New LiFePO4, all else same?

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schrater

schrater

Senior Member
Joined
Sep 4, 2016
Messages
130
Location
USA
Vessel Name
Matilda
Vessel Make
Ponderosa (CHB) 35' Sundeck
I have 3x 8D AGM 200Ah each. They are about 10 years old now and are no longer holding a strong charge (engine struggles to turn over on start). Plan is to replace them with LiFePO4 of same specs (200Ah, same dimensions). Charger is Xantrax Trucharge 40+, doesn’t have Li setting, but does have AGM which should work.

My question: Is there any reason I can’t just do a one-for-one swap of these batteries and leave ALL else the same (cabling, fusing, charging, etc)? I hope!
 
I would use a LiFePO4 charger. Compared to the cost of those batteries, the charger is cheap. Not to mention cheap insurance for not having to worry about your boat.
 
schrater said:
I have 3x 8D AGM 200Ah each. They are about 10 years old now and are no longer holding a strong charge (engine struggles to turn over on start). Plan is to replace them with LiFePO4 of same specs (200Ah, same dimensions). Charger is Xantrax Trucharge 40+, doesn’t have Li setting, but does have AGM which should work.

My question: Is there any reason I can’t just do a one-for-one swap of these batteries and leave ALL else the same (cabling, fusing, charging, etc)? I hope!
Click to expand...

I changed my lead acid batteries 4 months ago on my sailboat for LFP and made no physical changes to my boat. All I did was change my settings for my solar controller and alternator/regulator and change the battery charger to a Gel setting that the upper limit was well below a problem to the LFP (I have a bigger charger than you).

Be sure you check that the LFP you chose is OK for use as a starting battery if it is going to be used as such.
 
If the charger allows custom absorption and float settings you should go to what the battery manufacturer recommended voltages are. Perhaps on absorption, you can go 0.2V lower than the recommended as this will increase the charging/discharging cycles dramatically. No need to go all the way up. LiiFePo4 prefer not being pushed all the way up to the allowable voltage. For prismatic Cell Batteries I always use 3.5V/Cell or 14V as absorption setting and 3.4V/cell as float. That puts the battery at about 95-98% charged
 
If you change one for one, and do not updrade your charging capability to utilize the higher charge currents LIFEP04 can accept, what are you really gaining, by making the change???

My opinion very little gain for your dollars spent.
 
ksanders said:
If you change one for one, and do not updrade your charging capability to utilize the higher charge currents LIFEP04 can accept, what are you really gaining, by making the change???

My opinion very little gain for your dollars spent.
Click to expand...
While I agree with you in general, he is still gaining charge at the max current that his charger can provide to the the very end of the charging cycle without tapering off and the last 20% to require 80% of the time to fully change as on lead acid or AGM batteries.
 
Besides getting the full output of a charging source to go into the batteries longer instead of the tapering down like lead acid, the next big plus to the LFP is that you don't have to worry about them fully charged all the time.

If LFP sits around at 50% state of charge for weeks it matters nothing. If lead acid does that there will be an issue down the road.
 
SeaMaster101 said:
While I agree with you in general, he is still gaining charge at the max current that his charger can provide to the the very end of the charging cycle without tapering off and the last 20% to require 80% of the time to fully change as on lead acid or AGM batteries.
Click to expand...

He only has a 40 amp charger on a 46 foot trawler.

My educated guess is that he is only putting 15 amps into his batteries anyway much of the time when you count boat loads at anchor

Seems like very little benefit for thousands of dollars in outlay.
 
ksanders said:
If you change one for one, and do not updrade your charging capability to utilize the higher charge currents LIFEP04 can accept, what are you really gaining, by making the change???



My opinion very little gain for your dollars spent.
Click to expand...



Agree with optimizing charging as much as possible. But main gains are:

1. Significantly lighter weight batteries for tight quarters in ER (47lbs ea vs 140lbs ea).
2. Keeping same form factor and wiring, but with much less weight, means I can DIY, saving significant cost.
3. I have found that LiFePO4 are no longer more expensive from many vendors. In fact, like for like, they were actually half the price it would have cost for new AGMs at West Marine.
 
ksanders said:
He only has a 40 amp charger on a 46 foot trawler.

My educated guess is that he is only putting 15 amps into his batteries anyway much of the time when you count boat loads at anchor

Seems like very little benefit for thousands of dollars in outlay.
Click to expand...

Not $1000s, can get a drop in 200ah LFP off Amazon for a little over $600.
 
Oof. Well, further rsearch indicates that LiFePO4 might be fine for house batteries, but will NOT work as my starter battery, due to discharge limits placed by the BMS. I guess I still need AGM for that one. Hope I can mix types on the same charging system.
 
schrater said:
Oof. Well, further rsearch indicates that LiFePO4 might be fine for house batteries, but will NOT work as my starter battery, due to discharge limits placed by the BMS. I guess I still need AGM for that one. Hope I can mix types on the same charging system.
Click to expand...

Yes. Read the article on LFP batteries on marinehowto.com before you proceed. Rod knows his sh*t on electrical work.
 
SeaMaster101 said:
While I agree with you in general, he is still gaining charge at the max current that his charger can provide to the the very end of the charging cycle without tapering off and the last 20% to require 80% of the time to fully change as on lead acid or AGM batteries.
Click to expand...
Is that really true when using a FLA pr AGM setting?
As V increases A is decreased
 
schrater said:
Oof. Well, further rsearch indicates that LiFePO4 might be fine for house batteries, but will NOT work as my starter battery, due to discharge limits placed by the BMS. I guess I still need AGM for that one. Hope I can mix types on the same charging system.
Click to expand...
Mixing not a good idea.
Read Rods / CMS article. You NEED to consider the whole system.
So called "Drop Ins" are not air what the marketing implies.
Just my opinion, but unless you separate start & house charging you will regret it.
How does your alt charging work now while underway?
If you aren't sure where & how house & start are connected its worth figuring out... B4 less expensive than after/ the hard way
Also understand any hi amp demands on house... thrusters, windlass, inverter, etc and be sure they can be handled from house.
 
You can separate with FET. Lots of people using LFP house with a lead acid start battery
 
What does the battery manufacturer say the charger settings need to be, and will all your charging sources be within that range?
 
schrater said:
Oof. Well, further rsearch indicates that LiFePO4 might be fine for house batteries, but will NOT work as my starter battery, due to discharge limits placed by the BMS. I guess I still need AGM for that one. Hope I can mix types on the same charging system.
Click to expand...

Not necessarily true. Check out:

https://dakotalithium.com/product/d...r-starter-deep-cycle-lifepo4-battery-1000cca/

They sell several sized and voltage, and are designed with BMS that they claim will work as start batteries. No affiliation, but we're considering them.
 
Bacchus said:
Mixing not a good idea.
Read Rods / CMS article. You NEED to consider the whole system.
So called "Drop Ins" are not air what the marketing implies.
Just my opinion, but unless you separate start & house charging you will regret it.
Click to expand...

How do I find the article you mentioned? My house and start batteries combine for 24v to power the thruster -- would that require separation (from an electrical load perspective, I don't see how one bank would know about the other)? And is there any reason not to replace the start batteries with the fancy ones, other than max current draw? How big a bank would I need to be able to handle 500 amps (just guessing, probably less, but that is the fuse size in my current setup for a pair of QSM11 engines with 12 v starters). These are the questions I am trying to research, among many others, but I think the other issues can be handled. For example, if my charger/inverter can't properly charge the fancy batteries, it would be an easy matter for me to add a new charger, since the boat has lots of redundancy, including two separate charging systems. If I were to do that, I would keep the current charger/inverter in place, but disable its charging function. Similarly, since my genset is necessary to handle the boat's electrical demands when not connected to shore power, I don't really need the alternators at all. If their charging profile creates problems, I can remove them.
 
MYTraveler said:
How do I find the article you mentioned? My house and start batteries combine for 24v to power the thruster -- would that require separation (from an electrical load perspective, I don't see how one bank would know about the other)? And is there any reason not to replace the start batteries with the fancy ones, other than max current draw? How big a bank would I need to be able to handle 500 amps (just guessing, probably less, but that is the fuse size in my current setup for a pair of QSM11 engines with 12 v starters). These are the questions I am trying to research, among many others, but I think the other issues can be handled. For example, if my charger/inverter can't properly charge the fancy batteries, it would be an easy matter for me to add a new charger, since the boat has lots of redundancy, including two separate charging systems. If I were to do that, I would keep the current charger/inverter in place, but disable its charging function. Similarly, since my genset is necessary to handle the boat's electrical demands when not connected to shore power, I don't really need the alternators at all. If their charging profile creates problems, I can remove them.
Click to expand...
Sorry... meant to include the link.
https://marinehowto.com/drop-in-lifepo4-be-an-educated-consumer/
 
I have just done all my research on this. I have ordered the batteries. Have special components coming in to make it all work. I should probally start a new thread on it.

life pods are not starting batteries. Most limit current to 200 amp at best. Most starting batteries are 8d like the op are 1005 with two giving you 2005 amps. You cannot draw that kind of power out of lifepods. Starters have super high shock/start draw.

lifepods have a very specific charge profile. You need the appropriate charger.

It is better to have separate start batteries anyway house and start. . This way you have redundancy to start. If the house goes dead you can still start the engine.

lifepods are designed more for the long draw. To power things for long periods, deep discharge, and super fast high amp recharge. Offering High life cycle count. A standard led acid can last for meny years as a starting battery.; but under house conditions they average 3 years or so. Lead acid draw down to 50 % generally gets 500 cycles. 500 / 365 = 1.36 years with daily charge / discharge. Draw them lower than 50% and the count really crashes. The lifepod shine here , even the low end bats claim 3000 cycles at 80%. 3000/365= 8.2 years of daily charge / discharge. Added bonus of no watering. And they protect themselves with the bms tuning them off before damaging them. Normally at the 80% discharge mark.

They both have there place and have there own charge profiles.
 
That article is an interesting read. This is an excerpt. Informative.

DC Motor In-rush


"The reason most drop in batteries cannot be used for starting is the in-rush. The in-rush of large DC motors looks like a dead short to the ( bms) FET’s. Imagine sitting there and intentionally shorting your battery multiple times each day…..That is what starting your motor, running a windlass, electric winch or Bow thruster looks like to the FET’s. There are LFP batteries that can be used for starting but they are very expensive at this point in time."
 
There are a couple of things you have to take into consideration when you change to LIFEPO4.
1. The charging profile is completely different. AGM will accept lower chargers the closer you get to 'full'.
Lithium on the other hand will keep charging until they are full and when 'Full' happens you need to be carfeful since the alternators or solar are charging at maximum, but when the battteries say "full' you can get a power surge in your system, which can cause a lot of damage. In order to prevent that you should always keep a few AGM batteries on board (e.g. your start batteries) where you excess load will be send once the Lithiums are full.

2. The alternators can charge at max capacity, however doing that for a prolonged period of time could result in overheating your alternators. Better is to have them regulated at roughly 80 % of max capacity. That way they won't overheat.

3. LIFEPO4 is indeed not for starting engines, they are typical house bank batteries, so you will need your standard start batteries.

4. If you want to charge the batteries via generator or shore power you will need to adjust the chargers, they need to go in a different profile.

5. LIFEPO4 can handle a lot of temperatures, but you should avoid charging at freezing temperatures (of the batteries). So if your batteries are in the lazarette and temp drops there below freezing level you will need to add heating plates to the batteries.

6. Normal LIFEPO4 batteries will come with a BMS, but if you happen to buy a battery without BMS you basically need a BMS for every battery. Also need to make sure all the cells are charged separately to the required voltage. If you don't do that the life of the batteries is shortened drastically. Also, make sure never to short the poles of the batteries, that is an instant end of the batteries. You will fry the BMS and sensors, would need to replace them.

There are some more items you need to be aware of, but these are the most important ones. A simple drop in is not going to work, I agree that Youtube has very good videos on LIFEPO4 installation, so can recommend studying them.
Good luck
 
schrater said:
Oof. Well, further rsearch indicates that LiFePO4 might be fine for house batteries, but will NOT work as my starter battery, due to discharge limits placed by the BMS. I guess I still need AGM for that one. Hope I can mix types on the same charging system.
Click to expand...
Those limits are placed because of the battery specs dictated by the manufacturer. Different LFP manufacturers have more robust BMS units, and mine (Lithionics) function just fine as a starter battery. But they aren't $600 for 200 Ah.
 
Greg QS said:
lifepods are designed more for the long draw. To power things for long periods, deep discharge, and super fast high amp recharge. Offering High life cycle count. A standard led acid can last for meny years as a starting battery.; but under house conditions they average 3 years or so.

Lead acid draw down to 50 % generally gets 500 cycles. 500 / 365 = 1.36 years with daily charge / discharge. Draw them lower than 50% and the count really crashes. The lifepod shine here , even the low end bats claim 3000 cycles at 80%. 3000/365= 8.2 years of daily charge / discharge. Added bonus of no watering. And they protect themselves with the bms tuning them off before damaging them. Normally at the 80% discharge mark.

They both have there place and have there own charge profiles.
Click to expand...

Greg
I agree with most all of what you posted. The one exception I have questioned others about is the " so called" 50% cliff that if you exceed that the cycle life reduces drastically. I have never seen a batty mfgr life cycle charts that reflects what you & others frequently state.
I have done calculations from life cycle charts at various DODs and for FLA & AGM and within a reasonable range... like up to about 70% DOD there is very little loss of total AHs provided by a given batty. The charts show about a 10% rather gradual degradation with higher DODs but nine I've seen show a precipitous drop.
IMO you can't simply compare reduction in # cycles... you need to consider the AHs delivered by those cycles. For instance if a 30% DOD represents one day/ night use and you recharge daily. Now run that same batty for 2 days, to 60% DOD and recharge every otherday it is unreasonable to claim a 50% reduction in life w/:considering the AH delivered. When I ran the #s the total AH delivered were within about 10%+/- for high vs low DOD total AHs delivered over batty life.

Do you gave any life cycle charts that demonstrate what you stated?

BTW... I am not anti LiFePO I just think the marketing literature and most proponents portray an incorrect case for FLA & AGM to justify the benefits of LiFePO.
 
Bacchus said:
Greg
I agree with most all of what you posted. The one exception I have questioned others about is the " so called" 50% cliff that if you exceed that the cycle life reduces drastically. I have never seen a batty mfgr life cycle charts that reflects what you & others frequently state.
I have done calculations from life cycle charts at various DODs and for FLA & AGM and within a reasonable range... like up to about 70% DOD there is very little loss of total AHs provided by a given batty. The charts show about a 10% rather gradual degradation with higher DODs but nine I've seen show a precipitous drop.
IMO you can't simply compare reduction in # cycles... you need to consider the AHs delivered by those cycles. For instance if a 30% DOD represents one day/ night use and you recharge daily. Now run that same batty for 2 days, to 60% DOD and recharge every otherday it is unreasonable to claim a 50% reduction in life w/:considering the AH delivered. When I ran the #s the total AH delivered were within about 10%+/- for high vs low DOD total AHs delivered over batty life.

Do you gave any life cycle charts that demonstrate what you stated?

BTW... I am not anti LiFePO I just think the marketing literature and most proponents portray an incorrect case for FLA & AGM to justify the benefits of LiFePO.
Click to expand...

I have had a boat in registered in my name since 14. 56 as of the 30th. Never gotten more than 3 yars out of a house battery . Even the boat I purchased in 22 , all batteries dead in capacity were from 2018 , 4 YEAEAS old . I cycle too much power through them. Starting up to 10 years. Its how much power you cycle through a led acid. Its simple chemistry. the more power you cycle through the led the more degradation of the led. Resulting in battery failure.

Regardless of Weather or not you accept my documenting. Just look at spec of lead acid. 500 cycles at 50% . lifepods ( my selection ) 7000 cycles at 80%. Simply if the led gets more 2x and the lifepod gest 1/2 your still looking at a cycel of 1000 led verse 3500 lifepod.
 
Last edited:
Mambo42 said:
There are a couple of things you have to take into consideration when you change to LIFEPO4.
1. The charging profile is completely different. AGM will accept lower chargers the closer you get to 'full'.
Lithium on the other hand will keep charging until they are full and when 'Full' happens you need to be carfeful since the alternators or solar are charging at maximum, but when the battteries say "full' you can get a power surge in your system, which can cause a lot of damage. In order to prevent that you should always keep a few AGM batteries on board (e.g. your start batteries) where you excess load will be send once the Lithiums are full.

2. The alternators can charge at max capacity, however doing that for a prolonged period of time could result in overheating your alternators. Better is to have them regulated at roughly 80 % of max capacity. That way they won't overheat.

3. LIFEPO4 is indeed not for starting engines, they are typical house bank batteries, so you will need your standard start batteries.

4. If you want to charge the batteries via generator or shore power you will need to adjust the chargers, they need to go in a different profile.

5. LIFEPO4 can handle a lot of temperatures, but you should avoid charging at freezing temperatures (of the batteries). So if your batteries are in the lazarette and temp drops there below freezing level you will need to add heating plates to the batteries.

6. Normal LIFEPO4 batteries will come with a BMS, but if you happen to buy a battery without BMS you basically need a BMS for every battery. Also need to make sure all the cells are charged separately to the required voltage. If you don't do that the life of the batteries is shortened drastically. Also, make sure never to short the poles of the batteries, that is an instant end of the batteries. You will fry the BMS and sensors, would need to replace them.

There are some more items you need to be aware of, but these are the most important ones. A simple drop in is not going to work, I agree that Youtube has very good videos on LIFEPO4 installation, so can recommend studying them.
Good luck
Click to expand...

All good points . All of this has been addressed . Look at the diagrams.

1 That is the basis of thsis system full communication between batteries and the victron system. It controls the system so the spike you are talinig about cannot happen

2 The wakspeed 500 communicates with the Victron. It has temperature sensors to protect the alternator and will be told to shut down before the batteries shut off. As a secondary note the alternator protect protects from a shutdown.

3 as stated this is house bank only not starting

4 charging is all done through the Victron multiplus as stated is designed and programable for lifepod.

5 These batteries have high and low temp sensors.

6 these batteries each have a bms. They all talk to each other. All readings from each batterie down to the cell are visible on the Victron 7 " display. In the desighn of a rac server system , if a battery drops out, it will not shut down the system , only reduce overall capacity .

These batteries even come with and integral fail safe. Small fire extinguishers in the units as a last line of defiance


This system is not made up . I is designed by Professionals.
 
Delfin said:
Those limits are placed because of the battery specs dictated by the manufacturer. Different LFP manufacturers have more robust BMS units, and mine (Lithionics) function just fine as a starter battery. But they aren't $600 for 200 Ah.
Click to expand...

Again as the design . This is a house bank independent down to the charge sources . All isolated from the Lead acid banks. These are not $600 batteries. Top of the line with all the high end bms , fail safes, even breakers on the batteries. Full communication with the Victron system. The bms's control the system. They are linked to 1 battery that drives the system.
 
Lots of good advice and perspective here. The one part I’m not following is the assertion that the AGM and LiFePO4 must be on separate chargers due to needing different charging profiles, when other people say it’s fine to use the AGM setting for charging LiFePO4. I wonder if we’re splitting hairs here?
 
Greg QS said:
I have had a boat in registered in my name since 14. 56 as of the 30th. Never gotten more than 3 yars out of a house battery . Even the boat I purchased in 22 , all batteries dead in capacity were from 2018 , 4 YEAEAS old . I cycle too much power through them. Starting up to 10 years. Its how much power you cycle through a led acid. Its simple chemistry. the more power you cycle through the led the more degradation of the led. Resulting in battery failure.

Regardless of Weather or not you accept my documenting. Just look at spec of lead acid. 500 cycles at 50% . lifepods ( my selection ) 7000 cycles at 80%. Simply if the led gets more 2x and the lifepod gest 1/2 your still looking at a cycel of 1000 led verse 3500 lifepod.
Click to expand...

Greg
I'm not questioning your experience. And certainly not cutting down benefits of LiFePO. My house AGMs are going on 9 yrs. They have been treated well and I try not to leave them extended time at partial charge... I consider FULLY charging adequate about once / wk. Our season is short in NE but I can't charge during 6 mo storage. I have anchored multi days w /o ability to get them fully charged.
In a way, what you say I agree with that LA battys degrade w power consumed (AH consumed). If only going to <50%DOD your point, they should last longer... or mine should die very prematurely.
I have chosen not to consider LiFePO not because I doubt the longevity... I figure I won't be boating or MHing long enough to realize a breakeven... he'll, I may not be alive that long.
Not trying to argue the plusses of Li, only that many exaggerate the performance of LA. I dont believe for a minute that before the Li crowd switched, they replaced batty every 2 yrs... sorry if that's your stand we can agree to disagree.
 
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