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

[OceanSeaSpray]

Originally Posted by hellosailor

"DC likes skin,"
DC?? I thought that was AC that had a skin effect.

Actually, it is frequency-dependent. DC or low frequency AC travel through the bulk of the conductor regardless as the skin region would generally be thicker than the conductor. HF shows very pronounced skin effect and then foil must be used.

Resistance = resistivity x length / cross-section
Power lost through the link = resistance x current^2

For copper, resistivity is ~1.7E-8 Ohm-metre, so for a 11mm2 cross-section at I=300A, it gives:

P = 1.7E-8 x length / 11E-6 x 300^2 = 139 W per metre of conductor, or about 7W for a 50mm long link. It would get fairly warm (hot!), but definitely hold.

Voltage loss would be P / I = 7 / 300 = 23mV per link.

Since 300A is not normally a continuous operating point, you can see where they are coming from. In case of short, those links would blow.

Aluminium flat bar can make good links, bus bars etc, it is inexpensive and very easy to source. It needs to be about 1.7 times thicker than copper for the same resistance.

[Dsanduril]

Originally Posted by OceanSeaSpray

...It would get fairly warm (hot!), but definitely hold. ...

In case of short, those links would blow. ...

I think "hot" may be an understatement given that a link 6 times as thick (and thus 1/6 the resistance) is designed around a 30C temperature rise. Of course it all depends on how long you run at that current.


Also consider that when it does blow molten copper will be flying around the area. One reason fuses are encased is to contain all the flying metallic debris when they do their job.


Personally I prefer to use fuses as fuses and bus bars as bus bars and keep the functions separate. YMMV

[OceanSeaSpray]

Originally Posted by Dsanduril

I think "hot" may be an understatement given that a link 6 times as thick (and thus 1/6 the resistance) is designed around a 30C temperature rise. Of course it all depends on how long you run at that current.

Also consider that when it does blow molten copper will be flying around the area. One reason fuses are encased is to contain all the flying metallic debris when they do their job.

Personally I prefer to use fuses as fuses and bus bars as bus bars and keep the functions separate. YMMV

You just suit yourself. 7 watts is just 7 watts and I didn't tell you to use the links as fuses or use the CALB cell links. The primary markets for CALB are EVs and power storage and it is reasonably easy to see why their skinny little links might do the job in these applications.

Temperature rise depends on the amount of natural cooling available in the end and the hotter the easier it gets to transfer the heat out. They most certainly wouldn't reach hundreds of degrees if this is what you are suggesting.
You were asking a question, as you can see, you can do the numbers. It doesn't go any further.

[caipirinha]

Hello,

Originally Posted by msmith132

CALB bus bars - are they truly up to the task?

I just received my order of 12 X 180 AH cells and bus bars, and the bars look awfully light to me. Before I install them on my boat in a 12 V 540 AH 3P4S configuration, I am looking for a second opinion and am hoping somebody in this group can help me. The bus bars are copper, 0.5 mm thick X 22 mm wide for a cross section of 11 mm², about the equivalent of 8 AWG wire. Frankly I am quite concerned about passing 300 amps thru these bars. Am I missing something? Thanks all.

I am surprised at the quoted thickness (or rather lack thereof), you can find recommended links for this size battery here
EV-Power | Terminal Connectors for CALB CA180FI
and if you click on the photos you will see those links are as thick as a 1€ coin (this is about 2 mm, not 0.5 mm)
Also in a 3P configuration I would assume the links will typically see only 1/3 of the (assumed total current) 300 A

[UnNamedBeneteau]

Why am I getting a voltage drop?
Last month I bought and installed 4 x 700Ahr cells from Balqan (with their BMS) to replace a Lead Acid house bank with a 700Ahr 9Kwh LifePO4 battery. I essentially just swapped out the 2 stock batteries and left the rest of the configuration of starting and bow thruster-auxiliary Lead Acids unchanged. At the same time, I upgraded to a 160 amp alternator with Balmar smart regulator. This represented an enormous undertaking for me, because I really am a full novice in electrical systems. I was rather proud to install it all myself and connect it in our 2011 Beneteau 40.
We left a few days later for a family vacation and have been at anchor now for 27 straight days.
Something isn't quite right yet and I need advice to fix it.
After motoring for about 20 straight hours and approaching our anchorage, I got a low voltage alarm. Bow Thruster battery showed 15 volts (at the dock, one relay I believe connects to bow thruster was making a clicking noise - thruster wouldn't turn on- fuses intact) I have switched off the leads to that battery in case it is burning out and somehow siphoning off voltage).
The Li appears to charge. My Victron monitor reports we maintain a typical state of charge between 65-80%. The big problem is that the voltage drops quickly. While charging I see approx 13.5 v. Then I need to recharge within about 18 hours because the voltage drops to under 12v. This can follow a session of running the motor anywhere from 2 hrs to 7 hrs.
Our boat is drawing only about 4-8 amps at any given time.
I have my regulator set to "Gel" and for:
Bulk 13.99 (shortest time possible)
Absorption 13.7 (2 hrs)
Float 13.12 (shortest time possible)
Field threshold (float to absorption) at 25
Field threshold (bulk to absorption) at 90.
Adjusted the Belt Load (or "Amp") Manager to approx 80%.
*Time frames are following Balmar's suggestions to accommodate lithium batteries.
Is my problem:
- In the regulator programming?
- Lead Acid in the system (maybe a bad cell)
- Isolators somehow interfering?
- Bad or low balanced Li cell (The cells were shipped with approx 65% charge and balanced.)
I've read through hours of postings. My family isn't happy because the system isn't performing as promised. Any assistance will be much appreciated.
I need to solve for the voltage drop and the loss of bow thruster.
Bob
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[nimblemotors]

May I suggest you start a new thread with your questions.

Originally Posted by UnNamedBeneteau

Why am I getting a voltage drop?
Last month I bought and installed 4 x 700Ahr cells from Balqan (with their BMS) to replace a Lead Acid house bank with a 700Ahr 9Kwh LifePO4 battery. I essentially just swapped out the 2 stock batteries and left the rest of the configuration of starting and bow thruster-auxiliary Lead Acids unchanged. At the same time, I upgraded to a 160 amp alternator with Balmar smart regulator. This represented an enormous undertaking for me, because I really am a full novice in electrical systems. I was rather proud to install it all myself and connect it in our 2011 Beneteau 40.
We left a few days later for a family vacation and have been at anchor now for 27 straight days.
Something isn't quite right yet and I need advice to fix it.
After motoring for about 20 straight hours and approaching our anchorage, I got a low voltage alarm. Bow Thruster battery showed 15 volts (at the dock, one relay I believe connects to bow thruster was making a clicking noise - thruster wouldn't turn on- fuses intact) I have switched off the leads to that battery in case it is burning out and somehow siphoning off voltage).
The Li appears to charge. My Victron monitor reports we maintain a typical state of charge between 65-80%. The big problem is that the voltage drops quickly. While charging I see approx 13.5 v. Then I need to recharge within about 18 hours because the voltage drops to under 12v. This can follow a session of running the motor anywhere from 2 hrs to 7 hrs.
Our boat is drawing only about 4-8 amps at any given time.
I have my regulator set to "Gel" and for:
Bulk 13.99 (shortest time possible)
Absorption 13.7 (2 hrs)
Float 13.12 (shortest time possible)
Field threshold (float to absorption) at 25
Field threshold (bulk to absorption) at 90.
Adjusted the Belt Load (or "Amp") Manager to approx 80%.
*Time frames are following Balmar's suggestions to accommodate lithium batteries.
Is my problem:
- In the regulator programming?
- Lead Acid in the system (maybe a bad cell)
- Isolators somehow interfering?
- Bad or low balanced Li cell (The cells were shipped with approx 65% charge and balanced.)
I've read through hours of postings. My family isn't happy because the system isn't performing as promised. Any assistance will be much appreciated.
I need to solve for the voltage drop and the loss of bow thruster.
Bob
Sent from my iPhone


Sent from my iPhone using Cruisers Sailing Forum

[hellosailor]

Un-
I would second Jack's suggestion and go one step further:
You must (MUST) include a complete schematic of your system. It is way too complex for any meaningful discussion without a schematic and I suspect you may have to crawl through the boat to generate one from scratch.

Mixing two battery types, bad idea.
Using "isolators" which usually means isolation diodes, bad idea.
15V at any point in the system? Indicates a regulator failure that may destroy the entire electrical system, or a regulation failure due to the way the system is configured. Generally a VERY BAD IDEA to run the boat at all if you are getting an accurate 15VDC reading at any point since 15V will destroy electronics of all kinds and radically shorten light bulb life. And if it is a regulator failure, you need to consider that is a fire risk and worth being a bit paranoid about.

[goboatingnow]

Originally Posted by UnNamedBeneteau

Why am I getting a voltage drop?
Last month I bought and installed 4 x 700Ahr cells from Balqan (with their BMS) to replace a Lead Acid house bank with a 700Ahr 9Kwh LifePO4 battery. I essentially just swapped out the 2 stock batteries and left the rest of the configuration of starting and bow thruster-auxiliary Lead Acids unchanged. At the same time, I upgraded to a 160 amp alternator with Balmar smart regulator. This represented an enormous undertaking for me, because I really am a full novice in electrical systems. I was rather proud to install it all myself and connect it in our 2011 Beneteau 40.
We left a few days later for a family vacation and have been at anchor now for 27 straight days.
Something isn't quite right yet and I need advice to fix it.
After motoring for about 20 straight hours and approaching our anchorage, I got a low voltage alarm. Bow Thruster battery showed 15 volts (at the dock, one relay I believe connects to bow thruster was making a clicking noise - thruster wouldn't turn on- fuses intact) I have switched off the leads to that battery in case it is burning out and somehow siphoning off voltage).
The Li appears to charge. My Victron monitor reports we maintain a typical state of charge between 65-80%. The big problem is that the voltage drops quickly. While charging I see approx 13.5 v. Then I need to recharge within about 18 hours because the voltage drops to under 12v. This can follow a session of running the motor anywhere from 2 hrs to 7 hrs.
Our boat is drawing only about 4-8 amps at any given time.
I have my regulator set to "Gel" and for:
Bulk 13.99 (shortest time possible)
Absorption 13.7 (2 hrs)
Float 13.12 (shortest time possible)
Field threshold (float to absorption) at 25
Field threshold (bulk to absorption) at 90.
Adjusted the Belt Load (or "Amp") Manager to approx 80%.
*Time frames are following Balmar's suggestions to accommodate lithium batteries.
Is my problem:
- In the regulator programming?
- Lead Acid in the system (maybe a bad cell)
- Isolators somehow interfering?
- Bad or low balanced Li cell (The cells were shipped with approx 65% charge and balanced.)
I've read through hours of postings. My family isn't happy because the system isn't performing as promised. Any assistance will be much appreciated.
I need to solve for the voltage drop and the loss of bow thruster.
Bob
Sent from my iPhone


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I suspect you are not charging the thruster lead acid set with the settings that is good for the lithium. Hence your Li set is fine, but the LA is not.

Dave


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[msmith132]

Originally Posted by msmith132

CALB bus bars - are they truly up to the task?


As well, the HPBMS has no information regarding the current carrying capacity of the relay and alarm channels so I don't know if I need intermediate relays for the various alarms and solenoids, can anybody enlighten me? Thanks again. I'm getting very anxious to get these installed but can't get past these questions.

Sorry for the bump, but can anybody please provide any guidance on the hpbms relay power handling capabilities?

Thanks to several on the bus bar power capabilities, i have doubled them up. Thanks.

[UnNamedBeneteau]

Thanks Dave,
It is the monitor for the Lithium that is reporting the voltage drop. The others show normal.
My understanding was that the lithium would 'hog' the charge and the lead acid would only be able to capture what it could - which is 25% at a time.
And yes, the regulator is set to benefit the lithium.
Bob



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[UnNamedBeneteau]

Hi,
I really wanted my question to be part if the "lithium for those using them".
Hope it can be ok here.
Bob


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[nimblemotors]

Originally Posted by UnNamedBeneteau

Hi,
I really wanted my question to be part if the "lithium for those using them".
Hope it can be ok here.
Bob


Sent from my iPhone using Cruisers Sailing Forum

Just answer one question, did you read all 3,800 posts in this thread before asking your question. If the answer is no, then start a new thread.

[OceanSeaSpray]

Originally Posted by UnNamedBeneteau

Hi,
I really wanted my question to be part if the "lithium for those using them".
Hope it can be ok here.
Bob

Bob,

This is not a great project without reasonable electrical understanding because each boat is different.

Your post is unclear, you talk about flat bow thruster battery, but also 15 volts on it, which would be too high for whatever reason.
Also very average charge and low voltage problems with the lithium. State of charge can be pretty meaningless anyway unless the gear is set up properly. Are you charging through splitting diodes or direct from the alternator? It could change everything and explain why the lithium bank is not performing.

Trying to charge lead-acid cells and lithium cells from the same source (i.e. alternator) is a no-go, because they have different end of charge voltage requirements and charge curves. It only "works" with engine starting batteries, because they are effectively always near-full - they don't really need to charge in the first place. If they did, you would get into the same trouble.
You won't be able to recharge your bow thruster battery now. A separate alternator for it could be one option. Another could be getting rid of it and run the bow thruster off the lithium bank if practical. You wouldn't get much voltage sag at the battery, but that would also mean heavy cables going forward. You might want to find out how much current it draws and how long the cables would be to assess your options.

You are also going to need to find out why the lithium cells don't charge properly (likely) or get discharged early (maybe). It might not be much, but without seeing the charging circuit...

12.0 volts on a lithium bank is pretty close to the edge of the cliff. Is your BMS set up properly and does it cut out if a cell takes a dive from there? It is clearly going to happen at the moment. Is it able to cut out your alternator if it plays up and stops regulating or if you wire the voltage sensing wrong?

You are going to have to sort it all out now, but don't feel too bad about it because I have seen "professionals" that had made a similar mess with cells being lost in the end after adding numerous gadgets without ever fixing the cause. Your #1 priority should be making sure you can't lose the cells because you could make a few more mistakes along the way.

Make sure you are properly balanced at the top, that your BMS is really able to protect the bank from over-discharge and over-voltage at cell level and find out whether you are splitting the alternator output before going to the batteries. Your engine battery is also going to fit somewhere in this picture. Also find out where the alternator voltage sensing is coming from.

Eric

[Maine Sail]

Originally Posted by OceanSeaSpray

Bob,

This is not a great project without reasonable electrical understanding because each boat is different.

Your post is unclear, you talk about flat bow thruster battery, but also 15 volts on it, which would be too high for whatever reason.
Also very average charge and low voltage problems with the lithium. State of charge can be pretty meaningless anyway unless the gear is set up properly. Are you charging through splitting diodes or direct from the alternator? It could change everything and explain why the lithium bank is not performing.

Trying to charge lead-acid cells and lithium cells from the same source (i.e. alternator) is a no-go, because they have different end of charge voltage requirements and charge curves. It only "works" with engine starting batteries, because they are effectively always near-full - they don't really need to charge in the first place. If they did, you would get into the same trouble.
You won't be able to recharge your bow thruster battery now. A separate alternator for it could be one option. Another could be getting rid of it and run the bow thruster off the lithium bank if practical. You wouldn't get much voltage sag at the battery, but that would also mean heavy cables going forward. You might want to find out how much current it draws and how long the cables would be to assess your options.

You are also going to need to find out why the lithium cells don't charge properly (likely) or get discharged early (maybe). It might not be much, but without seeing the charging circuit...

12.0 volts on a lithium bank is pretty close to the edge of the cliff. Is your BMS set up properly and does it cut out if a cell takes a dive from there? It is clearly going to happen at the moment. Is it able to cut out your alternator if it plays up and stops regulating or if you wire the voltage sensing wrong?

You are going to have to sort it all out now, but don't feel too bad about it because I have seen "professionals" that had made a similar mess with cells being lost in the end after adding numerous gadgets without ever fixing the cause. Your #1 priority should be making sure you can't lose the cells because you could make a few more mistakes along the way.

Make sure you are properly balanced at the top, that your BMS is really able to protect the bank from over-discharge and over-voltage at cell level and find out whether you are splitting the alternator output before going to the batteries. Your engine battery is also going to fit somewhere in this picture. Also find out where the alternator voltage sensing is coming from.

Eric

Eric makes good points. I will add:

#1 We need a LOT more information to be even begin to help.

#2 Who designed and installed this system?

#3 No LFP cells I have ever seen come "pre-balanced". I have never seen that. Even companies like Genasun spend considerable time re-balancing cells before building a pack and they are a huge customer for CALB and CALB cells come as closely balanced as any I have ever seen..... Even if they do "claim" they are balanced they should be manually checked at top balance levels. Throwing in any LFP pack without balancing it is simply NOT A GOOD IDEA......

#4 Sounds like you have quite a mess and proper installation practices were not followed..

#5 What are your LFP charging voltages set for?

#6 12V on a LFP pack = 3.0 VPC a good BMS properly installed would have cut you off by now....You should never see 12V on an LFP pack.......

#7 Who's BMS?

#8 We need a schematic..

#9 Do you have a loads and charging bus? Are they separate relays/contactors?

#10 Is the alternator properly protected to prevent blowing it up with a disconnect?

#11 How are the other batteries getting charged? Isolator, combiners? Second alternator? Seeing as you LFP voltage should not be above 14.0V this means any cycling LA battery will get chronically under charged.

[Jd1]

Has anyone come up with a safe way of keeping both flooded lead acid batteries and lithium batteries happy in an installation?
What I am thinking of is a system where the alternator is set up to charge the lead acids but there is a tap off the feed from the alternator that goes through some magic black box and produces a safe charging method for a lithium bank. The two banks do NOT provide power to the boat at the same time but rather are switched so that only one set of batteries feeds the boats electrical system.
I know this will likely freak out many people but trust me, I have a reason for asking .....
Let's say I have a boat with a battery system good for a day but I would like to go for a multi day trip. Normally the batteries will charge up from the alternator but what happens if I luck out in the wind department and don't need to run the engine? Or what if I require extra power during a particular trip for some reason or another? What if I had an electric outboard that I wanted to power with a lithium bank? If I have a semi portable box with a lithium pack and all required electronics to prevent over/under charging as well as voltage correction, I could take this pack from one boat to the next without having to worry about setting up the boat itself for lithiums.
Thoughts (other than to tell me I should never attempt such a foolish thing) ?
BTW, I do realize that the lithiums will not be able to show their full potential such as the ability to charge up with mundo current but I am ok with that.