Battery does not reach float Voltage after upgrade to MPPT and Lithium.

[Mattb4]

I.E. our new gas tank holds more gas so we need to put more gas in it initially. If all other things are the same we simply maintain more reserve (more gallons in our larger tank) than with our old tank.

You analogy is not wrong. It indeed partly explains my point. If the new lithium batteries the OP got needs more to charge than her previous AGM batteries did than she can find herself having not enough solar power to charge them.

A complication with batteries over fuel tanks is batteries you want to fully charge if possible. You can get by only filling a tank part way with no consequences.

 

[Katsikas]

are you turning off your AC every day when your solar is less then 30 amps with the Lithium battery?

Hi. What I do is I try to reduce the use as soon as it start to go down keeping the eye on the % screen of the battery not to less than 60% then stop normally. It depends of course what electrical devices I will need to use each evening...

 

[Katsikas]

Dear friends, thanks a lot for taking the time to read and for all the help.
I have news, a few hours ago I got the Wifi unit to configure the Epever Controller, after some hours of fighting to connect and then make it work for sufficient time. I did manage to read quickly the parameters of the user profile for lithium and find out that Float Voltage WAS 13.4 Volt!!!!
I have no explanation for this because when I was in the place were they set all the parameters I did manage to read that parameter and surely I remember that was 13.8 Volt. What I did not remember was Boost. So I quickly changed the value of Float to 13.8 Volt save and check it. Here now is sunset time (Israel) so tomorrow it will be the real test.
I will let you know what will happen ....
Thanks again.
Many Blessings.

 

[Checkthisout]

Dear friends, thanks a lot for taking the time to read and for all the help.
I have news, a few hours ago I got the Wifi unit to configure the Epever Controller, after some hours of fighting to connect and then make it work for sufficient time. I did manage to read quickly the parameters of the user profile for lithium and find out that Float Voltage WAS 13.4 Volt!!!!
I have no explanation for this because when I was in the place were they set all the parameters I did manage to read that parameter and surely I remember that was 13.8 Volt. What I did not remember was Boost. So I quickly changed the value of boost to 13.8 Volt save and check it. Here now is sunset time (Israel) so tomorrow it will be the real test.
I will let you know what will happen ....
Thanks again.
Many Blessings.

Why set the boost at 13.8?

 

[wmgeorge]

Yes, the AC is a very small 300 Wats. unit. The compressor is running all the time (it does not depend on heat) and it is demanding no more than 30 Amps together with computer and lights I know because I check all the time the PWM controller and turn it off the AC everyday as soon as it began to demand from the Gel battery (when the sun begin to give me less than 30 Amps) because I need energy battery for the evening-night. I normally began evening with no less than 12.5 Volts with the Gel battery 12.6 was common . It is exactly the same amount of power that I use but now with an expensive battery and controller is not sufficient. Amazing.

I don't understand how a 300 watt AC unit on 120 volts is going to draw 30 amps if it does the system is not large enough.

Greetings
I recently made a controller and battery upgrade from PWM and Gel to MPPT and Lithium, but I’m a bit disappointed by the poor performance of the MPPT controller and I need help please, it hardly reach the Float Voltage when in use and never the Boost voltage neither. I use a day permanent load of 30 Amps 12 Volts in sunny days and with the old configuration the battery reached the Boost and Float voltage from the morning until evening but now almost never.
This was my old and new configuration.
3 x 300 Watts. 12 Volt 16.5 Amp Solar panels. Connected in parallel.
Epever 60 Amp PWM ControllerVS6024AU
250 Amp. 12 Volt. Gel battery.
New Configuration.
3 x 300 Watts. 12 Volt, 16.5 Amp Solar panels. Connected in series.
Epever 60 Amp Tracer 6415AN
300 AH LIFEO4 Lithium battery
The MPPT controller reaches easily a 50 Amp but voltage hardly 13.5 when in load and the result is not a 100% charged battery at the end of the day.
The controller configuration was set in the place where I purchased it. It was done for a 300Amp lithium battery (Wifi using the android application). I remember as I was watching quickly the parameters that float was 13.8 Volt and Boost 14.4 Volt (not sure maybe 14.6) and reconnect 13.2 Volt.
Can anyone please let me know if it is normal not to reach float and boost voltage with a clear day with a load of 30 Amps like my old setup or a malfunction?
If I do not use the system the battery reach 100% and the voltage reaches float.
Thanks very much ahead

With that load on, (23-24 amps, 12.8 vdc) even in the daytime with 5 or 6 hours of good charging amps its not enough to power that load and charge the LiFePO4 battery to full charge at the same time. You need more panels or less daytime load. LA or Gel batteries can be charged to full but you can only draw 50-70% from them. Float on the LiFePO4 should be 13.5 - 13.8.

 

[Katsikas]

are you turning off your AC every day when your solar is less then 30 amps with the Lithium battery?

I use it more that the Gel battery but turn it off at some point (60% normally).

 

[Katsikas]

I don't understand how a 300 watt AC unit on 120 volts is going to draw 30 amps if it does the system is not large enough.

With that load on, (23-24 amps) even in the daytime with 5 or 6 hours of good charging amps its not enough to power that load and charge the LiFePO4 battery to full charge at the same time. You need more panels or less daytime load. LA or Gel batteries can be charged to full but you can only draw 50-70% from them.

Hi. Is 220 Volts here.

 

[Katsikas]

Why set the boost at 13.8?

I checked it now, boost was 14.4

Why set the boost at 13.8?

Sorry my mistake Float 13.8 Boost 14.4

 

[Checkthisout]

I checked it now, boost was 14.4

Sorry my mistake Float 13.8 Boost 14.4

You need more panels.

When it comes to panels, more is always better.

 

[GSXR1000]

I use it more that the Gel battery but turn it off at some point (60% normally).

if you are using more resources then it not keeping up.. the battery provides zero more power available... just provides more cushion for cloudy days... but it take more solar to charge when fully drained.

solar panels are the only thing that gives you more resources to use your appliances longer...

pwm vs mttp at mid day preform almost the same..
mttp advance is dust and dawn and overcast days

 

[acdoctor]

I would suggest checking the specs for the new solar charge controller for the maximum panels on 12 volts. Most are 7 to 8 hundred watts. The balance is just cut. Also I agree you have a larger battery now that maybe has never been fully charged.

 

[400bird]

If you have shading one or two of your panels, the will not produce as well as parallel.

Hi. What I do is I try to reduce the use as soon as it start to go down keeping the eye on the % screen of the battery not to less than 60% then stop normally. It depends of course what electrical devices I will need to use each evening...

What screen says 60% soc?
If it is the inverter or charge controller that is a huge part of the problem (good find on the charge voltage, that's huge too)
If you want to know state of charge, look at the battery information. Hopefully your's has an app or display.

Thinking upon this a bit and researching where I can there is another possibility for why your new setup is not achieving the same as your previous setup with the same loading. Different battery chemistry might be giving a increase in charge needed compared to discharge available. It seems for lithium battery vehicles the loss for charge discharge is around 70%.

Everyone is concentrated on DOD (depth of discharge) and hardly no one is testing or listing efficiency.

There are many, many studies on this. Google will help.
One of the lowest I've seen a lithium battery as 90% efficient. Most say 95-99% round trip efficiency (battery only, most round trip numbers include the inverter and charger)
This study has lithium at 96-98% efficient:

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.osti.gov/servlets/purl/1409737&ved=2ahUKEwiX9b6t06n5AhXwK0QIHa0VD_w4ChAWegQIBxAB&usg=AOvVaw1GaTrQfOu8dXneqjrCCmsB

While lead acid is known to be significantly lower. Part of the normal charge process is equalization where some energy is purposely wasted as heat.
This lists lead acid as 70-85% depending on the state of charge.

https://www.sciencedirect.com/topics/engineering/ah-efficiency#:~:text=Lead%E2%80%93acid%20batteries%20typically%20have,the%20higher%20is%20the%20efficiency

More links are available on request, just ask the Googles or duck duck go.

 

[Katsikas]

If you have shading one or two of your panels, the will not produce as well as parallel.


What screen says 60% soc?
If it is the inverter or charge controller that is a huge part of the problem (good find on the charge voltage, that's huge too)
If you want to know state of charge, look at the battery information. Hopefully your's has an app or display.



There are many, many studies on this. Google will help.
One of the lowest I've seen a lithium battery as 90% efficient. Most say 95-99% round trip efficiency (battery only, most round trip numbers include the inverter and charger)
This study has lithium at 96-98% efficient:

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.osti.gov/servlets/purl/1409737&ved=2ahUKEwiX9b6t06n5AhXwK0QIHa0VD_w4ChAWegQIBxAB&usg=AOvVaw1GaTrQfOu8dXneqjrCCmsB

While lead acid is known to be significantly lower. Part of the normal charge process is equalization where some energy is purposely wasted as heat.
This lists lead acid as 70-85% depending on the state of charge.

https://www.sciencedirect.com/topics/engineering/ah-efficiency#:~:text=Lead%E2%80%93acid%20batteries%20typically%20have,the%20higher%20is%20the%20efficiency

More links are available on request, just ask the Googles or duck duck go.

Thanks for the links. The 300 Amp battery got a small display with %.

 

[hclarkx]

katsikas, I'm a bit puzzled. You mention charging at what looks to be a bulk level for the solar that you have (though it could be from the 13.8 float if the battery is severely discharged). Are you watching close enough to know that the MPPT charger is not going into bulk?. Voltage will rise above 13.8V only at the end of the bulk stage and from there will hit 14.4 within a minute or two and then drop back to float in another minute or two depending on load. Are you watching closely enough to see action which takes only a couple of minutes? Also, what monitor are you using to track SOC? It will be accurate only if voltage is getting up to 14.4 V. You need to get up there for balancing and SOC monitor "synchronization." But, it should tell you what's going on. Finally, is the battery getting down to 13.2 volts overnight? If not, the SCC will not trigger into bulk mode in the morning. Note that 13.2V entered on the MPPT controller for the bulk trigger may actually be a bit lower at the battery.

 

[Ampster]

This is claimed but mostly due to the ability to have greater depth of discharge and higher rates of charge.

Also a Lithium battery does not need an extended absorb stage or float to keep it full which is a fact, not just a claim. That alone is possibly the biggest factor in charging efficiency. Depth of discharge has nothing to do with charging efficiency.

 

[Katsikas]

katsikas, I'm a bit puzzled. You mention charging at what looks to be a bulk level for the solar that you have (though it could be from the 13.8 float if the battery is severely discharged). Are you watching close enough to know that the MPPT charger is not going into bulk?. Voltage will rise above 13.8V only at the end of the bulk stage and from there will hit 14.4 within a minute or two and then drop back to float in another minute or two depending on load. Are you watching closely enough to see action which takes only a couple of minutes? Also, what monitor are you using to track SOC? It will be accurate only if voltage is getting up to 14.4 V. You need to get up there for balancing and SOC monitor "synchronization." But, it should tell you what's going on. Finally, is the battery getting down to 13.2 volts overnight? If not, the SCC will not trigger into bulk mode in the morning. Note that 13.2V entered on the MPPT controller for the bulk trigger may actually be a bit lower at the battery.

 

[Katsikas]

View attachment 105387

 

[Katsikas]

View attachment 105388

Thanks for the post. Here are the settings. I'm testing the system for a few days before I decide what to do. Since I change the Float Voltage to 13.8 thinks are better and I saw for the very first time yesterday the battery showing 100%, I was not in the van during the day. I almost never saw the voltage go to 14.4 or near. But the voltage is higher than before toping 13.8 Volt when in use with full sun.
According with the configuration Boost suppose to run for 120 Minutes? Maybe 120 seconds? Still feel that it was working better during sunny hours with PWM, the voltage was 13.8 Volt and sometimes 14.2 Volt for a while then, and it was really hard to bring it down. (AC, fridge, computer and more was necessary). The voltage today in the morning was more than 13.2, I understand by what you said that this trigger Boost in the morning and not the sun light reaching the panels. The roof of the Van is cover with panels no option to put more. I'm thinking that if I change Boost Reconnect Charging Voltage to 13.4 it will keep the battery full until the sun will begin to fall. Is it to high?

 

[Mattb4]

Also a Lithium battery does not need an extended absorb stage or float to keep it full which is a fact, not just a claim. That alone is possibly the biggest factor in charging efficiency. Depth of discharge has nothing to do with charging efficiency.

Problem is what parameters you select to describe efficiency. If you based it on DOD than indeed the lithium battery is more efficient. 80-90% battery utilization versus 50% battery utilization without impact on total life time. Hard to argue that.

What would be handy is if someone would take both a LiFePo4 battery and a AGM battery of the same capacity. Subject both to the same load for a given time period to achieve around 50% discharge. After that recharge them both to full based on standard charging practices and measure the amount of watts to do so. It would also be of interest to give the time it takes for each style of battery to reach full charge (not keeping them there because as you mention LA have self discharge happening).

I don't run lithium batteries myself but am interested in them. So far from what I read on this Forum they seem to be more problems than they are worth. The need of BMS and monitoring of individual cell voltages adds a lot of complications to deal with.

 

[Ampster]

What would be handy is if someone would take both a LiFePo4 battery and a AGM battery of the same capacity. Subject both to the same load for a given time period to achieve around 50% discharge. After that recharge them both to full based on standard charging practices and measure the amount of watts to do so.

The data is out there. Lots of those tests have been done. Google is your friend.

I don't run lithium batteries myself but am interested in them. So far from what I read on this Forum they seem to be more problems than they are worth. The need of BMS and monitoring of individual cell voltages adds a lot of complications to deal with.

Everyone gets to choose their priorities. I gave up on LA twelve years ago because I did not like the inconvenience of having to charge them after each run on the ebike I built. I belong to another forum where there are more Lead Acid users and it seems they have to constantly water them and check the specific gravity. Too much work for me. It all depends on where you are standing.