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Lithium (LiFePO4) for Dummies

mpearson

mpearson

Mark Pearson
Staff member
I'm thinking about making the jump to a LiFePO4 house battery bank.

I don't have enough brain cells left to become an expert on the subject, so I'm asking folks like Warren and others who know the subject to tell me if I'm doing something stupid. ;)

I hate buying from Amazon, but there are some relatively inexpensive options that have very high user ratings. I don't have enough boat bucks to get the very nice US-built systems like Battleborn.

I'm considering replacing 3 of my old 12V lead acid batteries (88 Ah each) with this 410 Ah beast:


It's an incredible capacity upgrade given the much higher real drawdown on LiFEPO4.

Other background info: I'm planning on keeping my Lead Acid starter battery. My relatively new Yanmar came with a big 120A alternator. I've got a relatively new ProMariner Battery Charger (ProNautic 1230P) 30 amp.

Given all of that, is this the best approach??:
  1. Wire the battery charger, alternator, and solar so they charge the new house bank. Or I’ve heard I could fry my alternator going to LiFePO4, so maybe they should all be wired into the starter battery?
  2. Configure the battery charger so that it is optimized for LiFePO4 (if that is where it is wired)
  3. Get a DC to DC charger (like 30A Victron), and use it to charge the other battery bank
  4. Should I keep the A/B battery switch?
  5. I have an older Blue Sea battery State of Charge monitor, but it doesn't have a profile for Lithium banks. So I'm thinking of getting a Victron monitor
  6. I know people get religious about this, but I'm thinking of keeping my Windlass on the starter battery to avoid spikes, etc. that can fry electronics.
Are there other big ticket items I'm forgetting?
Thanks in advance for any advice.
-Mark
 
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I encourage you to read the detailed discussion of this upgrade at Attainable Adventure Cruising. John at AAC is not an opponent of the switch, but he and those who contribute to the site have lots of good advice and cautions. Oh, and you might consider a Wakespeed regulator if you make the switch. I may spring for one even with my old flooded lead batteries.
 
Here is the executive summary. 1st, you can choose from a "drop-in" (which isn't) or build a bank from cells. Building from cells is much more complex, but offers better ways to deal with some issues. I would suggest drop-in for you based on your not wanting to become an expert.

I offer 2 brands that while I have not used personally, from my research are the only 2 I would consider. Kilovault, or Epoch. Neither are top-tier expensive, and neither are as cheap as what you will find on Amazon. But both seem to be the best you can get in a drop-in at any price.(IMHO better than Battleborn even though they are half the price) The issue with cheap amazon batteries is that unless you cut one open and look, you have to assume that even though they are rated for 100A, they are wired internally with 10AWG wire and components that might stand up to 100A for a short time, but not continuously.

LFP will smoke that 120A alternator, unless you convert it to externally regulated and get a wakespeed (preferred) or balmar regulator for it-with a temp probe to monitor the alternator temperature. So, connect the alternator to the start battery, and all other sources to the LFP battery. Use a DCDC from the start to LFP to charge the LFP with the alternator. If you need more than 30A charging while the motor is running, do the alternator upgrades.

The Bluesea won't work with the LFP. I have one, and it is useless for SOC (but fine for everything else it does). The Victron is dead on exact for LFP SOC. Be sure to set it up correctly, the defaults it ships with are for lead-acid.

Do whatever you want with the windlass. It will (probably) work fine either way. If connected to the LFP, you will want to check the current requirements and the current limits of the LFP battery (remember, the cheap Amazon batteries often have 10AWG wire inside!) But, if the LFP can handle the current, the higher nominal voltage will work better. But, it works fine now at the lower voltage, so... do what you want.

Some issue regarding the A/B switch. I would not attempt to start your engine from a random Amazon LFP. I might attempt it in an emergency with a Kilovault or Epoch.

LFP is without a doubt the single best upgrade I have done. It is a game changer. The upgrade you are considering will more than triple your usable capacity. And you won't need to worry about damaging the battery by not fully charging it like you do with lead. In fact, they prefer not to be fully charged, so the best thing you can do is just ignore them unless they get really low (like less than 10%). You can run them to zero (where the BMS turns them off) without damage, other than your loss of power on the boat. I expect mine (and expensive system built from cells) to last me 20 years. If I ever sell Eliana, the LFP batteries will go in my next boat.
 
Wow, thanks for that executive summary, Warren! That's exactly what I was hoping for, and I appreciate it. Where are you living now, anyway? Someplace around the SF bay area? If so, I'll buy you lunch or dinner the next time I'm down there. Are you living on dirt or Eliana?

Yeah, I'm checking out Balmar's adapter thing that would allow me (I think!) to use their alternator regulator on the newer Yanmar's alternator. I need to get back to Zia to see if the alternator that came with the engine is the Valeo. From my memory, it sure looks like it.

balmar.net

Smart Ready Retrofit for Yanmar - Balmar

Smart Ready® Retrofit for Yanmar EnginesEquipped with Valeo AlternatorsNow Yanmar Owners can Easily add Balmar Multi-Stage Regulationwithout Disposing of the Valeo Alternator Present on Recent Production Yanmar Engines A Simple Retrofit of the 120A/12V or 60A/24V Valeo Alternator Converts the...
balmar.net balmar.net

It would be very nice to be able to use ~120 amps out of the alternator instead of only ~30. If by chance that gizmo works, would you recommend then sending the alternator output to the house bank too? and the DCDC feeding the start battery?

I'm also checking out Kilovault and Epoch per your recommendation.

Thanks again!
-Mark
 
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Thanks, Terry - I'm checking into Wakespeed too. I can't remember: do you have one installed?

I've been reading about my alternator on the web (correct or not?) that realistically I'll never see 120A out. More like 60-65A. If that's the case, I'm re-thinking going down the alternator gear upgrade path. If I got 4 times the charge from a well-behaved alternator, I'd be more inclined to lay out some significant boat bucks.

And I think our use pattern will let us use solar for most our routine big loads (fridge and watermaker). Both of which we have super energy efficient systems.

So maybe for the next year or two, we will direct the alternator to the start (lead acid) battery, solar to (LFP) house, and DCDC charger to feed from the start to the house. Which is what Warren was (I think) recommending if I don't go down the upgraded alternator/regulator path.

Gosh, I remember when going "off grid" only required a buck knife, some matches and a piece of waxed canvas. ;) I guess my "creature comfort" requirements are higher now.
 
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With the wakespeed or balmar, your alternator will put out 120A, for a short time, and then slowly ramp down to where the temp stabilizes at a safe level. It might be higher than the estimates you read online. 50% is a "safe" level for setups without the temperature probe. With the probe, you can run full tilt until it gets hot, and then only back off enough as is necessary to protect the alternator. My point being, if you want to charge from 0% to full, then the alternator will be crippled. But if you want to put 50Ah or 100Ah in the battery fast, it might run at near 120A long enough to do that. Since you have solar, and LFP isn't damaged by not fully charging, a little boost of 50Ah when the battery is very low might be all you ever need.
I currently have a DCDC charging my LFP from the start battery, even though I also have a balmar with a temp gauge. I primarily rely on Solar, and really dislike the balmar even though it is highly regarded. It's 40 year old tech, barely updated to mostly be compatible with LFP.
 
I have run a Balmar regulator for years. I agree it is not smart like a Wakespeed ( and the price reflects that) but it has served my limited needs (400 amp hours of house bank and a started battery. I have not decided if I will invest in a Wakespeed this year. I have also run a 100 amp Balmar alternator for two decades, with one precautionary rebuild at 15 years. But it is a large case and very robust. Unfortunately the new Balmar 100 and 125 are small case devices and not as strong. My new Beta will come with a Balmar 125 and I will downrate it by 10 or 15% since it is not as robust. I have for years carried a spare 100 amp on board. But both alternators are useless on the Beta, which has double foot mounting. So, I will have two perfect alternators to dispose of. I have listed one of them on our site, on EBay, and on Craig's list in Seattle, Portland, and the Bay area. No sale for three months. I will also have a Perkins 4-108 and spare parts. It still always starts and runs well, but I got tired of replacing worn parts. Maybe I should have kept it.
 
I did more research and talked with other folks. Ended up buying a Kilovault Lithium battery (like Warren recommended. Thanks Warren!).

I'm cooking up a schematic of how to put this all together.

Following drawing is a "work in progress" and although it looks a little nasty, it's no where near as bad as my hand drawing was. ;)

If anyone has any comments or suggestions about this, I'd love to hear them. This is the first phase of the upgrade. Eventually, I'd like to install an alternator regulator (as discussed with Terry & Warren) and perhaps have the alternator and battery charger feeding the lithium, and the B2B feeding the starting battery from the lithium.

1680188348830.png
 
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That looks pretty good. The main fuse (you marked with a ?) should be a Class-T fuse. And there is no reason to spend extra money for an isolated DCDC charger because your two batteries are not isolated from each other (they share a common negative bus). Be cautious using the battery combine to start the engine. It will _probably_ be fine, but the currents will probably exceed what the kilovault is rated for. I would leave it as you drew it, and then make sure I never get into that emergency. Mine is actually set up the same way, and what I have done when my start battery was drained is combine the two batteries, let the LFP charge the start, then uncombine them and start from the normal start battery.

With 400W of solar you should need very little if any alternator charging. I have heard 2nd hand that Yanmar warranty doesn't allow alternator upgrades (???) so the DCDC instead of an alternator upgrade is probably fine for you.
 
Warren - roger that on combining only in emergency. And good idea to (if time permits) to let the LFP charge the ‘start’, then disconnect and use the ‘start’ only.
Thanks for all your advice!
 
Hi Terry - we only have the stock 120a alternator (and regulator) that came on our new Yanmar.
 
The path of least cost is to leave your stock alternator and starting battery in stock configuration. Add a 40 or 60 amp DC/DC converter to charge the LiFePo battery bank. I would not put the A/B switch in the system, ( in the BOTH) position you are asking for trouble). Wire your solar panels and your battery charger to the house bank. Victron makes a vary nice bi-directional DC/DC converter that will charge the house bank with the alternator running, and then charge starting battery from the house bank when the engine is not running. Using a DC/DC converter will guarantee that the load on the alternator current will not exceed 40 or 60 AMPS and prevent early life failure.
One more thing, buying a UL listed battery is the only way you can insure a good product, remember most of these batteries are made from Chinese manufactured cells.

my two cents...
 
Thanks for the input John & Jose.

Jose - you suggest the battery charger should go to the house bank (instead of the Start battery as shown in my drawing above). And that the B2B Victron charger would charge the House bank from the Starting when the alternator/engine is running, and feed from the House bank to the Starting battery when the alternator/engine is not running. That seems like it would work, too, but maybe be a bit more complicated?? I guess one reason would be to avoid having a potentially problematic BOTH/Combine switch if the Starting battery is dead?

Under your scenario, I wouldn't need a switch that did BOTH/Combine. Because the House would always be topping off the Start if need be.

Did I get that right?

How about a situation where there is some kind of unintentional draw on the Start battery while we are off the grid? And it would then drain both the Start and House?

What do you think about Warren's idea of only using the BOTH/Combine switch to charge the Start battery, then disconnect before starting the engine? I know that is less than fool-proof, but in a pinch?

I appreciate the conversation.
 
Mark, yes you got it right. It is not a good idea to connect banks of different capacities and internal resistance characteristics. If you have a large bank trying to charge a smaller one with a shorted cell, very bad things can happen. I use a 1/2/both switch to select which bank starts the engine. I will provide a schematic later,
 
I left my 1/2/ both switch in place mostly because I was lazy, it was already there when I did the conversion and I just left it. I agree it is probably better to replace it with an on-off for the start battery. The LFP as its own on-off.

That said, my start battery is showing age, and I don't have a shore charger, solar is direct to the LFP, so my start only charges when the engine is running. Turning it to All for a few minutes before starting brings it back to voltage. This could be an issue if a cell shorted in the start battery, but otherwise not a problem.

On my endless list is a re-engineering of my battery bank. I'll be replacing my Balmar with a Wakespeed, a shore charger, and a way for solar to charge both banks. At the time I installed LFP I was in Virginia, and I needed an upgrade, but was time and budget constrained to get back to the west coast.
 
Mark,
mpearson said:
Thanks for the input John & Jose.

Jose - you suggest the battery charger should go to the house bank (instead of the Start battery as shown in my drawing above). And that the B2B Victron charger would charge the House bank from the Starting when the alternator/engine is running, and feed from the House bank to the Starting battery when the alternator/engine is not running. That seems like it would work, too, but maybe be a bit more complicated?? I guess one reason would be to avoid having a potentially problematic BOTH/Combine switch if the Starting battery is dead?

Under your scenario, I wouldn't need a switch that did BOTH/Combine. Because the House would always be topping off the Start if need be.

Did I get that right?

How about a situation where there is some kind of unintentional draw on the Start battery while we are off the grid? And it would then drain both the Start and House?

What do you think about Warren's idea of only using the BOTH/Combine switch to charge the Start battery, then disconnect before starting the engine? I know that is less than fool-proof, but in a pinch?

I appreciate the conversation.
Click to expand...
Mark, here is the electrical system on Siboney. I am using AGM bbatteries because at the time I needed the batteries the new tech was still too pricey. To change over to LiFePo batteries, the VSR/breaker combination would be replaced by the DC/DC converter and the battery charger would be connected to the start battery, this would eliminate the need for a bidirectional DC/DC converter. This is the battery charger and the DC/DC converter play nice together.
 

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jose santin said:
Mark,

Mark, here is the electrical system on Siboney. I am using AGM bbatteries because at the time I needed the batteries the new tech was still too pricey. To change over to LiFePo batteries, the VSR/breaker combination would be replaced by the DC/DC converter and the battery charger would be connected to the start battery, this would eliminate the need for a bidirectional DC/DC converter. This is the battery charger and the DC/DC converter play nice together.
Click to expand...
After further examination the changeover to LiFePo house bank would also require re routing the alternator output to the starting bank. I would leave the solar hooked up to the house bank.
 
Mark, here is a rough sketch of what a LiFePo house bank would look like. Yes I drew in 6v agm's instead of the 200 Ah LiFePo batteries but you get the idea. I am not sure if the combination of a battery charger feeding a DC/DC converter would work, some consulting with the manufacturer might be needed.
 

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jose santin said:
Here is an interesting option to those that have re-powered with engines that use the mitsublshi 120A alternators, The nice thing about this product is that it allows external charging without the need to modify the alternator.

VRC-200 Charge Reference Controller | Nordkyn Design

Advanced alternator and charger control for high-performance charging solutions.
nordkyndesign.com nordkyndesign.com
Click to expand...
That is more expensive that an external regulator, and does not monitor alternator temperature. It says it is for LFP, but for LFP you really need to monitor alternator temperature.
 
Warren Holybee said:
That is more expensive that an external regulator, and does not monitor alternator temperature. It says it is for LFP, but for LFP you really need to monitor alternator temperature.
Click to expand...
Yes, it does not monitor alternator temperature, it it does allow you to set maximum charge current, which in turn will control max temperature. As far as price, the price is quoted in NZ dollars, this price is equivalent to US $350, This is cheaper than the price I found for the Wakespeed. As as I mention, it requires no modification to the alternator. Let me know if I am mistaken.
 
NZD makes a big difference. Even still, if spending that kind of money I would do it differently. It's very personal though. In my case I have enough solar, so it isn't an issue. My alternator charges my start battery. I have a DCDC charger, but also have a switch to turn it off, and it is always turned off.
 
Hi guys! I’m “off the grid” now up in the Canadian islands of BC, north of Desolation Sound. Amazing place! No cell service, but Starlink works just fine
And thanks to all your advice, I’ve installed the system described above and everything is working as planned.
The only thing I want to change: the charging from the engine/alternator is slower than I want with the 30A DCDC charger I've got. Which charges the House lithium from the LA starter battery.
The alternator that came on my new Yanmar is (theoretically) 120A. It sure would be nice to get more like 60-100A.
I was reading that I can add another DCDC charger in parallel. Heat is one of my concerns with this. My existing Victron DCDC gets pretty darned hot. And heat translates into loss. And sweat on hot days.
Does anyone have any experience with Clark's battery BankManager? It almost seems too good to be true.

I'm gonna read back up on the Wakespeed and alternator protection schemes.
Any other suggestions?

Overall we are very happy with our system. We love the lithium batteries, solar is awesome (we have 400W), and Starlink is truly amazing.

I’m researching what improvements to make over winter.
Thanks!
Mark (blissed out in BC)

1724101787853.jpeg
 
Sounds like you are really enjoying it and living! Don't rush back. Someday maybe I will cruise that area. But it's a tough sail to get there, and I really like warmer weather.

Yeah, the bank manager thing is nonsense. It is a solution looking for a problem. What I ask myself is, why does he keep messing with it? A good LFP install just works. All you need to do is make sure you recharge before the meter hits zero, without anything else to worry about. Clark is worrying about too much, and is on his 3rd revision of a system to create more things to worry about.

You have 3 concerns (all of which the DCDC solved) The first is the alternator overheating. Check with Yanmar or whoever made the alternator. Many newer alternators have a built in temperature sensor, and that actually works fine, just as well as using an external regulator. So concern 1 might not be. The second is damage from a load dump/voltage spike. That is easily addressed with an alternator protection device. Even without one, they will only occur if your BMS disconnects, and if you never overcharge the battery, that shouldn't ever happen. It is really human error in the setup of everything that causes disconnects. The third issue is the charge voltage from the alternator. If it charges to a higher voltage than LFP wants (no more than 14.6V) then you will have a disconnect, leading to issue 2. If it is or can be lowered to 14-14.4V, then you shouldn't have an issue. (13.8 would be ideal if you can get there). So, it is _possible_ you could just connect your alternator to the LFP and be fine. But without some research into what you have it is pretty risky.

There are quite a few in the RV world that do nothing special. A modern alternator on a truck/motorhome is capable of adjusting it's output to prevent overheating, and if the voltage is low enough from the alternator it will not trip the BMS. I think some even have TVS diodes that take care of the need for an alternator protection device.

Of course, the best option is an external regulator (Balmar, Wakespeed, or now Zeus) that will monitor temperature and allows close voltage control. After a season of using a DCDC you might be ready to spend that kind of money, as it is the best solution.
 
Bank manager will do nothing to solve your problems. What you need is another DC/DC converter to give you more charging current. Of course, this will make your alternator work harder (get hotter) but will still limit your charging current to about 60 amps. There is nothing you can do about heat, the more power you produce the more heat you will generate. Try adding some 12v fans to help cool down the converters.
 
mpearson said:
Victron DCDC gets pretty darned hot.
Click to expand...

The new Orion XS runs significantly cooler and at higher amps - 50.

Do you now have the two battery banks completely isolated?

The dismissal of the bank manager isn't really correct. It's a question of how correct Clark is. Bank manager certainly isn't nonsense. Too complicated? Maybe. But the question is to what degree are you rewarded by protecting your LFP bank along the lines advocated by Clark, vs. what amount of degradation is acceptable over time with an eye towards replacement costs dropping.

The device that Warren pointed to a year ago comes from a website that probably has the best technical defense of the concept Clark is trying to honor- that charging an LFP battery according to voltage alone, as most chargers do, is fundamentally wrong for the that particular chemistry.

Charging Marine Lithium Battery Banks | Nordkyn Design

nordkyndesign.com nordkyndesign.com

As the argument goes, measuring current taper is necessary to understand a true state of charge, and thus when to stop so as not to overcharge. I'm not familiar with the product Warren linked from that site, but the description does include the language "By tracking both battery voltage, current and temperature". How does it gauge current? One of the complexities of Clark's device is his use of a clamp sensor for just this purpose.

Probably the best layman's explanation as to the why you'd want to parallel the two chemistries is here:

Hybrid Battery Bank – Introduction – Wildebus Home

wildebus.com wildebus.com

Another element of Clark's product is to allow the LFP to run down rather than expose it to constant charging. This point has now been taken up by car manufacturers interested in LFP-

Now if we jump to the opposing argument, that argument is that LFP is actually quite robust and charging to voltage is perfectly fine as long as that voltage doesn't exceed something like 13.8v. The best advocate here is Rod Collins discussing his 15 year old LFP-

Always charged according to voltage, no higher than 13.8, at a rate no greater than .5C.

Clark is probably correct on the technical details he points to. So to what degree are you rewarded? With a 25 year old battery in perfect shape?

OR, assuming you don't overcharge and wreck your battery in the short term, would a 15 year lifespan be acceptable using the present method of charging according to voltage? And when you do have to replace the battery, costs are so low or technology so new, it doesn't matter.

Personally, I'm interested in mixing both conclusions. LFP is indeed robust (provided its not overcharged) and paralleling the batteries together directly, sans disconnect, is ideal. Then just charge according to the lower lithium voltage regiment. No absorption or float for the lead, but instead incessant pressure / trickle charge from the attached LFP.

Yachting monthly covered hybrid systems back in 2022, though the way they talk about charging - relying on the BMS shutoff - is now considered a no-no.
www.yachtingmonthly.com

How to install lithium boat batteries - Yachting Monthly

Duncan Kent looks at lithium boat batteries and explains what’s needed to guarantee a safe and trouble-free system onboard
www.yachtingmonthly.com www.yachtingmonthly.com
 
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Clark is simply making something simple complicated. The earlier LFP installations on boats are now over 15 years old. Some of those didn't even have a BMS at first, only a balancer. BMSs were added later. Just set the charger to some voltage >13.8 and < 14.6, and disconnect charging when that voltage is reached.
Those early installations still have better than 90% of rated capacity, and seem to have a lot of life left. Some have kept track of charge cycles and are in the thousands.
There just is nothing to gain with Clarks system. There is no evidence the LFP will last any longer. But, it flys in the face of abyc rules, and if your insurance requires a survey, you will probably be called out on it and need to remove it.
LFP is actually pretty simple. Just to many ideas about it, an some of them make it complicated.
 
Just a thought on DC/DC converter, most claim an efficiency of over 90%. If you look further into the spec sheet you might find that this efficiency is achieved fairly close to the 50% load point. The difference in power is going up as heat.
 
Warren, I'm trying to be more circumspect. You're commenting as if there is no such thing as a damaged LiFePO4 battery. Collins in his video above mentions the many batteries he destroyed before understanding how to handle them. Says he started working with them in 2007. Would be interesting to hear more on that.
 
For the benefits of LiPo batteries, I'll never go to them over lead acid. Open one up, so many components to give trouble, and their failure modes can be downright dangerous, along with the various other bms components needed. Where space and weight is a real issue, ok, I get it, but on a 38' yacht, not so much. I'm a hard pass on them, sorry.
Dave.
 
Stewart said:
Warren, I'm trying to be more circumspect. You're commenting as if there is no such thing as a damaged LiFePO4 battery. Collins in his video above mentions the many batteries he destroyed before understanding how to handle them. Says he started working with them in 2007. Would be interesting to hear more on that.
Click to expand...
I am not at all commenting as if there is no such thing as a damaged LiFePO4 battery. I am saying that all you need are properly setup chargers, and a BMS as a last resort protection device. Clark's system is no more safe than that. In 2007, chargers that supported LFP didn't hardly exist. Now, just about any charger does. Also, in 2007, it was commonly recommended to charge to 14.8V. Now, that is considered overcharged.

With modern chargers that support LFP profiles, 100's of thousands of batteries have been sold(if not more), almost none of them use Clark's system, and they are *not* failing en masse.
 
DGA said:
For the benefits of LiPo batteries, I'll never go to them over lead acid. Open one up, so many components to give trouble, and their failure modes can be downright dangerous, along with the various other bms components needed. Where space and weight is a real issue, ok, I get it, but on a 38' yacht, not so much. I'm a hard pass on them, sorry.
Dave.
Click to expand...
Lipo != LiFePO4
It might be worth some reading. Lithium Iron Phosphate isn't any more dangerous than a 2x4 piece of wood. It will burn if you light it on fire, but it will not go into thermal runaway, and if you remove it from the source of ignition, will often self extinguish. That property is why LFP are the only Lithium batteries commonly installed on boats. A few car manufactures are beginning to switch to LFP because of this safety. ABYC performed testing, and did everything they could, all of the dangerous overcharging, short circuits, and physically damaging a battery, and couldn't get one to ignite. Then, they set the boat on fire and used it for firefighting practice, and the LFP batteries did not contribute in any way to the burning of the boat.

Other than space and weight, LFP charge much faster. Lead Acid charging will slow down dramatically as SOC rises above 80% That doesn't happen will LFP. In the real world, that means you get more power from your solar panels, and get to full charge faster, when with Lead Acid of the same size you might need to run a generator for part of the day to ensure you get to 100%. And, with LFP, there is no need to get to 100%, so they require much less babysitting. One of the greatest things about my LFP bank is that I ignore it. It is almost like being on shore power.

There are more components, but don't be intimidated. If buying a drop in, get a quality brand. If you have multiple in parallel, then one can fail and you only lose some capacity. If your chargers are set properly, you can bypass the BMS if it fails. It only does 2 things. It prevents overcharging (which if you chargers are set right won't happen anyway) and it balances the cells, which will stay in balance on their own for a month or so.

Even with the extra components, LFP are *far* more reliable than lead-acid. Lead-Acid are constantly degrading, leaving you with an unknown amount of energy left. Lead-acid suffer from damaged plates, shorted cells, evaporated electrolyte, etc.

LFP batteries are currently priced about equal to FLA. It might not be worth switching if your installed bank is fine, but you should really consider it if the lead acid bank is end of life.
 
Warren Holybee said:
a BMS as a last resort protection device. Clark's system is no more safe than that.

With modern chargers that support LFP profiles, 100's of thousands of batteries have been sold(if not more), almost none of them use Clark's system, and they are *not* failing en masse.
Click to expand...

I would point out that Clark's relay switch that measures current prior to the BMS is probably safer than relying on just the BMS, which should be understood as a protection of last resort.

The Nordkyn Design site best makes the case ("Charging Marine Lithium Battery Banks", direct link posted above) that the ideas behind Clarks device are worthwhile, which is to say your assertion that the standard practice of charging to voltage is less than optimal. You linked to their VRC-200 device - maybe you don't realize that contradiction?

The issue is you're ahead of your skiis when you declare it nonsense. You're also not answering the guy's question. The standard isn't a mass failure of all LFP batteries installed. It's as I pointed out - how far out does one go to appreciate the benefits derived.

The benefits of Clarks device are-

You can add LFP without changing any of your existing charge components.* People can say hogwash, just replace everything when you migrate to lithium! But they're talking past the point some may care about.

Yes, you can damage your LFP battery with existing chargers if incorrectly set. This won't happen with Clark's device (which if it should fail, has the BMS as final protection as you note). You don't even need a lithium profile on your chargers. Conceptually, Clark's device is relocating the lithium settings from each charging source - alternator, solar controller, shore power - and consolidating the protection into his unit right before the lithium battery bank.

Always-on, constant charging / topping up of your LFP is detrimental to long life. Yes, I'd prioritize the Tesla study above your opinion. But as I'm pointing out, the benefit is derived in out-years. How far out? No one knows. Car manufacturers are obviously interested in a battery that lasts the life of the car. Clark's device allows an additional layer of logic, preventing a new charge cycle until a chosen level of discharge has been achieved. Existing charge controllers don't do this - if there's power to charge, they'll initiate a charge cycle.

The principal argument behind Clark's device is that due to LFP's flat voltage profile and its sensitivity to overcharge, the optimal way to know when to stop charging is done by measuring the current taper. Components that charge until a certain voltage is reached don't do this. The current practice when charging to voltage is to stop early, just to be safe. That your charging source has the option to set custom profiles / voltage parameters is recommended - pay more for the better components; shore power, solar, and alternator. Or use Clark's device.

Current practice is to segregate the banks. In this, if you draw down your lead acid, it will take lead acid times to recharge. If you parallel the banks, the LFP keeps the lead acid topped up. I'm not sure where "starter" lithium batteries now stand - it was held they were a mismatch for purpose. Starting from lithium meant having a large lithium bank.

Anyway, I'm not really interested in arguing. These are the proposed benefits. There's good theory and research to say yes. There is a caveat that the return is measured in decades. And if you simply replace all components with new top shelf hardware and install a larger lithium bank, maybe it's not worth it. But if people are asking about costs, that statement itself is a contradiction.

The NEGATIVES of Clark's system are-

*Your alternator most likely needs external regulation, unless it's very small.

Lead acid suffers from shorted cells, which might go unnoticed if paralleled with LFP.

It may get flagged by a surveyor. Interestingly, Clark was recently asked to submit an ISO proposal to develop a standard.
 
Stewart said:
I would point out that Clark's relay switch that measures current prior to the BMS is probably safer than relying on just the BMS, which should be understood as a protection of last resort.

The Nordkyn Design site best makes the case ("Charging Marine Lithium Battery Banks", direct link posted above) that the ideas behind Clarks device are worthwhile, which is to say your assertion that the standard practice of charging to voltage is less than optimal. You linked to their VRC-200 device - maybe you don't realize that contradiction?
Click to expand...
No, I did not. Someone else in this thread did. I pointed out a problem with it.

Stewart said:
The issue is you're ahead of your skiis when you declare it nonsense. You're also not answering the guy's question. The standard isn't a mass failure of all LFP batteries installed. It's as I pointed out - how far out does one go to appreciate the benefits derived.

The benefits of Clarks device are-

You can add LFP without changing any of your existing charge components.* People can say hogwash, just replace everything when you migrate to lithium! But they're talking past the point some may care about.
Click to expand...
You don't change any existing components, but you are adding some.

Stewart said:
Yes, you can damage your LFP battery with existing chargers if incorrectly set. This won't happen with Clark's device (which if it should fail, has the BMS as final protection as you note). You don't even need a lithium profile on your chargers. Conceptually, Clark's device is relocating the lithium settings from each charging source - alternator, solar controller, shore power - and consolidating the protection into his unit right before the lithium battery bank.

Always-on, constant charging / topping up of your LFP is detrimental to long life. Yes, I'd prioritize the Tesla study above your opinion. But as I'm pointing out, the benefit is derived in out-years. How far out? No one knows. Car manufacturers are obviously interested in a battery that lasts the life of the car. Clark's device allows an additional layer of logic, preventing a new charge cycle until a chosen level of discharge has been achieved. Existing charge controllers don't do this - if there's power to charge, they'll initiate a charge cycle.

The principal argument behind Clark's device is that due to LFP's flat voltage profile and its sensitivity to overcharge, the optimal way to know when to stop charging is done by measuring the current taper. Components that charge until a certain voltage is reached don't do this. The current practice when charging to voltage is to stop early, just to be safe. That your charging source has the option to set custom profiles / voltage parameters is recommended - pay more for the better components; shore power, solar, and alternator. Or use Clark's device.
Click to expand...

Ideally, you would stop charging LFP before the current begins to taper. There is almost no additional capacity between 3.5vpc and 3.65vpc. But, at 3.5vpc, the taper isn't visible unless you are charging with a huge charge source. With normal charge rates for a boat, under say 100A, an LFP will still take all of it at 14V. The most recommended charge voltage now is 13.8V.

Stewart said:
Current practice is to segregate the banks. In this, if you draw down your lead acid, it will take lead acid times to recharge. If you parallel the banks, the LFP keeps the lead acid topped up. I'm not sure where "starter" lithium batteries now stand - it was held they were a mismatch for purpose. Starting from lithium meant having a large lithium bank.
Click to expand...
A lead acid start battery won't ever be drawn down enough to take more than a couple minutes to fully charge. LFP *are* used for starter batteries. The only obstacle is that FET based BMS's often aren't up to the task, but several drop in manufacturers make LFP start batteries with BMSs that are designed for it. And there are a number of people, including one on this forum, that have given up a separate start battery altogether and only have a single LFP battery. I am going that direction soon. When my current FLA start battery fails, I will be reconfiguring to do that.

Stewart said:
Anyway, I'm not really interested in arguing. These are the proposed benefits. There's good theory and research to say yes. There is a caveat that the return is measured in decades. And if you simply replace all components with new top shelf hardware and install a larger lithium bank, maybe it's not worth it. But if people are asking about costs, that statement itself is a contradiction.

The NEGATIVES of Clark's system are-

*Your alternator most likely needs external regulation, unless it's very small.

Lead acid suffers from shorted cells, which might go unnoticed if paralleled with LFP.

It may get flagged by a surveyor. Interestingly, Clark was recently asked to submit an ISO proposal to develop a standard.
Click to expand...

I have watched Clark's videos and explanations for a few years now, and had this conversation with many people, and also followed other experts that actually are experts. I am also years into my conversion and did a whole lot of research for it. Importantly, I am not saying it doesn't work. But there isn't a problem that it is solving. It will perform exactly as well as a basic installation. No better. No worse. It has been proven that stopping charging by voltage works for more than15 years, and the battery still tests fine and has plenty of life left. So, what is the problem with doing that?

Yes, constantly "topping off" is detrimental. And there *are* chargers that won't do that. Some Victron chargers will fall into a "storage mode" and not charge the LFP beyond 13.5 volts until you allow it to. More common chargers will fall into "float" (which with LFP isn't actually float the term is a holdover) and drop to 13.5 volts until the next charge cycle. And importantly, charging to 100% is NOT detrimental, what is detrimental is HOLDING full charge. It is perfectly ok to fully charge and immediately start a discharge cycle. Lots of chargers do that. And even then, the damage is temperature dependent, and if the batteries are in the cabin and not the engine area, the damage is minimal. There is lots of test data showing that temperature is the bigger problem than charging to 100%. Not to mention the fact that LFP doesn't ever need to be fully charged, so you can just ignore it and never let it get there, until you think you might need it and force it to.

The real issue with Clark's system is that conversations like this scare people away thinking LFP is complicated and that it hasn't been figured out yet. KISS, and an LFP battery will last 20 years. Don't complicate it. A very simple system with drop-ins is 100x better than lead-acid, and no more expensive with recent price drops.
 
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