Lithium Cells in Float Charge. Will it destroy your battery?

Can you float charge lithium batteries? Should you float charge lithium batteries? What are the best settings for your charge controllers? Will float charge destroy your cells?
I played around with a lot of solar charge controllers trying to understand and find the best absorption and float charge settings. It can be very confusing and it's a bit hard to fit this all in one video. Please let me know if you want to see more details about a specific setting and how this works out in reality. I will break this down and make a separate video about that then...
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[@John-xu3jk]

wow .... literally years of being confused and 20+ minutes clears all the fog !!! Thank you

[@junkerzn7312]

Just a side note, once you've charged a LiFePO4 (and I think other lithium types too) up, say up to 13.8V or 14.0V and then stop applying voltage, the battery voltage will actually drop down to around 13.6V fairly quickly (well, probably closer to 13.55V). It remains fully-charged, that's the just the natural stable voltage for 4 x fully charged cells. So don't be surprised if you charge the battery up higher that you see it drift back down to that voltage. It just doesn't take a whole lot of current for the voltage to almost instantly drop back to around 13.55V. It can happen fairly quickly (depending on the BMS's vampire draw) even if no load is attached. So, for absolutely definitely sure, never set the float voltage above around 13.55V... that will cause the charge controller to apply a little current quite often due to the battery wanting to return to its stable voltage... and that is bad for the battery. And, of course, as the battery ages, even 13.55V will cause a constant current. Hence you probably shouldn't set the float above 13.4V or so regardless... and lower values are even safer. Up to a point. Remember to use the discharge curve, NOT the charging curve, to figure out what float settings you want. This means that, in fact, if you charge the battery up to 100% and start discharging it with the float set to 13.4V, the battery will still remain at least 90% charged as the charge controller starts matching amps below 13.4V against the load. However, if you discharge the battery sufficiently and the charge controller does not go back into BULK mode, then the battery's charge level will probably sit at just below 90%. So, to figure out the worst case charge level for the battery, you want to look at the discharge curve and at the voltage point where the charge controller switches back into BULK charging mode. So lets say float is set to 13.20V and the charge controller flips back into BULK mode at 13.10V. Thus, 13.10V on the discharge curve is the worst case charge state that the battery will ever be left in... lets call it 50%. Definitely NOT ideal. -- This creates a conundrum. If you set the float TOO low, the worst case state of charge that the charge controller might leave the battery in will be too low. Things can get iffy below 13.2V, so my recommendation is that the float be set at roughly 13.4V in order to ensure that the charge controller goes into bulk at a reasonable voltage (say, 13.3V, depending on the charge controller). This way if the voltage only drops to 13.31V and the charge controller stays in FLOAT, the battery will still be at around an 80% state of charge. You can safely set the FLOAT voltage to anything under 13.55V for a new battery, but to deal with battery aging you should consider not setting it higher than 13.45V or so. If you want to be conservative, then use 13.3V or 13.35V. I would not recommend 13.2V for the float because that means the battery could be seriously discharged before the charge-controller decides to go back into BULK mode. The state of charge drops precipitously enough below 13.3V that you just can't depend on setting the float below that voltage. This is why the Victron's Float is set at 13.30V. Its a good conservative value that will deal with battery aging but isn't too low to cause the battery to be left in too-low a state of charge when it could be charging. Now Bulk and Absorption are a different matter. In order to charge the battery, voltages in excess of 13.6V are required. 14.0V is a typical target voltage for BULK. Absorption is basically irrelevant... so set the voltage to something inbetween Float and Bulk Target and then set the absorption time to 0. HOWEVER, on some (most?) Victrons, the Absorption *IS* the bulk target voltage. Therefore, you should set Absorption to 14.0V (for roughly 80% charge) and set the absorption time to 0. If the Bulk target (or Absorption, depending) on the Victron is set too low, and the battery is being charged up from a low state of charge, it will probably never reach even 50% charge before the charge controller decides it is done. Once LiFePO4 reaches the target voltage during charging (Bulk target of 14.0V or so for 80% charge), the charge is done. The battery will remain at 80% charge even as its voltage slowly drops back down to 13.55V, and the percent-charged during discharge will head south from there on down. When you are discharging the battery, you should refer to the discharging voltage curve and not the charging voltage curve. This target voltage is really what you are comfortable with. Most people use 14.0-14.2V. Use 14.6V only if you want to actually charge the battery to 100% (most people do not as this reduces the life of the battery). This is my understanding. -Matt

[@OffGridGarageAustralia]

Thanks so much Matt. These are the comments we need with good, easy to understand explanations and examples. Great. I have planned to set the absorption to around 3.35V-3.37V and the floating just a tiny bit lower. As there will be more batteries following in the future, I'm not planning to charge them to 100% on a regular base. Maybe once in a while to do a test or so but I try to keep them between 85-90%. The same at the bottom, going below 3.1V is almost pointless, there is almost no capacity left und voltage will decrease very quickly under 3V anyway.

[@junkerzn7312]

​@@OffGridGarageAustralia Yup. Maybe even slightly higher. The exact setting will depend on the device's voltage measurement error. This might be why identical settings in the two charge controllers you tested yielded different results. The voltage sensors used by charge controllers, BMSs, etc, particularly cheap ones, typically have around a +/- 1% error factor. So the settings on one charge controller verses another may not manage the battery to the same exact targets. 1% is massive. e.g. at 13.0V the error is +/- 0.13V. Very significant. Higher quality equipment might cut that error in half, and if really done properly the equipment will be factory-calibrated and the firmware will temperature-compensate readings to get the voltage sense error below 0.3%. The balance lead voltage sensors are usually a bit more accurate but even so we're still talking 0.5% or so (0.016V @ 3.35V). On a cheap BMS even these are probably only 1% accurate. They can still balance the cells because the same inaccurate circuit is typically round-robined across each pair of balance leads, so the error winds up being the same for each pair. But in terms of relying on absolute voltage readings, you need to take some care when dialing in settings. How to get a more exact voltage reading? Difficult. A typical Multi-meter is usually calibrated to 3.5 digits or so... roughly 0.5% accuracy. Getting higher accuracy gets expensive real quick. -- Hence why it is a good idea to do a real capacity test with your charge controller settings to make sure its doing what you want it to do. These are longer tests (I'm specifying for LiFePO4). (1) Discharge the battery to 50% or lower, charge it up with the charge controller, then do a full discharge capacity test to the low voltage cut-off. Record the resulting Wh. (2) Charge the battery up with the charge controller, then apply a current-limited 14.6V to the battery with a power supply (limit current to 0.5C) and watch it like a hawk until the current begins to drop off to see how much more the battery could have taken. Record the resulting Wh that was additionally charged. And from those two results you will know what the charge controller is actually charging the battery too. -Matt

[@junkerzn7312]

@@OffGridGarageAustralia One other thing to keep in mind is that there is a voltage barrier somewhere in the 3.35 to 3.40V range. If you are below the barrier, the battery will basically not charge much at all, as you noted in your reply. More importantly, if you are above the barrier for long enough, even slightly, the battery will eventually get to around 90% charge without further intervention (albeit with ever-dropping current). The key word is 'eventually'. If you set your charge target too low and the charge controller then cuts off the voltage the instant it hits that target you could easily end up with a battery that is only 20% charged. -- This is perfectly fine for a 'Float' voltage set below this value, e.g. to 3.3V for example (remember, the discharge curve is very different from the charge curve!). But it is NOT fine for a Bulk or Absorb voltage set below around 13.8V (3.45V per cell or so). Anything below a Bulk/Absorb of 13.8V (3.45V per cell) or so is going to give you inconsistent results with a charge controller. Your Bulk/Asborb really needs to be at least 13.8V to get any sort of consistent charge percentage on the battery. The reason is as stated above... its because you aren't holding the voltage there. The charge controller is immediately dropping the voltage once it hits that target. You can dial-in your Bulk/Absorp voltage. Between 13.8V (unknown but usually at least 50% charged) and 14.6V (95%+). 13.8V (3.45V/cell) - usually at least 50% but wiggles around a lot. (charge to target voltage and then stop). 14.0V (3.5V/cell) - usually around 70% charged. (charge to target voltage and then stop). 14.2V (3.55V/cell) - usually around 80% charged. (charge to target voltage and then stop). 14.4V (3.6V/cell) - usually around 90% charged. (charge to target voltage and then stop). To get to 100% charge requires holding a charging-level of voltage (typically 13.6V or higher) for a period of time before ending the charge. The battery will continue to charge up to 100% or close to it. Faster with higher voltages, slower with lower voltages. Basically until the Cell stops accepting current (goes below 0.1C in current draw). With a charge controller this can be accomplished by setting the Absorption time to some value larger than 0. Of course, most people do not want to charge a lithium battery to 100%. (And again for other readers, never set the Float voltage that the charge controller drops to above the cell's nominal voltage of 13.55V or so or you will over-charge the battery. 13.3V is still an excellent setting for Float). This is also why, when testing, you have to start with the cell fairly significantly discharged... discharge it 50% or more. If you do not discharge the battery prior to testing, your will get a false result from your charge controller bulk charge test. -Matt

[@OffGridGarageAustralia]

Matt, you're saying: "Anything below a Bulk/Absorb of 13.8V (3.45V per cell) or so is going to give you inconsistent results with a charge controller." But if I charge to say 3.4V only and have a long absorption time, this result should be fairly accurate and repeatable. I can set the Absorption time as well as a Tail Current in the Victron to end Absorption and switch to Float. So if either the Absorption time runs out OR the current goes under the Tail Current threshold the controller switches to Float. I've done this before and could observer that it won't take longer than ~1h (if the sun is out) to drop the current from 20A to under 1A at 3.4V CC charging. That would mean the cells have fully absorpt at this voltage of 3.4V. And I should be able to get back to this exact point with the next cycle.

[@junkerzn7312]

@@OffGridGarageAustralia At lower target voltages, the current drops off very quickly, even before the battery gets much above 50%. At 3.40V you could easily see the current drop off to close to zero with the battery only 50-70% full (its a very wide range). If you trickle-charged it forever at 3.40V the battery would eventually get up to probably around 90% full, but the problem is that the time required is completely indeterminate. So the issue with using 3.40V for you is that you could wind up leaving quite a bit of your solar array's power sitting on the table unused due to the current drop-off. Now the question is... how much? And the answer is I don't know because your charge-rate is already really low so you might actually be putting most of the array's power into the battery through a good chunk of the current drop-off. I just don't know the answer with regards to how much solar power you wind up wasting during the current drop-off period. You will need to determine just how much the state-of-charge shifts around with target settings that low. My expectation is that even with the low charge rate, 3.40V/cell target could result in a battery bank that shifts around between 50% and 75% of full at the point the charge controller thinks it is done, depending on starting conditions. I think you would probably get more deterministic results with a 3.45V/cell target. At least I, personally, would not use a target lower than that even if I were trickle-charging at an ultra-low C-rate. The other issue still remains as well... small differences between cells will get magnified around 3.40V due to the voltage/current curve around that voltage, resulting in more out-of-balance cells. Another reason to have your charging target be at least 3.45V. -Matt

[@dennisbosworth3665]

I am glad I found you, here on KZbin. I just am in the process of switching my solar system from lead acid to lithium and I am finding the charging algorithms to be completely confusing - that is, until I found your channel. Now, things are starting to make sense! Thank you for sharing your knowledge.

[@capecoaster69]

Thank you very much for addressing the setting parameters relative to the chemistry of the battery. That is the fundamental feature that need to be look at first ,before embarking on the charge/discharge of batteries.

[@steve82608]

Another great video. You explained it well. I tend to think of the float voltage as mainly keeping the cells at a pretty high state of charge, and allowing you to run loads off the solar power when you have good sun. As you said, if you use either no-float (my CC does provide a 2-stage with no-float) or a really low float, you are missing out on using the sun when you have it.

[@BeepingMad]

Thank you for posting this, I am running a 24v hybrid system and have set the back to recharge voltage at 25.5v and the float charge at 25.1v. I have learned so much from you. Thank you again for your good work.

[@FloryJohann]

You took years of mysteries away in just a few minutes and showed how it is working.

[@OffGridGarageAustralia]

Thanks a lot for your feedback!

[@bimmerjones3266]

I have found your observations to be spot on, especially for EPEVER charge controllers, which many think are faulty, or don't work with Lithium batteries. Their default settings are way too high for LIFEPO4, and the gap between boost and float create the challenge exactly as you mentioned. Your video was the most informative and educational one I have seen, and rectified what I thought was an issue with my 3 different EPEVER Charge controllers in my off grid setup.

[@OffGridGarageAustralia]

Thanks a lot for sharing and your kind feedback. That is great that you could understand the problem and finally fix it.

[@fishhuntadventure]

I have had a persistent problem across various models of Epever charge controllers. When battery is at a near full charge with FLA batteries or anything above ~13.x Volts on my recent LiFePo batteries the charging suddenly ‘drops out’ to only a couple amps or so. In good sun it will not recover to ‘normal’ charging until the following morning (darkness having occurred overnight) OR if I happen to be home I can turn off the panels, turn them back on, and it immediately tracks mppt and begins charging at 25, 30, 38A or whatever the sun position can muster. This occurs and has occurred on a 3210AN, one older tracer 4210AN and a newer triron 4215AN, a 5415AN, and a 6420AN. This does not occur /has not occurred with my MPP Solar AIO hybrid, nor with my 30A P30L PWM controller. Only the Epevers. I was about to sell everything Epever but I am going to attempt again with 14.2 boost and float and see how it goes. Seems a bit ridiculous that these otherwise excellent mid-shelf products have not been able to work dependably. Others on forums report similar issues so I’m not alone and would love to solve this.

[@ididntknowthatsr6993]

Any update did you fin the problem

[@LaBamba690]

Nice video. Lithium batteries have been around for decades now so there's no excuse for these charge controller companies not to have a lithium battery setting that ELIMINATES all the old lead acid terminology and just uses the correct lithium battery parameters. Then you could simply edit them per your particular lithium battery manufacturer's recommended settings. All this "float", "boost", and "bulk" stuff is useless and misleading.

[@fc436]

no. the terminology is still correct. only the electric physic is important to management of the battery. if you reason by terminology or name of algorithms, then you dond understand the basic of electricity, like ohm laws

[@sethje]

@@fc436 Nope, he is correct. Terms like float do not work with LFP so should be avoided. They only confuse things. If the voltage drops under the treshold then the charging should start.

[@SVAdAstra]

Perfect demonstration. I've been using the same method for 3 years.

[@kingjnr2677]

Hi Andy, wish I had came across your video earlier. I just finished my first campervan power distribution build and found out during testing the cheaper BCDC charges all have the same issue you have explained in your video e.g no float charge. Therefore losing the top part of your battery capacity. Not a major issue but definitely something ill take into consideration for future builds. Thanks for taking the time to explain everything, I will definitely be looking at buying a more expensive BCDC charger for future builds with a float charge / setting as to primarily cover the connected loads when charging power is available.

[@BTKCuk]

Excellent work. There is a lack of correct information in this field so this video was very helpful.

[@bambino3162]

Love the way you explained it.Easy to understand and demonstrate it. Thanks

[@thedebrakuhn]

Wonderful timing on this video! Just received my 200ah LiFePo4 battery on 1/8/21 to replace four 100ah SLAs (moved to old Harbor Freight system for backup backup). Using Epever Tracer 40A CC with 500w of solar panels. Hope that I got CC settings correct because the com port of Epever CC just failed to connect to MT50 or eBox-wifi. Keep up the good work, very educational, enjoy your videos, watch almost every day.

[@donaldsteele6276]

Change the coms port channel for the mt50. That fixed mine .

[@solarute5486]

Good video mate :-) I have run my offgrid LFP bank (nearly 8 years ) in pretty much the same way. There is some research suggesting that the "mini" charges that the "float" setting does detracts from the cycle life more than if you could do one or two top up charges per day. So if the Charge controller, after bulk ("Top Up") charge cycle, could just supply make up current so the battery was not getting discharged - (but at the same time not charging the battery). .Then either at a lower threshold voltage or time (3PM in Brisbane) , the "Top Up" cycle could recommence. This will be the way I'll do it in the next incarnation of my system.

[@AveRage_Joe]

Excellent explanation and visual on a subject that many dont understand.💥🤘

[@jeffbowers950]

Excellent video explaining why float shouldnt or cant be used with lithium. You made it more clear than my battery manufacturer and solar componant supplier, both of whom did ok but not as well as you. Thanks for the effort. Glad to see you escaped from that tiny box.

[@fratermus5502]

> explaining why float shouldnt or cant be used with lithium I'd say it explains that "float" for Pb and Li means different things, and the Vfloat setpoint is used for different purposes.

[@urbanbeeman5402]

I agree wholeheartedly. If anything if you have a minimal load the "float" could keep you topped of at a very low charging rate...... Good job. I've been watching some of your videos for awhile but today you get a subscription.

[@OffGridGarageAustralia]

Thank you very much and welcome aboard!

[@learningpower9437]

Very good explanation mate !!! .... I appreciate your effort ... it takes time and even nature must collaborate in these types of videos !!! Thanks!!! You have a new subscriber!!!

[@philboyer2036]

I have been searching for a good video like this to help me set up my Mid Nite Kid solar controller to charge my LifPo4 batteries. Great explanation of absorb and float. I will follow your advice. This will be used in my solar electric boat I am building.

[@Deiseboi]

I have set my victron controller to 13.40-13.30 as you pointed out...new to the world of solar...so i wont have to doing anything more now and stop worrying???...many thanks for such a simple explanation of how it all works.

[@sharonpointon4929]

Thank you, thank you, thank you. From a women who lives in a caravan and knows nothing about LifePo4 batteries, this has really helped me to understand how they work. Good to know that they don't have to go into float. 😁

[@Marc-vl7wp]

Thank you. Finally LIFEPO4 bulk and float settings make sense because my inverter has no Lithium battery selection but a user defined one instead which still has the Float setting required.

[@Nadeeja94]

You're a life saver Andy. I just finished wiring up my DIY battery pack and solar inverter and was so confused on what to set for bulk and float charge values. There's no absorption option in my inverter and this is exactly what I needed. Its all working smooth as butter now. Thank you so much. Love from SL

[@j.k4825]

Good that you brought that up. Because of your video I took a second look into the way you charge lifepo4 and in the Inverter/battery charger combie I ordered, which is advertised for lifepo4. Turns out they use a IUoU charger which floats the battery constantly and would have ruined the lifepo4 cells over time...

[@dantronics1682]

if the cells are not absorbing any charging current since your battery pack have a bms then how would this ruin the battery?

[@Retired-Not-Expired]

Great review. You've answered some very valid concerns/problems. good work :) For the record I use victron gear, so this will be an easy change in my settings..

[@patrickvanneck]

Thank you for this very comprehensive explanation. It is very helpful in setting the right parameters for my new 16s2P liFePO4 battery bank. Nowhere else I could find such a good explanation.

[@stevefuchs5868]

I have 2 6volt golf carts at 12v and wanted to add 16s lifpo4 in series par 12 volt . so sounds like 12.4 trickle is ok am i getting this right thanks in advance

[@JohnP58]

I wish I had this information before doing my campervan setup. Now it’s done correctly… with your help understanding this news way to go.

[@catch22frubert]

Very happy to see you got a Victron controller for your main battery bank. Its a quality piece of equipment that actually works like it should. Keep those beautiful cells safe, so you get many years of use. Love watching you test all the different electronics and cells. Looking forward to seeing everything set up and also looking forward to the solar gate project. Good luck!

[@OffGridGarageAustralia]

Thanks a lot. It is very exciting for me to test all this equipment and see what works and what does not so much.

[@catch22frubert]

@@OffGridGarageAustralia Testing is also my favorite part of the build. It just so much fun trying different configurations and figuring out the best combination for your needs. It makes for great content as well. Looking forward to the next videos.

[@FloryJohann]

Man...that is very good information. I did not know how that worked with lead acid batteries and I did not not know how to set a simpler charge controller that does not has a lithium setting to the proper bulk and float voltage . Thank you.

[@benediktschluter7313]

Best video I've seen on this topic.

[@mannyfragoza9652]

yes and simple enough for a dummy like me to understand.

[@farmerjhemp]

If you want to shorten the life of your battery follow his advice. Setting the float and absorption so close is foolish. It will cause charge microcycles and shorten the lifespan of the battery. You should really just stick with the preset settings of the victron. When the sun's out I might be getting 800 watts going. My voltage might be showing let's say 27v once a cloud rolls over it immediately drops to 26.5. this proves that the cells aren't really at 27 volts. Their actual voltage is much lower. So if I was having my absorption at 27 volts I might only be utilizing 50% of my potential capacity. I might as well just go buy some lead acid batteries if I'm going to only use 50%. What is this guy trying to leave his cells to his great-grandchildren?

[@mannyfragoza9652]

@@farmerjhemp yeah we will have to wait and see 10- 15 years from now. Im not going to hold my breath lol

[@Sparklift]

Hands down best explanation

[@lebogangmogashoa8817]

I've been struggling for 3 days with charger settings for my lithium battery. Found useless contradictory info all over the internet, until I stumbled on this video. Great advice. Looks like I have now set my charger correctly. Only if I had seen this video sooner

[@gregronan4592]

Same here , longer than 3 days

[@OffGridGarageAustralia]

Thanks a lot for your kind feedback, guys! Much appreciated. I felt the same when I started, reading through endless forums and found information which did not make much sense.

[@williamcarpenter8902]

The inconsistencies are astounding!

[@marktheunitedstatescitezen185]

Another very good teaching ! Thanks for making a point we already know but we do not do well setting up !

[@Springwood_Auto_Elect]

Well done Andy , these setting need to be correct and to be setup for each appreciation to maximise battery SOC selected , as a discharge will always be there as add components (inverters, fridge, online monitors) are consuming power at different times and condition. Cheers

[@OffGridGarageAustralia]

I need to do more testing once the whole system is setup to confirm all this. From what I could experience so far, this seems to work the best.

[@bathfun]

My goodness, I actually understand this now. Thank you. The frog is fast becoming a star!

[@CryptoNut82]

Great video!! I love all my victron products, alittle pricey but they seem to just work and have great software to boot.

[@hedfuka8608]

Thanks Andy... I’m always informed and happy when I watch your videos.. 👍

[@bobby1970]

Great info. It's the exact video I needed to watch. Very important to know this about float voltage. Thanks, man.

[@OffGridGarageAustralia]

No problem! Thank you.

[@peterwalker7869]

G'Day Andy. Just found your channel. Nice to find an 'no nonsense' channel with descent content. I can send you a few frogs to help out with the background chorus. I have plenty here. It started raining here in Townsville Christmas night and we have had some rain every day since, so our frogs are in heaven at the moment.

[@adjrasta9365]

Thanks for taking the time to explain this...very informative 👍

[@thomasreynolds9713]

Finally found a great video explaining float voltage on Lifepo batteries. Thank you.

[@OffGridGarageAustralia]

You are welcome!

[@genxgamerdad141]

Wow, glad YT recommended your video, this cleared up a lot. Recently on a forum where people adamantly said not to float Li batteries. Even a representative from a certain inverter/charger company said Li should not be floated. As a solar newbie, I was confused by this. Looks like Float for lead and Li are two different things entirely. My battery manufacture even recommends a float voltage for their Li batteries. I set my batteries up per my manufactures recommendation including float, and all seems fine.

[@tradingtechautomation693]

And what floating voltage did they recommend olvs its full capacity!?

[@genxgamerdad141]

@@tradingtechautomation693 I have 48v EG4 LP4 batteries. From their spec sheet: Charging Voltage (Bulk/Absorb) 56.2V (+/- 0.2V) Float 54V (+/- 0.2V)

[@2hotscottpro]

So there not all the same it seems.Battle Borns Green Dragon says to shut off float.And bulk or absorb ,don’t remember because I can’t do it with this Jamboni mppt.Learning and will upgrade mppt.

[@1sailfast]

Very helpful. You explained this very well and now I’ll have a better understanding about my Victron controller settings. Thanks

[@alexakis.st37]

I like watching u. Its like watching myself in my system in Greece. Every measurements i make always telling me stay victron. My batteries also are lifepo4 victron. I don't have the courage not even to take another brand in batteries

[@vmw2dxtreme1]

Thank you for taking the time to explain this, and great footage also...

[@chasethames2845]

Whenever I’m reading anything regarding my solar system or in solar forums it’s Andy’s voice in my head and if it’s not for you then I’m sorry we can’t be friends 😊

[@ToddDesiato]

Excellent! You provided exactly what I was looking for. Thank you.

[@kareldelvoye8928]

Your video is what I needed. I use a Rebelcell outdoorbox 12.50 AV (Lithium-ion). Ask Rebelcell what setting to use to charge it with a solar panel, they didn't answer and all I could find was to use absorption not higher than 12.6V. The Victron controller 75 | 15 is set to Absorption 12.6V and Float to 12.3V and after your video I know I did the right thing.

[@ceeweedsl]

Most LFP mfr suggests 14.2 absorption. 13.3-6 float.

[@barrydavies2977]

Great information. Thanks. Could this be why some people are complaining about their lithium batteries not charging? I have read various comments where people have said "used it once and it wouldn't charge".

[@radusdirect]

Thanks for sharing this knowledge. It really helped clearing many doubts in my mind..

[@scantrain5007]

This was very helpful. Thanks for uploading! / Thumb up off course ...

[@OffGridGarageAustralia]

Thank you very much!

[@bassman53]

Hi Andy, congratulations to your new LIFEPO-channel, I watch your channel in Germany, it´s not very hot here, we have Minus C° and snow. I`ve found a lot of information for handling with the cells and how to buy at alibaba, Thank you very much, and please...don´t kill the frog

[@harrymuurling2742]

Great explanation and very logic, that's why I did charged for a while with and buck stepdown converter and that's worked very well, I changed it with my mppt charger developed for lifepo4. more security but exactly the same result as the buck converter, only 2 milly amps different

[@OffGridGarageAustralia]

Yep, they pretty much work the same way.

[@ElectricCarAustralia]

Well done Andy on explaining the differences using practical demonstrations. This stuff needs to be right otherwise people will wreck their solar/battery gear.

[@briancalvery5704]

Thanks, this was great information and I'm glad I saw it before setting up my lithium battery in my trailer!

[@getfaith]

Andy your the best dude, i now have my settings correct for my mppsolar charge controller....thanks!

[@april7_]

Thank you for all this information and testing! I found good about Victron products just that you can adjust almost everything and in RV use it often is critical not to miss PV charge at some times so you just have to be quite aware of technic basically just like to adjust like Flow charge values then. With my old MPPT charger (more than 10 years old) did not have anything to control, and it was for Lead only type, but it worked still quite good I have to say!

[@OffGridGarageAustralia]

Yes, the Victron stuff is not cheap but really awesome.

[@jimthannum7151]

This was a great video, highly useful and important topic so as to not damage lithium batteries. Exactly what I needed to understand.

[@OffGridGarageAustralia]

Thank you!

[@robertkosovich1232]

Nice job! Thanks for the information. I would like to see the epever in use if possible, waiting on batttery order to upgrade my system. Thanks again! Happy New Year!

[@robertkosovich1232]

@Glen Osborne I don't think so, never saw one.

[@frankdg7090]

Many Thanks Andy....I Use a 100/30 MPPT Victron Smart and I only set the absorption-time for my 180A Lifepo4 to max 1 hour (instead of the standard 2 hours) but the absorption remained up to 14,4v....13,6v is actually 99% SoC. With your video I will decrease the absorption to 13,5v....and see what it gives...We are cooking very often with a induction plate, using a Nespresso, water cooker and toaster...with a 2Kw inverter

[@OffGridGarageAustralia]

Thanks Frank. You have to play around a bit with these settings. 14.4V is definitely on the high side but start with 13.8V as absorption voltage and leave it there for 1h or if the current drops below 10%. That should get you 99.8% capacity. Float could then be 13.4V to keep the battery 100% filled without any stress. If you have loads running the SCC will supply the power at this stage if they can.

[@CotyCondry]

thank you, this was the info I was trying to find about what exactly float charge means

[@willtaylor8904]

Another super interesting video, thx! Looks like the float charge setting introduces a hysteresis function. I can't think of good use for it but it's fun to know it's there...

[@liamlawler609]

Thus guy is hysterical

[@jogo9996]

I have 2 new battle born batteries..i had it by mistake on agm. For a month it float charged a number of times..did i hurt my batteries..it's on the right setting now.. thank you...

[@NJ2A]

Very helpful to help me understand float voltage. Thank you!!

[@ihorkukharchuk]

Yeah! That is the explanation that I was looking for the last few hours! Thank you, good man.

[@OffGridGarageAustralia]

Thank you. LiFePO4 is a bit different to the good old lead acid batteries we had before...

[@georgesackinger2002]

Thanks again. I have built many solar systems with LiFeO4 batteries. It is nice to have a lithium setting but understanding the float settings helps in use of cheaper or just older charge controllers. Unfortunately, not all let me change this float voltage. Great information. I now know which controllers to upgrade. I also use mostly the Tracer series. They work fine for me and are much....cheaper than victron. I also like there higher solar voltage of 150vdc for the solar input.

[@HarmonyExpressSkoolie]

Very very interesting discussion on float charge. I would be very interested to see your experience with the EPEver Tracer AN. This is what I have for my Skoolie (School Bus RV conversion) and I'd love to know what to set my settings... Any advice would be welcomed!

[@aubreyj.tennant1123]

Me too!

[@mikenr]

Many thanks Andy! As always great, useful and understandable info 🙂👍🏼

[@OffGridGarageAustralia]

My pleasure, Mike!

[@rb-qc1fn]

Brilliant. So thorough, so helpful!

[@spyke556]

Late to the party here, but here is a perspective you may have missed, and that is charge current... So I want my batteries to charge to 3.4V, however when I set my charger to this voltage as we approach this voltage the current in the battery will start to drop, eventually reaching 0A at 3.4V when the battery is fully charged. This will take a long time. So I set my boost charge to 13.8V so that I can make maximum use of available charging power and keep the current high even at the desired 13.4V. Yes it means I am "over charging" my batteries past my target for a few hours, but at least I charge as fast as possible. Then when we switch to float charge, my loads will bleed off the excess charge and we will then reach my desired 13.4V and solar will kick in an supply the load. This way I get my batteries charged as fast as I can to take advantage of available sun.

[@organicngreen9156]

Excellent Explaination and Demonstration .Many Thanks and Best Wishes !!

[@immrnoidall]

I'm not trying to brown nose here but, seriously, you should get some kind of kindness to humanity award, lol, for your educational generosity. Just this one video has a classroom size of 127 k so far. I believe when teaching, there is nothing better than real world lessons.

[@scrapyardwars]

Excellent. Thank you. Trying to work through all of this and the misinformation that exists everywhere has been a journey. Inverter working. My batteries are floating but not floating:) Lifepo4 :) Also good to find our from your other video I don't need to worry about batteries shut off. Hopefully starting the Grid connection today as I have been testing DC and wiring. Fingers crossed.

[@TechieTard]

This was PERFECT for what I was looking for.

[@OffGridGarageAustralia]

Thank you. There is more about this topic in other videos I made.

[@lifepolicy]

Now revisiting your video two years later: on my Victron the Lifepo settings are bulk 14,2V and float 13,5V. That makes perfect sense because like you said in another video the voltage from a fully charged battery drops to 13,5V after a while no matter what if you charge it with 14.2V or 13.8V (13.5 is 100% from my mfg's handbook). When the charger hits float, you must restart it to start a new cycle.

[@GSCork]

Can't wait to see the EPEver video as I have the BN series and a 120Ah Lithium Iron Phosphate battery. New Subscriber :)

[@OffGridGarageAustralia]

Welcome aboard!

[@view360deg]

WhAT an eye opener!! saved me few thousand precious Rupees for a Victron import, which we dont get in India :(. I will try same setting on my Systellar MPPT. Big Thank You!!

[@AnilMaurya-cb8bx]

I am also using in india Very deep information I found from this channel ❤❤

[@dig1035]

Just watched the new version of this but still had to watch this again! Different conclusions.

[@ahaveland]

Great explanation and demonstration! I think the PCM60x that Pete from HBPowerwall has can also float properly with lithium, and cope with a decent sized array. Seems the consensus now is that LiFePO₄ cells last longer if their rest state is 100% SoC, unlike LiCo and Lipo cells which age faster at the longer they are held at 100%.

[@OffGridGarageAustralia]

I don't know if they live longer at 100% but it certainly does not really hurt them as long as the voltage is not to high. Floating at 3,35V seems to be their natural rest voltage anyway, so we go with that.

[@kuhrd]

What you are talking about is not really self-discharge. You are talking about the surface charge going away which is a product of battery internal resistance. A fully charged flooded lead-acid battery is fully charged at 12.8V and some AGM Lead Acid batteries are fully charged at 13.0V. So the float voltage for most charge controllers will be slightly above that to keep the voltage high enough to prevent sulphation while also keeping the voltage low enough to reduce water loss. Most quality lead-acid batteries will lose about 5% per month due to self-discharge. So a 280Ah FLA or AGM battery will have a self-discharge rate of about 20mA @ 12.8-13V. When you charge most lithium chemistries they will still have a small amount of surface charge but they have lower internal resistance and also a lower self-discharge rate at about 0.5-2% per month. The self-discharge rate of your 280Ah cells will be about 2-8mA. Your lithium batteries will still draw power to match their self-discharge rate at whatever voltage you charge them to but your meter is likely not accurate enough to show the current at that rate. The reason you don't float charge your lithium batteries with the same settings as lead-acid is that the charge curves are different enough that you can use a differential instead and prevent the lithium battery from staying at a high charge state when you are trying to get the maximum number of cycles out of the cells. You typically try to cycle most lithium battery chemistries between 10% and 90% state of charge to get the maximum cycle life while also taking into account the trade-off with calendar aging.

[@OffGridGarageAustralia]

Thanks for your great explanation.

[@kuhrd]

@@bobby1970 Can you point me to a credible source that states that doing a discharge down to 10% capacity even one time will irreversibly damage the cells? Every cell type and manufacturer generally quotes their charge cycle life at 100% DoD to 70%-80% capacity. So a typical NMC cell can do 300-1000 cycles at 100% DoD. A typical LiFePO4 cell is can do 1500-2500 cycles at 100% DoD. The only reason people stay in the middle 80% of the capacity (so between 10% and 90% SoC) is that the cycle life improves enough to hit the sweet spot between calendar aging and cycle life while still having most of the capacity. Staying between 90% and 10% SoC will generally net you 4000-6000 cycles to 80% original capacity (this varies a bit between manufacturers, batches and battery chemistries). This is 11 to 16 years of service being cycled once each day in a typical solar installation use. Most of the information available states the calendar life of LiFePO4 cells to be around 10-15 years. The point here is that these cells will degrade at a specific rate over time even if they are being stored on a shelf at a storage charge for their entire life.

[@veryinteresting591]

@@bobby1970 : You are referring to Lead acid chemistry, NOT LiFePo4. LiFePo4 can discharge 100%.

[@dannyhaining4080]

Watching the younger kid demonstrating charge cycles, he was saying you can get beyond 10,000 cycles if you stay between 75% down to 35%. That is over 30 years. Now, I understand conditions would have to be most ideal ..like temp of the battery and ambient temps which can minimize battery life but damn.. that is j credible. Even this fellow is bulking to about 75%. For me.. with 1450 watts solar tied into my Victron 150/100 charge controller. Theoretically , I can charge back to 75% or 13.4 volts using solar, then use solar on whatever I’m discharging, unless it exceeds that 1450 watts.. then at night discharge three 300 Ah batteries to the 40-50% only to bring it back up to my set high end parameter at 13.4 volts or 75% of maximum. Right now, I am running eight 125 Trojans six volts set in four pairs. I have a residential fridge too. This winter, I’ll sell my 8 batteries.. which are in excellent shape and two years old, go to three monster lithium batteries and call it a life.

[@martinhansen9517]

Nice to see you got an victron. Great info and video

[@OffGridGarageAustralia]

Thanks 👍

[@ayubshaikh9156]

Nice ,natural ,jovial experiment With valuable info …….

[@stevewilson8267]

I just found your video. I was confused on this exact topic. Thank you much for educating me about the requirements of the lead acid and lithium batteries.

[@brucew4726]

I appreciate that this video is 2 years old. Thank you for this video; it is very informative. Sterling Power supply a Battery to Battery (B2B) 12 DC charger which I have in my van. My Sterling BB1260 also has a setting for Lithium. For LifePO4 lithium batteries, their default charging presets are; Bulk/Absorption 14.4v, condition13.8v and float 13.8v. They also default to Min abs of 30 mins and max abs of 30 mins. The maximum I draw from my 105amph lead acid battery is 15amp a working day. I was thinking about buying a replacement lithium as my current battery has lost capacity as it's nearly 3 years old.

[@OffGridGarageAustralia]

Can you adjust the settings on this B2B charger? I would lower them a bit, they are a quite on the high site. You can easily have 13.8V as Bulk/Absorption and 13.4V as Float. This will keep the battery 100% charged at a lower voltage level and is stress free for the battery

[@brucew4726]

@@OffGridGarageAustralia Thank you for the reply. Yes I can adjust those settings. It's a lot more complicated than the victron b2b charger as there is no app. Your experience over the past few years is very helpful. My BB1260 is rated at 60amp which is too high for a 100amph lithium battery, but there is also provision to reduce that to 30 amp. Thanks again.

[@davidsolomon9085]

Awesome explanation ,i will use your settings on my 320 ah lithium iron phosphate battery , good job

[@whitepitohui]

Very clear now greetings from Holland

[@cbiizzy]

I think you are awesome, man. You educated me big time. Your lecture is clear as a bell. 👍👍👍👏👏👏

[@asterixtug]

I've just replaced the AGM bank with a lifepo4 bank and was wondering about the parameters of the DC-DC charger and couldn't find any sensible advice on what to do until I watched the videos and at least I think this is the solution. On my boat when underway the consumption is around 25A and I don't want to charge the batteries around 14.6V, however I would like the batteries to be around 80-90% SOC, so I believe your advice is the solution vs the charger's standard lifepo4 setting, at least I am experimenting with this. Thank you yours videos and greetings from Finland!

[@pgo301]

Learned a lot here for sure. And wouldn't that also extend the life longer with a single constant charge setting?

[@jimhanty8149]

I am working on this exact issue with my new Victron SCC. Your theory is perfect for a constant user of all available sun power…. One just needs to decide how high you want to keep it charged and then what voltage numbers to plug in so as to not waste the sunshine.. It would seem one would not not need a tail current enabled ( ? ) … or perhaps very low (1 amp) .. you didn’t state that …what do you say on the tail current if your ending abs at the same value of float.? "………BTW Great vid ,thanks..

[@hommerdalor6301]

Great way to explain. Thanks. The frog sound is better than any free music used in youtube videos. :) Chicken could bring some more rythme. :D

[@BackyardRacing1]

Excellent work, Thankyou 👍👍

[@leotheevinci]

Very helpful indeed! Next video should be about maximizing the lifespan of your lithium batteries by SOC and DOD.

[@OffGridGarageAustralia]

Voltage is the killer, not SOC. Keep the charge voltage low and the discharge voltage high. 3.1V-3.4V is perfect to use almost 95% of capacity.

[@leotheevinci]

@@OffGridGarageAustralia So even if the SOC is always at 100% (3.6v) it won't reduce the lifespan of my batteries? Isn't the voltage correlated to determine the State Of Charge? Example would be a 50-60% Depth of Discharge (3.0-3.1v) with maximum of 90% (3.4-3.5v) State of Charge would prolong the lifespan of Lifepo4 batteries.

[@aubreyj.tennant1123]

Great instructional vid! Do you think the same applies to DC-DC chargers? Thanks again 😊

[@proudaussie3522]

Thank you .I do not have a great understand or electricity but I understood you very well. You are a good teacher .

[@Sparklift]

Very important topic and explained really well.

[@OffGridGarageAustralia]

Thank you very much.

[@AussieDownUnder604]

Excellent presentation. Thank you.

[@OffGridGarageAustralia]

Glad it was helpful!

[@amxmm]

Thanks a lot, that was very helpful. Didn't understand this stuff before.

[@OffGridGarageAustralia]

Thank you!

[@jonathanhampshire8405]

thanks for the information. always informative and fun. If you could do a video on setting up the epever tracer charge controller for a LifePO4 battery pack that would be great. Just building my battery pack now and not exactly sure how to reconfigure my charge controller (currently using AGM batteries). I have a 24 v system, so presume I should be doubling the numbers (e.g. set absorption and float to 26.8). I don't have a MT50 - would be good to know if i really need one to reconfigure the controller? Many thanks!

[@philbarnes494]

Very well explained, thanks