Are Pylontech UP5000 and US3000C compatible with Axpert MKS II 5kW?

[Coulomb]

9 hours ago, Green Power said:

The voltage disagreements seem to be he says "Low DC cut-off voltage 47V" and you suggest (post of Jan 16 in this thread) 46.5V or 46V (option 29)

The other disagreement he has float voltage 52.5V whereas you suggest 51.8V.

Yes, sorry, I was going from memory, and I got it wrong. So the dealer's recommendation wasn't too bad, really. A little high on the float voltage, as you say.

With the extra battery module, just add its recommended maximum charge current to your present limit. Usually it works out to C/2, so for a 14.4 kWh total battery, that's around 300 Ah, so I'd expect the total to come to about 150 A for the maximum charge current. If you have two inverter-chargers, you could use a limit of 80 A on one and 70 A on the other.

I have no idea what has to happen at the battery end: who is master, how to wire the comms wires, will they even talk to each other.

[hoohloc]

7 hours ago, Coulomb said:

Yes, sorry, I was going from memory, and I got it wrong. So the dealer's recommendation wasn't too bad, really. A little high on the float voltage, as you say.

With the extra battery module, just add its recommended maximum charge current to your present limit. Usually it works out to C/2, so for a 14.4 kWh total battery, that's around 300 Ah, so I'd expect the total to come to about 150 A for the maximum charge current. If you have two inverter-chargers, you could use a limit of 80 A on one and 70 A on the other.

I have no idea what has to happen at the battery end: who is master, how to wire the comms wires, will they even talk to each other.

Thanks, you just confirmed that I was on the right track. The new UP5000 is going to be a muster and Pylontech confirmed that they are compatible and they will talk to each other. There is comms wires that goes from one battery to the next 

[Green Power]

21 hours ago, Gnome said:

The lower your voltages on Lithium the longer the battery will last. (same for temperature).  But lower voltage = lower state of charge.  So you can potentially have less capacity.

Thanks for this.

It was previously discussed in the forum that Pylontech recommended  "Low DC cut-off voltage 47V" and another poster recommended 46.5V or 46V (option 29).

Pylontech recommended float voltage 52.5V whereas the forum recommendation was 51.8V.

For lithium ion, does the float voltage relate to the % charge (i.e. when you said "lower voltage" above is that "lower float voltage"? If you choose a lower float voltage, can you stop the battery charging at a certain % capacity? If yes, what is the float voltage that corresponds to about 70%, 80% or 90% charged?

Also stated LFP is "within 0.15 volt for 95% of its capacity" which makes me wonder how you can control capacity with voltage. So still a little confused and not managing to google my way to the answer.

This is for 2x US2000C (used with Axpert Mk 11 5kW).

Edited January 30, 2022 by Green Power

[Green Power]

On 2022/01/29 at 1:42 PM, Tinbum said:

That's easy, just put an Arduino, Raspberry Pi or Teensy or similar in the CAN line between the battery and the inverter.

Presumably this is an option if I end up with an inverter with communication with the battery but not if I continue with the current inverter which does not have communication.

[Coulomb]

6 hours ago, Green Power said:

Presumably this is an option if I end up with an inverter with communication with the battery

As I understand it, ICC and other monitoring software, usually running on a Pi, are able to talk to the battery BMS, and control an inverter that doesn't have the ability to talk directly to the BMS. So the Pi acts as a sort of translator, or man in the middle. Or if you like, the Pi provides the missing functionality for the inverter, that functionality being the ability to talk to the battery BMS. But with the Pi, you have a little more flexibility; you're not totally at the mercy of the manufacturer's ideas and decisions (as far as battery management is concerned).

[Tinbum]

1 hour ago, Coulomb said:

As I understand it, ICC and other monitoring software, usually running on a Pi, are able to talk to the battery BMS, and control an inverter that doesn't have the ability to talk directly to the BMS. So the Pi acts as a sort of translator, or man in the middle. Or if you like, the Pi provides the missing functionality for the inverter, that functionality being the ability to talk to the battery BMS. But with the Pi, you have a little more flexibility; you're not totally at the mercy of the manufacturer's ideas and decisions (as far as battery management is concerned).

I dont know about ICC and if it can do that but as I mentioned earlier that is what I do to talk to some Eltek chargers that I have. They operate at a different baud rate and use a different CAN protocol to the Plylontech. I also use it to lower the max voltage to that recommended by Victron for my inverter. All is done in a fail safe manor.

Edited January 31, 2022 by Tinbum

[Don]

11 hours ago, Green Power said:

Pylontech recommended float voltage 52.5V whereas the forum recommendation was 51.8V.

My float settings for my 2 x UP5000 batteries are 51.9V. My bulk charge voltage setting is 52.5V. At 51.8V my one battery only goes to 99% SOC. At 51.9V both go up to 100%. 

11 hours ago, Green Power said:

If you choose a lower float voltage, can you stop the battery charging at a certain % capacity?

Yes, I am sure you can limit the SOC with the charge voltage setting. If you for example only charge the battery to say 51.2V, the SOC will only go up to say 90%. You will have to increase the charge voltage to get it to 100%.

[Green Power]

Further email conversation between me and Jeff (him in red):

 

I'd wondering about improving battery longevity by charging to less than 100%.

 

If 30A is Ok, then I guess 20A and 10A for charging current must be OK for charging to less than 100%. But never >30A. Do you agree?

(That's right! Actually for your battery system, you can achieve a 50A charging current max. when there is a communication. But to protect the cells and if there is some problem in one of the batteries, the smaller 30A current value will help protect the other one from been damaged in this critical conditions.)

 

If float charging voltage of 52.5V is OK, then I guess a lower float voltage 51.0V or 52.0V might be OK for charging to less than 100%. But never >52.5V. Do you agree?

(That's correct! Because sometimes the voltage sensors on the inverter terminals are not very accurate, the full battery voltage is around 53.2V(smaller than 54V). So 52.5V is a charge voltage value that has been limited in a safe range! You do not need to worry about this. ) 

 

________________

 

 

Is there a need for float and bulk voltage to be related in any way, or are they independent? Like if you change way do you have to change the other, or do they have to be with the same, or one higher/Lower than the other, of within a certain range? Or are they completely independent parameters?

Edited January 31, 2022 by Green Power

[hoohloc]

23 minutes ago, Green Power said:

Further email conversation between me and Jeff (him in red):

 

I'd wondering about improving battery longevity by charging to less than 100%.

 

If 30A is Ok, then I guess 20A and 10A for charging current must be OK for charging to less than 100%. But never >30A. Do you agree?

(That's right! Actually for your battery system, you can achieve a 50A charging current max. when there is a communication. But to protect the cells and if there is some problem in one of the batteries, the smaller 30A current value will help protect the other one from been damaged in this critical conditions.)

 

If float charging voltage of 52.5V is OK, then I guess a lower float voltage 51.0V or 52.0V might be OK for charging to less than 100%. But never >52.5V. Do you agree?

(That's correct! Because sometimes the voltage sensors on the inverter terminals are not very accurate, the full battery voltage is around 53.2V(smaller than 54V). So 52.5V is a charge voltage value that has been limited in a safe range! You do not need to worry about this. ) 

 

________________

 

 

Is there a need for float and bulk voltage to be related in any way, or are they independent? Like if you change way do you have to change the other, or do they have to be with the same, or one higher/Lower than the other, of within a certain range? Or are they completely independent parameters?

I had communication and four US2000 that were charging at a max of 25A even though I had lots of sunshine. This I tested for over a year with Pylontech pointing fingers at the inverter and growatt pointing fingers at the batteries until I decided to get rid of the comms. Now my system works as intended and much better

[Don]

2 hours ago, Green Power said:

If 30A is Ok, then I guess 20A and 10A for charging current must be OK for charging to less than 100%. But never >30A. Do you agree?

No, the amps only determine how long it takes to charge your battery to reach your bulk charge voltage and then float charge voltage. The lower the amps, the longer it will take to charge. If you want to limit the SOC, you need to reduce the bulk charge voltage and float voltage, not the charging amps. The amps is the rate at which you charge the battery. You can charge a battery to 100% SOC at 2A, it might just take a few days. 

[Green Power]

Thanks Don. I do understand that one. However I think in practice if I limit the charge current to 10A it would only charge at 10Ax48V per hour =480W. A 4.5kWH battery (total, combined of two) would I think require 9 hours during the day with at least 480W spare, and that's assuming no periods when the battery is helping with loads. It's unlikely I'll have 9 hours with 480W spare. There may typically be only 1-5 hours with that much energy to spare. Therefore, the battery will not charge to 100%. Does that seem right?

But if it can be done in a more controlled and relatively precise way with voltages that would be better I guess. You state: "If you want to limit the SOC, you need to reduce the bulk charge voltage and float voltage".

You said 51.2V float for 90%, what would be the bulk voltage needed for 90%?

And what about for 80%?

Thanks for your help.

[Don]

@Green Power, I am not sure why you don't want to charge your batteries to 100% SOC? That is my first priority. If I run my Pylontech's through the night, once the sun comes up, the solar panels will start to take over the load from the batteries and at some stage start charging the batteries. To fully charge the batteries will take anything from 3-5 hours, depending on clouds. Once the batteries are fully charged, I switch on my 2 x geysers one after the other to heat them up. I have my geysers wired into my essential load. I use CBI Astute Smart Controller to manually switch them on or off when I want to, depending on when I have solar available. Thereafter the solar only supply the load till the sun sets. Once the sun sets, my batteries are at 100% SOC and my geysers steaming hot.

If you do not fully charge the Pylontech batteries, the BMS will not activate to balance your batteries. From what I can gather you are planning to install 2 x US2000 batteries. Therefore, you have two batteries to balance and each have 15 cells per battery. You have 30 reasons to fully charge your batteries. If you continuously only charge your batteries to 90% SOC, they will never balance. This will create their own problems. 

The recommended charging rate for the US2000 is 25A. If you have 2 batteries, set the charging rate to 50A and charge them as quickly as possible. Depending if you have sufficient solar panels to charge them at that rate and carry the load at the same time. If you do not have sufficient solar power available, they will just charge at a lower rate and take longer to fully charge. Once the batteries are fully charged, all the solar power will be available to supply only the load. 

[Scorp007]

54 minutes ago, Don said:

@Green Power, I am not sure why you don't want to charge your batteries to 100% SOC? That is my first priority. If I run my Pylontech's through the night, once the sun comes up, the solar panels will start to take over the load from the batteries and at some stage start charging the batteries. To fully charge the batteries will take anything from 3-5 hours, depending on clouds. Once the batteries are fully charged, I switch on my 2 x geysers one after the other to heat them up. I have my geysers wired into my essential load. I use CBI Astute Smart Controller to manually switch them on or off when I want to, depending on when I have solar available. Thereafter the solar only supply the load till the sun sets. Once the sun sets, my batteries are at 100% SOC and my geysers steaming hot.

If you do not fully charge the Pylontech batteries, the BMS will not activate to balance your batteries. From what I can gather you are planning to install 2 x US2000 batteries. Therefore, you have two batteries to balance and each have 15 cells per battery. You have 30 reasons to fully charge your batteries. If you continuously only charge your batteries to 90% SOC, they will never balance. This will create their own problems. 

The recommended charging rate for the US2000 is 25A. If you have 2 batteries, set the charging rate to 50A and charge them as quickly as possible. Depending if you have sufficient solar panels to charge them at that rate and carry the load at the same time. If you do not have sufficient solar power available, they will just charge at a lower rate and take longer to fully charge. Once the batteries are fully charged, all the solar power will be available to supply only the load. 

Looking at these tables you will notice a drop of 25% in cycles if you operate a lithium between 25 and 85% vs 25 and 75%.

Comsumers demand the maximum capacity and thus charge to 100% for more energy storage at the expense of cycle life.

Charging only to 100% to allow balancing to take place say once every 14 days gives a long life.

Using 50% from 25 to 75% seems to be the sweet spot. This from battery university Web.

Edited February 1, 2022 by Scorp007

[Green Power]

The reason that I want to avoid charging the batteries to 100% is to improve the battery longevity by cycling between 75% and 25% daily perhaps rather than 100% to 50%. We are talking about a 4.5kWH batery pack, but we probably only need about 2kWH from sunrise to sunset in summer.

So it seems to me that charging the battery to 100% in summer would reduce battery longevity for no gain.

Keep in mind that we have perhaps one cloudy day every month or two in the summer, so there is no sense keeping the energy for the next day either.

I am aware of the need to balance cells occasionally by charging to 100% (I even mentioned this myself on page 2 of this thread, but it's been a long thread). So if I do limit to a lower charge then I will still charge to 100% now and then for balancing.

What I need is the relationship between bulk and float voltage and max % state of charge.

Edited February 1, 2022 by Green Power

[Don]

2 hours ago, Scorp007 said:

Charging only to 100% to allow balancing to take place say once every 14 days gives a long life.

 

2 hours ago, Green Power said:

So if I do limit to a lower charge then I will still charge to 100% now and then for balancing.

No. Balancing does not take place overnight. It can take up to 14 days to balance all the cells.

If the OEM states that you should achieve 4000 - 6000 cycles out of a battery, it is assumed you fully charge the battery to 100% SOC every day and it allows the cells to balance.

Why would anyone charge the battery between 25-75% every day and think that is good for a battery? I would love to see the response of the OEM when you return the battery for a warranty claim and show them your charts that you only charged the battery between 25-75% daily and only fully charged it to 100% one day every two weeks for balancing purposes. Don't expect a pat on the back for doing the right thing. 

It is your battery, you paid for it, you do what you think is best. I personally would not recommend it. 

Edited February 1, 2022 by Don

[Nexuss]

11 hours ago, Scorp007 said:

Looking at these tables you will notice a drop of 25% in cycles if you operate a lithium between 25 and 85% vs 25 and 75%.

Comsumers demand the maximum capacity and thus charge to 100% for more energy storage at the expense of cycle life.

Charging only to 100% to allow balancing to take place say once every 14 days gives a long life.

Using 50% from 25 to 75% seems to be the sweet spot. This from battery university Web.

These specs are for EV batteries which use mostly NMC chemistry . LFP cells are not the same and can be cycled 100% to 10%SOC (90% DOD) daily without negatively affecting lifespan. 

[P1000]

The way these BMSs are designed, you should definitely be charging to 100% everyday. Although the cell life is higher when cycling 75-25%, that would already be built into the battery by over-provisioning. The SoH algorithm of the BMS likely also relies on the fact that the batteries get charged to 100%.

[Coulomb]

18 hours ago, Green Power said:

What I need is the relationship between bulk and float voltage and max % state of charge.

Unfortunately, you can't reliably use voltage as a measure of SOC.

You could use say a Victron BMV to count coulombs, and give an accurate measure of SOC, but without charging to 100%, if will gradually drift off and become very inaccurate.

[Green Power]

Thanks everyone. I checked the battery university article that shows 75%-25% beating 100%-50% in longevity and it has a source that leads us to this study:

https://www.researchgate.net/publication/303890624_Modeling_of_Lithium-Ion_Battery_Degradation_for_Cell_Life_Assessment

It states: "Section V presents a set of model parameters derived from LMO battery degradation test data". Within section 5 it states "Table I shows a set of model coefficients tuned using LMO battery degradation test data from the same manufacturer."

So it looks  like the data showing 75%-25% wins is for the LMO chemistry (lithium manganese oxide) rather than LFP.

 

I believe I may have been confused by the Western EV forums where they recommend to charge to 80% daily rather than 100% but I think many Western EVs are NMC rather than LFP.

I just managed to find this: "Here’s what the revised Model 3 owner’s manual for the US says in this respect.“If your vehicle is equipped with an LFP Battery, Tesla recommends that you keep your charge limit set to 100%, even for daily use, and that you also fully charge to 100% at least once per week.” Also "Another recommendation covers the instance where a Model 3 has been parked for longer than a week, in which case “Tesla recommends driving as you normally would and charge to 100% at your earliest convenience.” Source: https://insideevs.com/news/557527/tesla-model3-lfp-charging-recommendations/

So OK, I probably will allow the battery to charge to 100%. Seems like LFP is an ideal choice for home solar.

 

EDIT February 16th: I have now bought the batteries and preparing to install. Discussion continues here: https://powerforum.co.za/topic/11579-correct-inverter-settings/

 

EDIT May 16th: The battery already has a fault and they are going to send me a new BMS board. At the moment, it looks like they will respect the guarantee.

EDIT June 14th: They put in a new board and nothing was charged, so guarantee has been shown to be valid in this case.

Discussion continues here: https://powerforum.co.za/topic/12071-pylontech-high-voltage-alarm/

I was also able to register the battery online a while back and stated which inverter I was using, and got back a registration confirmation that seems to imply the warranty is valid.

 

 

 

Edited June 15, 2022 by Green Power

[GoodMorning]

Anyone with coms wiring diagram for pylontech up5000 n infinisolar V II-5KW inverter