Progress with Lithium Battery Installation

[alanfw]

I've successfully wired in my new Lithium battery as house battery, keeping the remaining good lead battery as a dedicated start battery. Still trying to get my head around charging process to maximise life of the battery.
My boat has a Statpower Truecharge 20 (isolated) with two positive outputs. Up until now, I left the boat plugged in to shore power to keep the batteries charged and to run the fridge. There is also solar (supposedly 200W, but I'm lucky to get 120W). I now have the Statpower Truecharge connected only to the start battery, but I'm worried that the solar might not supply enough current to stop the lithium battery going flat (and I'm also thinking daily discharge/charge will reduce the lifetime of the lithium battery).
I'm now thinking I could use the second Statpower outlet to keep the lithium battery charged and run the fridge without drawing on the battery - it has several settings that appear similar to recommended settings for conservative charging of the lithium battery. (Specifically I was thinking of the 14/13.1 bulk/float settings - see attached photo).
Any thoughts?
As an afterthought, I have the two batteries isolated from each other - the house circuits do not appear to be earthed to the engine. To charge both batteries I would need to have a common negative. Are there any pros or cons in keeping the two batteries isolated?

 

[mckenzie.keith]

Seems OK. Maybe 13.8 / 13.4 would be OK, too (hot gel setting). But probably 14 / 13.1 is the best choice. The 13.1 float voltage might not be enough to keep it fully charged is my only reservation. But then again at times the solar will be topping it off, so it will probably all work out. Do you happen to know how long the absorption stage is? Also you should make sure it doesn't do equalization as that could ruin your LFP battery.

 

[alanfw]

Fortunately equalisation must be manually implemented (by inserting something like a pen point into a hole - like a reset on some electronic devices).
I was hoping to avoid 100% charging in order to maintain life, so I have conservative settings on my solar controller. I was thinking of trying to match the settings on both so solar is only functioning when off mains power.

 

[b393capt]

Nothing is simple when it comes to Lithium and/or working with electrical systems with multiple battery technologies.

When I see a question like this, I think deck chairs and the Titanic.

I provide this link below of vital advice for you to consider about your Lithium install. If you have the skills to understand it, and address all the problems you may have fallen into as outlined in it, then and only then focus on the Victron ARGOFET, or DC to DC chargers, each included in the article as potential components of your solution.

Drop-In LiFePo4- Be an Educated Consumer

Lead is Dead (almost) Warning: This article is long and detailed. It may require two reads so the nuances and detail are not missed. You may be wondering why I am saying lead is dead ?The answer to that is simple; lead acid battery makers dug their own graves

marinehowto.com

Of course, the best time to read this well-written article, is before purchasing Lithium. Laying out the various upgrades in a crowded battery compartment is easier when done once.

 

[deminimis]

I'm running a SOK 206AH 12v with a separate LA for the starter (for now). SOK parameters are as follows:
Charge Current (Per battery): 40a Preferred (50a Maximum)
Absorption Voltage: 14.6v preferred (14.4 Minimum)
Float Voltage: 13.8v preferred (13.6 Minimum)
Equalization: DISABLED
Low Voltage Disconnect (LVD): 11v

I use Victron solar controllers (very tweakable) and a Victron 30amp shore charger (IP22 -Not very tweakable). The relevant IP22 specs are below
Charge voltage 'absorption' Li-ion: 14,2 V
Charge voltage 'float' Li-ion: 13,5 V
Charge voltage 'storage' Li-ion: 13,5 V

I my solar has no problem keeping things on the up and up. Regardless, I still have the IP22 to use as needed. Although the IP22 does not 100% jive with SOK's parameters, it has worked flawlessly thus far. I'd rec (if you are asking) you toss your charger for the Victron as it's not a ton of money and it seems more on-point than what you have.

 

[221J]

You might want a switch for solar charging that toggles between the starting battery and the house battery. When the boat is idle, charge the starting battery and when there are significant loads (like instruments, autopilot) you switch to house charge. I'm thinking the switch gets toggled once or twice a week.

 

[caius]

I disagree that lithium batteries are not simple if talking about Lifepo4 ones which are quite easy to handle. They are just a bit different to lead acid and need to be treated as such, but there’s nothing particularly difficult about it. Problems arise when people don’t take account of the differences and assume they work the same as lead acid batteries, and because of the large amount of energy involved those problems can sometimes be dramatic. More exotic lithium chemistries have to be treated with a lot more caution however and I’d question their use on a boat.

Most of the settings on that charger will work ok for a Lifepo4 battery, with the exception of the 14.8v/13.9v one which is too high on both voltages and the 14.6v/14.2v one which has too high float voltage. You don’t want to charge above 3.65v per cell or 14.6v for the battery. The BMS should cut off charging above this anyway, but it’s not a good idea to rely on that.

Personally I’d use the 14.4v bulk/13.5V float setting, because that will give a 100% charge in bulk with the float voltage sitting just under the typical 13.6v fully charged resting voltage. Lifepo4 batteries don’t really need a float charge as they have minimal self discharge, but if you will be on board using power it will maintain the battery state of charge while connected. If you use a lower float voltage, any power usage will come from the battery not the charger.

In my opinion people overthink the charging cycles thing. You can use a more conservative bulk charge voltage and still get the majority of usable capacity out of them, but I’m not sure it makes a lot of difference in practice. You might get more charge cycles in the long term, but is it actually an issue? If you get 3500 cycles by charging normally that’s nearly 10 years of use if you fully cycle the battery every single day continuously. Are you going to be using them that intensely that the extra cycles are important? I suspect the battery is likely to die of old age before it runs out of cycles.

I don’t think it’s a good idea to use the same charger to charge both types of battery simultaneously however, unless it has properly isolated and independent outputs. Mixing chemistries would seem to me to be inviting problems. I would suggest it would be a better idea to have your mains charger supplying a single battery and then use a DC-DC charger to charge the other one.

On our boat we have the alternator and mains charger going to the starter battery, and a DC-DC charger feeding the lithium battery. That means that the lithium battery can have its own charge profile set, and it also protects the alternator from continuous large charging currents and sudden disconnections.

 

[mckenzie.keith]

I disagree that lithium batteries are not simple if talking about Lifepo4 ones which are quite easy to handle. They are just a bit different to lead acid and need to be treated as such, but there’s nothing particularly difficult about it. Problems arise when people don’t take account of the differences and assume they work the same as lead acid batteries, and because of the large amount of energy involved those problems can sometimes be dramatic. More exotic lithium chemistries have to be treated with a lot more caution however and I’d question their use on a boat.

Most of the settings on that charger will work ok for a Lifepo4 battery, with the exception of the 14.8v/13.9v one which is too high on both voltages and the 14.6v/14.2v one which has too high float voltage. You don’t want to charge above 3.65v per cell or 14.6v for the battery. The BMS should cut off charging above this anyway, but it’s not a good idea to rely on that.

Personally I’d use the 14.4v bulk/13.5V float setting, because that will give a 100% charge in bulk with the float voltage sitting just under the typical 13.6v fully charged resting voltage. Lifepo4 batteries don’t really need a float charge as they have minimal self discharge, but if you will be on board using power it will maintain the battery state of charge while connected. If you use a lower float voltage, any power usage will come from the battery not the charger.

In my opinion people overthink the charging cycles thing. You can use a more conservative bulk charge voltage and still get the majority of usable capacity out of them, but I’m not sure it makes a lot of difference in practice. You might get more charge cycles in the long term, but is it actually an issue? If you get 3500 cycles by charging normally that’s nearly 10 years of use if you fully cycle the battery every single day continuously. Are you going to be using them that intensely that the extra cycles are important? I suspect the battery is likely to die of old age before it runs out of cycles.

I don’t think it’s a good idea to use the same charger to charge both types of battery simultaneously however, unless it has properly isolated and independent outputs. Mixing chemistries would seem to me to be inviting problems. I would suggest it would be a better idea to have your mains charger supplying a single battery and then use a DC-DC charger to charge the other one.

On our boat we have the alternator and mains charger going to the starter battery, and a DC-DC charger feeding the lithium battery. That means that the lithium battery can have its own charge profile set, and it also protects the alternator from continuous large charging currents and sudden disconnections.

OP is using a charger with dual outputs that are isolated from each other. I agree with you that you should not put LFP and lead acid together in the same battery bank. Lead acid chargers often have a lengthy absorption phase.

I am not sure it would be a good idea to hold an LFP battery at 14.4 for a long time. That is 3.6 V per cell. I think for an LFP charger that has a short or programmable absorption duration 3.6 per cell would be fine. But the lead chargers, well, I am not so sure.

 

[caius]

It depends on the operation of the charger. LFP batteries will have a very short absorption phase - they will pull full current until they reach the bulk charging voltage, but it will very quickly drop once it is reached. Most chargers sense the reduced current and switch to float but some fancy multi-stage ones have other equalising and desulfating stages that should be avoided with LFP batteries. As long as it’s a standard CCCV charging profile it should be fine.

I don’t think it’s a problem with OP’s charger as the equalisation is manually initiated and it doesn’t do any desulfating.

I did check the manual for that charger and although it has independent isolated outputs, the voltage regulation is common between them, so having mixed battery types connected to it would not be a good idea. The manual specifically warns against that. The other thing that should be disabled for LFP batteries is temperature compensation, as they don’t need it.

 

[b393capt]

Nothing is simple when it comes to Lithium and/or working with electrical systems with multiple battery technologies.

When I see a question like this, I think deck chairs and the Titanic.

I provide this link below of vital advice for you to consider about your Lithium install. If you have the skills to understand it, and address all the problems you may have fallen into as outlined in it, then and only then focus on the Victron ARGOFET, or DC to DC chargers, each included in the article as potential components of your solution.

Drop-In LiFePo4- Be an Educated Consumer

Lead is Dead (almost) Warning: This article is long and detailed. It may require two reads so the nuances and detail are not missed. You may be wondering why I am saying lead is dead ?The answer to that is simple; lead acid battery makers dug their own graves

marinehowto.com

Of course, the best time to read this well-written article, is before purchasing Lithium. Laying out the various upgrades in a crowded battery compartment is easier when done once.

OP is using a charger with dual outputs that are isolated from each other. I agree with you that you should not put LFP and lead acid together in the same battery bank. Lead acid chargers often have a lengthy absorption phase.

I am not sure it would be a good idea to hold an LFP battery at 14.4 for a long time. That is 3.6 V per cell. I think for an LFP charger that has a short or programmable absorption duration 3.6 per cell would be fine. But the lead chargers, well, I am not so sure.

It is unrefutable, "Nothing is simple when it comes to Lithium and/or working with electrical systems with multiple battery technologies.".

Perhaps you should read the sentence this way "Nothing is simple when it comes to Lithium and/or working with electrical systems with multiple battery technologies.".

Take for example, you wire it so that someone can choose "both" on a battery switch and the power flows to the battery with the lower voltage, did you design for that? Where is the alternator output going? To your starter battery, which will then limit how much charging current is picked up depending on other choices. How about to to your lithium battery to make the most of the available power? Then what if the engine is pulling 1 Amp power from the lead acid starter battery while it is running, but the alternator is sending current only to the Lithium battery? The starter battery will (i) begin to deplete (ii) be discharging more deeply than starter batteries are usually discharged (usually up to 5% for a strict starter battery design). Lets go on some more. If you motor say multiple days on a longer trip, at some point your starter battery will be depleted to much to start the engine. Confused the user will be. Maybe change the battery switch position to "both" connecting a partially charged lithium battery to a depleted starter battery. Perhaps as the current rushes at greater than 200 Amps the lithium protection circuit trips, and the lights go out. You have no power at all to start the engine.

Just saying, the good people at Marine How To have a great article. Best to read it before installing your first Lithium battery, as it is easier to design upgrades to your electrical system once.

 

[mckenzie.keith]

It is unrefutable, "Nothing is simple when it comes to Lithium and/or working with electrical systems with multiple battery technologies.".

Perhaps you should read the sentence this way "Nothing is simple when it comes to Lithium and/or working with electrical systems with multiple battery technologies.".

Take for example, you wire it so that someone can choose "both" on a battery switch and the power flows to the battery with the lower voltage, did you design for that? Where is the alternator output going? To your starter battery, which will then limit how much charging current is picked up depending on other choices. How about to to your lithium battery to make the most of the available power? Then what if the engine is pulling 1 Amp power from the lead acid starter battery while it is running, but the alternator is sending current only to the Lithium battery? The starter battery will (i) begin to deplete (ii) be discharging more deeply than starter batteries are usually discharged (usually up to 5% for a strict starter battery design). Lets go on some more. If you motor say multiple days on a longer trip, at some point your starter battery will be depleted to much to start the engine. Confused the user will be. Maybe change the battery switch position to "both" connecting a partially charged lithium battery to a depleted starter battery. Perhaps as the current rushes at greater than 200 Amps the lithium protection circuit trips, and the lights go out. You have no power at all to start the engine.

Just saying, the good people at Marine How To have a great article. Best to read it before installing your first Lithium battery, as it is easier to design upgrades to your electrical system once.

That article has been shared here on Sailing Anarchy before. I have read it at least twice and am also an electrical engineer. I don't know whether the OP has read it or not, but I agree that the OP SHOULD read it (and should have read it before installing a battery at all). From the OP's first post, I got the impression that the batteries were not connected together at all. There is no way to connect LFP with lead acid that can do anything good (except maybe help start a motor in an emergency, maybe, with a bunch of other caveats too long to go into). So if you want to harangue the OP go ahead. But please don't harangue me. It is not necessary or productive.

 

[eliboat]

That article has been shared here on Sailing Anarchy before. I have read it at least twice and am also an electrical engineer. I don't know whether the OP has read it or not, but I agree that the OP SHOULD read it (and should have read it before installing a battery at all). From the OP's first post, I got the impression that the batteries were not connected together at all. There is no way to connect LFP with lead acid that can do anything good (except maybe help start a motor in an emergency, maybe, with a bunch of other caveats too long to go into). So if you want to harangue the OP go ahead. But please don't harangue me. It is not necessary or productive.

The guy from Emily and Clark’s adventure YouTube channel…. Clark I guess, is big on connecting the two chemistries. If I remember correctly, and it’s quite possible that I don’t , his reasoning has to do with the LA protecting the lithium as it gets low during the night. When the lithium is then getting charged during the day, it can comfortably charge the LA bank. It sort of makes sense, but his whole position comes from a strange place to begin with because he had a large LA bank that he didn’t want to get rid of, but he wanted lithium batteries, so he kept both. So in addition to all the extra and needless weight and space he didn’t want to add the requisite charging equipment for the lithium, so he came up with his workaround, which worked OK, except he realized at some point that he could never really optimally charge his lithium bank. To solve this he invented something he calls a BBMS that manages this process, which again presumes you want to have to giant battery banks of different chemistries…

 

[mckenzie.keith]

The guy from Emily and Clark’s adventure YouTube channel…. Clark I guess, is big on connecting the two chemistries. If I remember correctly, and it’s quite possible that I don’t , his reasoning has to do with the LA protecting the lithium as it gets low during the night. When the lithium is then getting charged during the day, it can comfortably charge the LA bank. It sort of makes sense, but his whole position comes from a strange place to begin with because he had a large LA bank that he didn’t want to get rid of, but he wanted lithium batteries, so he kept both. So in addition to all the extra and needless weight and space he didn’t want to add the requisite charging equipment for the lithium, so he came up with his workaround, which worked OK, except he realized at some point that he could never really optimally charge his lithium bank. To solve this he invented something he calls a BBMS that manages this process, which again presumes you want to have to giant battery banks of different chemistries…

Interesting take. That is not a channel I follow. I may (or may not) check it out.

 

[b393capt]

Interesting take. That is not a channel I follow. I may (or may not) check it out.

I am big on multiple chemistries as well, such as an isolated starter battery.

It just gets complicated when you decide you want to also insure your lead acid batteries get the right charge profile, and that the system can be reconfigured reasonably should you not be on the boat at the time a battery misbehaves or is discharged. Managing charge profiles, getting the most out of your charging sources to your advanced battery, protecting your overall boat electronics and alternator from being damaged, and doing all of the above while meeting the ABYC standards is moderately difficult DIY stuff. Rod Collins spotted a subtle ABYC requirement I missed while getting too cute getting everything to fit in a small space, in one of my designs meeting the needs of my Odyssey TPPL lead acid house batteries to have a slightly different charging voltage than the existing lead acid starting battery.

Then I see these designs where people stick lead acid batteries into circuits with lithium batteries in them, with no attention paid to using t-fuses or meeting the charging profiles of the lead acid battery, and/or intentionally sacrificing the life of a small lead acid battery to protect boat electronics if the lithium battery disconnects, and just have to wonder why people say there is no fire hazard. Sure, no fire hazard from the lithium battery self-destructing, but perhaps some more thought is needed to make the boat just as safe as having all lead acid batteries.

After all, if a hundred boats hap hazardlly combine battery chemistries, there is going to be at least one case a year of disappointment between them, be it a lost investment in the lithium battery, a fried alternator, a stranded boat, or something else. If a million boats do so, there will be at least one fire no doubt.

 

[caius]

I don't see the benefit of mixing battery chemistries. The reasons that guy gives seem largely centred around making use of his existing lead acid batteries, and in doing so he is complicating the system unnecessarily.

Having them in parallel means that the lead acid batteries are always pulling the voltage of the LFP batteries down, and effectively receiving a continuous float charge from them. He said in his video about it that he wants to avoid things like the LFP BMS shutting off suddenly and leaving with no power available. In practice there is minimal reason for that to occur - the reasons he gives such as a cell going wildly out of balance should not happen during ordinary use assuming the battery was properly balanced and set up initially. If that does happen it's usually for a reason and you want it to happen to protect the battery. The low voltage cut off is also not something that people should be running in to regularly if they have properly sized the battery for its intended use. There are BMS which can give advance warning of impending shut down if that is desirable, and decent a decent BMS should be able to disable charge and discharge seperately.

The space and weight taken up by the lead acid batteries could contain additional LFP batteries with at least twice the usable capacity and probably more, with all the advantages of extra cycle life and longevity over lead acid. The arguments about alternator protection also don't make a lot of sense - the simple way to resolve that is use a DC-DC charger which will regulate the charging current to something suitable and provide a proper charging profile for the LFP cells. Lead acid does work well for starting batteries and running loads with large inrush currents such as thruster motors, but the capacity and charging speed isn't usually an issue for those types of loads.

He says that existing chargers aren't really any good for LFP, but they don't require anything particularly complicated, just a CC-CV charge profile with customisable voltages. There are plenty available on the market that can do the job even if they weren't originally designed with LFP batteries in mind.

It all seems a bit of a Heath Robinson way to get a system that isn't as effective as one that's designed from scratch to use one battery chemistry. I can see the logic of wanting to make use of existing batteries, but surely it would be more sensible to just wait until they need replacing then do the job properly. I'm not really sure what advantage having a hybrid bank is supposed to provide.

 

[alanfw]

Thankyou everyone for the interesting input. I've now got everything connected and working as I want it to. The original mains charger is connected solely to the starter battery and a Victron Orion dc-dc charger connected from starter to house battery. The Orion is set up to only operate when the engine is running or the charger is on.

I may be over obsessive about charge limits, but I understand LiFePO4 batteries don't like sitting at 100% for extended periods. I've tweaked the solar controller and Orion so they will maintain the battery at about 85% (by setting the Orion up in "Power Supply" mode with voltage matching float voltage of the solar controller). This way, any loads will be supplied by either solar or shore power while the boat is in the marina. When I'm going out I can switch the DC-DC to charger mode to boost the house battery if necessary. (The Orion has an "engine detection" function that can be tweaked very effectively, and an input voltage cut-out that I've set high enough so the start battery won't be drawn below 80 or 90% even if engine detection fails to switch off the Orion)

 

[alanfw]

Nothing is simple when it comes to Lithium and/or working with electrical systems with multiple battery technologies.

When I see a question like this, I think deck chairs and the Titanic.

I provide this link below of vital advice for you to consider about your Lithium install. If you have the skills to understand it, and address all the problems you may have fallen into as outlined in it, then and only then focus on the Victron ARGOFET, or DC to DC chargers, each included in the article as potential components of your solution.

Drop-In LiFePo4- Be an Educated Consumer

Lead is Dead (almost) Warning: This article is long and detailed. It may require two reads so the nuances and detail are not missed. You may be wondering why I am saying lead is dead ?The answer to that is simple; lead acid battery makers dug their own graves

marinehowto.com

Of course, the best time to read this well-written article, is before purchasing Lithium. Laying out the various upgrades in a crowded battery compartment is easier when done once.

Thankyou for that link. Interesting reading! Fortunately I have everything pretty well covered - I'm no professional engineer, but have a good background in physics, electronics, maths and chemistry that makes it pretty easy to read, comprehend and apply this stuff. Still, there are many things I've learnt in this process!

 

[CapDave]

The guy from Emily and Clark’s adventure YouTube channel…. Clark I guess, is big on connecting the two chemistries. If I remember correctly, and it’s quite possible that I don’t , his reasoning has to do with the LA protecting the lithium as it gets low during the night. When the lithium is then getting charged during the day, it can comfortably charge the LA bank. It sort of makes sense, but his whole position comes from a strange place to begin with because he had a large LA bank that he didn’t want to get rid of, but he wanted lithium batteries, so he kept both. So in addition to all the extra and needless weight and space he didn’t want to add the requisite charging equipment for the lithium, so he came up with his workaround, which worked OK, except he realized at some point that he could never really optimally charge his lithium bank. To solve this he invented something he calls a BBMS that manages this process, which again presumes you want to have to giant battery banks of different chemistries…

That's not even wrong.....

 

[jbchrist]

- Retaining a lead battery on the boat is good economy, as all old charging sources (solar, alternator, ...) do not need to be changed.
- Battery chemistry must NEVER be mixes/connected. All power generated (cf. above) should passe through a DC-DC device (and there are many other brands than Victron, not least Sterling-Power who have devices which handle 60A).
- A fully charged LiFePo4 battery has an output potential of 13,2V. So, charging can take place at all voltages between 13,2 and 14,6V. The latter is too close to harmful levels, so never go above 14,4V. The difference between charging with the low voltage and the high voltage is the time it takes to reach full charge (you can squeeze the coulombs faster into the battery when you apply a higher force = higher voltage).

Sorry if above repeat some points stated before in this thread.

 

[CapDave]

- Retaining a lead battery on the boat is good economy, as all old charging sources (solar, alternator, ...) do not need to be changed.
- Battery chemistry must NEVER be mixes/connected. All power generated (cf. above) should passe through a DC-DC device (and there are many other brands than Victron, not least Sterling-Power who have devices which handle 60A).
- A fully charged LiFePo4 battery has an output potential of 13,2V. So, charging can take place at all voltages between 13,2 and 14,6V. The latter is too close to harmful levels, so never go above 14,4V. The difference between charging with the low voltage and the high voltage is the time it takes to reach full charge (you can squeeze the coulombs faster into the battery when you apply a higher force = higher voltage).

Sorry if above repeat some points stated before in this thread.

This might make sense on smaller systems, but not on bigger systems. My boat is 24V, and I have two 140A alternators. That's ~8kW at the top of the voltage range. It would not make sense to retain a PbA interface battery and use a DC-DC charger for me.

In fact I would argue that many people making the lithium upgrade are looking at also adding and/or powering by inverter high power consumers such that the DC-DC route doesn't make much sense - once you're over ~1kW loads it's impractical.

I'm just planning a lithium upgrade to start March 1. I'm going to buy a pair of Lithionics 315A@24V batteries with their external BMS with the dual channel option. I like the dual channel because it manages the charge and discharge sides separately. A disconnect fault on the charge side (most likely problem) doesn't affect the load side so you don't have a dark ship. This device also has a field control circuit which shuts off the alternators and any other charge sources if there's a charge side disconnect - critical item. It also has a pre-charge circuit so you don't melt anything with inrush current when connecting my twin 5kW inverters. I'm also going to switch from Balmar to American Power System Wakespeed regulators for the two 140A alternators, much smarter and data-integrated with the BMS. Aside from that my Xantrex solar charge controllers can be set to the correct voltages, and my 400W wind turbine can also. My 2009 vintage Victron Skylla TG-100 Universal shorepower charger will have to be replaced with the new version as the old one can't be adjusted for the correct voltages.

It's going to be a pretty big project, but I'm looking forward to losing 200 lbs, and no longer being the bitch of my PbA batteries.....