LI batteries normal running temperature

[Antonio de Sa]

I would like to get some expert comments/advice of what is normal/ acceptable on LI batteries temperatures.

I've contacted the OEM of my battery and the response was that they are within spec's, herewith graphic of the last 6 hours of the temperatures on my battery been charged at 40 Amps.

 

[FixAMess]

I've got pylontechs, never seen them above 29C even when discharging at 90A which is about C/3.

Excessive temperature is what kills them, apparently they're happy between 10-30C.....

Edited November 14, 2021 by FixAMess

[Nexuss]

For Pylontech.

[Antonio de Sa]

12 minutes ago, 87 Dream said:

Hi @Antonio de Sa, you have this data well documented on grafana. Do you have more data like the same type of info with a time scale vs SoC...I think this will allow for better interpretation. Also where are your packs kept? This temp data is not usual at all. But one needs to see the data in correlation with other stats to make a proper assessment.

87

@87 Dream, Yes, I basically have everything stored an archived on our home server. My son is a top IT programmer, let me show you some of the data I have. I'm going to send you a few.

[Antonio de Sa]

52 minutes ago, 87 Dream said:

Hi @Antonio de Sa, you have this data well documented on grafana. Do you have more data like the same type of info with a time scale vs SoC...I think this will allow for better interpretation. Also where are your packs kept? This temp data is not usual at all. But one needs to see the data in correlation with other stats to make a proper assessment.

87

@87 DreamThe battery is a LISA 51.2 V, 100 AH, 5.1 KWh, I've sent the same data to they technical department as I was a bit concerned, they assured me it's normal, here is the response from them and I quote : 

Hi Antonio,

 

All looks good.

The temperatures are within range.

 

Edited November 14, 2021 by Antonio de Sa

[Antonio de Sa]

9 minutes ago, 87 Dream said:

Without knowing the exact charge profile off the top of my head, Im not that good of a boff unfortunately. What your data shows is that the only time your battery pack went above the 30 degrees mark was when your charge amps went above 39A to 40A. +- 08:30 to 09:30.

I have no clue about the pylontech or even in which environment you keep these batteries but what i can suggest if you are very concerned and have the time to test and evaluate data. Set your charge setting to 30A and check your temperature profile data on completion of the charge cycle. Then do another adjustment to 35A and check the temperature profile again.

That way you can eliminate the environmental site of your batteries or the Charge amps being too high. What i will comment on is that if charging at 30A vs 40A buys you a more stable cooler battery, i think you will benefit from that Amperage adjustment in terms of cycles long term. Less stress on your pack and it will take marginally longer to charge. Its a trade off but in your favor.

Maybe other Pylontech operators can comment but in my experience of machine and battery operations this is what my gut tells me.

87

@87 Dream the battery is not Pylontech, it's a LISA battery, they are rated to 50 Amps charge, but I will reduce the charging current to 30 amps and monitor it for a few days. Thanks for the reply. Regards.

[Antonio de Sa]

4 minutes ago, 87 Dream said:

My apologies for this assumption. So i will make another assumption and apologise if this second assumption is incorrect. Are the Batteries LBSA?

87

@87 Dream, Let me add that the information I have is retrieved straight from the battery, so those values are pretty much  accurate. Yes, sorry the battery is LBSA indeed, I have my settings as per OEM recommendation in the manual, the only difference is the charging current that I've set to 40 Amps, in stead of 50 Amps, I will do as you say, reduce the charging voltage to 55 V, at present the discharge is at 44 V as recommended, now stops at about 7 AH +_ about 7% I will set that value to 45 V and monitor it for a few days. I will give you feed back in a few days. 

 

[Antonio de Sa]

12 minutes ago, 87 Dream said:

Please dont just make these settings changes without some thought. My recommendations come from the following calculation and consideration.

This is a 16s battery: So whatever voltage is divided by 16 cells. So if you charge bulk to 55V you will not reach 100% SoC maybe you will reach 93% and you need accept this. Why because 55V / 16s = 3.43V per cell. At 56V recommendation / 16s = 3.5V per cell. The MAX voltage per cell is 3.65V. So i clip this and aim for the lower value to absorb charge. Less stress...

The same with the dicharge cut off. At 44V recommendation /16s = 2.75V per cell. This is very very low and is stress on the cells. I rather aim for around 49V at the least = 3.06V per cell. Zero stress at this voltage.

I believe if this battery or any LFP pack is treated with these very conservative settings they will out last the 10yr warranty and will never get damaged. So cycles beyond 6000. 

87

@87 DreamI also done some calc's and it makes 100% sense what you said above, the idea is to maximize the battery life span, even if I have to use a bit more grid power every day, the savings on a few KW/H it's senseless if one is stressing the battery. I've change the settings, let's wait and monitor the results. see attached. There is a bit of a lag between the inverter and battery voltage due to different scanning time.

Edited November 14, 2021 by Antonio de Sa

[FixAMess]

21 hours ago, 87 Dream said:

If you meant LBSA then this is a shot of their data and manual...I say again and say this with a massive pinch of salt. Sometimes we need to set more conservative settings so that a product can last longer. As can be seen once again its my assumption that this is what you meant to say is that its a LBSA pack.

You have the data and the data has a trend. Another example I can give you is that LBSA suggests a Charge Bulk of 56V. I dont setup my batteries like this at all. I reduce this to 55V and only do a top balance as a procedure once a month. So i only set the battery charger to 56V once in 30 days. I also dont discharge all the way to 0% i leave at least 15% left over. 

I am making well researched and informed positive decisions in the favor of the batteries longevity and cycle life. My point here is that Batteries are not cheap items, make sure you respect the chemistry and why get close to any of the limits. Its not healthy for any machine to operate near limits for too long. Engines and high EGT comes to mind in the world of machanics.

87

!00% DoD, this flies in the face of all the research I have done, batteries are best kept at between 10-90% SoC, certainly not 100% DoD.