Changing from AGM to LFP

[John Simmons]

Hello everyone,

I am on a 47 foot sail boat and my 800AH AGM battery system is in need of replacement.

I have 500W of solar going to a morning star mppt controller. I contacted morning star and they have sent me a programming sheet to reconfigure for LFP. No worries there.

I also have a 90 amp Balmar alternator with a mc612 regulator. Balmar was also kind enough to send new programming values for LFP. Also no worries there. The alternator has the alternator protection device on it in case of an accidental disconnect while the engine is running.

There are also separate AGM start batteries for both the 59hp Volvo diesel and for the 6kw Northern Lights diesel.

There is a battery switch that will allow you to parallel the house bank with the Volvo start battery, (1, 2, Both, Off) for the boat systems or for starting the diesel.

There are two different 120v based programmable battery chargers. One for the start AGM banks, the second for the house bank. The manufactures have also been great to work with.

There is also a link lite battery monitor for amps in/out of the house bank, Ah used, etc.

My goal is to replace the 800Ah AGM with 400Ah LFP. I would like to use the 100Ah Fortune batteries that Will recently reviewed. I will be buying 16 of them.

My questions are:
1) Should I build 4 12V packs, then put them in parallel like the drop in replacement batteries?
2) Should I do as Will showed in one of his videos and go with 2 cells in parallel, and then put 4 of these double cells in series for 8 per battery. Then put two of these in parallel?
3)Go for it all, 4 cell packs in parallel. Then series up these 4 for 16 per battery.

What does everyone think would be the best option? Case 1 uses 4 BMS, case 2 needs 2, and with case 3 I would also use 2 in parallel.

High draw loads are the windlass at 80 Amps, and in the case of the start battery for the Volvo going bad, probably the same.

I have also read about placing a AGM in parallel with the house bank in case the BMS goes offline. Others advocate not using a BMS at all and simply controlling your charge and closely monitoring the discharge in order to protect the batteries.

I got 10 years of daily liveaboard use out of my old AGM's so I must have been doing something right.

Any help would be greatly appreciated.

 

[jasonhc73]

If you buy new LiFePO4, go parallel then series.
If you buy used LiFePO4, series then parallel, that way you can monitor every cell with the BMS.

What Voltage is your system now?
How much space to you have?
How much "weight" does your space allow?

 

[DThames]

<snip>
My questions are:
1) Should I build 4 12V packs, then put them in parallel like the drop in replacement batteries?
2) Should I do as Will showed in one of his videos and go with 2 cells in parallel, and then put 4 of these double cells in series for 8 per battery. Then put two of these in parallel?
3)Go for it all, 4 cell packs in parallel. Then series up these 4 for 16 per battery.
<snip>

I would agree option 3, electrically, but.....suppose you have to troubleshoot something someday in the battery bank. If you could easily split your parallel groups by removing a 4 bus bars or 4 cables you could split your battery in two so you could test half of it without disassembly and keep the other half in service. Then you could swap your tests to the other half. By having something you could split up without disconnecting a lot of stuff you could also have options to do periodic maintenance type testing if you had a need to validate cells or strings of cells. I like to build in options. I could draw it out if what I said is not clear.

 

[John Simmons]

Thanks for the double votes on parallel. I am going to buy all new cells and I really like the option to be able to disconnect to divide and conquer if possible. Great idea.

My old batteries were 4 Fullriver 400Ah 6 volt cells, hooked up in series-parallel. Each of these things weighs over 120 pounds. They are monsters.

The space I have to work in is 16" deep x 30" long x 16 inches wide.

I noticed on a couple of Wills videos that he uses a multiple battery volt meter. Does anyone know where he got that so I can always see the cell voltages? Alternatively I believe that the 4s LIFEPO4 BMS on his website can display the cell voltages through Bluetooth or am I mistaken?

Thanks again for clearing up some things.

 

[jasonhc73]

Thanks for the double votes on parallel. I am going to buy all new cells and I really like the option to be able to disconnect to divide and conquer if possible. Great idea.

My old batteries were 4 Fullriver 400Ah 6 volt cells, hooked up in series-parallel. Each of these things weighs over 120 pounds. They are monsters.

The space I have to work in is 16" deep x 30" long x 16 inches wide.

I noticed on a couple of Wills videos that he uses a multiple battery volt meter. Does anyone know where he got that so I can always see the cell voltages? Alternatively I believe that the 4s LIFEPO4 BMS on his website can display the cell voltages through Bluetooth or am I mistaken?

Thanks again for clearing up some things.

What is the final voltage your system uses?

 

[Steve_S]

A point of note. You are trying to replace 800AH (gross) of AGM with 400AH of LFP. Off the top that may seem ok but your thinking 100% discharge which is not a good idea. I would urge you to consider 500AH total, as that would leave a bit of room so as to not fully discharge, LFP is happiest with 10% left at the bottom for long life and reliability.

Building packs in series (internally) affords the best use of a BMS allowing each cell to be monitored, balanced & managed. 4 cells in series = 12V, 8 cells = 24V and 16 cells = 48V. Paralleling packs @ the same voltage adds resiliency & fault tolerance and should one pack all of a sudden decide to fail, you can pull it out and still have appropriate voltage to continue. Imagine being 1000 miles from shore and you have power problems.... fault tolerance & redundancy is important IMO, especially on a boat !

Make sure you pay attention to individual cell measurements as they do vary a LOT in physical size, even same AHr rated cells by different manufacturers. Never assume !

Marine Battery Pack design, build information GOLD:
http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/

Best Bang for buck. 280AH cells for $85.00 USD ea:

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[John Simmons]

What is the final voltage your system uses?

Final value is 12v.

 

[John Simmons]

A point of note. You are trying to replace 800AH (gross) of AGM with 400AH of LFP. Off the top that may seem ok but your thinking 100% discharge which is not a good idea. I would urge you to consider 500AH total, as that would leave a bit of room so as to not fully discharge, LFP is happiest with 10% left at the bottom for long life and reliability.

Building packs in series (internally) affords the best use of a BMS allowing each cell to be monitored, balanced & managed. 4 cells in series = 12V, 8 cells = 24V and 16 cells = 48V. Paralleling packs @ the same voltage adds resiliency & fault tolerance and should one pack all of a sudden decide to fail, you can pull it out and still have appropriate voltage to continue. Imagine being 1000 miles from shore and you have power problems.... fault tolerance & redundancy is important IMO, especially on a boat !

Make sure you pay attention to individual cell measurements as they do vary a LOT in physical size, even same AHr rated cells by different manufacturers. Never assume !

Marine Battery Pack design, build information GOLD:
http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/

Best Bang for buck. 280AH cells for $85.00 USD ea:

Hot Rechargeable 3.2v 280ah Lifepo4 Lithium Battery For 12v 48v 96v Solar System - Buy Lithium Ion Battery,Rechargeable Lithium Ion Battery,Lifepo4 Battery Solar Product on Alibaba.com

Hot Rechargeable 3.2v 280ah Lifepo4 Lithium Battery For 12v 48v 96v Solar System , Find Complete Details about Hot Rechargeable 3.2v 280ah Lifepo4 Lithium Battery For 12v 48v 96v Solar System,Lithium Ion Battery,Rechargeable Lithium Ion Battery,Lifepo4 Battery Solar from Lithium Ion Batteries...

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The amp hour meter on my existing bank never went below -120Ah usage during the night. This was on a passage when running GPS, ais, radar,nav lights, auto pilot etc. A normal night at anchor is 40Ah.

My usage pattern is to run the generator in the morning for the water maker, the holding plate refrigeration, battery charger, and hot water heater. This is usually one hour per day of generator run time.
The solar panels then take over charging and everything is topped off before 2.
I am confident that 400Ah is enough for my needs.
I read the nordkyn design website and agree on many of his items.
Being offshore and having the batteries go out is not inconvenient, it is life threatening.

 

[Turd Furguson]

I'd say option two or three. You want at least two parallel banks for redundancy should a cell/bank/BMS fail along the way.

Another restriction to consider is the current capacity of the BMS. The unit Will recently showcased supports 120a with some surge capability. You'll need 2+ to support higher loads such as a windlass and emergency start capability for the engine. Daly claims 200a in the larger units but I'm skeptical.

Your windlass is 80amps but you need to rate for the starting/jammed load... most are 135-150amps. Starter will be similar.... both are moot with a parallel bank.

If you want a single BMS you're getting into higher dollars or a smaller unit with relays; these introduce another potential point of failure and draw current when activated. Relays also bypass the current restriction capability provided by the BMS, You'll fuse it anyways but lose a protection point in the chain and possibly the shunt monitoring capability of the BMS if this feature is included.

This was my reasoning when planning two 150ah banks.

 

[Steve_S]

This is 4 Lifepo4 CELLS (3.2 V ea) which are connected up to make One 12V Battery. These Cells are in SERIES.

 

[Danny]

I use a MC-614 with Small Engine mode in the documentation so you don't blow up your alternator. I would think about bypassing your BMS for high loads like windlass, starting and inverter loads. Will has a video on using a relay to kill the by pass if your BMS gets into alarm state. I only have 4S so I can't answer the other questions. I use a Victron Smart Battery Protect for the house loads low voltage disconnect before the BMS trips at the pack level. Only charge to 13.8 at pack level to keep balancing at a minimum risk level with all those cells you have. I use a cheaper BMS but it is integrated so the Smart Battery Protect shuts off if the BMS has a low cell. I would think about keeping Lead Acid for starting and windlass as I have done. Lead acid for starting is a proven technology and it is really cheap for Starting! Lifepo4 for the house banks is a great idea for your situation I think.

 

[DeValency]

The amp hour meter on my existing bank never went below -120Ah usage during the night. This was on a passage when running GPS, ais, radar,nav lights, auto pilot etc. A normal night at anchor is 40Ah.

My usage pattern is to run the generator in the morning for the water maker, the holding plate refrigeration, battery charger, and hot water heater. This is usually one hour per day of generator run time.
The solar panels then take over charging and everything is topped off before 2.
I am confident that 400Ah is enough for my needs.
I read the nordkyn design website and agree on many of his items.
Being offshore and having the batteries go out is not inconvenient, it is life threatening.

John, I’m almost in a similar situation, and highly interested in what you have done so far and any initial results.

My boat is just a smaller (except the oversized original Volvo Penta TMD31B, 100HP), Contest 43’ cutter with lower numbers on the battery banks; 240A cranking and backup AGM and currently house of 300A AGM that is definitely a limiting factor at sea - hence looking at LFP upgrade. I have 300W solar that works well. One difference; not living aboard and have no interest in long cruises if more than 2-3 overnights are involved.

After 15 years the boat was in the Caribbean, she is on her way home in Boston, currently docked in Florida, looking at upgrading the house only to LFP of around 250-350A.
Most important is your last line; the life threatening situation of power loss at sea - I have been there... Hope to never again.
So when planning on going LFP, reliability and redundancy are my first concerns.
My initial approach is to keep everything as-is as possible for multiple reasons.
Keep all the charging; alternator, solar, shore power connected to the cranking/backup AGM bank only. Meaning no adding/changing anything on that side.
Build a stand-alone new LFP bank, using the exact 3.2V cells mentioned, in 2-3 separate BMS groups of 4 cells each in a new cabinet and charge it from the cranking/backup AGM bank circuit with a 50A Victron DC-DC charger-controller.
I think the better way for me would be to connect, or assure connection of the bow thruster, power winches and windlass to the AGM and use the new LFP house bank for all the rest. Will need to add switches and separate things at the master 12V panel and wiring but very much, as of that point, safely move clients from the old house AGM to the new house LFP one by one, measuring the effect on both charge and discharge.

Happy to read any comments, also from any other forum member here. Thanks!

 

[John Simmons]

I ended up buying 20 of the 100 amp hour Fortune cells that Will talked about. For the Bms, I decided to go with the electrodaucus Bms which is more like a battery monitor and charger cutoff than a battery cutoff. It cannot shut the battery down, it shuts the charging source down. This was key for me. I also bought the 12V 4s battery balancer from electric car parts company. I ordered a mass of extra parts fuses, terminal blocks etc to get an safe and decent installation. Main battery fuse is 750 amp which is more than enough as I don’t start the engine while running the windlass and running the inverter to power the microwave etc.

I wanted to stay away from any FET that could just simply shut down and disable the battery. That was very very important to me. I have seen a boat that had a NEAR lightning strike and the EMP was big enough to take out lots of their electronics. Their diesel still started though. I know of another boat that had a direct hit on the mast. Every piece of electronics was fried. The diesel still started. AGM‘s in both cases.

I also purchased an alternator protection device from the electric car parts company. I talked to Balmar tech support about programming my regulator for LiFe and during the conversation they strongly recommended having the APD on every alternator to save your electronics from voltage transients. They said that sometimes the (Batt1, Batt2, Both, Off ) battery switch which is supposed to be a make before break, isn’t. When that happens you can get high voltage spikes for a few milliseconds and unless something is in the system to dampen them out, BAD things can happen to electronics. Accidents can also happen if you mistakenly switch the thing to off, poof no more alternator diodes and possibly no more electronics.

My plan is to make one big 12 V 500 amp hour battery, 5 cells in parallel, then each parallel set in series. The electrodaucus thingy will give me an individual cell readout, and no matter how bad things get the balancer should be able to fix it. I probably in truth don’t even need the balancer with all new cells from same manufacturer but I bought it just in case. I also have a separate amp hour meter from link lite. The 500 watts of solar go to a Tri star MPPT solar controller that can be set up for LiFe, the MC612 from Balmar can also be set for LiFe. The temp sensor must be used to prevent alternator over temperature failures. The 120 V house battery charger is 50 amps and is not really set up to play nicely as the voltages are 0.2 volts too high for the new LiFe batteries. I am loath to replace it as it is the least important of my charging systems and would only be used if the batteries were way down. I might use the electrodaucus thingy to try and control the charger, but since it is only running when the generator is on and I can monitor cell voltages and amp hours this might be a non issue. When I am plugged into the dock I never run the charger, the solar takes care of all my charging needs. Since I am live aboard I am always monitoring the state of my batteries things like low voltage disconnect and low temp shutoff are not important to me.

For my system there will be one AGM engine cranking battery, and one AGM generator cranking battery that ONLY is connected to the generator and gets charged through the very dinky generator alternator or through a wimpy 20 amp 120 Volt AC charger, and of course the LiFe house bank. The AGM volvo start battery can be paralleled or separated from the LiFe house battery. I know that a perfect installation would have a DC to DC charger to go from the LiFe to the Volvo start battery. Maybe later. For now the plan is to start the engine with the AGM, run for a bit until I believe that enough has gone back in to replace the discharge from the start, then switch over to the LiFe house battery while motoring. It’s not perfect and will probably result in degraded start battery life, but I replace starter batteries every 3 years anyway I would like to get rid of the engine start battery completely and just start the Volvo from the LiFe house bank. The Volvo starter motor is a tiny little thing, about the size of two fists; the windlass motor is actually physically larger.

Right now, I have nothing to report as to how things work or pictures etc. I am in Panama and the entire country is locked down. People are only allowed to leave the house for groceries or to visit the doctor or pharmacy. Men can only go out on Tuesday and Thursday. Women only on Monday, Wednesday, and Friday. No one can go anywhere on Saturday or Sunday. The time that you are allowed outside (2 hours per day) is determined by the last number on your ID or passport. For instance if your last number is 9, then you can leave your house at 8:30, grocery shop, dr, or pharmacist from 9 until 11,(the police actually check your ID before you enter the store) and you have to be back in your house before 11:30 or you could be arrested.

With that said my shipment of stuff from the United States is in limbo. The shipping company says it is in Panama, but no one is working here except for groceries, doctors, or pharmacy. No auto parts stores, no hardware stores, and no shipping of my stuff.

John.

 

[DeValency]

John et al -
Interesting and thanks for the extensive details!
My plan was actually going the other way. Might be more conservative at this point but as mentioned, the new LFP house bank will only be charged by the existing cranking (engine, generator) AGM bank.
All the chargers: alternator, generator, solar, shore power will only charge the AGM bank, very much as it is now.
Understand the pain of running such a project in Panama, especially at such times. I went through a major painful refit in St. Lucia as of April last year that had to take two months but dragged through December, Continued in Sint Maarten (thanks god) during Jan-February and sailed with a plan to slowly visit the islands during March and dock in George Town, Exumas. PR and DR were great but as of heading to T&C and the Bahamas, they all shut down denying entry, refueling and any provisions. So we had to rush to Palm Beach, where I plan to run the LFP project with hope to escape north before the hurricanes season.
Looking forward to your good news - I will be happy to post mine.
Best of luck and stay safe!
Nitzan
S/V GDY-Kids

 

[Danny]

I ended up buying 20 of the 100 amp hour Fortune cells that Will talked about. For the Bms, I decided to go with the electrodaucus Bms which is more like a battery monitor and charger cutoff than a battery cutoff. It cannot shut the battery down, it shuts the charging source down. This was key for me. I also bought the 12V 4s battery balancer from electric car parts company. I ordered a mass of extra parts fuses, terminal blocks etc to get an safe and decent installation. Main battery fuse is 750 amp which is more than enough as I don’t start the engine while running the windlass and running the inverter to power the microwave etc.

I wanted to stay away from any FET that could just simply shut down and disable the battery. That was very very important to me. I have seen a boat that had a NEAR lightning strike and the EMP was big enough to take out lots of their electronics. Their diesel still started though. I know of another boat that had a direct hit on the mast. Every piece of electronics was fried. The diesel still started. AGM‘s in both cases.

I also purchased an alternator protection device from the electric car parts company. I talked to Balmar tech support about programming my regulator for LiFe and during the conversation they strongly recommended having the APD on every alternator to save your electronics from voltage transients. They said that sometimes the (Batt1, Batt2, Both, Off ) battery switch which is supposed to be a make before break, isn’t. When that happens you can get high voltage spikes for a few milliseconds and unless something is in the system to dampen them out, BAD things can happen to electronics. Accidents can also happen if you mistakenly switch the thing to off, poof no more alternator diodes and possibly no more electronics.

My plan is to make one big 12 V 500 amp hour battery, 5 cells in parallel, then each parallel set in series. The electrodaucus thingy will give me an individual cell readout, and no matter how bad things get the balancer should be able to fix it. I probably in truth don’t even need the balancer with all new cells from same manufacturer but I bought it just in case. I also have a separate amp hour meter from link lite. The 500 watts of solar go to a Tri star MPPT solar controller that can be set up for LiFe, the MC612 from Balmar can also be set for LiFe. The temp sensor must be used to prevent alternator over temperature failures. The 120 V house battery charger is 50 amps and is not really set up to play nicely as the voltages are 0.2 volts too high for the new LiFe batteries. I am loath to replace it as it is the least important of my charging systems and would only be used if the batteries were way down. I might use the electrodaucus thingy to try and control the charger, but since it is only running when the generator is on and I can monitor cell voltages and amp hours this might be a non issue. When I am plugged into the dock I never run the charger, the solar takes care of all my charging needs. Since I am live aboard I am always monitoring the state of my batteries things like low voltage disconnect and low temp shutoff are not important to me.

For my system there will be one AGM engine cranking battery, and one AGM generator cranking battery that ONLY is connected to the generator and gets charged through the very dinky generator alternator or through a wimpy 20 amp 120 Volt AC charger, and of course the LiFe house bank. The AGM volvo start battery can be paralleled or separated from the LiFe house battery. I know that a perfect installation would have a DC to DC charger to go from the LiFe to the Volvo start battery. Maybe later. For now the plan is to start the engine with the AGM, run for a bit until I believe that enough has gone back in to replace the discharge from the start, then switch over to the LiFe house battery while motoring. It’s not perfect and will probably result in degraded start battery life, but I replace starter batteries every 3 years anyway I would like to get rid of the engine start battery completely and just start the Volvo from the LiFe house bank. The Volvo starter motor is a tiny little thing, about the size of two fists; the windlass motor is actually physically larger.

Right now, I have nothing to report as to how things work or pictures etc. I am in Panama and the entire country is locked down. People are only allowed to leave the house for groceries or to visit the doctor or pharmacy. Men can only go out on Tuesday and Thursday. Women only on Monday, Wednesday, and Friday. No one can go anywhere on Saturday or Sunday. The time that you are allowed outside (2 hours per day) is determined by the last number on your ID or passport. For instance if your last number is 9, then you can leave your house at 8:30, grocery shop, dr, or pharmacist from 9 until 11,(the police actually check your ID before you enter the store) and you have to be back in your house before 11:30 or you could be arrested.

With that said my shipment of stuff from the United States is in limbo. The shipping company says it is in Panama, but no one is working here except for groceries, doctors, or pharmacy. No auto parts stores, no hardware stores, and no shipping of my stuff.

John.

I am going to redo my existing Lifepo4 with a new 280ah 4s bank and am going to change form the FET BMS to the electrodacus SBMS0 also. I have a Sterling BB1260 DC DC charger and am keeping all charging except solar at Lead Acid voltage levels. I"m going to purchase a Blue Seas ML-RBS and wire it to SBMS0 output LVD and HVD as a fail safe. Is is also my plan to integrate the SBMS0 to the following : Victron Smart Battery Protect for dc loads, Windlass control (not decided if LA or Lifepo4) , inverter, DC / DC charger. I'm keeping my lead acid for starting and maybe windlass. I highly recommend using the belt manager or Small Engine Mode on the MC-614 limit charging. It is very easy to turn the alternator off if you want to disconnect the voltage sense wire temporary in case of a SBMS0 alarm. I envision a bit of complexity wiring up some relays and control wires so I can shut off individual devices in case of a SBMS0 alarm event then, I'll have a big fail safe of everything shutting down with the ML-RBS. I also wanted to warn you all I have had issues with negative bus wire connections when running hybrid LA and Lifepo4. Here my current system where I'm running hybrid LA and Lifepo4. The SBMS0 is part of a upgrade project I'm starting to work on when I get rid of my LA 4D bank. Here is my setup.