LiFePO4 for House bank final designs

[ColdEH]

Get the lead out , you can start your engines from your lithium bank , even if you have tripped the lvc there is still lots of juice to start your engine .

Regards


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[ColdEH]

Also you have your echo charger charging both your lithium and your lead . You know not to do that . Big bad !

Sorry looked at it wrong . Just get that lead out and the charger unless you can program it for Lithiums

Regards


Sent from my iPhone using Cruisers Sailing Forum

[gpeacock]

Originally Posted by exMaggieDrum

My current high level diagram (subject to change of course):

Thanks for this!
You've made some specific choices that have caused me headaches trying to sort out in my system. I go around and around, get confused and then start over. You are right. At some point you have to just diagram it, build it and see what happens.

1: As I understand it the HP BMS has HV/LV alarm relays and the HV/LV protection level relay. Your diagram has helped me confirm my assumptions. I notice though that in your case, A LV alarm will trip the LVC Contactor but the pumps will still be connected. I know many people that have had battery death due to floats on pumps sticking. You still have the Main Disconnect so its not end of the world stuff, but the system wont recover without your input. If the pumps were on the LV alarm contactor then solar could recharge things and maybe the next time the pump came on it would shut off the way it should. Maybe not either... I like the idea of the alarms connected here though...BMS power as well?

2: What scenario would you use the parallel switch to the start battery? If your start bank is discharged and you parallel your house bank will try to charge the start battery. Depending on your house bank level (or condition of the start battery) this could drain your house bank before you get a chance to start either the genset or engine. This would be especially bad because the parallel switch position negates the protection of the main contactor A better way might be to have the parallel switch be a 1,2,all switch which would then allow you to choose to only connect house to the starters and keep your start battery isolated. If you haven't already, consider putting it on the other side of the main contactor.

3: Echo charger. Oh how I've agonized over this. My understanding is that any of these "smart" relays get foiled by LiFePO4 because the resting voltage is so much higer than in FLA's meaning it's on even when no charging is happening. The other issue with them as mbartosch just mentioned is that your voltage never gets high enough to keep the Start battery happy. He's spending the big bucks to switch to the sterling product which I think is a true DC-DC charger. My latest itteration (since I already have an echo charger) is to throw a timer relay on it like mbartosch has now and not care about the slightly reduced battery life. My start battery can be equalized so I might just do that when Im at the dock (only a couple of times a year).

4: Lastly, the solar controller. I just emailed Bluesky(the controler I have) and they dont want to see a HV relay shutting things down in front of the controller. Their suggestion was to put it on the solar panel side to keep the possibility of voltage spikes to a minimum.

Great work! It's inspired me to get my thoughts locked down. I will hopefully post in a few days and then you can all rip me apart as well.

[exMaggieDrum]

Originally Posted by typhoon

Get the lead out , you can start your engines from your lithium bank , even if you have tripped the lvc there is still lots of juice to start your engine .

Regards


Sent from my iPhone using Cruisers Sailing Forum

Typhoon,
I understand what you are saying. My "new" boat came with three banks of batteries. I will remove the biggest one but am reluctant to get rid of the start battery. I would just have to throw it away any way if I removed it and not that much more work to leave it in. I may get rid of it someday.

Simpler is definitely better. Right now it is anything but.
Cheers, Joe

[exMaggieDrum]

Originally Posted by typhoon

Also you have your echo charger charging both your lithium and your lead . You know not to do that . Big bad !

Sorry looked at it wrong . Just get that lead out and the charger unless you can program it for Lithiums

Regards


Sent from my iPhone using Cruisers Sailing Forum

I do want to rethink the Echo Charger. It is not really designed for a lithium setup. My other charge sources can be setup for my lithiums so no worries there. As you noted, the Echo Charger is one way: lithium to start. The issue (as peacock has noted) is whether it will be good with the normal 13+v of the lithiums which will keep it on all the time until the lithiums are below the LVC when it will be disconnected. I think the EC will stop when the start battery gets full so may be it won't be a problem. It should be almost full all the time anyway, whether I am at the dock or cruising. I really like mbartosch's dc-dc charger but that is another $250 or so. I haven't put anything in yet so it can be changed.

Thanks for your suggestions. Cheers

[exMaggieDrum]

Originally Posted by gpeacock

Thanks for this!
You've made some specific choices that have caused me headaches trying to sort out in my system. I go around and around, get confused and then start over. You are right. At some point you have to just diagram it, build it and see what happens.

1: As I understand it the HP BMS has HV/LV alarm relays and the HV/LV protection level relay. Your diagram has helped me confirm my assumptions. I notice though that in your case, A LV alarm will trip the LVC Contactor but the pumps will still be connected. I know many people that have had battery death due to floats on pumps sticking. You still have the Main Disconnect so its not end of the world stuff, but the system wont recover without your input. If the pumps were on the LV alarm contactor then solar could recharge things and maybe the next time the pump came on it would shut off the way it should. Maybe not either... I like the idea of the alarms connected here though...BMS power as well?

This is always a dilemma. I was looking at it from the POV that I would want the bilge pumps to work until the bitter end to save the boat from sinking. The boat will sink whether I turn them off at LVC protection level (and still have a good battery on the bottom of the ocean) or whether they just quit because the battery is flat (and ruined) and then sink to the bottom of the ocean.

You are quite right that float switches can stick. It is an issue. If I am on the boat I will be able to sort it out with alarms (if I can). The real issue then becomes what happens at anchor or in the slip when no one is on the boat. The charger will be on at the slip so that should be OK but bad for the bilge pump. The solar will be on all the time and the panels may keep up with the pump (everything else would have been shut down at LVC warning) but still bad for the pump. It seems to me it is better to keep the pumps on the main bus and have the BMS protection level and the main switch cut power to them if it gets to that. Always some risk to manage with trade-off scenarios.

2: What scenario would you use the parallel switch to the start battery? If your start bank is discharged and you parallel your house bank will try to charge the start battery. Depending on your house bank level (or condition of the start battery) this could drain your house bank before you get a chance to start either the genset or engine. This would be especially bad because the parallel switch position negates the protection of the main contactor A better way might be to have the parallel switch be a 1,2,all switch which would then allow you to choose to only connect house to the starters and keep your start battery isolated. If you haven't already, consider putting it on the other side of the main contactor.

If I need to parallel the house to the start switch it would try to charge the start battery I guess but I would only have it on long enough to start the motor/genset and then turn it off. If the start battery were dead and it would be bad to leave in the circuit then I could disconnect it at the battery and fix later when I could. I hadn't thought of putting the parallel switch on the other side of the main switch. I'll have to think about that but I would want to be able to at least try to start the motors with whatever juice was left in the house since they would be my main charging source to get everything back up and running.

I have always liked having a separate parallel switch. I've been on too many boats where the first mate put a 1-2-all switch in the wrong position in error and left it. I understand what you are saying though.

3: Echo charger. Oh how I've agonized over this. My understanding is that any of these "smart" relays get foiled by LiFePO4 because the resting voltage is so much higer than in FLA's meaning it's on even when no charging is happening. The other issue with them as mbartosch just mentioned is that your voltage never gets high enough to keep the Start battery happy. He's spending the big bucks to switch to the sterling product which I think is a true DC-DC charger. My latest itteration (since I already have an echo charger) is to throw a timer relay on it like mbartosch has now and not care about the slightly reduced battery life. My start battery can be equalized so I might just do that when Im at the dock (only a couple of times a year).

See my response to typhoon above. I will look deeper in to this. I don't want to add a timer and make it even more complicated. Big bucks is right though for the Sterling, especially since that is all it would be doing. I had the Echo Charger already but may opt to return it and get a dc-dc charger. I like the idea. And, I may get rid of the start battery in the future anyway. Not yet though.

4: Lastly, the solar controller. I just emailed Bluesky(the controler I have) and they dont want to see a HV relay shutting things down in front of the controller. Their suggestion was to put it on the solar panel side to keep the possibility of voltage spikes to a minimum.

I have an Outback controller. I'll check with them to see if they think it is an issue.

Great work! It's inspired me to get my thoughts locked down. I will hopefully post in a few days and then you can all rip me apart as well.

Well, I appreciate your thoughts, but don't look to me as any kind of knowledgeable expert on any of this. I'm paddling as fast as I can to keep above water. I may be the proverbial DIYer who thinks he knows more than he actually does. There is a definite benefit to getting feedback from each other though. May be we will both be able to muddle through. In the end we may decide that all this complexity is not really needed. There are a few cruisers who claim to be doing fine without it.

[mbartosch]

Originally Posted by typhoon

Get the lead out , you can start your engines from your lithium bank , even if you have tripped the lvc there is still lots of juice to start your engine .

I have considered doing that, but decided against it:

Although even a flat LiFePO4 bank will still have enough Mojo to start the engine, the dependencies for operabilities are more numerous than for the lead acid battery. Unless you attach the starter directly to the battery, this might mean that a failure in the BMS, wiring or a blown fuse in could prevent the engine from starting.

My traditional lead acid starter battery is a simple, dedicated and completely separated device (I'll have jumper cables ready in case the starter battery dies...). And it is understood by most service personnel who might want to start the engine in our absence (currently we leave the boat alone quite some time. The LiFePO4 bank is offline then. The nice people looking after the boat have the task to start the engine every few weeks and let it run for a while.)

[exMaggieDrum]

I should have given the other reason to why I want a starter battery and not just rely on a single lithium battery, even if it would "normally" give far more power than needed to start the engine even at low charge. I want two water tanks and backup fuel and autopilot spares and water pump spares etc. to always have critical systems available even if it takes an hour or so to bring them online.

The lithium setup is very complex with multiple potential failure points. I want a backup battery of some sort. Right now I have an AGM start battery that is next to new. I am going to keep it. I might replace it with a small lithium battery in the future but only if it does not need so much complexity to keep it reliable.

Since it is AGM it would be happier with often full recharge (in the 14+v range). But it will rarely ever see more than a couple of Ah usage, unless, something goes wrong and I need it as a house backup for a short period. I am looking at the Sterling 12v dc to 12v dc charger (thanks to mbartosch). It looks like it will handle keeping the AGM happily charged during normal operation with a good lithium house battery.

With a main switch with manual override capability and my alternators wired to the main bus (not to a charge bus) and a parallel switch and a manual alternator field override switch I will be able to charge my start battery with those sources and it would be an easy matter to reroute the solar panel output to the main bus, I will always be able to keep a good charge on the AGM. I might have to reprogram my alternator regulator but that is a simple process.

The load side of the system will be less elegant vis a vis a workaround for a BMS failure. I will have to take the lead from the main bus to the LVC contactor and move it to the switched side. One thing I haven't completely thought out is how to isolate the lithium battery completely from the start battery. I could always just take the lithium fuse out if need be but that doesn't seem very elegant (if that is a requirement??).

I haven't shown the details of my BMS system design and the relays but I will as soon as I can put it all down in my crude drafting software (MS Excel) so it is legible. My hand drawings are only readable by me.

I want backups on all critical systems needed to get me back to a port so my design reflects that goal. I just need to make sure it is as simple as possible and has everything necessary for normal and emergency operations.

I appreciate the suggestions to all, even things for which I may still do different. It all makes me re-evaluate and often change my thinking, as weak as it may be.

[Emerald Sea]

Originally Posted by typhoon

Get the lead out , you can start your engines from your lithium bank , even if you have tripped the lvc there is still lots of juice to start your engine .

I believe any good and safe arrangement with separate engine battery(s) will have a battery cross-over switch installed to allow you to start your engines from your house batteries. Should your engine not start due to a weak battery it will happen at the worse moment and running battery cables is too time constraining. A battery cross-over switch is inexpensive and quickly installed.

Not sure about starting your engines with a tripped lcv. A tripped lcv is a safe guard where further voltage depletion can permanently damage the battery and potentially worse. Careful here!

[ColdEH]

This is why why have separate charge and load bus bars . Starting your batteries from a tripped LVC is not a problem . This small amount of amp hours that are used to start your engine is insignificant against the power of the force 🤓

Regards


Sent from my iPhone using Cruisers Sailing Forum

[OceanSeaSpray]

Originally Posted by Emerald Sea

I believe any good and safe arrangement with separate engine battery(s) will have a battery cross-over switch installed to allow you to start your engines from your house batteries. Should your engine not start due to a weak battery it will happen at the worse moment and running battery cables is too time constraining. A battery cross-over switch is inexpensive and quickly installed.

Not sure about starting your engines with a tripped lcv. A tripped lcv is a safe guard where further voltage depletion can permanently damage the battery and potentially worse. Careful here!

A cross-over switch also exposes the LFP cells to the SLA charging regime. Besides, on a cat (i.e. with two engines), it is much smarter to ensure that both engines charge both starting SLAs, as well as the lithium house bank. Then it leaves no real reason for a cross-over, even between the two starting batteries, where it could be done.

If the system is decently designed, an engine starting SLA should never have any reason to become depleted and it is easy to have in place measures ensuring it is always kept full (as it should). At the end of its life, the SLA is going to appear getting weaker very gradually.

If a LFP bank is so discharged that it is at risk of going under the 2.0V/cell limit, it is also way past cranking an engine successfully. You need some luck to crank even at 2.8V/cell and with lithium at the bottom end, you only have one go. If you fail, it is all over.
To me, hanging the engine off the LFP is senseless. Not only it eliminates good, very low-cost redundancy, but having a SLA in the system is very useful in many ways.

[Anjin]

I posted a full description of my system over in the other thread but here's the answers to the questions that started this thread.

(1) The bank is 1440 AH consisting of 32 CALB CA180 batteries in an 8P4S configuration

(2) We've just completed the installation and testing and are still getting used to its performance. In two complete cycles using consistent 150A loads, the capacity tested out higher than design, closer to 1600AH.

(3) I've been monitoring the configuration in smaller test cycles before I installed the batteries on the boat and the 8P "cells" have never been more than 3mv apart. As a result I'm just monitoring at the pack level. A Victron BMV 700 provides high HV and LV alarms and (slightly outside those ranges) a Lightobject programmable voltmeter will drive Bluesea solenoids to cutoff the charge bus or load bus as needed.

(4) My alternators are stock hitachi internally regulated 80A that came with the 2 Yanmar diesels. They charge the start batteries which also provides a buffer to be able to turn on/off the charge from them going to the house bank without worrying about blowing diodes. With them connected and the engines at idle I get about 25 amps per side, up to the about 70 amps per side at full power. I use a manual battery switch to control that flow, but in my scheme, the alternators are backup chargers. Solar and generator are primary. I don't use alternator power for the house bank unless I have the time to monitor and control it manually. A high voltage event would isolate the chargers but leave the loads in place.

(5) The alternators keep the start batteries charged - I did not alter the charge programming for them.

(6) My other chargers are a Victron Muti which is primary when we are connected dockside or running the generator. I was able to reprogram it's charge profile to 13.8 volts for absorption and 13.25 for float. The Cristecs that came with the boat are auxilliary chargers and I reprogrammed them for 13.8 volts also. My solar control is also Victron MPPT and was also easily reprogrammed for 13.8 absorption.

(7) If you're not a marine electrical engineer get help before you set out to do this. This forum (the other huge thread especially) helped me make all of my key decisions. Then, after you think it's all designed, have a professional look it over and don't expect his review and advice for free. I did much or most of the work myself but I had helpful advice from a local electrical supply house (where I bought a lot of stuff) and I recruited professional assistance from a local electrical installer when it came time to do the on board recabling. I think the installation I now have is way better and safer than what I started with.

Cheers -

- Art

[exMaggieDrum]

Originally Posted by Anjin

I posted a full description of my system over in the other thread but here's the answers to the questions that started this thread.

(1) The bank is 1440 AH consisting of 32 CALB CA180 batteries in an 8P4S configuration

(2) We've just completed the installation and testing and are still getting used to its performance. In two complete cycles using consistent 150A loads, the capacity tested out higher than design, closer to 1600AH.

(3) I've been monitoring the configuration in smaller test cycles before I installed the batteries on the boat and the 8P "cells" have never been more than 3mv apart. As a result I'm just monitoring at the pack level. A Victron BMV 700 provides high HV and LV alarms and (slightly outside those ranges) a Lightobject programmable voltmeter will drive Bluesea solenoids to cutoff the charge bus or load bus as needed.

(4) My alternators are stock hitachi internally regulated 80A that came with the 2 Yanmar diesels. They charge the start batteries which also provides a buffer to be able to turn on/off the charge from them going to the house bank without worrying about blowing diodes. With them connected and the engines at idle I get about 25 amps per side, up to the about 70 amps per side at full power. I use a manual battery switch to control that flow, but in my scheme, the alternators are backup chargers. Solar and generator are primary. I don't use alternator power for the house bank unless I have the time to monitor and control it manually. A high voltage event would isolate the chargers but leave the loads in place.

(5) The alternators keep the start batteries charged - I did not alter the charge programming for them.

(6) My other chargers are a Victron Muti which is primary when we are connected dockside or running the generator. I was able to reprogram it's charge profile to 13.8 volts for absorption and 13.25 for float. The Cristecs that came with the boat are auxilliary chargers and I reprogrammed them for 13.8 volts also. My solar control is also Victron MPPT and was also easily reprogrammed for 13.8 absorption.

(7) If you're not a marine electrical engineer get help before you set out to do this. This forum (the other huge thread especially) helped me make all of my key decisions. Then, after you think it's all designed, have a professional look it over and don't expect his review and advice for free. I did much or most of the work myself but I had helpful advice from a local electrical supply house (where I bought a lot of stuff) and I recruited professional assistance from a local electrical installer when it came time to do the on board recabling. I think the installation I now have is way better and safer than what I started with.

Cheers -

- Art

Art,

I'm just starting to top balance my 16 100Ah cells. It looks to be a very labor intensive process. How did you do yours?
Joe

[Anjin]

Originally Posted by exMaggieDrum

Art,

I'm just starting to top balance my 16 100Ah cells. It looks to be a very labor intensive process. How did you do yours?
Joe

Joe,

I used a benchtop power supply set initially to 3.5 volts and I balanced first in groups of four. I monitored them closely and found that once they hit 3.4 volts things started to happen quickly. So I set the voltage down to 3.4, measured with a voltmeter at the output of the supply, not relying on the built in meter.

So in groups of 4, I let all of the cells absorb at 3.4 until current flow from the supply was a couple of amps. My cells were 180 AH rated so YMMV.

After that was completed, I wired them all in parallel (32P in my case) and set the supply for 3.8 volts to increase the current flow and them monitored the cells as the voltage started to rise. When it got to 3.52, I set the voltage back down to 3.55 and just let it sit there until there was virtually no current flow.

To help ensure that the charging was even I attached the positive lead at one end of the bank and the negative at the other and kept checking measurements of individual cells. There were some differences during charging with voltages at each end of the bank being a few millivolts higher, but once I disconnected them and let them settle I had a measured variance of only 1 millivolt and only on a few cells.

A word of caution - connections matter. Polish the battery connections, make sure the busbars are shiny and tightened down well but not over tightened and pay special attention to the connections to the power supply.

My top balance was only to 3.55 because watching the behavior of the cell (the rapid rise in voltage once you pass 3.4) I could tell I was well into the charging knee. Experts may disagree with that and there might well be some chemistry argument that top balancing at 3.65 or even 3.8 has some value. But having spent $8K on the batteries I decided to follow my own observations.

Since then I've charged and discharged many times and the cell voltages have stayed within a millivolt. That's may be partly because my 8P4S configuration helps to average out the minor differences between cells but your 4P4S configuration should enjoy a similar benefit. I used my Victron Inverter charger and my Victron battery monitor to test the 8P4S configuration along with a variety of "standard" loads - a hair dryer, microwave oven and a room heater that each drew in excess of 100amps (see photos) It allowed me to rapidly cycle the batteries up and down (even with 1600 AH) and get a feel for how the pack would behave.

Hope this is helpful -

- Art

[exMaggieDrum]

Originally Posted by Anjin

Joe,

Hope this is helpful -

- Art

Art,

This was a very helpful reply. I have only started with two 100Ah cells. I set my power supply (bench top type recommended by Maine Sail) to voltage limited at 3.5v with a 17amp current limit. I also found that the voltage goes VERY fast at the knees so I need to monitor very carefully as you noted. I charged both cells to 3.6v and let them sit. They both went down to 3.33v +/-. I'm not sure if I need to give them a slower charge or not but I expected them to accept this .17C current and keep the voltage up.

Any ideas on why this is happening would be useful. The brand new cells all had the identical voltage of 3.29v when I received them this week.

I'm going to go back and review the posts and other sites for top balancing and see if I can find anything out there.

The charger is rated for 20A. The leads which came with it are 2.5mm and they got very warm when I charged the first cell so I made some 10ga leads up and they stay cool. The batteries have not warmed up more than about 5 degrees over room temp.

Thanks, Joe