LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[Maine Sail]

Originally Posted by typhoon

That was my thought as well . Maine sail always speaks of the tailing off current being an indicator of a full battery level . I don't get any tailing of of the current . So I will just charge to my 14v and be done .
Regards

I only really go to full when I need to reset my battery monitor, about every 6-10 cycles.. They simply get out of sync within a few cycles and there is not much that can be done about it as this is just the nature of Ah counters.. I use 13.8V and less than 10A as my reset point for a 400Ah bank..

[SV THIRD DAY]

Originally Posted by Maine Sail

I only really go to full when I need to reset my battery monitor, about every 6-10 cycles.. They simply get out of sync within a few cycles and there is not much that can be done about it as this is just the nature of Ah counters.. I use 13.8V and less than 10A as my reset point for a 400Ah bank..

I have two different brands of AH counters on my 400AH bank and Mainsail nailed it...I resent mine about once per month ans use the same criteria.

[Jd1]

I am currently experimenting with a 14.4V bulk charging voltage. I have had issues with too low a charge current so upping the voltage a bit for more current. I am still below 100A and I have a 200A alternator.
It would be great if someone could list their settings for a 614 external regulator.
Currently I still have both lithium and lead acid hooked up to charge at the same voltage setting (through an isolator) but I am contemplating putting a diode into the charge path for the lead acid batteries to drop the charge voltage a bit there while leaving the higher voltage for the lithiums.
It just seems a waste to have a 200A alternator and charge at 80 or 90 A when still at 60 to 70 percent capacity on a 700 AH lithium battery bank.
Having said all that, I do the voltage sensing about half way between alternator and lithium bank(where the charging path splits between lithium and lead acid) so maybe I am seeing excessive voltage drop .... something I should really check out too.

[offpist]

Jd1.
Voltage sense on the battery is very important for a good result, as well with thick good cables.

But dont expect to get 200A continous from an 200A alternator.

[Maine Sail]

Originally Posted by Jd1

I am currently experimenting with a 14.4V bulk charging voltage. I have had issues with too low a charge current so upping the voltage a bit for more current. I am still below 100A and I have a 200A alternator.
It would be great if someone could list their settings for a 614 external regulator.
Currently I still have both lithium and lead acid hooked up to charge at the same voltage setting (through an isolator) but I am contemplating putting a diode into the charge path for the lead acid batteries to drop the charge voltage a bit there while leaving the higher voltage for the lithiums.
It just seems a waste to have a 200A alternator and charge at 80 or 90 A when still at 60 to 70 percent capacity on a 700 AH lithium battery bank.
Having said all that, I do the voltage sensing about half way between alternator and lithium bank(where the charging path splits between lithium and lead acid) so maybe I am seeing excessive voltage drop .... something I should really check out too.

14.4V on the input side of the isolator is still just 13.8V at the LFP battery and this would be at low current and high current you could be dropping as much as 1.1V. When we discuss charging voltage it s always what is at the physical battery terminals that matters...

Unless your regulator is seeing the voltage of the LFP bank you will likely not see the desired current. A diode isolator can drop as much as 1.1V passing near full current and approx .6V passing marginal current. Your lead bank will always be taking minimal current so will see about a .6V drop across the isolator but your LFP will see more drop as it is taking more current across the diode. Sense the LFP bank (regulator + sense and reg black wire are the sensing circuit not just red sense) and you should see a major improvement. However your lead battery will now be seeing .4V +/- more than LFP at high current. With an MC-614 I don't understand why you are not protecting the alt by interrupting the red B+ reg power wire in a BMS event..?

[Jd1]

Originally Posted by Maine Sail

14.4V on the input side of the isolator is still just 13.8V at the LFP battery and this would be at low current and high current you could be dropping as much as 1.1V. When we discuss charging voltage it s always what is at the physical battery terminals that matters...

Unless your regulator is seeing the voltage of the LFP bank you will likely not see the desired current. A diode isolator can drop as much as 1.1V passing near full current and approx .6V passing marginal current. Your lead bank will always be taking minimal current so will see about a .6V drop across the isolator but your LFP will see more drop as it is taking more current across the diode. Sense the LFP bank (regulator + sense and reg black wire are the sensing circuit not just red sense) and you should see a major improvement. However your lead battery will now be seeing .4V +/- more than LFP at high current. With an MC-614 I don't understand why you are not protecting the alt by interrupting the red B+ reg power wire in a BMS event..?

My isolator is FET based so almost zero voltage drop.
I am not sure why you you are mentioning shutting down the alternator ?

[exMaggieDrum]

I have a Perkins 4-108, a Balmar alternator, and a Balmar 614 regulator. My tach gets it RPM signal from the regulator. How do folks keep their tach operating when cutting the B+ to the regulator?

That is not a huge deal to me as I usually drive by sound and boat speed (considering conditions etc.). But it's nice to have a tach reading. Although losing the tach would be an indicator at the helm that the high voltage setpoint has been reached, and normally, you wouldn't want to go there anyway. But when motoring long distances you may want to stop alternator charging if the battery is already at "full" charge. Perhaps that won't be a problem as there will some loads going at the same time but sometimes minimal.

[mbartosch]

Originally Posted by exMaggieDrum

I have a Perkins 4-108, a Balmar alternator, and a Balmar 614 regulator. My tach gets it RPM signal from the regulator. How do folks keep their tach operating when cutting the B+ to the regulator?

The MC614 has a "Ignition" (#3, brown wire) input which - as far as I understand - basically acts as logical switch for the field output.
In order to disable charging it should be sufficient to isolate #3 from +12V.

It is possible (without having tested it) that the tach output generation might still work when #3 is off. This can only work if the Stator output of the alternator produces a sufficient signal even with field off (only possible if there is a tiny residual field exciting the stator).

It is worth a try. However, as Maine Sail has pointed out, performing a HVC is safer with cutting +12 V to the entire regulator. If you are cutting Ignition only, you are relying on the correct operation of the MC614. A malfunction could lead to a situation where HVC turns off ignition but a defective MC614 is still exciting the alternator field. That would be bad (TM).

[exMaggieDrum]

Originally Posted by mbartosch

The MC614 has a "Ignition" (#3, brown wire) input which - as far as I understand - basically acts as logical switch for the field output.
In order to disable charging it should be sufficient to isolate #3 from +12V.

It is possible (without having tested it) that the tach output generation might still work when #3 is off. This can only work if the Stator output of the alternator produces a sufficient signal even with field off (only possible if there is a tiny residual field exciting the stator).

It is worth a try. However, as Maine Sail has pointed out, performing a HVC is safer with cutting +12 V to the entire regulator. If you are cutting Ignition only, you are relying on the correct operation of the MC614. A malfunction could lead to a situation where HVC turns off ignition but a defective MC614 is still exciting the alternator field. That would be bad (TM).

I agree with you and Maine Sail on the failsafe desirability of cutting the B+ to the 614 to disable the alternator charging. Although it seems to me that cutting the field wire to turn off the alternator is a failsafe method as well. Cutting the regulator B+ is done to come to the same result. I am sure I am missing something. I went back to look for previous explanations of this and to Maine Sail's excellent writeup on issues and setting up LiFePO4 battery systems. I couldn't find, and can't remember, a complete discussion on why one rather than the other. I may just have missed it though. This thread is huge.

The issue I have is when you are motoring a long ways (sometimes for literally days in some situations), the batteries are "full" but not yet at the HVC and I want to disable the alternator without disabling the tach as well. I can manually disable my solar charge regulator so that wouldn't be a problem. This may be a situation that only occurs occasionally and can be tolerated for the duration of the motoring, but it is an issue to understand and deal with. It is also reliant upon the BMS so not completely failsafe anyway.

I guess one possibility would be to install a separate manual field disable switch. Of course, if the 614 is working and the voltage parameters are set correctly then the battery should never exceed HVC.

[SV THIRD DAY]

Bingo...the alternator/Tach issue.

Living on a mooring like I do my alternator only runs for about an hour every weekend when I head to and from the pump out dock so I have done nothing with it yet in terms of adapting it to the LiFePO4 battery bank. I do all my charging with Wind/Solar/Battery charger. But while being out cruising there have been times (more than a "real cruiser" should admit) that we motored for days...4-5 days. So I wouldn't want to lose the Tach for that long of period and I wouldn't want to kill the batteries either....so that's a solution I will need to get nailed down before THIRD DAY heads South to Mexico again as soon as these damn...uh...I mean loving kids move out....

[Maine Sail]

I was recently shipped a $9,000.00 24V LiFePO4 marine battery that had been severely over discharged. The eight 160Ah prismatic cells inside ranged from 0.760V to 0.813V when I received the battery.

Due to these voltages, and an overall pack voltage of just 6.117V, for a 24V nominal pack, I did not want to attempt to charge this as a bank.

I disemboweled the battery & removed the cells and began charging them independently at 2A to 3.0V. Once at 3.0V they were allowed to sit for 24-30+ hours and resting voltage monitored. If the voltages remained stable I continued to charge them to 100%.

Not only had these eight cells been over-discharged (though never hitting 0V) they had also been over-charged.

This bank had been charged at 29.2V or the equivalent of 14.6V for a 12V pack or 3.65VPC. The owner thinks the system held 29.2V for about 4 hours. The case design did a poor job of containing the lower third of the cells and as a result the end cells were bulged a bit down low, not bad but definitely bulged from over charging.

I then decided to begin capacity testing one of the cells. I charged cell #2 to 3.55V and allowed current to taper to 5A. I then applied a 25A constant load at 75F and discharged the cell to 2.5V and counted the Ah's & time.

The first capacity test came in at about 110Ah but I did not record because I was just considering scrapping the cells. Remembering that I had seen recovery of capacity in LFP before, after multiple 100% discharge/recharge events, I decided to push on with Cell #2.

Discharge - 25A @ 75F to 2.5V - Recharge - 40A to 3.55V & 5A

Capacity Test #1 = 110.? Ah (did not write it down forgot tenths)
Capacity Test #2 = 119.8Ah
Capacity Test #3 = 131.4Ah
Capacity Test #4 = 139.6Ah
Capacity Test #5 = 145.2Ah
Capacity Test #6 = 145.9Ah

Once capacity stopped climbing I ended the capacity testing.

It should be noted that even after a complete 100% discharge to 2.5V (note I do not recommend this) the resting voltage of this cell bounced back to 3.019V. This is a clear reason why voltage is a horrible indicator of SOC with LFP.

A fair number of folks, here and elsewhere, have noted diminished capacity under fractional "C" use and I suspect much of this capacity is still inside the cells waiting to be reawakened.

My own cells on my own bank have barely budged in capacity in nearly 800 cycles and are 2009 cells. I do however cycle them deeply before a capacity test. I may repeat this same test strategy on my own bank on the next capacity test.

In this very abused cell I was able to take it from 68.75% of its 160Ah rating all the way back to 91.2% of its as new factory rating. I suspect when new these prismatic cells delivered 110% +/- (many prismatic cells do) but I can't say for sure, so am using 160Ah as a baseline. These cells have been in hard use since 2010 and have March 23, 2010 or an almost 6 year old date code.

I am astounded at how well these abused cells responded to the six 100% discharges followed by compete 100% recharges.

Moral?

If your cells are not meeting your assumed or desired capacity cycle the heck out of them a few times and repeat the test.

I found this quite interesting hopefully others can glean something from it too...

[SV THIRD DAY]

Originally Posted by Maine Sail

Moral?

If your cells are not meeting your assumed or desired capacity cycle the heck out of them a few times and repeat the test.

I found this quite interesting hopefully others can glean something from it too...

I think another moral could be that these LiFePO4 cells are a lot more forgiving than everyone is talking about.

I think a lot of this "oh treat them careful and gentle" talk is due to the high price and the back of mind thinking that your boat will go up like the Hindenburg if you mess something up. So far all the data points I'm seeing tells me that I'll never go back to Lead again.

[ScottMeilicke]

As people are getting more experience with LiFePO4, it seems like you don't always need the BMS, hvc/lvc, etc?

I have a Balmar 614 and a xantrex prosine 2000, both of which can be adjusted for Li voltages, and current in the case of the 614. We live aboard, so I am tempted to replace my lead acid golf carts with Li, adjust charge voltage and be done with it.

Sane?




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[SV THIRD DAY]

Originally Posted by ScottMeilicke

As people are getting more experience with LiFePO4, it seems like you don't always need the BMS, hvc/lvc, etc?

I have a Balmar 614 and a xantrex prosine 2000, both of which can be adjusted for Li voltages, and current in the case of the 614. We live aboard, so I am tempted to replace my lead acid golf carts with Li, adjust charge voltage and be done with it.

Sane?

Living aboard isn't "sane", and as a live aboard I can say that.
So it's all about risk management and how good are you at keeping track of your batteries and boat system. A DIY simple system is not for everyone...but it is perfect for some.

I have been running my 400AH LiFePO4 bank now for nearly two years with no BMS, no LVC, no HVC...just individual cell monitoring and two AH monitors to help me relate the voltage to the SOC. I have my Xantrex battery charger and Sterling battery charger both set for my desired voltage, I have my solar controller set for the same voltage and ka-pow....I've been a happy camper and would do it again.

Let me also be perfectly frank and honest here.

I started this project with the eye of importing these batteries from China myself and selling them...but I've since ran away from that about as fast as a politician from truth serum.

Why? Well I will say this with love and admiration to my fellow boaters and cruisers, but there are some really ignorant people out there about boat electrical wiring and systems. I quickly saw the HUGE liability I would have in selling and trying to help design everyone's system for them. Every boat is different and trust me...no one wants to pay for designing anything for them. They bought parts from you, so they now own you and your time. No matter how custom or how much hand holding is needed in "black to black and red to red" connections. No offense folks and the only reason I'm saying this is that I'm a few beers into a Friday night afloat with no one else here except Cortez the cat. Otherwise my wife would beat some sense into me and hit delete! So I bailed on the idea, but on the bright side, my company bought me a R&D battery bank...

[ScottMeilicke]

Rich, two questions:

Have you found the individual cell monitoring to be useful? Or asked differently, would you put them in on a new system?

Without a BMS, how do you monitor the individual cell voltage? Four little displays?

Thanks!


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