Swapping AGM Batteries for Lithium Lifepo4

[nhislander]

2020 Swift Trawler 44 - Existing house batteries (two 12v AGM 140ah) barely make it through a night. Anyone know if I can just replace these two house AGM batteries with two 12v Lithium/Lifepo4 batteries?

I read up about the “CRISTEC” chargers (which I have on the ST-44), and it seems that they can be configured to a charge setting for Lifepo4.

Also, when the main engines are running the batteries are charging too (I assume from the engine alternators) – will this work alright with the Lifepo4 batteries?

Thoughts? Anyone done this on a swift trawler?

Thanks in advance for your help...

 

[Portage_Bay]

Suggest you start by reading this Drop-In LiFePO4 Batteries – Be an Educated Consumer Then you will be more able to absorb what the experts here on TF have to share. I'm not one. There is a lot to consider and change on your boat.

2020 Swift Trawler 44 - Existing house batteries (two 12v AGM 140ah) barely make it through a night. Anyone know if I can just replace these two house AGM batteries with two 12v Lithium/Lifepo4 batteries?

I read up about the “CRISTEC” chargers (which I have on the ST-44), and it seems that they can be configured to a charge setting for Lifepo4.

Also, when the main engines are running the batteries are charging too (I assume from the engine alternators) – will this work alright with the Lifepo4 batteries?

Thoughts? Anyone done this on a swift trawler?

Thanks in advance for your help...

 

[Iggy]

The easiest way to do this and after reading about drop in batteries. Let me also add, if you not good with wiring, let the pros do it.

To add lithium, first do.... Most likely, but conform that your Alt is charging your house bank directly. If so, move the wires so the Alt is charging the stating bank and remove the VSR/combiner between the two banks. With the new Lithium in place. Install a DC to DC charger between the two banks. I would also add if not already done, a heat sensor to the ALT.

The house bank's charger must be setup for lithium. Not knowing the shore power charging setup. You may need a small charger for the starting bank. Now this is the SHORT how to version in doing this!

Now this is one of many ways to do this. Do your research on the topic! Or get a pro to do the work. I added lithium to my house bank 2 years ago and its worked out for the better!

 

[Helmsman]

I would suggest reading this guy’s articles on lithium. He covers all of the things you need to consider for a lithium install. There are several articles. I would start with the first one and go from there. His articles are thorough and easily understood.

https://gilwellbear.wordpress.com/

 

[SteveK]

2020 Swift Trawler 44 - Existing house batteries (two 12v AGM 140ah) barely make it through a night. Anyone know if I can just replace these two house AGM batteries with two 12v Lithium/Lifepo4 batteries?

I read up about the “CRISTEC” chargers (which I have on the ST-44), and it seems that they can be configured to a charge setting for Lifepo4.

Also, when the main engines are running the batteries are charging too (I assume from the engine alternators) – will this work alright with the Lifepo4 batteries?

Thoughts? Anyone done this on a swift trawler?

Thanks in advance for your help...

what the others have said.
You have not discussed if the alternators plan to charge these LFP and your plan to set that up.

But what I want to know is how do you manage with 2-300 Ah on a boat that size.

 

[ranger58sb]

2020 Swift Trawler 44 - Existing house batteries (two 12v AGM 140ah) barely make it through a night. Anyone know if I can just replace these two house AGM batteries with two 12v Lithium/Lifepo4 batteries?

If that turns out to be a bridge too far...

You might investigate Lifeline 6V AGMs as an alternative. Boatloads of capacity, especially if you look at their L16 equivalent.

You'll still want to ensure sufficient charging capability... but at least that may well be fine with your existing systems.

-Chris

 

[lipets]

six or eight 6volt batteries are good alternative also

 

[mvweebles]

I gotta ask the "Devil's Advocate" question. What would happen if he did a simple drop-in replacement? No changes to the charging system? OP's charger has a LFP setting so really the question comes down to Alternator charging.

Video from Battle Born seems to suggest the issues are only minor, though is quiet on topic of alternator charging vs 120VAC charger.

https://youtu.be/l3Zk--RAR4Q

Seems to me the OP can get relatively inexpensive LFP batteries and get most of the benefits without the hassle/expense of converting his entire system. Sure, won't be optimized, but what is the problem with that?

Thoughts?

Peter

 

[Don L]

I have cheap drop in LFPs, didn't change anything on boat except setpoints

 

[mvweebles]

I have cheap drop in LFPs, didn't change anything on boat except setpoints

Is your alternator internally regulated or externally? If external, any changes? I assume it's either a Balmar or Wakespeed??

I did the "Goat Rodeo" dance of upgrading my charging system and while it was a PITA, I'm glad I did. But the OP just wants to get through the night with a bit of buffer. Sounds like a simple drop-in replacement gets him 80% of the benefit with 20% of the effort. But I really don't know.

Peter

 

[Helmsman]

The basic tenet of a competent lithium install is to consider the entire system, as opposed to “just another battery type”. Common concepts that are agreed on by many knowledgeable writers on the subject are fairly consistent.

Every set up is different, but these will apply to most.

Alternators will probably need external regulation and temperature control.
With two alternators, a centerfielder is recommended.
Leaving a lead acid battery in the system will provide a place for the alternator charge to move to, if the lithium BMS shuts the batteries down. Otherwise, you have a real risk of frying the alternator.
A DC to DC charger between the chemistries is necessary to change the voltage to the proper level for each chemistry down stream.
The charger using Shore Power should have the capability to charge at the proper voltage for each chemistry.
There are some discussions emerging that some generator alternators are not sufficient to handle lithium charging. I saw a discussion on this on the MTOA forum, I believe. So, a call to the generator manufacturer would be in order.
All battery cables, fuses, etc. should be assessed to ensure they can handle the higher charge acceptance rate that lithium batteries can handle.
Engine room temperatures may exceed temperature limits for lithium batteries. Some have moved the batteries out of the engine room due to this.
Insurance concerns are also an issue. For instance, several people have reported that Markel has certain requirements and limits for lithium installs, including a professional install using ABYC guidelines.
The ABYC recommendations are still maturing, and are subject to change, which could create downstream survey and insurance issues.

These are some of the caveats I have gathered in my own research. I hope these thoughts help with your decision. I am not an expert by any means, and if others have other thoughts, or feel like any of this is incorrect, please jump in.

 

[mvweebles]

Suggest you start by reading this Drop-In LiFePO4 Batteries – Be an Educated Consumer Then you will be more able to absorb what the experts here on TF have to share. I'm not one. There is a lot to consider and change on your boat.

The linked article is long and rambling with many nuggets of good information, though requires a bit of dedication to mine.

Deep into the article is the following:

CAN I USE MY STOCK ALTERNATOR?

The short answer is we do not advise this for charging lithium iron phosphate batteries directly.You can however use your stock alternator if i it is behind a DC to DC charger that serves to protect it and that provides the proper charge profile for the lithium iron phosphate batteries.

WHY?

1-A stock alternator rarely has the correct charging voltages for lithium iron phosphate batteries.
2-They can over absorb the batteries resulting in over-charge damage
3-The absorption voltage is very often too high (see below)which can lead to BMS load-dumps
4-Stock alternators do not FLOAT, they only do bulk and absorption.
5-Alternator heat damage
​

One gripe I have about Rod Collins when it comes to LFP is he talks a lot about Absorb/Bulk charging parameters for programming external regulators, but won't give specific information on what these should be, or a process to determine what they should be based on battery OEM specs. He seems to shy away from specifics for LFP - lots of information on what not to do, lean on what to do.

OP - since your battery bank is relatively modestly sized, you might consider the DC-DC charger route.

Again, from the article linked above:

The only drawback to using DC to DC chargers is that you give up charging your lithium ion phosphate batteries quickly. Seeing as that is one of the major benefits of LFP batteries we would strongly advise considering an externally regulated alternator with an external regulator such as the BamaMC-618 or Wakespeed WS-500these regulators can be programmed for LFP and have an alternator temperature sensor to protect the alternator from heat damage. This will also result in considerably faster charging!​

If you're in the US, I recommend finding a Victron dealer with decent tech support (vs just off Amazon). I've had good success with PKYS. Here's a 30A DC-DC charger. Note that Rod Collins in the article specifically warns against Renogy products, a sentiment I echo. The price is attractive but I replaced a Renogy DC-DC charger less than a year after install.

https://shop.pkys.com/Smart-DC-Chargers_c_887.html

Peter

 

[SteveK]

Before LFP my alternators charged with a 14.4 voltage as they do now afterwards. Did not pay attention to amps before so no comparison.

My install went by recommendations of not charging LFP directly with internal regulated ALTS but rather to an FLA start battery and then through DC2DC chargers. Did I need to do that, may never know. It is working well and I feel safe from burning out my ALTS.

But I never understood what a direct connection v. thru DC2DC does to protect ALTS. Maybe it is the limiting of max amps charge of the DC2DC rather than what the ALTS are capable to produce is what keeps them from burning. I followed recommendations to do so with DC2DC output amps lower than ALT rated max amps.

I would never suggest to the OP to go ahead charge direct and find out his ALTS fried. Only a few can share their stories of doing so with no problem, none have shared what the gurus say will happen, happened.

 

[tpbrady]

Since an LFP BMS can disconnect the house bank suddenly if some parameter is exceeded, it would also probably shut off all 12v systems. I don’t plan on that happening on FLA batteries, should I consider that in planning an LFP install?

 

[tiltrider1]

As far as I can tell Standard internally regulated alternators do not produce enough voltage to overcharge LiFePo4 batteries. The issue is with a potential shut off of the BMS causing a spike in the alternator that burns out the diodes.

If your boat always has DC loads then this would not be an issue. So technically the concern is warranted but practically it is not likely an issue with internally regulated alternators.

 

[Portage_Bay]

According to my reading there is risk of burning out internally regulated alternators when charging lithium direct. I have no real world experience.



Internally regulated alts are designed for over the road charging of start batts which recharge quickly. Then the alt is asked to carry a moderate running load. They don't get too hot.



LFA batts, even a large depleted house bank, exit bulk charge long before the bank is fully charged. Reducing load on the alt keeping alt temp reasonable.



Lithium will accept high.alt output for nearly the full charge cycle cooking the alt.


External regulation has the ability to manage alt output to control alt temp. A good DC to DC charger can offer the same protection.



I seem to remember Simi60 having this problem and solving it with DC to.DC charging.

 

[Don L]

Is your alternator internally regulated or externally? If external, any changes? I assume it's either a Balmar or Wakespeed??

External. Balmar with an ARS-5. Changed setpoints to 14.1V bulk/absorption for 12 minutes and then 13.4V float. When it goes into float it acturally is discharging the batteries. If I want to end a long motoring trip I just cycle the key and restart the program toward the end of the trip. I was more concerned about burning up the battery, but it hasn't gotten very close to the 95C temp I programmed in.

 

[Don L]

As far as I can tell Standard internally regulated alternators do not produce enough voltage to overcharge LiFePo4 batteries. The issue is with a potential shut off of the BMS causing a spike in the alternator that burns out the diodes.

The biggest issue is that with LFP the alternator runs at max output all the time e and just overheats. But yes if you started at close to full charged and start motoring you can hit the high voltage setpoint, trip off the batteries, and the alternator suddenly doesn't have a load and burns out.

I sometimes forget there are still people with internal regulators and are way behind the times.

 

[tiltrider1]

According to my reading there is risk of burning out internally regulated alternators when charging lithium direct. I have no real world experience.



Internally regulated alts are designed for over the road charging of start batts which recharge quickly. Then the alt is asked to carry a moderate running load. They don't get too hot.



LFA batts, even a large depleted house bank, exit bulk charge long before the bank is fully charged. Reducing load on the alt keeping alt temp reasonable.



Lithium will accept high.alt output for nearly the full charge cycle cooking the alt.


External regulation has the ability to manage alt output to control alt temp. A good DC to DC charger can offer the same protection.



I seem to remember Simi60 having this problem and solving it with DC to.DC charging.

Technically this is correct and practically it is not correct. Internally regulated alternators would take for ever to charge up a depleted bank. Much longer than a 4 to 8 hour cruise. The only practical thing to do would be to run the generator while traveling until the bank is charged.

Now there are those whose cruising style might not work for internally regulated alternators. Those cruisers should build a different system.

 

[Iggy]

The linked article is long and rambling with many nuggets of good information, though requires a bit of dedication to mine.

Deep into the article is the following:

CAN I USE MY STOCK ALTERNATOR?

The short answer is we do not advise this for charging lithium iron phosphate batteries directly.You can however use your stock alternator if i it is behind a DC to DC charger that serves to protect it and that provides the proper charge profile for the lithium iron phosphate batteries.

WHY?

1-A stock alternator rarely has the correct charging voltages for lithium iron phosphate batteries.
2-They can over absorb the batteries resulting in over-charge damage
3-The absorption voltage is very often too high (see below)which can lead to BMS load-dumps
4-Stock alternators do not FLOAT, they only do bulk and absorption.
5-Alternator heat damage
​

One gripe I have about Rod Collins when it comes to LFP is he talks a lot about Absorb/Bulk charging parameters for programming external regulators, but won't give specific information on what these should be, or a process to determine what they should be based on battery OEM specs. He seems to shy away from specifics for LFP - lots of information on what not to do, lean on what to do.

OP - since your battery bank is relatively modestly sized, you might consider the DC-DC charger route.

Again, from the article linked above:

The only drawback to using DC to DC chargers is that you give up charging your lithium ion phosphate batteries quickly. Seeing as that is one of the major benefits of LFP batteries we would strongly advise considering an externally regulated alternator with an external regulator such as the BamaMC-618 or Wakespeed WS-500these regulators can be programmed for LFP and have an alternator temperature sensor to protect the alternator from heat damage. This will also result in considerably faster charging!​

View attachment 143934

If you're in the US, I recommend finding a Victron dealer with decent tech support (vs just off Amazon). I've had good success with PKYS. Here's a 30A DC-DC charger. Note that Rod Collins in the article specifically warns against Renogy products, a sentiment I echo. The price is attractive but I replaced a Renogy DC-DC charger less than a year after install.

https://shop.pkys.com/Smart-DC-Chargers_c_887.html

Peter

I have not read every post word for word! So I hope I am not repeating others!

Anyways, you can add two Victron's 30A chargers totaling 60Amps. The Alt protective device in the diagram will not hurt but is not needed. The starting battery has no BMS to disconnect.

Totally agreed on "I recommend finding a Victron dealer with decent tech support (vs just off Amazon)"

Can you use the stock ALT? Maybe....... How big is it? I would suggest and this is me. Any ALT over 120amps as a rule of thumb. The DC to DC charger will suck up 60 amps or less depending on SOC. There is a setting in the Victron charger to wait, say 2mins and it is programable. To delay charging in order to give the starting bank time to recharge and the ALT will not get hit all at once.

 

[Portage_Bay]

I see your point. Thinking along those lines fot those of us running well below max RPM means the alts will be below max output. I typically ran my 3208s at 1600. Alt output was just over 50%. I had them tested. They put out 100% at their rated RPM. That will keep alt temps down.

Technically this is correct and practically it is not correct. Internally regulated alternators would take for ever to charge up a depleted bank. Much longer than a 4 to 8 hour cruise. The only practical thing to do would be to run the generator while traveling until the bank is charged.

Now there are those whose cruising style might not work for internally regulated alternators. Those cruisers should build a different system.

 

[SteveK]

I see your point. Thinking along those lines fot those of us running well below max RPM means the alts will be below max output. I typically ran my 3208s at 1600. Alt output was just over 50%. I had them tested. They put out 100% at their rated RPM. That will keep alt temps down.

derate was the word used to adjust the max rpm on the ALT (via belt and pulley) to avoid overheating if the main is run at rpm that would turn the ALT at full output.

Running below rated rpm is also derating the ALT.

I am thinking the DC2Dc act as if an external regulator by going thru the charge steps.
Only since installing LFP have I watched the gauges so closely. I see 14.4V and amps at max output, then volts remain but amps drop suggesting this.

@DonL did your bat get built with an external alternator. In the FLA world it was not needed.

 

[luna]

One has to be careful with turning some alternators at less than full speed for any significant length of time.

My Delco 40SI is rated at 6000 RPM where it will produce 240 Amps.

At 3000 RPM it will produce about 208 Amps. Thats about 87% of the rated output with only half of the fan speed. Its likely less than half the effective cooling as well.

Even though as RPM increases, the efficiency of the alternator decreases (a larger % of the total energy used, is turned to heat at higher speeds) the fan is less effective in keeping the alternator cool at 3000 RPM than it is at 6000 RPM, simply due to the lower fan speed.

The engineers at Delco advised not to run a fully loaded alternator at 3000 RPM consistently, unless you want to cook it.

Perhaps your alternator is different.

 

[Iggy]

One has to be careful with turning some alternators at less than full speed for any significant length of time.

My Delco 40SI is rated at 6000 RPM where it will produce 240 Amps.

At 3000 RPM it will produce about 208 Amps. Thats about 87% of the rated output with only half of the fan speed. Its likely less than half the effective cooling as well.

Even though as RPM increases, the efficiency of the alternator decreases (a larger % of the total energy used, is turned to heat at higher speeds) the fan is less effective in keeping the alternator cool at 3000 RPM than it is at 6000 RPM, simply due to the lower fan speed.

The engineers at Delco advised not to run a fully loaded alternator at 3000 RPM consistently, unless you want to cook it.

Perhaps your alternator is different.

This is where a heat sensor comes into play.

 

[Don L]

There is a min for cooling. On my engine it is 1400rpm. At 1800 rpm it is doing rated amps.

People should learn what theirs is.

 

[catalinajack]

All of the answers here focus on the "how", but do not address the question of "why". The OP seems to have a simple overnight capacity problem which is easily solved by adding LA capacity and foregoing all of the issues associated with going to LFP. Just an assumption, but it appears that the OP, at least generally, is a "one-night guy", that is, someone who spends only one night in a particular location before moving on to the next spot. If that is his, or anyone's cruising style, especially marina-to-marina guys, LFP offers little advantage over LA batteries. Why? Because the following day's cruise (assuming 5 hours or more) will charge a battery bank of 900 Ah depleted to 50%. And, AGMs, with their somewhat faster charging, for one-nighters, AGMs, at about double the cost of FLA, are not cost efficient. And FLP (extreme cost, all-in) for one-nighters, I ask, why bother. Now if the cruising style is much the opposite, then, sure, a well-designed whole house system makes sense, but not for guys who are overnighters.

 

[SteveK]

All of the answers here focus on the "how", but do not address the question of "why". The OP seems to have a simple overnight capacity problem which is easily solved by adding LA capacity and foregoing all of the issues associated with going to LFP. Just an assumption, but it appears that the OP, at least generally, is a "one-night guy", that is, someone who spends only one night in a particular location before moving on to the next spot. If that is his, or anyone's cruising style, especially marina-to-marina guys, LFP offers little advantage over LA batteries. Why? Because the following day's cruise (assuming 5 hours or more) will charge a battery bank of 900 Ah depleted to 50%. And, AGMs, with their somewhat faster charging, for one-nighters, AGMs, at about double the cost of FLA, are not cost efficient. And FLP (extreme cost, all-in) for one-nighters, I ask, why bother. Now if the cruising style is much the opposite, then, sure, a well-designed whole house system makes sense, but not for guys who are overnighters.

In the other thread on FLA to LFP I posted an answer to your question

 

[Don L]

The OP seems to have a simple overnight capacity problem which is easily solved by adding LA capacity and foregoing all of the issues associated with going to LFP.

What "issues"?

There are no issues of changing to LFP unless you decide to go down the "science project" installation method.

Compared to acid, and especially AGMs, LFP have no "issues". Far as I am concerned AGMs have no home anymore on a boat for a house bank of batteries. You get SLA or FLA for your start batteries and LFP for your house.

 

[tiltrider1]

All of the answers here focus on the "how", but do not address the question of "why". The OP seems to have a simple overnight capacity problem which is easily solved by adding LA capacity and foregoing all of the issues associated with going to LFP. Just an assumption, but it appears that the OP, at least generally, is a "one-night guy", that is, someone who spends only one night in a particular location before moving on to the next spot. If that is his, or anyone's cruising style, especially marina-to-marina guys, LFP offers little advantage over LA batteries. Why? Because the following day's cruise (assuming 5 hours or more) will charge a battery bank of 900 Ah depleted to 50%. And, AGMs, with their somewhat faster charging, for one-nighters, AGMs, at about double the cost of FLA, are not cost efficient. And FLP (extreme cost, all-in) for one-nighters, I ask, why bother. Now if the cruising style is much the opposite, then, sure, a well-designed whole house system makes sense, but not for guys who are overnighters.

I get the sense that you haven’t priced Lifepo4’s lately. I switched because replacing my bank with LA was $2800 and 900 lbs vs $2500 and 280 lbs.

 

[CarlF]

Some insurance companies won't cover boats with owner installed lithium banks. They will ask for the name of the ABYC certified electician that did the work. If you don't tell them about the batteries, then they may not cover you if you make a future claim.

So I would locate a nearby electrician who has done a bunch of these and have him make a proposal. It will cost a bit more than DIY but avoids lots of potential problems.