LI battery tuning

[JRHill]

I can't remember if you disabled temp. compensation - that will lower the target voltage but typically not by as much as your are seeing.

Yup, its disconnected. Just getting to the end of the charge cycle now. This is the excitement in my life during rainy season....

[raysun]

I can't remember if you disabled temp. compensation - that will lower the target voltage but typically not by as much as your are seeing.

Yup, its disconnected. Just getting to the end of the charge cycle now. This is the excitement in my life during rainy season....

LOL!

Hang in there Jim! Rainy season will be over in 6 months, tops!

BTW. Today was a very strange day. It was the 1st time in nearly 5 years that I forgot to look at OpticsRE to check on my system. Then somebody texted me with a question, and I was like: Oh yeah, let's see. Oh look at that! 100% SoC. OK, cool, whatever.

[JRHill]

I can't remember if you disabled temp. compensation - that will lower the target voltage but typically not by as much as your are seeing.

Yup, its disconnected. Just getting to the end of the charge cycle now. This is the excitement in my life during rainy season....

LOL!

Hang in there Jim! Rainy season will be over in 6 months, tops!

BTW. Today was a very strange day. It was the 1st time in nearly 5 years that I forgot to look at OpticsRE to check on my system. Then somebody texted me with a question, and I was like: Oh yeah, let's see. Oh look at that! 100% SoC. OK, cool, whatever.

I'm just taking notes. Sure enough the charge kicked out before 54.7. The key to this is in the Battery Status screen. I forced a Bulk and its climbing again at full amps incoming. I have .2 to go to hit the Days Since voltage reset (I lowered it to 54.9 temporally).

Son of a gun, the charge kicked out again at 54.7. Forced another Bulk and its charging again at full amps in. What the heck? Why can't I get to the Absorb set point of 55.2? Why does this have to be so hard?

BTW, one thing is obvious and that's a lot of generator run time happens above 54.4 for the few amp hours going into the batteries above that voltage at full charge load. I will be rethinking generator charging above 54.5 or 54.6. If it was sunlight, cool. But this is like generator run time on a lead acid battery for absorb finishing - or at least thats the way it feels.

More to come....

[JRHill]

OK, I'm done. Fully met all the parameters and couldn't get the FNDC to self reset. My eyes are getting blurry staring at the Mate3. Good 'ol Honda needs a break.

[raysun]

Yup, its disconnected. Just getting to the end of the charge cycle now. This is the excitement in my life during rainy season....

LOL!

Hang in there Jim! Rainy season will be over in 6 months, tops!

BTW. Today was a very strange day. It was the 1st time in nearly 5 years that I forgot to look at OpticsRE to check on my system. Then somebody texted me with a question, and I was like: Oh yeah, let's see. Oh look at that! 100% SoC. OK, cool, whatever.

I'm just taking notes. Sure enough the charge kicked out before 54.7. The key to this is in the Battery Status screen. I forced a Bulk and its climbing again at full amps incoming. I have .2 to go to hit the Days Since voltage reset (I lowered it to 54.9 temporally).

Son of a gun, the charge kicked out again at 54.7. Forced another Bulk and its charging again at full amps in. What the heck? Why can't I get to the Absorb set point of 55.2? Why does this have to be so hard?

BTW, one thing is obvious and that's a lot of generator run time happens above 54.4 for the few amp hours going into the batteries above that voltage at full charge load. I will be rethinking generator charging above 54.5 or 54.6. If it was sunlight, cool. But this is like generator run time on a lead acid battery for absorb finishing - or at least thats the way it feels.

More to come....

Interpreting the graph today, between 54.4V and 100% SoC, the system added 60AH of charge to my battery.

At 450AH capacity that's pretty well in line with the old lead acid Absorb phase in terms of state of charge (mid to high 80's) and added charge, though the correlation is basically meaningless. The time to was 1 hour to full charge @ 60A charge current. Again an essentially meaningless correlation with lead acid charging.

I guess the takeaway here is 54.4V is well away from full charge, and it takes a lot of additional charge to "move the needle" on battery voltage.

What you describe isn't much different than one of our fellow users in Haiti described when trying to charge from grid or gen and using the lower Absorb voltage @ 1 hour spec that Phi used to publish. After much experiment, I suggested he switch to the higher voltage Absorb @ 0.1 hour spec, and he's not reported any issues in months.

I tried the 54.x @ 2H absorb profile, and it worked OK for me. Absorb terminated at 1:29 on the dot for a week. I switched back to the higher termination voltage, and haven't had problems with it either. However, I don't rely on generator/inverter charging for reaching much more than 80% SoC. On a couple of occasions when letting it run toward its 56.0V termination, it did stop charging early, however, I didn't pursue the reason for it.

When I commissioned the battery, I charged it using a single inverter charger, and the generator ran for 12 straight hours to 56.4V termination.

I wonder is there's a calibration issue at play? When I set up the battery, I was very careful to "tweak" both charge controllers, the FNDC, and both inverters. The FM80s are the most precise, the FNDC is "off" by 0.05V (it would seem), and the 0.4V precision of the inverters has them wandering +/- 0.2V relative to the FM80s.

Solar charging is faultless. Inverter charging rarely gets to where it would show calibration fault. The FNDC is pretty dutiful in tracking charge termination. It may be my imagination, but calibrating voltage seems to have improved its SoC tracking as well. Maybe something to do with Peukerts, even though the constant is fixed at lead acid curve rather than lithium.

[raysun]

This is the 2nd day in a row with enough solar harvest to charge the battery to 100%. Watching progress, the battery voltage reached 54.4V right near the end of the 11AM hour. The 12PM graph bar represents the voltage rise from 54.4 to 56.4V. As yesterday, the battery accepted almost exactly 60AH between the two voltage points.

Note: The screen capture was slightly prior to charge termination, which occurred approximately 3 minutes later.

[raysun]

My version of float. IMO, lithium batteries do not benefit from being held at 100% SoC. Here the float voltage is set to a point that permits a small, but continuous discharge from the battery.

This is 2.5 hours after full charge.

[gtarolli]

I have read multiple times that LI batteries don't like being at 100% SOC all the time, e.g. for a backup supply. However, for off-grid, where we discharge them every day, does it still hurt to keep them at float (e.g. 54v) for 3-6 hours before the sun goes down?

[raysun]

I have read multiple times that LI batteries don't like being at 100% SOC all the time, e.g. for a backup supply. However, for off-grid, where we discharge them every day, does it still hurt to keep them at float (e.g. 54v) for 3-6 hours before the sun goes down?

I don't know. In my case I don't need to, so I don't

[sodamo]

I hit 56.4 briefly then seems to hover 98-99. Probably related to load as well.

[JRHill]

OK, I'm done. Fully met all the parameters and couldn't get the FNDC to self reset. My eyes are getting blurry staring at the Mate3. Good 'ol Honda needs a break.

I take it back. Return amps weren't satisfied as I kept forcing a Bulk but killed the genset manually at 55v. So the charge didn't fall back normally. Tonight's charge run will be yet another test. The one thing that I am curious about is y'all are charging via your FM. I'm doing this with the FX. To the FNDC it should not matter?

Edit: I originally wrote 50v above - it was 55)

[JRHill]

BTW, it occurred to me on the trip to town yesterday that this VFX charging behavior may coincide with the failure of the AGS which is most likely the AC board. I've NEVER had this problem (or any other problem) with the VFX before. So there may be a problem with the control board as well.

Anyway, I have the new VFXR ready to swap with the my problematic VFX. So before I do any more whining I should get myself in gear and do what I've been putting off. Zonna has the VFX control board at $345. It has to be worth it since I hate throwing a circuit board at something that may have multiple problems that could take the replacement AC board out.