Hello All

I know it has been discussed a million times and I have read a lot of the posts regarding this but I want to clarify something if possible.

At present I have the bulk charge set to 52.4 volts and the float to 52.0volts and I have been using the system for over a year. After reading a number of posts it struck me that I may have the float a bit too high and that I might need to lower the bulk too. I have an Axpert King (badged as a Conversol V7) 5.0Kw inverter and 7 x420 watt panels that work quite well. I set the battery to user, as it seems to pump the voltage up a lot on the  "Pyl" setting, 56.0v I believe and I have read that this is way above the max recommended voltage per cell in these batteries for a long life. I do not use all of my power per day so I have no isue with the batteries getting too low.

I would however be interested to know if anyone has a definitive answer to the best settings when using the "user" catagory on an inverter. I have the above set but would equally be happy to chage these if there was a better way to preserve the life of the batteries. The other thing I may be incorrect in assuming is, that there is in fact a bulk charge for these batteries and there is no absorbtion voltage and time to be set. This is currently set to Auto.

Any suggestions or qualification of these settings would be appreciated, I might add that I am not electical technician or expert so if you could explain it in straight forward terms that would be a great help. I think I have over read so much about the settings that I have possibly confused myself.

Many thanks

Bony999

On 2024/05/28 at 10:26 AM, bony999 said:

Hello All

I know it has been discussed a million times and I have read a lot of the posts regarding this but I want to clarify something if possible.

At present I have the bulk charge set to 52.4 volts and the float to 52.0volts and I have been using the system for over a year. After reading a number of posts it struck me that I may have the float a bit too high and that I might need to lower the bulk too. I have an Axpert King (badged as a Conversol V7) 5.0Kw inverter and 7 x420 watt panels that work quite well. I set the battery to user, as it seems to pump the voltage up a lot on the  "Pyl" setting, 56.0v I believe and I have read that this is way above the max recommended voltage per cell in these batteries for a long life. I do not use all of my power per day so I have no isue with the batteries getting too low.

I would however be interested to know if anyone has a definitive answer to the best settings when using the "user" catagory on an inverter. I have the above set but would equally be happy to chage these if there was a better way to preserve the life of the batteries. The other thing I may be incorrect in assuming is, that there is in fact a bulk charge for these batteries and there is no absorbtion voltage and time to be set. This is currently set to Auto.

Any suggestions or qualification of these settings would be appreciated, I might add that I am not electical technician or expert so if you could explain it in straight forward terms that would be a great help. I think I have over read so much about the settings that I have possibly confused myself.

Many thanks

Bony999

First 3.65 per cell is highest you should go so 54.75 is max and should only be charge to this volts if your BMS is out of calibration . 

Let the lithium rest for an hour after charging to 54.5 volts and see what's it's resting voltage is and add one volts more for float normally 51v to 52v volts is good for float .

Floating at to high volts will reduce the batteries life . 

If I can remember right  when I had 48v 15 cel lithium it rested at about 50v 

3 hours ago, GMAC said:

First 3.65 per cell is highest you should go so 54.75 is max and should only be charge to this volts if your BMS is out of calibration . 

 

NO! that is way to high for the battery- that will damage the BMS.

Max the pylontech will ever request is 53.2v.

Hello Tinbum and GMAC and thank for the replies.

I think given the responses I will set float to 51.5v  and perhaps the bulk down to 52.0v. Interestingly I also got a reply from Pylontech today after asking if they had a definitive value and they said set bulk and float to 52.4v. Which confused my thinking even more!

I am sure you can see how it can become confusing for someone whithout any in depth knowledge of the battery chemistry of these particular batteries.

I was under the impression the bulk was to get the battery above the float so that when the battery voltage settled after the charge, it rested at the floating voltage and the reason for the bulk being higher was that the battery voltage settled after the bulk charge was removed.

I am grateful for the replies and if anyone else has anything to add I would be more than glad to hear from them.

Regards

Bony999

 

Hello Again all

After a response from Pylontech regarding float and bulk charg rates I have now set bulk and float to 52.5v ,this was there recommendation so I will see if it works OK.

Checking all of the rest of the settings I see the battery re discharge setting is 52.0v and this has made me wonder if this also needs to be altered? What exactly is re discharge voltage and what does it do? Is it the voltage at which the battery starts to discharge to the load or is it something else?

The terminology in the manual confounds me sometimes and I was hoping it would be simply explained as the voltage at which the battery will start to power appliances in the absence of the solar power. I have settings to SBU but have no utility on at this time of year.

If someone has a straight forward explaination and /or a suggestion of the voltage to set on this I would be grateful to hear from you.

Thanks and regards

Bony999

1 minute ago, bony999 said:

Hello Again all

After a response from Pylontech regarding float and bulk charg rates I have now set bulk and float to 52.5v ,this was there recommendation so I will see if it works OK.

Checking all of the rest of the settings I see the battery re discharge setting is 52.0v and this has made me wonder if this also needs to be altered? What exactly is re discharge voltage and what does it do? Is it the voltage at which the battery starts to discharge to the load or is it something else?

The terminology in the manual confounds me sometimes and I was hoping it would be simply explained as the voltage at which the battery will start to power appliances in the absence of the solar power. I have settings to SBU but have no utility on at this time of year.

If someone has a straight forward explaination and /or a suggestion of the voltage to set on this I would be grateful to hear from you.

Thanks and regards

Bony999

Sorry i dont know anything about your inverter to help you.

Hi Tinbum

Thats OK, I am hoping somene may have the secret code to these weird named settings.

I thought it might just be the voltage at which the battery starts to provide power to the loads once it is fully charged but as the charge is 52.5v then the battery would be supplying to the loads before it was fully charged to 52.5v.

I think it may be a translation from Chineese thing too.

Regards

bony999

I know I will get a lot of flack for this, but I am going to post it anyway. 😈

After a lot of research I have found the best voltage for bulk and float are the following: 

Bulk: 3.5V per cell;  to avoid any memory writing charges (yes even a LiFePO4 cell does have slight memory effect from partial charge cycles) 

Float: 3.32V (or less) per cell; to avoid holding the cell at a constant full voltage (floating at full voltage will reduce battery life)

So for a 15s pylontech I would set bulk at  52.5v & float at 49,8v 

I know I will get MANY disagreements, but these settings have kept my system running nonstop for 4 years. I also have two clients (both farmers) using second hand LiFePO4 batteries using these settings for the past 3 years and no problems at all. 
 

I learned a lot from this website: https://nordkyndesign.com/charging-marine-lithium-battery-banks/

42 minutes ago, Gandalf said:

I know I will get a lot of flack for this, but I am going to post it anyway. 😈

After a lot of research I have found the best voltage for bulk and float are the following: 

Bulk: 3.5V per cell;  to avoid any memory writing charges (yes even a LiFePO4 cell does have slight memory effect from partial charge cycles) 

Float: 3.32V (or less) per cell; to avoid holding the cell at a constant full voltage (floating at full voltage will reduce battery life)

So for a 15s pylontech I would set bulk at  52.5v & float at 49,8v 

I know I will get MANY disagreements, but these settings have kept my system running nonstop for 4 years. I also have two clients (both farmers) using second hand LiFePO4 batteries using these settings for the past 3 years and no problems at all. 
 

I learned a lot from this website: https://nordkyndesign.com/charging-marine-lithium-battery-banks/

I agree with you 100%, on my 16 Cell battery I also see the ideal cell voltage are 3.5 V bulk charge and 3.32 V float.

1 hour ago, Gandalf said:

I know I will get a lot of flack for this, but I am going to post it anyway. 😈

After a lot of research I have found the best voltage for bulk and float are the following: 

Bulk: 3.5V per cell;  to avoid any memory writing charges (yes even a LiFePO4 cell does have slight memory effect from partial charge cycles) 

Float: 3.32V (or less) per cell; to avoid holding the cell at a constant full voltage (floating at full voltage will reduce battery life)

So for a 15s pylontech I would set bulk at  52.5v & float at 49,8v 

I know I will get MANY disagreements, but these settings have kept my system running nonstop for 4 years. I also have two clients (both farmers) using second hand LiFePO4 batteries using these settings for the past 3 years and no problems at all. 
 

I learned a lot from this website: https://nordkyndesign.com/charging-marine-lithium-battery-banks/

Not sure why you think you will get flack for this- sounds absolutely fine.

1 hour ago, Tinbum said:

Not sure why you think you will get flack for this- sounds absolutely fine.

I thought I would get flack and many disagreements because I hear so many different ideas of how to charge a lithium battery. 

The thought of charging and floating at the exact same voltage seems absurd to me, but I have heard it so many times. Strictly speaking a lithium battery doesn’t want to be floated at all. The only reason we do it is because all our MPPT’s were designed for lead acid batteries so we have to input some voltage…. 😂

Glad to hear that at least two forum members agree with me. 😁

14 hours ago, Gandalf said:

I thought I would get flack and many disagreements because I hear so many different ideas of how to charge a lithium battery. 

The thought of charging and floating at the exact same voltage seems absurd to me, but I have heard it so many times. Strictly speaking a lithium battery doesn’t want to be floated at all. The only reason we do it is because all our MPPT’s were designed for lead acid batteries so we have to input some voltage…. 😂

Glad to hear that at least two forum members agree with me. 😁

@Gandalf Another thing that I think it's very important is the charging current. My battery OEM recommends 40 Amps, depending on the weather conditions I change it accordingly, but never charge my battery over 30 Amps. after all, even in winter we have at least a good 5 hours to charge.

Hello Antonio de Sa, Gandalf and TinBum.

I have read your replies with interest and have set my us5000 to the suggested float and bulk settings. They do seem to make sense given the reasons for doing so. I am still in the learning stage of this solar stuff but am always happy to learn new things. It have my charge set to 30 amps as I think that is quite adequate in the scheme of things. My last inverter had a 60 amp default and I changed that too.

Always good to hear about different ways of doing things. Do any of you know what a "Battery re-discharge voltage" is or what a good setting for it may be? Mine seems to be set to 52.0 v by default but I am not sure what it is supposed to be. My initial thought is that it is the voltage at which the battery starts to be used when there is not charge being supplied by any other source but I can't be certain.

Any advice would be welcome

Regards

Bony999