minor with the engine off.

Lights, water pump, car radio.

Works for us . After a day or two at anchor we use which ever battery has been used for the house for starting , so it gets the full output from the alt.

A few hours in, I will combine both 8D with the start switch.

After shutdown the Start is rotated OFF, and the house sourced by the batt that was unused previously.

Not sure it can get simpler to live with than this system.

 

[CMS]

Finding true pros like CMS these days is a treat...the thirst for knowledge and the best practice is a true blessing in an industry full of amatuers.

As my grandfather and father used to say; "Any job worth doing, is a job worth doing right." In my opinion, if you are not constantly challenging yourself, your industry, area of expertise, pushing the envelope, pushing your comfort zone, reading, reading and more reading & questioning even "well accepted" practices, you're simply not doing your job, in any field..

Doing my job well, in the white collar world, MBA yada, yada, yada, is what financially allowed me to walk away from it at a young age & go back to doing what I really enjoy, and making a lot less money, and that is boats.

In regards to the marine industry, the ABYC has made some strategic changes recently that will help to create a stronger, better & more competent field of techs.

A lot of this drive came from existing techs, yards & builders trying to hire new techs and finding out they essentially knew only enough to barely get by, even after passing the test. They passed the test, could talk the talk, but when you hired them and handed them a tool, & an actual task, they had no real understanding of what to do. More importantly, if they did know how to connect the dots, they had little understanding of the why behind what they were actually doing.

This exact scenario happened to me, and it was actually Landing School graduate, not just a "test passer". I reached out to guys like Ed S., Charlie J. and more inside the ABYC only to find out I was not alone in my experience, and the ball was already rolling.

The ABYC is now requiring a minimum of 2 years physical and documented field work experience, and passing the test, before you can be an actual "certified tech". A great move!

The certification testing is also required to be re-taken every 5 years. On top of this the ABYC is now also requiring CEU's or continuing education units so techs will have less ability to become lazy. All in all it's a move in the right direction..

 

[Insequent]

The BYD battery packs seem pretty much 'drop-in', provided you have a 48V house bank/inverter/charger setup. These batteries are in big demand for solar-home storage systems now that the grid feed-in tariffs have been slashed around the country. There is a real boom in progress. BYD is significantly larger than Tesla. Just why home owners want LFP batteries instead of an AGM bank I don't know. The latter would be significantly cheaper at present, but don't come in a pretty enclosure.

Using the BYD B-Box modules a suitable sized house bank for a boat would be easy to establish, albeit they are still a bit pricy unless you have a catamaran and really want to trim weight down.

http://www.byd.com/energy/download/B-BOX spec EN.pdf

My 60 V solar panels would be a good match, the Outback 80 charge controllers can be configured easily. And I would only need one of them, not both! But I would need a 48V inverter/charger to get AC. I'm not sure how readily available 48V alternators are for engine either. So the consequential changes mount up for retrofit situations. But I'd love to be starting a refit with a clean slate!

LFP is where the future is, and their chemistry is not a fire-risk. BYD apparently scores an F for marketing/PR, but they are about to become very well known. They are already the price-setter in the USA market.

 

[Delfin]

Delfin's 1380 amp, Northstar AGM 24v house bank is now 14 years old and exhibiting signs of declining capacity. In considering replacement, I looked at carbon foam that don't much care if you re-charge them fully between cycles, a night time generator to replace the existing 20kw genset for re-charging batteries (leaving the 20kw for hydraulics), and LiFePO4. Took a lot of noodling to decide on a solution that will work for us, given the equipment we have, and that is LiFePO4 600 amp, 24 v house bank, charged by a 120 amp programmable charger built into the Trace 4000 charger/inverter, and supplemented by a large frame Balmar 200 amp 24 v alternator turned by a 10 hp hydraulic motor powered by the genset. In this setup, a day's usage of electricity of around 300 amps can be replaced in the Lithium batteries in around 1 hour and 15 minutes run time from the genset powering the Trace charger and simultaneously turning the 200 amp Balmar alternator/hydraulic motor combo.

The drop in Li batteries are Lithionics, using their BMS. I'll let you know how it works out.

 

[sunchaser]

Delfin

Yes indeed, this will be fun to follow. You mentioned carbon foam - what do you see as pros and cons compared to Lithionics? Thanks Carl

 

[Delfin]

Delfin

Yes indeed, this will be fun to follow. You mentioned carbon foam - what do you see as pros and cons compared to Lithionics? Thanks Carl

Hi Tom,

Assuming the data sheets are correct, carbon foam is indifferent to partial recharge, which kills a typical Pb acid battery. IMO, carbon foam is so superior to typical batteries both in terms of cost per cycle and charging characteristics that I don't know why their use isn't universal. In Delfin's case, when I bought her as an empty shell she had a brand new NL 20kw genset. I added a hydraulic pump to the front of the genset to add flow to the pump on the Cat, and to allow using hydraulics without firing up the Cat while at anchor. Charging any Pb type battery at 3.5 kw from a 20 kw source is bad for the genset, noisier than needed and the charge acceptance rate of the carbon foam is still pretty similar to ordinary chemistry so I'd have to run the 20 kw inefficiently for quite a while longer than with lithium batteries.

So, with Delfin's existing equipment, my choice was to run the NL, or buy a quiet 5kw nightime genset, like a NexGen to recharge carbon foam batteries. In terms of cost, buying the Lithionics and jiggering up a hydraulic motor turning a large frame alternator that supplements the existing battery charger lets me use the genset much more efficiently and only run it for an hour or so per cycle to replace 300 amps of daily use at anchor. And, because of how long lithium batteries last (if they aren't killed by the user), these will be the last batteries I'll deal with in my lifetime.

That's my thinking, anyway.....

 

[john61ct]

When you guys say "carbon foam" you mean Firefly Oasis, right?

Until there is an effective competitor as a category of one, I would think the latter would be clearer. . .

 

[john61ct]

IMO, carbon foam is so superior to typical batteries both in terms of cost per cycle and charging characteristics that I don't know why their use isn't universal.

Well they sure would need to ramp up production! Currently waitlisted. . .

G31 size only, until the production quality from the Indian factory has passed US QA, only maybe later this year.

Many buyers want to see a longer public testing / feedback period to verify vendor claims.

And some consider $500+ per 100 AH to be on the spendy side.

 

[Delfin]

Well they sure would need to ramp up production! Currently waitlisted. . .

G31 size only, until the production quality from the Indian factory has passed US QA, only maybe later this year.

Many buyers want to see a longer public testing / feedback period to verify vendor claims.

And some consider $500+ per 100 AH to be on the spendy side.

The cost per AH doesn't tell you much. Bit like cost per pound of a car. Cycles and charge time might be more informative measure and on that basis, carbon foam batteries are cheaper than the usual LA battery and are significantly harder to kill.

They've been around in military applications for around 10 years. http://mobiledevdesign.com/news/carbon-foam-liberates-lead-acid-batteries-emerging-military-missions

 

[john61ct]

I'm not saying Firefly isn't excellent value, especially if your PSOC situation is unavoidable.

And being able to routinely draw down 80% makes 100AH worth maybe 130AH other lead banks.

Just giving some reasons they aren't a "universal fit" for all use cases.

 

[Delfin]

What I've learned so far about Lithium batteries...

Manufacture: I expect most of the other drop in manufacturers take the same approach but Lithionics purchases 3.2 vdc cells from an Asian supplier. They test each cell for impedance and match 8 cells before wiring them within a case. When shipped via truck, they are fully charged to a resting voltage of 27.2 vdc (for 24v installations).

Each cell is individually shunted within the case for balancing voltages between cells automatically.

Charging settings: Our existing Balmar 624 regulator and Trace 4000 battery charger will work fine. Li batteries need to be treated like a fuel tank - fill them, then turn the hose off. Consequently, no float is needed or desired since the charge efficiency is so high any float voltage above resting voltage just generates heat and shortens the life of the battery. The bulk voltage setting will be at 29 volts, absorption at 18 minutes @ 29 volts and float at 26.8 volts. This float voltage will basically mean no continuous float because it is below resting voltage, but the alternator, when running, will keep the batteries at around 97% full charge without overheating since there will always be a bit of capacity left to accept the charge rather than just generate heat. The absorption phase of the charge on Li batteries is critical for balancing. Once the battery reaches the bulk charge voltage of 29 volts, they are essentially "full", but during the absorption phase individual cells are shunted to achieve top end balancing with even voltage across each cell, although I gather such balancing isn't needed very often.

The new Lithionics batteries will weigh 290# and will replace around 1300# of our current Northstar AGW batteries. I'll actually have to remove some starboard side ballast to offset the loss of weight on the port side. I'm hoping to be able to install these vertically on their narrow side. I'm told this isn't ideal, but no one makes it sound like a big deal if you do. I'll be leaving that up to the Lithionics tech folks to make that final decision, but if I can mount them like this, they will take up about 1/4 of the room the AGW batteries are.

Speaking of which, I think these Northstar still have some life in them, as I have babied them. Should any forumites want a few, let me know. They are 205 Ah Northstar AGM.

 

[Delfin]

I have three questions for Rod (CMS) if you have the time, so perhaps you can help me avoid making a mistake.

In addition to the 600 amp 24vdc bank I will have two 8D LA starter batteries. I am installing the field control circuit to protect the alternator charge sources in the event of a high voltage cut out at the BMS, but would like to keep the LA batteries connected to all charge sources as a backup through a Blue Seas combiner already installed. Question 1: Is this ok, or will the different chemistry of the LA interfere with the BMS if both the Li and LA batteries are regulated to the same voltages?

I like and understand your recommendation not to exceed charging to > 28 vdc, and after studying your incredibly helpful information, intend to set the Trace 4000 and Balmar 624 to that peak bulk with nearly no absorption period. But I'm confused why Lithionics recommends 28.8 for the Balmar 624 but also say that the "ideal lithium charge setting" is 29.2 volts. I've asked them to explain the difference but haven't got a straight answer and in any case both seem too high to me now that I understand your position. Question 2: Is there any reason to charge at bulk to more than 28 vdc that would explain their recommendations?

I have also asked Lithionics what float voltage should be set, recognizing that you don't want to float these batteries at all. Their recommendation is to set it below the resting voltage, at 26.8 vdc. I then asked if there was a rationale to set it lower than that and was told I could set it just above the low voltage cutoff "if I wanted". Question 3: Do I "want" to? At the dock, I'll be disconnecting the Li batteries from all charging sources, so I guess the answer is to keep the float so it maintains the LA batteries (26.8 vdc), but your help clarifying would be much appreciated.

Thanks so much for all the work you have done in this area. We are in your debt.

 

[twistedtree]

I'll take a crack at this since I'm trying to plan out a LiFePO system myself and need the practice talking it through out loud ....

It's very important not to over charge the batteries. Thats why its recommended to charge o something less than the full charge voltage. But the lower you set the voltage, the less capacity you are getting from the battery. So each system/operator needs to find the balance between lost capacity and risk of over charging. I think the difference between the recommendations you have received just reflects different tradeoffs between the two.

As for float, to me the real advantage is to allow the charge source to carry some or all of the power load. If it's set above the resting voltage then it will continue to charge the batteries which isn't good. And if it's way below the resting voltage (like at the LV cutoff) then you will be needlessly cycling your batteries even though there is a power source available to power the loads. Why cycle your batteries when you have shore power, right?

So if you set float at say the 80% resting voltage, if the battery is above 80% it will carry any loads, but when the battery gets down to 80%, the charger will carry the loads. And if it's below 80%, the charger will carry the loads and slowly bring the battery charge level up.

I think the trick is to be sure you don't have any errant charge sources that can continue to charge after the batts reach your chosen full charge voltage. Some chargers continue an absorption stage for a fixed time with not ability to change that. A charger like that could quickly lead to ruin ed batteries. LA batteries are very tolerant of over charging, and tolerant of varying voltage ranges, and that has driven the design of chargers for decades. LIFEPO is much more demanding of precise charge protocol, so you need to watch conventional charger really carefully. CMSs recommendations to only utilize the 20%-80% range is a great way to protect yourself from existing chargers.

As for combining with other batteries, I'm planning to NOT do that. I don't even want to try to think through what the cross charging/equalizing dynamics will be between two battery types operating at slightly different voltage ranges. And I don't want to risk exposing the Li bats to any fixed voltage alternators on accessory engines.

 

[Sailor of Fortune]

Jeez, I'm dumb! I have no clue whatsoever about Delfins question and Twisted Trees' answer,lol

 

[Art]

My goodness... why do some boat owners like to get so very complicated regarding battery banks, independent batteries, and mixing battery types as well as utilizing various batt charging sources at different levels?

After all the battery type and charger style confusion... that obviously gets hashed-out over and over again... does the end result to these $$ expensive and time consuming efforts actually offer positive enough outcome that outweighs the ongoing confusion? Or... would it be easier with still productive electric output to simplify the whole battery system aboard boat?

I play KISS on much aboard boat; especially regarding batteries and charging systems.

 

[john61ct]

a Blue Seas combiner already installed. Question 1: Is this ok, or will the different chemistry of the LA interfere with the BMS if both the Li and LA batteries are regulated to the same voltages?

Set everything to suit LFP and that won't harm FLA starters much, just take a little longer to get to full. If expensive AGM, then maybe get a DCDC charger instead so each gets its own charge profile.

Also since LFP resting volts is always higher than lead, there will be a "perpetual float" current flow from LFP to lead, unless the ACR/VSR cutoff is lower than the LFP resting voltage.

Regarding voltage levels, the only advantage I can imagine of going to 3.65Vpc as opposed to 3.45, is the bank will store a higher total AH that way.

To be cynical about it, what vendor would want to see their banks last for decades?

Float below resting should mean no actual current flow until a load comes online. The lower voltage would seem to make no difference AFAICT, except in a storage situation, when the bank should be near empty and isolated anyway.

Constant topping up at **any** voltage does not "maintain" an LFP bank, does no good at all, and apparently is likely to reduce lifespan. Purely "holdover lead based thinking".

 

[FlyWright]

My goodness... why do some boat owners like to get so very complicated regarding battery banks, independent batteries, and mixing battery types as well as utilizing various batt charging sources at different levels?

After all the battery type and charger style confusion... that obviously gets hashed-out over and over again... does the end result to these $$ expensive and time consuming efforts actually offer positive enough outcome that outweighs the ongoing confusion? Or... would it be easier with still productive electric output to simplify the whole battery system aboard boat?

I play KISS on much aboard boat; especially regarding batteries and charging systems.

1. This is relatively new technology with its own unique requirements. CMS is an expert in this field and has been generously providing his expert advice for those who need it.

2. Many folks here like Delfin and TT have more capable and complex boats than many of us and are equipping and maintaining their boats for passagemaker missions.

 

[Art]

1. This is relatively new technology with its own unique requirements. CMS is an expert in this field and has been generously providing his expert advice for those who need it.

2. Many folks here like Delfin and TT have more capable and complex boats than many of us and are equipping and maintaining their boats for passagemaker missions.

I realize that the "mechanics/designs/types/styles" of batteries and charging systems are nearly always on the cutting edge of improvements and breakthroughs. Appreciate CMS's input and expertise!

Also realize that compared to boats like yours and mine those such as Delfin's and TT's have larger requirements for electric batt power and charge systems... due to increased navigational/trip jaunts and conditions.

What does seem unnecessary to me is the seemingly consistent extra efforts placed toward repeat semi-successful attempts and/or failed combinations of battery types and charging system style/capability units.

Would it not be automatically beneficial on many levels of reduced cost and less effort as well as product longevity to have similarity of battery type as well as same style/model charging systems throughout the boat?

Jus Wonderen!

 

[FlyWright]

If you didn't improve, you'd be stuck with the same limited capabilities. Look how carbon-foam batteries have changed Darren's liveaboard-cruising life.

Different battery types cater to varying duties and accessibility issues. There's something to be said for commonality, but it's not paramount for success. IMO, guys like Delfin, TT and Darren push the leading edge for the rest of us.

Why try to put the kabash on that?

 

[Jeff F]

1. This is relatively new technology with its own unique requirements. CMS is an expert in this field and has been generously providing his expert advice for those who need it.

2. Many folks here like Delfin and TT have more capable and complex boats than many of us and are equipping and maintaining their boats for passagemaker missions.

I'm enjoying this thread. I've followed battery development closely for a while as an owner of hybrid and electric vehicles. Interesting to listen in on the possible application for our boats.

For those interested there is lots of smart conversation on lithium batteries and their management in the EV forums. I've sort of drifted away, but those guys have been at this for a while.

 

[twistedtree]

Art, one gets sucked down this path when considering Lithium batteries which behave quite differently than lead acid batteries. Legacy chargers really aren't suited for Li, so you have to figure out how to shoe horn them in somehow. A couple of vendors have fully integrated power systems with li, but they are super expensive. In time everything will support Li in a useful way, but its still a ways away.

In the mean time us propeller heads want to take advantage of the huge benefits that Li offers to boaters. Much less space consumption, no watering, many many more cycles so longer life, faster charging so less generator time, no annoying declining absorption cycle to extend gen run time and create poor gen loading, and no problems running at partial state of charge. In short, they are better in very way, and eliminate all the annoying aspects of lead acid. So we are willing to tinker. But I'll be the first to admit it's not ready for the general marine market.

 

[john61ct]

If you are new to LFP and want your system to prove itself over time before you fully trust it

Then it makes sense to still keep some lead batts on board as reserve/backup, or just Starters.

Putting in a DCDC charger isn't rocket science and takes care of any "mixed chemistry" issues that may concern.

 

[Delfin]

I'll take a crack at this since I'm trying to plan out a LiFePO system myself and need the practice talking it through out loud ....

It's very important not to over charge the batteries. Thats why its recommended to charge o something less than the full charge voltage. But the lower you set the voltage, the less capacity you are getting from the battery. So each system/operator needs to find the balance between lost capacity and risk of over charging. I think the difference between the recommendations you have received just reflects different tradeoffs between the two.

As for float, to me the real advantage is to allow the charge source to carry some or all of the power load. If it's set above the resting voltage then it will continue to charge the batteries which isn't good. And if it's way below the resting voltage (like at the LV cutoff) then you will be needlessly cycling your batteries even though there is a power source available to power the loads. Why cycle your batteries when you have shore power, right?

So if you set float at say the 80% resting voltage, if the battery is above 80% it will carry any loads, but when the battery gets down to 80%, the charger will carry the loads. And if it's below 80%, the charger will carry the loads and slowly bring the battery charge level up.

I think the trick is to be sure you don't have any errant charge sources that can continue to charge after the batts reach your chosen full charge voltage. Some chargers continue an absorption stage for a fixed time with not ability to change that. A charger like that could quickly lead to ruin ed batteries. LA batteries are very tolerant of over charging, and tolerant of varying voltage ranges, and that has driven the design of chargers for decades. LIFEPO is much more demanding of precise charge protocol, so you need to watch conventional charger really carefully. CMSs recommendations to only utilize the 20%-80% range is a great way to protect yourself from existing chargers.

As for combining with other batteries, I'm planning to NOT do that. I don't even want to try to think through what the cross charging/equalizing dynamics will be between two battery types operating at slightly different voltage ranges. And I don't want to risk exposing the Li bats to any fixed voltage alternators on accessory engines.

Thanks TT,

I just got off the phone with the engineers at Lithionics and as always, learned a few things. They affirmed that what CMS recommends in terms of limiting maximum charge voltage to 28 vdc will give you nearly all the capacity of the batteries without pushing any limits. However, they said that their BMS was set to equalize cells at 29 volts so their recommendation (since equalization isn't needed very often) is to set bulk at 28 vdc as CMS recommends, but once of month or every couple of months, set it up to 29 volts so the BMS will optimally balance any inequalities.

The also felt that there was no particular reason not to connect both LA and Li batteries to the same source. If the LA battery is not being optimally handled, it hardly matters since it is just the starter bank and will likely do ok with the voltage settings for the Li.

Float voltage s/b 26.8 volts. Apparently, LiFePO4 chemistry isn't going to know much of a difference between 26.4 and 26.8 - both are going to be around 60% capacity which is apparently the ideal state of charge for maximum life cycles. Not sure I understand why, but the 26.8 volts matches what all the experts seem to be saying, so I think I will go with that.

I'd attach a picture of the batteries - they're huge - but I can't figure out how to attach a picture anymore, unless it is located at a URL.

n/b Art: With these batteries, I will be able to replace a days usage in 25% of the genset time when at anchor. To me, that is simpler that the alternative.

 

[john61ct]

Better to just use cell "balancing", IMO calling it equalization may confuse some.

And let go of the voltage/SoC idea, not applicable in this case.

When float is set lower than actual, then that should functionally be the same as Off, no current flow into the battery, but any loads carried by the charge source. Only extremely high-amp loads should cause any voltage drop.

Also, there is no "ideal SoC" except for when not cycling, which is way down near the bottom of what the BMS allows. While cycling you will go between "full" and "empty" as defined by the BMS, passing through 60% twice each cycle.

Do you know if your BMS initiates a new bulk/absorb charge cycle based on SoC via coulomb-counting?

 

[john61ct]

I'd attach a picture of the batteries - they're huge - but I can't figure out how to attach a picture anymore, unless it is located at a URL.

Post the pics to Imgur then just their URLs here.