LV2424 Charging Problem

cotrailhead said:

With my lv2424 the absorption does happen very quickly. Now tictag says that the bulk phase of charging should be constant current but if I set my SCC to 50 amps max charging and I only have solar power (1380 watt array nominal) the current does not remain constant during the bulk phase. If I’m lucky my battery will achieve the bulk voltage I have on setting 26. Then the float voltage (setting27) will be maintained but my lv2424 display never shows 5/5 bars (full charge). Now I’ve barely ever charged from the grid but I did this week. I set my max utility charging amps (setting 11) at 20 amps. It charged exactly as it should. Constant current until absorption voltage. Then a quick absorption. Then float. And the display showed 5/5 bars or full charge. I don’t know how to explain it, but I wonder if it wouldn’t work for OP.

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Wow: That is interesting to me as guy with a couple of LV2424s to hook up and dial in (upcoming project).

For posters with less than ideal solar panel battery charge: I wonder how your solar panels are set up going into the LV2424 ? and ... I wonder if different PV configurations could make the MPPT Solar Panel to Batteries charging rate act differently ?

If this is not a configuration at LV2424 challenge to dial in with internal adjustments; I wonder:
How are is your Solar Input configured? and if different PV could produce different or contrasting battery charging results (do not know why it would, but wondering).

Here's my references for this question; which kind of present a side question for the LV2424:
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Re: My Efforts to eventually get 240v split phase: I will start with one unit, then add 2nd:

PV . Solar Panel Configuration Question: I obtained 6 x 345 watt solar input (for each of my LV2424s); w specs: 345 watts each / Open Circuit Voltage: 46.59 vdc/ Voltage at MPP 37.93 vdc /Current at MPP 9.10 amps:
against Specs / Max. PV Array Open Circuit Voltage: 145Vdc /and PV Array MPPT Voltage Range: 30~115Vdc
(and No max current spec)

Two Options for my PV array configuration:

I could Parallel two sets of 3 solar panels wired in series for max volts & less amps /my PV Panel specs x 3 = Voltage at MPP = 113.79Vdc / & Open Circuit Voltage = 139.77 ... just under max LV2424 PV specs) !!! (for about 115 vdc /@ max 18.3 amps )

OR:

I could Parallel three sets of 2 PV panels hooked in series that would be less volts @ higher amps (about 78 volts / 27 amps) ???

I have asked: IS the Higher voltage just under Spec limits of LV2424 most likely better / + makes better use of wire size ... from your point of view?

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I have a contrast of feedback from experienced solar folks: like a master Solar buddy who says for MPPT: "Voltage is King / always go with higher voltage/ and from some individuals this forum: also ssaying: go with higher voltage/ make better use of your wire sizes.

In contrast to USA-MPP-SOLAR / Ian's feedback to my question: I would not put more than 2 in series, as 3'x 38V is cutting it fine to the limit. 2s3p. And 47V x3 is too close to the max 145V for my liking.

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Note: The lower voltage feedback matched my original thoughts/ as that is closer to the 24+V LiFePO4 battery bank I will set up. I might test both ways at some later date.

Food for diagnostic thoughts? What is your PV solar input/ how is configured/ Could that make MPPT to Battery charge profile shift a bit?

I wired 2 345 watt used Sunpower panels in series and created 2 series (4 panels total). The two series are paralleled together. The panels are rated with an Open circuit voltage (VOC): 68.2V and a Short circuit current (ISC): 6.39 A. My research indicated that coming in at higher voltage was preferable for the reasons you mentioned.

I'll tell you the theory I'm testing now, and I don't doubt for a second that some folks on here would already have an answer for this juvenile theory.

If you have 50 amps available, constant, then it will charge faster than 20 amps constant. But how does 20 amps (for example) constant do against a current that varies all day? I get the feeling that not all watts are equal when it comes to charging a battery and that when they say constant current should be part of the bulk phase, that's an important bit. Probably wrong. Testing it out as I can.

cotrailhead said:

I wired 2 345 watt used Sunpower panels in series and created 2 series (4 panels total). The two series are paralleled together. The panels are rated with an Open circuit voltage (VOC): 68.2V and a Short circuit current (ISC): 6.39 A. My research indicated that coming in at higher voltage was preferable for the reasons you mentioned.

I'll tell you the theory I'm testing now, and I don't doubt for a second that some folks on here would already have an answer for this juvenile theory.

If you have 50 amps available, constant, then it will charge faster than 20 amps constant. But how does 20 amps (for example) constant do against a current that varies all day? I get the feeling that not all watts are equal when it comes to charging a battery and that when they say constant current should be part of the bulk phase, that's an important bit. Probably wrong. Testing it out as I can.

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The constant is the voltage for bulk. The amps will vary according to PV production. It will drop the voltage of PV to the voltage of your bulk for charging, which will result in more amps on the battery charging side than amps going through your PV wires. The watts should still basically work out the same, a multiple of amps times volts. But watts will vary with your PV production. Clouds and shade will decrease it, for example. Thus you'll see charging amps go up and down all day, particularly on partly cloudy days, unless you have really solid sun and no shading passing over.

erik.calco said:

The constant is the voltage for bulk. The amps will vary according to PV production. It will drop the voltage of PV to the voltage of your bulk for charging, which will result in more amps on the battery charging side than amps going through your PV wires. The watts should still basically work out the same, a multiple of amps times volts. But watts will vary with your PV production. Clouds and shade will decrease it, for example. Thus you'll see charging amps go up and down all day, particularly on partly cloudy days, unless you have really solid sun and no shading passing over.

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This is what I see. I have 2 hybrid units. Each with 1300 watts of solar 2s2p strings 325 watt panels. Open circuit voltage of 40 volts each panel. The strings themselves measure 75 volts at the combiner box. The voltage via the mppt fluctuates from 55 to 72 depending on wattage being produced. The inverter/ charger is constantly balancing the feeding the loads and the charging of the batteries. In addition the charging of the batteries is constantly handed off between the Inverters as necessary. For example if one inverter has an increased call to satisfy a load then the other inverter pushes more charging amps to the battery. If everything is equal (solar watts, load demand) then the both push about the same amount of wattage to the batteries.

Bear in mind I have my units priority set to have solar cover the loads so it's charging the batteries with any excess it has. If you set it with the priority for solar to charge the batteries first and you're connected to AC then it will flip the loads to AC and push all the solar wattage to the batteries which would likely result in more consistent and steady wattage for your charging cycle.

I'm configured the way I am so I can offset as much of my electric bill as possible with solar and my very expensive Lifpo4s. If I have a good solid sunny day I have no problem charging 285ah batteries over the course of the day as well as cover my loads and then I run them down at night.

Mac6792 said:

This is what I see. I have 2 hybrid units. Each with 1300 watts of solar 2s2p strings 325 watt panels. Open circuit voltage of 40 volts each panel. The strings themselves measure 75 volts at the combiner box. The voltage via the mppt fluctuates from 55 to 72 depending on wattage being produced. The inverter/ charger is constantly balancing the feeding the loads and the charging of the batteries. In addition the charging of the batteries is constantly handed off between the Inverters as necessary. For example if one inverter has an increased call to satisfy a load then the other inverter pushes more charging amps to the battery. If everything is equal (solar watts, load demand) then the both push about the same amount of wattage to the batteries.

Bear in mind I have my units priority set to have solar cover the loads so it's charging the batteries with any excess it has. If you set it with the priority for solar to charge the batteries first and you're connected to AC then it will flip the loads to AC and push all the solar wattage to the batteries which would likely result in more consistent and steady wattage for your charging cycle.

I'm configured the way I am so I can offset as much of my electric bill as possible with solar and my very expensive Lifpo4s. If I have a good solid sunny day I have no problem charging 285ah batteries over the course of the day as well as cover my loads and then I run them down at night.

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The Lion Energy batteries I have have a meter on them showing SoC independent of voltage. What I've learned is there is no good way to tell SoC via the LV2424 as it just reads voltage. I looked this morning, and my meters were 2-3 out of 5. So, I put it on battery priority most of the day. When they were all 5 on their meters, I switched to load priority.

You are right. What I described is more visible if you set the priority to battery. It's hard to discern when the priority is the load.

That said, I see the batteries drifting below 26.4V idle, and it's time to check the meters. I know they are full now. PV is no longer producing, so nothing is charging them. And it's back to 26.5V, where it likes to rest for a long time before drifting lower.

I'd like to one day automate the toggling in battery/load priority I do. To do that, I'll have to put an accurate SoC sensor (coulomb) on my bank. If I didn't have the meters on the batteries, I'd have one on there now.

tictag said:

Again, I'm not familiar with the LV2424 so can't offer anything useful on settings but @silgen's screenshot is a perfect example of what should happen. Note that up until 15:10 there's a constant current (Bulk or CC), then at 15:10 it transitions to a constant voltage and current begins to decrease (Absorption or CV) then once current has dropped to some threshold (e.g. C/100 Amps) at 15:14 it transitions into Float (another, lower level CV).

@silgen's screenshot also shows something else: that the charge cycle can be very quick if the batteries are already near fully charged. Is it possible that you're simply 'blink-and-missing' the Absorption phase?

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I was looking for this, excellent! @tictag

Now, expanding on this, how the charger algorith knows when to change from CC to CV and from there to float?

Event: Transition from CC (Bulk) to CV (Absorption) = When battery terminal voltage reaches absorption voltage e.g. 14.4V (28.8V etc)
Event: Transition from CV (Absorption) to CV (Float) = When charge current reaches threshold, usually around C/100 Amps e.g. 1A for a 100AH battery. Some charge controllers use time to mark the event e.g. 180 minutes in Absorption, but charge current is preferable.

tictag said:

Event: Transition from CC (Bulk) to CV (Absorption) = When battery terminal voltage reaches absorption voltage e.g. 14.4V (28.8V etc)

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It sure depends on the equipment, and as you mention you are not very familiar with the LV2424, so probably my algorithm can be different (Or maybe i didnt get it right). But for double checking..., i just re-read this answer from @Mtour and seems like the MPP-Solars change from CC to CV with the "float voltage value" instead of a predetermined value (14.4 / 28.8V):

Do not have your inverter, i have the lv5048. With mine i have to set the inverter to user bat selection, then you can program bulk and float voltages. Then in menu 32 you can set absorbtion time. For the lv5048 the absorotion clock starts counting down is triggered once the battery voltage get to be higher then the float voltage. So if you set bulk at say 27.7v and a float voltage of 26.7 and if you have menu 32, a safe absorbtion time could be set to 2 hours to start. Watch the voltages and make sure non of the cells go over 3.65v during absorbtion.

I have tried auto in menu 32, in auto the batts never get close bulk voltage. Tried one hour in menu 32 and the charger goes to float one hour after it passes float voltage. You would think you could just set it to a bulk voltage and program a 5 minute absorbtion time and be done.

Batteries not having the expected capacity?, or maybe my numbers are very bad?.

So im doing some testing in my system with the newly arrived 280AH LifePO4: And this are my test numbers: As you can see, i'm getting 3 and a half hours with a 500W load, so around 1750Whr, and considering the 50W that the inverter takes and some losses from efficiency and cabling its...

diysolarforum.com

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So my hypothesis:

• Bulk Charge State: CC From start up to the value predetermined by "float voltage". Once float voltage is achieved (26.40V in my case) the absorption stage starts
• Absorption Charge State: CV, it starts once you pass the float voltage and in the LV2424 it probably ends once you reach a threshold, probable the C/100AMP value that you mention, but not sure about this.
• Float Charge State: Once absorption ends (C/100), it goes to float. In the LV4048 you can adjust this timer or leave it auto. LV2424 doesnt have such option.

And:

• Re-start of the Cycle: What SOC should the battery have so the charger starts again the cycle?, maybe when it gets lower than float?, in that case, it goes directly to bulk and then absorption?

I had this problem, and I think it may come from the bms that they put on these units being set to cut off at 28v. I scratched my head for days when my inverter would go into alarm as the voltage passed 28v. Because my Epever software records the max voltage for the day, I was able to see that it hit 35.8v. LONG story short, my working theory is that the bms abruptly shuts the current off at 28v, the controller says "whoa, what happened" and shuts off its pv input relay, and the abrupt pv shutdown causes a small voltage spike on the charging circuit. The bms doesn't care, but my inverter doesn't like seeing > 32v, so it shuts off. My solution, not ideal, is that I now send the controller output directly to the battery. (You have to go into the cabinet and carefully add another cable to the negative battery post junction. Using this new cable bypasses the bms). The bms still functions and balances cells, but it can't shut off incoming current. This actually is not a big deal, as long as you trust your controller to charge only to its maximum set voltage. Mine does this fine, and I trust it. The other approach I initially used was to charge only to 27.9v. Again, not that terrible a solution, since 28v really does get you to 90+% charge for lifepo4. I don't know how to access the bms to change settings. If anyone knows how, please post.

If you look at the battery voltage (at the connector, which actually is the bms output voltage) after the current shuts off at 28v, it will be different than the actual battery voltage. Even after current starts flowing again, I've seen a difference of 1.5v remain for a while. This delta doesn't happen if you don't "trip" the 28v threshold.

So, assuming this is what's happening, it is not the controller's fault.

Fred S said:

I had this problem, and I think it may come from the bms that they put on these units being set to cut off at 28v. I scratched my head for days when my inverter would go into alarm as the voltage passed 28v. Because my Epever software records the max voltage for the day, I was able to see that it hit 35.8v. LONG story short, my working theory is that the bms abruptly shuts the current off at 28v, the controller says "whoa, what happened" and shuts off its pv input relay, and the abrupt pv shutdown causes a small voltage spike on the charging circuit. The bms doesn't care, but my inverter doesn't like seeing > 32v, so it shuts off. My solution, not ideal, is that I now send the controller output directly to the battery. (You have to go into the cabinet and carefully add another cable to the negative battery post junction. Using this new cable bypasses the bms). The bms still functions and balances cells, but it can't shut off the current. This actually is not a big deal, as long as you trust your controller to charge only to its maximum set voltage. Mine does this fine, and I trust it. The other approach I initially used was to charge only to 27.9v. Again, not that terrible a solution, since 28v really does get you to 90+% charge for lifepo4. I don't know how to access the bms to change settings. If anyone knows how, please post.

If you look at the battery voltage (at the connector, which actually is the bms output voltage) after the current shuts off at 28v, it will be different than the actual battery voltage. Even after current starts flowing again, I've seen a difference of 1.5v remain for a while. This delta doesn't happen if you don't "trip" the 28v threshold.

So, assuming this is what's happening, it is not the controller's fault.

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What BMS do you have FRED?

A 5 minutes ago, i did a quick test.

Starting from Battery "Charged" (At least from the Inverter point of view)

• Disconected AC Mains, leave it to uncharge around 1A (24W).
• Connected again AC main, equipment started charging...
• Suddenly stopped charging, wich its not expected since generally it goes from BULK (50A) to absorption (From 50 to 1A gradually).
• As charge stopped, bateries voltage went a little below 27V.

Would love to see Daly's datasheet or know how they work!..

PD: One disadvantage of leaving the charge up to 28V is that the BMS might never start to balance?... ass they start doing it at the end of charge, howemever still dont know where they are triggered to start this process.

i don't know what brand the bms is. I'd like to track that down, but haven't spent much time on it. I remember looking up what is on the bms label, and not finding anything definitive. I'm sure the info is out there somewhere. It seems to be a good unit. I checked cell voltages for the 1st time recently and found them to be consistent, so i think it is balancing like it should. I suppose it must be "active" balancing, since I have the charger bypassing the bms.

Larry S said:

I have a LV2424 connected to a 24v LiFepo4 from Big Battery. My problem is that when charging it hits about 28.2v then quits charging and goes to a float voltage of about 27.4v. I have Program 5 set to user, and currently, (for troubleshooting) program 26 set to 29.0v. Also, I currently (for troubling) have program 27 set to 27.7v. I have tried setting program 5 to flooded which I think would cause the charging voltage to reach 29.2v (I know that is the top of cell over-charge), but the results are the same. Any suggestions would help.

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Just scanning via a search subject, & running into this as a LV2424 owner: If you are charging with the grid; I suggest looking at configuration # 21 ... labeled as: "Battery Stop Voltage when grid is available. ... That may possible be limiting your max charge voltage if not set on the "FULL" setting.

Capt Bill said:

Just scanning via a search subject, & running into this as a LV2424 owner: If you are charging with the grid; I suggest looking at configuration # 21 ... labeled as: "Battery Stop Voltage when grid is available. ... That may possible be limiting your max charge voltage if not set on the "FULL" setting.

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Capt bill - also note that not all options are available for the LV2424. For example, I have the MPP PIP-2424LV-MDS and I don't have option #21.