Using default LiFePO4 settings for Bulk, Absorption and Float? Probably not... 

I love that you're asking these questions. You're also willing to admit that you didn't understand something and change your direction. I don't know what you do for an occupation, but IMO, that's the sign of a true engineer.

Thank you for your videos! I have learned more from watching your experiences then any other channel. Keep up the good work sir!

Andy, I just discovered your channel with this first video I watched. Excellent top thought process. This issue you have found is all the more important for mobile setups such as sailing off grid systems. We want the batteries fully charged at all times during the day to arrive at the night part of the ocean passage with full capacity available to power the autopilot, navigation electronics, navigation lights, radar, etc. Also any domestic loads at dinner times and the all too often inverter run hot water kettle for tea during the night watch. Thank you kindly for this and many more thoughtful videos to come. Best from the Med.

Hi Andy, I have just descovered your channel yesterday and it is so helpful with all the tests you do! I'm looking into building a 24v 400ah battery bank for my offgrid van this year! Keep up the good work and I lookf orward to seeing your huge battery shelf bank!

I like the deep dive into the charge controller settings. I have to hook up my panels again to see what my settings are. I am curious to read the comments on this one! Thanks again for making these videos. Even the frogs are cool!

YES, Time IS the constraining factor. You are doing fantastic. Thank you for sharing your knowledge.

Awesome! It's really good to see another analytical mind working through the same thoughts I've been having and experimenting with for the past couple of months. I'm still toying with different voltage settings for mine, however the voltages are all kept the same between float, bulk, absorption etc. And I've also got zero offset. This of course means the charger is simply a big lab style power supply, with a voltage limit, and a current limit. The current limit is just how much solar is available. Once the batteries are full, it prevents the batteries from doing any work unless the solar can't keep up. I figure the less cycles, the better. And while there are concerns regarding keeping batteries at a high SOC, the fact is that every night when the sun goes down, they start to discharge anyway. Most days I get back up to close to 100% with my setting at 54.2v. And overnight I will use 15% or more. This fine tuning is tedious, and not for the average user. However the benefits should be huge, both in power obtained from the solar panels, and in battery longevity.

I am not sure if someone answered this yet, but I was explained differently when the solar guy installed my first solar system on my first sailboat, I am explaining it in 48v terms, but my setup was a different voltage. The solar guy explained it this way. Float is your target cell voltage x cell count. So let's say you want 3.4v/each cell, that would make your float voltage 54.4v because that is your desired optimal voltage when your batteries are perfectly balanced. Now you need to figure out your charge cell offset, this is how far apart your cells become throughout a full charge. So in my case, the guy set absorption voltage to 54.4v and hooked a load up and discharged my cells to low cut, then he used a charger to charge the battery to full 54.4v. Then with the default 2hr absorption period, we viewed the BMS and noted the cell difference as soon as it went into absorption mode and he timed how long it took the BMS to balance the cells within 0.01v. The cell difference going into absorption is your charge cell offset and the length of time it took the battery bank to balance to within 0.01v during the charger pause period is what we use to adjust the settings. So let's give an example, on the flip from bulk to absorption mode you saw a 0.075v cell difference between your cells because they are poorly matched... well now we would adjust your absorption voltage to Float Voltage (54.4v) + Charge Cell Offset (0.075v) = 54.457 ~ rounded to 54.46v, so this new 54.46v would be your Absorption corrected voltage. In regards to absorption time, this is how long it took your battery BMS to complete the balance, so in regards to my BMS it was only 4 minutes to complete a balance. So the settings would be adjusted as follows based on this scenario: Absorption 54.46v, Absorption Time 0hr:04min, and Float 54.4v. Regarding the bulk voltage offset restart, the guy told me to turn on all my typical constant loads that are expected to be on every single day ex.. frig... and then compare the voltage of your battery bank for a minimum of 1 minute, so if your bank drops less than 0.1v, set it to 0.1v, if it drops to let's say 0.4v after a minute, set it to that.. otherwise, the controller will attempt to maintain the batteries to the float voltage at a lower charge current as needed. The whole point of the absorption cycle is mainly to balance the cells from charging up because they can't balance properly within float mode since the BMS uses voltage bleed for balancing. also.. you need to set your BMS start voltage as the float voltage.

Those frogs, verrrrrry cool shot!

Another great video ! I'm using LEAF Li-Ion NMC cells in my 14s battery and I set my LV5048 all-in-one parameters as follows: BULK Charge Voltage: 57.4V (4.10V), this is my 100% SOC FLOAT Charge: 57.4V LVD (Low Voltage Cutoff): 47.6V (3.40V), this is my 0% SOC I also DISABLED Equalization. Of course the exact values you use will depend on the battery chemistry, but for NMC these values work great for me.

Great video yet again and very interesting watching you work things out. Even the frog commented lol Cherry on the cake was your frog shots at the end. Had my off grid garage fix for a few days so all is well with the world.

ahhhh WatchFrogs are back! looking like more and more each time! Good video learning more each time! Thanks!

Hi from Puerto Rico in the Caribbean!!! I'd been seeing your videos for a couple of months now! I like how you present the "silly but important questions" we all have lurking around in our minds regarding solar energy projects! You drill down to the details, explaining things step by step in a simple manner. Keep your good work going!!!

Thank you so much for sharing your thoughts and experience.

I agree Andy, absorption at a safe level, and float at either the same or ALMOST the same level. I use 3.45v/cell for both in my caravan battery, (400Ah) works for me! 3.45v is not quite full, but high enough to top balance. When I’m not using the battery, I keep the charge level (and voltage) lower. LOVE your frogs- have you named them 🤣

Great video,your BMS will still balance with a float mode current.setting max voltage and float the same you will see the current shared between battery and charger for the load.never miss out on potential solar energy.this setting will also help with absorption.

Tolles Video 👍schön erklärt.

Great video, helps me a lot for my PV . greetings from Germany

The parameters and concerns you suggest are completely valid..!! This shallow cycle method allows you to set state of charge to let's say 80% and keep it held constant until the PV array stops producing. Any load introduced will be driven by the sun rather than cycling the batteries, thus minimizing deep charge/discharge cycles!!

Great work. I enjoy your videos. Informative

I want to re-balance my battery from time to time and also want to give the Victron BMV battery monitor a chance to synchronize. So I need to charge to 100% SOC once in a while. But not too often in order not to stress the battery unnecessarily. My approach is to keep the charger in float for many days or weeks and go to bulk/absorption only once in a while. To accomplish this I would set re-bulk-offset to a very high value. This will trigger a new cycle only when the battery is at low SOC after heavy usage during cloudy weather or if the charge controller is manually switched off and on again. Otherwise it will stay in float. I would suggest the following settings: Absorption: 3.55V (2h with tail current of 2.5% C) Float: 3.35V Re-bulk-offset: 0.15V per cell (2.4V in your application)

Wish I had seen this before installing my 16s lifepo4,I used preset lifepo4,it overvoltaged and inverter tripped on and off 3 times ,stuffed my fridge/freezer (2mths old)...have changed absorb to 55 and float to 54 ,no problems now....keep up the great content.....victron should be paying you

I have a mix of charge controllers victron, chinese x, etc, I found the cheaper ones have abs and float matched fairly close together. The renogy one had them far apart just like the victron. Great video sir 👍

Hi Andy Another great video. I have aps and float at the same with 0.1 in offset and been running it like that for 2 years

At 10:27, keep in mind that the surface charge at 56.8V dissipates very quickly when you begin to discharge the battery. Going from 56.8V all the way down to 54.4V (even down to 54.2V) or so does NOT deplete the battery in any meaningful way. The battery will still be at a 99.9% charged state. So basically, you don't lose any meaningful capacity by allowing the battery voltage to drop to the 54V Float setting before the charge controller kicks in and starts helping again. The battery is still nearly fully charged at that level. You don't want to set the float any higher... even victron's setting is a little hot (3.375V per cell... I honestly would not go over 3.35V per cell for the Float setting). If you set the float higher then you are basically either sloshing current around unnecessarily, or you are trickle-charging the battery 100% of the time (at least while the sun is out), even if the battery is already 100% full, which you absolutely do not want to do. -Matt

Thank you for the great information.

Good stuff, love the frogs!

At Microcare we set the absorption and float to the same value as a default on our charge controllers for li ion. I agree with you

i find this interesting. I have two complete house systems somewhat similar. But the usage in each household is different. Also my highest priority is battery life and it is better to cycle between say 30% and 80% charge. My charge controllers settings are handled with this objective priority. This again would often result in the solar panels producing at fairly high levels. But again it seems to depend on your personal usage. My highest demand is washer/dryer & evaporator cooler. Regardless, the battery will contribute in peak demand and then your comments are all still fully correct.

Great job👍🏻 (I'm still waiting for another full discharge/stress test) Conc. battery life: lots of comments about charge and discharge levels. I don't agree on keeping the batteries below 90% and above 20% state of charge. Does anybody believe in a lifetime marriage with your actual battery set? There will be inventions on battery technology we can't wait for to change over after... 1,200 to 2,000 cycles. So in my opinion let's use the max of battery capacity we own today.

Agreed, my understanding is that these profiles are for different battery chemistry’s, I have been setting absorption and float the same for my lifepo4 batteries for months now with no negative effects (that I have noticed) I like you came to the same conclusion, and decided to experiment with it.

I really enjoy your videos great content my friend keep it up ❕❕❕🌞🌞👍🏼

Just a thought is there any way to use current clamps to determine current flow direction (ie charge controller to battery and battery to load) to trigger the charger controller to start despite the float voltage settings?

It makes sense, to set the solar charging to "master" if the battery is not fully charged...very nice reserach! Greetings from Austria!

In my limited experience I think you are correct, obviously you want to cycle the batteries as little as possible and use the power directly from the sun when ever possible. Also your voltage settings are about what Dacian recommends with his Electrodacus controllers. My batteries currently have a difference of 3.33v where one battery is 3.4v and sometimes Ive seen the difference as high as .1v. Is this a sign of them becoming unbalanced?

Another great video. I have been experimenting with same setting for Bulk and Float for my 12V system.

Setting absorption an float mode the same that’s how I have it an it works perfect

So I get more confused on the settings when I try to incorporate the settings into my charge controllers. I have a victron for my 24volt lifepo4 battery bank which I can input these settings you suggest. However my 48volt charge controller is a all in one unit with far different terminology then the victron. My biggest concern is shouldn't your bms settings mirror the settings on the controller's? Great video as always love how you help explain things to us and keep your viewers thinking.

Hi there - I am going through / have partially been through this stage and agree totally with your logic - same CC as CV as FV. Additionally - why set the voltage so high in any case. If we use batteries we have losses going in and then losses coming out (on top of all the other equipment losses) so the lower the battery voltage- the sooner the battery hits float voltage the power is provided direct from the panels and circumvents the batteries (less use = more life). It seems like a win /win situation?

Its recommended to bulk charge to 80-90%. As the resistance rises above Bulk charge, use Absorption charge to bring it up to a full charge. A Float charge or a trickle pulse charge maintains a fully charged battery with a lesser voltage to keep the battery from building up gas pressures while maintaining a charge and prolong battery life, AFAIK

Love the frogs supplement Andy :) Your logic is spot on, I have the same setup as you are proposing, as soon as a reasonable heavy load is applied I want the solar power source to become the master source for the load. As I currently use lead acid batteries this happens anyway because the voltage droop on the battery under load is much higher than lithium batteries. I think it is ok to have a small difference between absorption and float that is equal to the voltage drop across your cables between the batteries and the solar charge controller at the load that you want as a trigger. So for instance if you want the solar charge controller to switch to bulk when you plug the car in then make the difference in absorption and float voltage equal to the voltage drop in the cables when you start the car charging. I think that the default settings are for users who want it to just work out of the box, but they are not optimised for specific cases. Sorry to say you are not an ‘out of the box’ type of guy Andy :)

First , I am a beginner . Second , thx for all the effort you put into all this. In short , you want to use all the energy coming from the solar panels and use the battery as a back up. Because your are off-grid. Right ? But are the setting different if you use it as a home-grid system with the use of an energie-meter like the EM24 or EM540 ?? And could you use these energy-meters in your setup ?

I keep my absorb voltage to the same as my float during the times of year when I am constantly using the battery (my camping season) but at times that am not using it, I adjust the float voltage to the lowest that I want to keep my batteries for longer life

Love watching your videos I value them as educational. I have a 5 KW setup I recently replaced my lead acid with lithium batteries two Pylontech UP5000; but my inverter is not intelligent. It doesn’t have BMS communication. Is there something I can add to it to make it communicate with my batteries?

Hi Andy - I love your thought process of asking the questions. I think people may have missed the question in the middle you posed where you said you want to use the direct solar power when it is there and when the charger kicks in it maybe too late in the day. It poses an interesting question when not using a Victron inverter that allows the direct source. I assume the preset is generic to set an everyday use. To be gentle on the battery. I guess what would be good it to have a charge controller that knows the time of day. Knows that you are home and want to use energy. Knows the cloud conditions at the time, and therefore change the charge profile accordingly. Default back to default , but make the voltage closer together to keep the system to 100% before night. It poses interesting questions and maybe a need for a smart smarter device that works to what the user needs.

Like the others who have commented: I also keep my absorption and float at the same voltage, but I keep mine on the higher side: 57.0 is what I use. I would argue that in a solar/off-grid set up you never want to allow your battery to sit fully charged. Not because it's bad for the battery (It's not really a big problem for LiFePO4) but rather because a fully charged battery means you're not making use of available solar energy. You want to always make use of the solar power that's available. So I have my chargers set to charge to 57v but I also have load shedding enabled: Whenever my cells reach 3.35+ volts and if there's still excess power coming from the solar panels I have some optional loads that kick on to make use of that extra power. (The shed loads are A/C units, heaters, and water heater) So my battery almost never gets charged to 57v. Because while the charging equipment is configured to charge to 3.56v per cell it rarely gets that high because my load shedding prevents it. Even if it does make it to 57v the shed loads ensure it drops down very quickly, within seconds in most cases. Also: 3.55v is not that high for LiFePO4. Most of the studies have shown that even charging to 3.65v does not have a huge affect on the longevity of the cells. Unless you hold them there for days at a time. Charging to the higher voltage makes absorption and balancing much faster (Especially if you have active balancers which you will probably end up needing eventually). You should be able to easily find ways to do load shedding: have your Tesla automatically start charging when the battery gets above 54.4v, for example. or put a window A/C unit in your garage and use the excess power to run that to take some of the heat out of the garage when the sun is at it's hottest. With solar a fully charged battery means you're leaving solar power on the table. It's better to find a way to use it rather than let your battery sit fully charged. Having the charger set to a higher voltage means the charger keeps pulling power from the panels as the load shedding kicks in to put that power to use. This is another advantage of using the wired Victron Shunt instead of the "Smart" wireless one: It includes a relay you can use to drive load shedding like this. I used to have it set up to have the relay on my MPPT set to come on anytime the PV is at a high enough voltage and the Victron Shunt set to come on at a high enough battery voltage. When both relays are on it turns on my selected shed loads. I've since switched to using a smart hub with MQTT capability. I now read the can-bus data from the Victron Color Control GX via it's MQTT service and use that data to intelligently turn on/off my load shedding devices. IE: Kick on the A/C if it's hot outside, or kick on the heater instead if it's cold. As far as the defaults: I believe the defaults are most applicable to people using these batteries in "standby" conditions rather than a true off-grid situation. IE: These are for people who are usually connected to the grid (and may even be exporting excess solar back to the grid) and the battery is just there for backup in case the grid goes down. In that case the defaults are fine: Charge it to 3.55v to get it to 100% and then drop float down to a voltage that's ideal for standby/storage.

Thank you for sharing your experiences. I wish that charge controller terminology would be similar across manufacturers of charge controllers. I have the Tracer AN 40 Amp charge controller, and they are not as customizable as the Victron. I have set my float as close to the max charge voltage as I can in an attempt to keep the solar engaged to run my loads during the day. It is so hard to figure out just how to set things!! Love your channel!

Hola que buenos videos realizas los veo desde Colombia

I found this video both informative and absorbing. I got a charge off of the content and really got amped up when the frog chimed in. I personally didn't have any resistance to any of the theories you floated. Watt I'd like to know is Victrons' take on why they chose the parameters they did. I enjoy the energy you put into each powerful video and see a lot of potential for the channel! Keep it up!

3.55V is 99%. 3.35V is also 99%. 3.325V is 90%. If you charge to 3.55V, for all intents and purposes you're at 100% state of charge. If you charge the battery to 3.65V, fully, no current going in, the voltage will settle in a matter of hours to something around 3.45V or even less once you disconnect. However, keeping your battery at 99% state of charge for prolonged periods of time is not good for the battery. This is why keeping a float voltage at 3.55V (or just high in general) is not a good idea and why Victron puts the float at 3.375V per cell... Victron's settings are there to maximize cell cycle/battery life, not maximize energy harvesting. However, this does not take away that between your 3.55V and your 3.35V you've used less than 1% of the capacity of the battery. The reason you don't set your float/absorption to the same level at 3.4V is that you limit the current going into the battery and slow your charging rate; if you have a big charge controller able to deliver 100A, you want to push 100A into the battery. You need the voltage to do this. Take the example where you pull the 2kW load, you got below the 52.8V threshold (3.3V per cell - under load - ) in a matter of minutes, meaning you pulled out almost nothing from your battery even at your 2kW load. So really, float and absorption aren't very far apart at all. In fact, they're within less that 1% of the total capacity of the battery - there is almost no energy in the battery past the elbow of the charge curve at the high state of charge yet this region has a big voltage delta (incidentally, also why you want to charge to that elbow if you want to do balancing, since it's the only region besides the one at the low end that gives you enough delta voltage to deduce some kind of state of charge from the voltage alone).

I am converting my RV to Lithium and wondering if the same principles apply to AC DC charging when on the grid?

This is why I like my hybrid MPP Solar charge controller. Solar takes priority to hour loads and battery. If the battery is full, the charger uses solar if it's enough. But for my setup I have it set to the same voltage of 57.4v for lithium-ion (4.1v per cell)

Wouldn't you keep the absorbtion higher than the float voltage to get the energy captured before pausing? If you then lose some power (waiting for the voltage to drop below either the float or float-offset levels) that's energy you've already captured earlier. Nothing to be lost getting that power into your cells?

I have a 24v lifepo4 system. So my absorb and float will be half: 27.2 for both. With .1v offset. But I think he says that even his lower voltage of 54.4 ( 27.2 for my bank) may be charging a bit high? For best life, should I only charge to 80% and discharge to 20%? So what absorb& float voltage should I set if that is the case? Im using Wizbang Jr, which will turn off the load at a preset bank voltage and turn it back on at a higher preset voltage.

There is not a lot of power in the batteries between 54v and 56.8v. The higher voltage absorption stage is important to give the BMS a chance to top balance. If your BMS will balance at a lower voltage then you can reduce it. The lower "float" is what stops the controller from keeping the battery at "full" all the time, which is hard on the battery. It should be below the balance voltage of your BMS. Usually once you have drawn the battery down to 54v, if your load attempts to draw it lower then "keeping it at float of 54v" means the controller will use as much current as it can to hold it at 54v. This is not "off". If the controller has not enough current available to hold it at 54v and the voltage drops to 53.6v that triggers the next bulk charge cycle. This is not the same as "turning on."

21:30 "Bbbwuh-duh-noh!!" You make some interesting points, and I think I'm going to have to emphatically agree with "Bwwuh-duh-noh!" I've sometimes seen my Victron SmartSolar feeding in 0 Amps to my non-full LFP battery bank during sunny midday and wondered what was going on. I need to do some experiments with the settings and see if this is why.

Fantastic!! This is great information! Thank you Sir. This is how I will run my batteries when I get them.

This makes sense, .. once I get the Viictron solar controller connected. Right now I am using the Victron IP65 12/15 which has 4 or 15 amps settings. I am wondering, what is the minimum voltage needed to for "absorption"? Vic sets it at 14.2 and the 200 amp battery I have says the 14.2-14.6... BB also says to do absorption for 20-30 min per 100 amps... the wall charger from V doesn't have all the same settings... but my ham radios like 13.8V ... so would I set absorption and float to ... what? 14.2? 14.4? and if I use a little will it cause the charger to do the whole charge cycle again and I've hardly used amps from the battery? I am wanting to get to where I am using the battery but not the 120V line voltage from the charger. I am learning for now but curious if I need the solar and then when it gets lower in the battery (Vic shut %) use 120V shore power if at night or too cloudy? I wonder if there are solar inverter types that will automatically use the solar even if battery is up ... and again settings settings settings. pb Also, slow use and having it not keep charging from shore power and recycle every few amps or watt use may not be a bad idea... as I could get days of use without having to keep pulling from the shore. That said, if solar is used, ... if there is any harm to the battery to keeping it topped up all the time, except at night (then we can use wind ... just tossing that in) it may be better to keep it separated. I do thinking using the solar energy directly bypassing the battery power ... even if small amount is worth it... which I think is your point.

does this correspond with Li-Ion NMC Batteries? i mean offset, time, voltage delta. With minding that top voltage for LI-ion is 4.2v, set Float to 4.1volts for example(i have a 14s 58.8 top voltage)

As you could see it needs little time for the battery V to go down. You know discharge diagram. After you apply load the V falls down the cliff. For a bigger load it falls even faster and even lower. And it is good that way. So you have 1-2 minute when inverter gets power only from battery. After that you get power from solar + battery. It is a DC coupled system after all. If you set float = absorption then you always charge the battery. Even when it is full. Do not do that, that is overcharge. Normal charge: Battery is full, charge stops, battery V lowers slowly to its relaxing V. If you do not let battery to relax, charging it again and again in float mode ... then that is the overcharge when you harm your cells.

I'm looking for the best parameters and I noticed something that happens to my inverter, is it normal that the following day it stops at float and doesn't go to bulk? Considering he never entered the bypass from the previous day

Lead Acid batteries (both sealed and unsealed) have three states while being charged, those being Bulk, Absorb, and Float. LiFePo4 batteries only use two, Bulk and Absorb. Your CHARGER is ALWAYS charging LiFePo4 at either of the two states as long as it has enough power coming in. Your specific charger when charging LiFePo4 uses a higher voltage when in the Bulk mode to decrease the time required to reach the battery's Absorb mode and then switches to the lower voltage until either the battery becomes fully charged or the voltage falls a little due to usage at which time it re-enters bulk mode until the battery again reaches full voltage. The re-bulk absorb setting on your charger is what switches between the two states. Your BMS is another story entirely since it receives whatever your charger supplies and by using it's own settings determines when to stop allowing the charger to charge the batteries. In your case, you have restricted it to either two hours or the batteries full or Absorb voltage. If your charger hasn't fully charged the batteries due to weather or shading your two hour charging limit will prevent the charger from fully charging the batteries. Since the high quality charger by it's settings can not overcharge the battery the two hour limit on the BMS is now potentially serving a useless, unnecessary, and negative function. You could set it higher to help compensate for cloudy days or shading.

Andy I have just got a Victron mppt 75/15 and one of the settings for Load Output is "Load switch high voltage level" Can you explain what is does ?, Is the the voltage that will turn off the load or is the voltage that the load will resume after a low voltage ? Do you have any ideas ?

The more I learn about lifepo4 batteries the more I believe they are similar to lead acid batteries. For that reason I think that victron settings are correct. These batteries are saggy and with any heavy load it will jump into bulk mode in a short time. So it doesn't matter if float or absorption are the same or not. After all victron engineers may have a pretty good idea why they come up with those settings.

Andy, This all makes good sense to myself being a total novice, but Im still not totally sure of my setting needed given I'm running a 2x 100ah lithium batteries at 12v I have the victron smart solar 100/50 and also not sure what amps I need to set given I only have 2 batterie, Any guidance would be appreciated. Greetings from a very cold and not sunny UK.

what if the software could ajust setting at different times of the day to make sure you have a good full amount before dark

could you not supply your solar directly to the load through diodes and from the batteries through another set off diodes? that way, the highest supply voltage wins? -k.i.s.s. ?

Superb! Answer my questions I think!

For your application it makes no sense to have two different voltages, you should set the charger to have a constant voltage (to the best of it's ability, of course) and be done with it. Now, going to a higher voltage has the advantage on the balancing of the cells, because the SOC x Voltage is much steeper at the top (bigger variation in voltage, by a small variation in SOC) it is much easier to make sure that your batteries are really balanced. And you might not want to keep them at that higher voltage for long, so you play with the settings to achieve that. Let's say, you want something like this: When bulk is demanded, take it to 3.50v, so you are sure that they will all charge and balance. But float at 3.45v, so while you have enough solar to keep up, you are basically not using the batteries... (SOC delta between 3.55 and 3.45 is minimal). And set your rebulk offset to, let's say 0.1v. Basically, if you have any power draw, you will sit at 3.45 during the day (assuming solar is keeping up) and if your loads at night take it below 3.35 you will get a top balance the next sunny day.

Hallo Andreas, sehr tolles Video und so weit ich es verstanden habe irre gut erklärt 👍 eine Frage hätte ich, kann ich die Einstellungen auch auf ein 4S System anwenden? Grüße aus Wien

There is not much in it between 3.55 and 3.35V, maybe 3% or so of battery capacity. That is why the Presets on the Victron work. There is very little loss of energy in reality as the SOC curve in this area is very steep. You saw also in your video, that the charger floated quite soon again, after a few minutes, even if you only had a small load on the inverter. For daily cycle applications, these are probably not the perfect settings, Absorption and float at the same level will probably give slightly more output. The exact voltages are still up to discussion. But Victron batteries and chargers are used in many different ways, and the default settings are probably the best compromise Victron could find.

Very interesting update. I enjoy your channel, very easy to understand. You should take a look at the Gro Watt Solar/Inverter/Charger combo units. They have a mode called SBU. On that mode, your load will first draw from Solar, then Battery, then Utility (grid). They are pretty impressive units. They can handle 2 PV arrays, and the Gro Watts can be put in parallel or provide 220/240v 2 phase power.

Do you know why Renogy has their settings for lithium iron phosphate 12.8 volt equalization 14.4 Boost 14.4 Float 14.4 Boost return 13.8 Is this harming my batteries?

According to the specs that I have seen on this battery, the End-of-Discharge Voltage is 2.5V. So 2.5v x 16 batteries is 40v.

Hi there, Those are really great videos you make there. I'm just starting to build an island system and found your videos about it. I have a Victron 150/100 Tr and found the presets set a bit too high as well. I've got a question. Did you connect your Lifepo4 batteries directly to the Victron or did you switch a BMS system in front of the battery? greeting dieter

I have four electric windows 🪟 and 4 battery 🪫 which is connecting the wifi and the door alarm 😮 so I will buy the lifeboat?

Andy, how many watts/amps solar do you have now?

I think you got it a bit wrong The charger restarts at 99% charge. 53.6v is the correct voltage. The 100% of the battery is 54.4v To charge batteries we need a higher charge voltage. Also a battery drops the current itself, if you had 10amps available it would and it needed 2 amps it takes 2 amps. Voltage isn't the same as you can feed a battery deadly voltages. You may have a surface charge on the battery above 100% as you set out, but when you've used 1% of the battery the system kicks in. On my system as soon as the voltage drops I get full power delivery from the solar. And I have to change one connection to beef it up as it gets hot from the load. I've a small Anderson on the positive, but I have a high current system. Getting changed tomorrow. So back to you. The cell charge voltage is 3.65 =58.4v 3.375=99% 54v If you're not using the power stored in the battery then you should drop the voltage to around 80% 3.325=52.5v This would give you a longer life, keeping batteries high all the time is bad for them. My 24v I charge at 29.2v I float at 26.7 when I know I'm going to use it or I drop it to 25.6 which is what I have my night voltage at. Then for the morning it's 28.6. and it's ready to run. Then I do math on what I'm using and what I discharge and what needs to go back in and the charge time for that. All manual... Can't wait for parts to come in so I don't have to.

Hi! Awesome video but you misunderstand one thing, if you have victron smart shunt and mppt in a victron smart network. It floats your batterys, if now big load comes on, the shunt will detect that and thell the mppt to go full speed now and you don't miss out on any solar power, it dosnt Wait for the Re bulk ofset. If it senses current draw, the mppt will kick in on 0.1 seconds and deliver the demanded power of the system, so it keeps batterys on low healthy float voltage and also delivers power to the system

Andy, good topic. I set my Victron 150/35 solar charge controllers to 27.6V Absorption and 27.4V Float on my 24V 280AH LiFEPo4 bank (I have a fairly small 1.2 kW array). I float a little higher and closer to the absorption voltage because I live in Michigan, USA and I'm not worried about my solar charge controllers driving the battery too hard or too long here (lol). I have the Virtual Switch on my Multiplus Inverter/Charger programmed to only charge from the AC grid if the battery SOC drops to 20% until it gets back to 60% SOC. My Multiplus charge settings are 27.4V Absorption and 27.0 Float, but in practical use, these charge settings never come into play because the virtual switch settings take the Multiplus charger off line before the battery gets to these levels. This allows me to prioritize the Solar Charge controllers to charge the battery ahead of my grid source. I try to make sure my battery starts the day no more than 60% SOC to maximize my solar input for that day. If I'm having a really good solar day, I find other load to use the solar energy. By the way, from a practical standpoint, I have found that there is not much capacity (

IF your most urgent need is to utilize the solar energy in the afternoon, after your battery has filled - without draining your batteries, that really sounds like you need a bigger bucket (more batteries to store the power somewhere and/or some opportunistic diversion loads). While I agree that the float settings are probably way off from what you would like to do with your system, they're probably not the best tool for the job of maximizing the incoming solar energy. Probably without intending such, you are making a good case for the PIP series of combined inverter/charge controller, because if I'm understanding the manual correctly, after they reach the charge level, they can power inverter loads directly from the solar/PV input power without drawing down the batteries. I don't have enough components for my system build to test this yet, but I think I'll go that direction. The other think that I think may be tripping you up, is that at least with Lithium batteries, it is much better to go by the actual state of charge, NOT the voltage, as the voltages can be misleading, but that would require a different set of instruments to measure that, and the most complete way of measuring/monitoring it that I'm aware of available to regular folks, is the Electrodacus SBMS0 system, with monitored current shunts installed on both the battery and the PV. I have an older SBMS120, which doesn't have all the features, and is much more limited in its capacity, but I bought it back when it was just a kickstarter idea, and the SBMS0 was still being developed. It doesn't support an external PV shunt, although it might have internal shunts on the PV connections. I don't know for certain.

Please I need some help with the setting of my mppt ( Renogy rover 40) I have 2 12V lifepo4 200ah Diy . I can’t find any good settings for my Renogy mppt . High volt disconnect Charge limit volt Equalize charge volt Boost charge volt Float charge volt Boost charge return volt Over disconnect return volt Low voltage alarm Over discharge volt Discharge limit volt Over disc delay time Equalize charge time Boost charge time Equalize charge interval

I now have 400Ah battery and setting abs at 14.05 and Float at 13.55 ... 12V system... I have solar and the multi plus II and run off the inverter only so that the solar can be charging rather than my power bill charging it. .. is the concept. So it makes sense the closer settings however if using the cerbo GX with all the cross communications I wonder about the settings of each the shore MPII charge settings and solar.. I guess put them both the same ... so IF I need to charge from shore I simply turn on the MPII charge feature... at night when solar goes lower than the close "float" then asap in the AM the panels with charge it up so that I can use it the next night. I am doing this is our winter so when spring summer comes all will be a piece of cake. I am curious what voltages are needed to balance the cells. I have four signals hard wire from the battery rack but all four together is rated at 400Ah ... so balance is only doing sets of batteries rather than individual cells.

i use an out back flex 80 and it does deliver power direct to load as needed after battery is charged.

QUESTION: If the (can the) LiFePO4 be set to 80%-90% of capacity as full charge (solar or shore power) and let the building run off batteries until 10-20% then recharge back to 80/90. does this use non shore power enough to "save money" .. than to keep it at the 80/90% by your settings mentioned in the video? In other words, running off batteries rather than shore power (maybe solar too) ... would/could save money from paying the power company, but recharging would cost. Solar in the system too means it would be longer before the 20% is reached when the shore charge would kick in. I think of night time too... considering some wind generation too.

Thanks

what are the settings for a 12 volt system my friend

So Andy, now this thread is 3 yrs old what settings do you now believe are ideal for a 16S battery?

If your float voltage is high enough to allow the the BMS to balance the cells, there is no need to have a higher absorbtion voltage. When your absorption and float voltage are the same, the charger is doing the same job in either mode and the only difference between absorption and float is which LED is lit. In that instance, the only difference between absorption/float and bulk is whether the charger or the battery is limiting current. There will be no need to have an offset setup in the controller as it will attempt to reach and maintain the same target voltage in any mode. If you wanted to have a float voltage that is below a point where the BMS can effectively balance the cells, you would set the absorption to a voltage where the BMS can balance, and the absorption time to a reasonable period of time to allow the BMS to do so. You would then set the offset so that absorption (and balancing) only occurs if the batteries cycle below a certain state of charge. Good cells should stay relatively closely balanced without constant intervention from the BMS, but the BMS will still pull down any cell that creeps up to high, or shut down if any cell gets too low. The frogs remind me of the old Budweiser commercials.

My all in one Chinese inverter always use solar power in priority to satisfy AC load, whatever is the soc of the battery.

Excellent video by the way....👍👍👍

I agree with your settings and logic. I'm keeping my batteries essentially at 80% capacity. Charge to 90% of capacity, then the BMS turns them off at 10%. Basically for me, I call the batteries full at 3.5v, and empty at 3.1v. Keeps the charge controller actively charging throughout the day.

I totally agree with you

Hi Andy Just wondering, what is the float-offset point for the Chinese solar charge controllers which don't have such many details and options.

yes in your case you need 2 Hrs Absorption (CV) that's because 30 mins per 4 cells are needed to equalize your cells. I have 4 cells of lithium and they recommend 30 mins total.

I think you bring up a good point what have you had a huge power wall 15 KW and you had it set like that it would go down to 2 KW before it started charging that would take days for it to recharge I think you make a good point

yes, i do the same for my small 350Wh (14.8Vx24A) Li-ion 18650's (4.2V-3.7V) home made solaraccu. i bulk just 15.8V (3.95Vx4S) and absorp 2h and than i float at 15.4V with offset 0.1V. so I still have a decent amount of Wh in the little accu but during the day of camping i use more the solarenergie and at the same time my battery stays relatively full. Also i use a small 16V max inverter to use small AC equipment. offcourse LIFEPO4 has another nominal voltage but the principe rest the main.

I use the relay of my SmartBmv712 that switches my SmartMppt 100/50 on and off via the VE-direct input based on the SoC. I switch between 80% and 85%. This only gives bulk charge, no absorption and float. Once a month I balance the cells to 14.2V with 2h absorption time but no float.

Hi, Very interesting video, I learned. I am planning a 310Ah 8S4P 24V system. And I have some comments. You say, that the Voltage of 58.8 (3.55 per cell) will drop to 54.0 (3.375 per cell) over time - maybe several hours, if there is only little load.

Do you use this parameters today ? In my opinion 54,4/3,4 is not enough When you have balance voltage 3,45V