Absorb/Bulk switching back and forth

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jstone
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Absorb/Bulk switching back and forth

Post by jstone » Sun Aug 02, 2020 11:32 am

Added to the problems with mini grid, currently I am connected to grid and solar. The absorb voltage is reached and it bounces back and forth between absorb and bulk...Anyone know what would cause this?


Event history:
Screenshot from 2020-08-02 11-27-22.png
Charger settings inverter:
Screenshot from 2020-08-02 11-29-25.png

Charger settings CC:
Screenshot from 2020-08-02 11-29-46.png

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Re: Absorb/Bulk switching back and forth

Post by raysun » Sun Aug 02, 2020 11:40 am

This is a common occurance when the charge controllers are receiving insufficient PV harvest to maintain the Absorb voltage. The controllers will drop back to Bulk until enough solar power is available.

The battery charge parameter Absorb Time (charge controllers) is preserved during these transitions. The ChgT counter increments only during the active Absorb phase.

If the PV harvest remains unable to drive the Charge Contollers to Absorb, then the Inverter Charger will complete the charge cycle (at its lower Absorb voltage).

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Re: Absorb/Bulk switching back and forth

Post by jstone » Sun Aug 02, 2020 12:27 pm

raysun wrote:
Sun Aug 02, 2020 11:40 am
This is a common occurance when the charge controllers are receiving insufficient PV harvest to maintain the Absorb voltage. The controllers will drop back to Bulk until enough solar power is available.

The battery charge parameter Absorb Time (charge controllers) is preserved during these transitions. The ChgT counter increments only during the active Absorb phase.

If the PV harvest remains unable to drive the Charge Contollers to Absorb, then the Inverter Charger will complete the charge cycle (at its lower Absorb voltage).
Thanks for that explanation. The problem I am having is I'm never going into Absorb mode for the prescribed 3 hours, either with the CC or Inverter charger. How can I resolve this to ensure adequate charging?

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Re: Absorb/Bulk switching back and forth

Post by raysun » Sun Aug 02, 2020 12:44 pm

jstone wrote:
Sun Aug 02, 2020 12:27 pm
raysun wrote:
Sun Aug 02, 2020 11:40 am
This is a common occurance when the charge controllers are receiving insufficient PV harvest to maintain the Absorb voltage. The controllers will drop back to Bulk until enough solar power is available.

The battery charge parameter Absorb Time (charge controllers) is preserved during these transitions. The ChgT counter increments only during the active Absorb phase.

If the PV harvest remains unable to drive the Charge Contollers to Absorb, then the Inverter Charger will complete the charge cycle (at its lower Absorb voltage).
Thanks for that explanation. The problem I am having is I'm never going into Absorb mode for the prescribed 3 hours, either with the CC or Inverter charger. How can I resolve this to ensure adequate charging?
I'm wondering if Absorb is getting tangled up in the Minigrid/HBX incompatibility.

Perhaps, to debug the charging issue, turn off Minigrid, and HBX (and anything else that attempts to sell to the grid.)

I'd also turn off Global Charger Control on the FNDC (if one is in the system) to allow the FM80 to charge autonomously.

Check the parameters on the FM80. Set End Amps to 0.

Start a session charging with PV only. Hopefully it will be a clear weather day, and a full charge cycle will be completed. A full 3 hour Absorb should be executed.

If not fully charged at the end of the solar day, switch on Grid input and charge with the Inverter. Note, the Inverter will have no clue as to the amount of time the FM80 has been in Absorb, so will attempt to run its Absorb for the full time on its internal timer (which may or may not be the 3 hour setting on the Battery Charging parameters.) Once the battery charge current has reached the End Amps value for the battery, manually terminate charge.

BTW, if you complete your profile with full equipment list, battery type/model/capacity and PV array model(s)/capacity/configuration, we will be able to answer questions more succinctly.

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Re: Absorb/Bulk switching back and forth

Post by EA6LE-ONE » Sun Aug 02, 2020 1:11 pm

like i stated on pss post, there is also a correlation between the loads on the inverter and the absorb/bulk on CCs, once you reach absorb on CCs any load change(maybe the more larger ones) on inverter is resetting the charging on CCs trying to determine the new current needed to keep absorb. same thing happening on float.

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Re: Absorb/Bulk switching back and forth

Post by jstone » Sun Aug 02, 2020 1:20 pm

EA6LE-ONE wrote:
Sun Aug 02, 2020 1:11 pm
like i stated on pss post, there is also a correlation between the loads on the inverter and the absorb/bulk on CCs, once you reach absorb on CCs any load change(maybe the more larger ones) on inverter is resetting the charging on CCs trying to determine the new current needed to keep absorb. same thing happening on float.
My loads never change more than about 100w or so. And I have 1.2k of panels, in Arizona, full sun generating around 1kw. Another thing I've noticed is, if I drop the AC, the PV used is much higher than if the grid ac is on. It's like it's not taking advantage of the full sun. I have disabled offsetting cause that really messed things up. I just want it to use full solar, and augment the charging with grid as necessary, and that appears impossible.

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Re: Absorb/Bulk switching back and forth

Post by jstone » Sun Aug 02, 2020 1:23 pm

When grid is turned on, look at the PV used (and it's full sun). If I drop AC, it jumps up .83. Why can't it use .83 from the PV and then supplement with grid?
Screenshot from 2020-08-02 13-20-55.png

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Re: Absorb/Bulk switching back and forth

Post by EA6LE-ONE » Sun Aug 02, 2020 1:29 pm

on inverters set the absorb voltage 0.4V lower.

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Re: Absorb/Bulk switching back and forth

Post by raysun » Sun Aug 02, 2020 1:31 pm

jstone wrote:
Sun Aug 02, 2020 1:23 pm
When grid is turned on, look at the PV used (and it's full sun). If I drop AC, it jumps up .83. Why can't it use .83 from the PV and then supplement with grid?

Screenshot from 2020-08-02 13-20-55.png
Not being able to see the rest of the data, I'm assuming the battery is still charging, probably in Absorb. When the Grid is connected to AC IN, I assume it acts as generator does when connected to AC IN. That is, the Inverter is no longer inverting, but switched to charging mode (through the Inverter Charger is inactive, because it's absorb voltage is below the battery voltage, or the charger is currently disabled.) The Grid services loads with Inverter bypassed.

If you drop the Grid now, I'd think the PV harvest would rise. But with such a small panel array, it likely won't service loads and charging simultaneously.

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Re: Absorb/Bulk switching back and forth

Post by jstone » Sun Aug 02, 2020 1:38 pm

raysun wrote:
Sun Aug 02, 2020 1:31 pm
jstone wrote:
Sun Aug 02, 2020 1:23 pm
When grid is turned on, look at the PV used (and it's full sun). If I drop AC, it jumps up .83. Why can't it use .83 from the PV and then supplement with grid?

Screenshot from 2020-08-02 13-20-55.png
Not being able to see the rest of the data, I'm assuming the battery is still charging, probably in Absorb. When the Grid is connected to AC IN, I assume it acts as generator does when connected to AC IN. That is, the Inverter is no longer inverting, but switched to charging mode (through the Inverter Charger is inactive, because it's absorb voltage is below the battery voltage, or the charger is currently disabled.) The Grid services loads with Inverter bypassed.

If you drop the Grid now, I'd think the PV harvest would rise. But with such a small panel array, it likely won't service loads and charging simultaneously.
Yes, that is what happens. I dropped it and it rose to .83. Here is what I don't understand...the PV is capable right now of .83 (cause right now that's what it is using with AC dropped)....logically, if it CAN produce .83, why does not continue to contribute that when I add AC to the mix? Seems like wasted RE to me to allow the inverter to assume all or most of the current. At one point today PV was ZERO and the CC was in silent mode..in full sun. I really need someone to pick through my entire system and adjust everything accordingly. It's probably very confused from all the config changes I've made.

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Re: Absorb/Bulk switching back and forth

Post by jstone » Sun Aug 02, 2020 1:41 pm

EA6LE-ONE wrote:
Sun Aug 02, 2020 1:29 pm
on inverters set the absorb voltage 0.4V lower.
It was 0.3 lower...changed to 0.4, but I highly doubt this will make my charger stay in absorb for 3 hours like I ask it to. ](*,) ](*,)

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Re: Absorb/Bulk switching back and forth

Post by EA6LE-ONE » Sun Aug 02, 2020 2:40 pm

you have have 24V system , 0.2V should be fine as long the inverters and charges are well calibrated.
for 48V is 0.4V.

the difference is needed to prioritize charging from solar over grid.
not sure why is your inverter staying on to charge in absorb with the timer set. did you tried to have the inverters charging only when is no solar charging? maybe if there is solar charging in the same time might not respect the timer.

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Re: Absorb/Bulk switching back and forth

Post by EA6LE-ONE » Sun Aug 02, 2020 2:42 pm

what settings you have to met charge on FNDC?

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Re: Absorb/Bulk switching back and forth

Post by raysun » Sun Aug 02, 2020 3:42 pm

jstone wrote:
Sun Aug 02, 2020 1:41 pm
EA6LE-ONE wrote:
Sun Aug 02, 2020 1:29 pm
on inverters set the absorb voltage 0.4V lower.
It was 0.3 lower...changed to 0.4, but I highly doubt this will make my charger stay in absorb for 3 hours like I ask it to. ](*,) ](*,)
O.2V is the typical value used to establish priority for a 24V system. 0.4V should not be needed, unless the devices are off calibration.

Make sure the charging program in the FM80 is properly configured. Besides the Absorb Voltage, Absorb Time, and float voltage, make sure:

• End Amps = 0
• Re-Bulk Voltage is set as appropriate for the system.

This value is tricky, as it does more that what appears in its name. Re-Bulk is, of course, the battery voltage that triggers another Bulk charge cycle. If the battery is not drawn down to the Re-Bulk voltage, the FM80 may wake up the next day, start a charge cycle, and proceed quickly to Float. There is a second, related function to Re-Bulk. For every minute the battery stays above Re-Bulk, one minute is subtracted from the Absorb Time internal counter (ChgT). For every minute below Re-Bulk, one minute is added to the counter. There's another level, but I forget the value, below Re-Bulk where every minute adds four minutes to the counter.

I'd suggest starting with a fairly high value for Re-Bulk (maybe 0.2V below Float) to force maximum time for ChgT. Once you see the 3 hour Absorb phase being executed, Re-Bulk can be adjusted down to a more practical point (that you will likely have to determine by experiment.)

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Re: Absorb/Bulk switching back and forth

Post by fcwlp » Sun Aug 02, 2020 5:16 pm

raysun wrote:
Sun Aug 02, 2020 3:42 pm
• End Amps = 0
• Re-Bulk Voltage is set as appropriate for the system.

This value is tricky, as it does more that what appears in its name. Re-Bulk is, of course, the battery voltage that triggers another Bulk charge cycle. If the battery is not drawn down to the Re-Bulk voltage, the FM80 may wake up the next day, start a charge cycle, and proceed quickly to Float. There is a second, related function to Re-Bulk. For every minute the battery stays above Re-Bulk, one minute is subtracted from the Absorb Time internal counter (ChgT). For every minute below Re-Bulk, one minute is added to the counter. There's another level, but I forget the value, below Re-Bulk where every minute adds four minutes to the counter.

I'd suggest starting with a fairly high value for Re-Bulk (maybe 0.2V below Float) to force maximum time for ChgT. Once you see the 3 hour Absorb phase being executed, Re-Bulk can be adjusted down to a more practical point (that you will likely have to determine by experiment.)
One of the reasons to use a FNDC.

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Re: Absorb/Bulk switching back and forth

Post by jstone » Sun Aug 02, 2020 6:33 pm

EA6LE-ONE wrote:
Sun Aug 02, 2020 2:40 pm
you have have 24V system , 0.2V should be fine as long the inverters and charges are well calibrated.
for 48V is 0.4V.

the difference is needed to prioritize charging from solar over grid.
not sure why is your inverter staying on to charge in absorb with the timer set. did you tried to have the inverters charging only when is no solar charging? maybe if there is solar charging in the same time might not respect the timer.
When it is supposed to kick on is when the voltage drops below 24v for 6 minutes as I currently have it set. That happens in the middle of the night based off the battery draw during consumption. It goes to absorb voltage and immediately drops to float voltage most of the time. Although last night, it completely ignored the mini grid voltage and almost killed my batteries. I've tried HBX which is marginal, but I really liked the "idea" of mini grid in that it shares the load as necessary to charge the batteries, either at night or in low PV production which is the case currently as I only have (4) 325w panels. I will be upgrading to 9 panels soon. That will solve the daytime PV issue on a sunny day, but still doesn't fix the issue that the charger doesn't respect timers.

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Re: Absorb/Bulk switching back and forth

Post by raysun » Sun Aug 02, 2020 6:51 pm

jstone wrote:
Sun Aug 02, 2020 6:33 pm
EA6LE-ONE wrote:
Sun Aug 02, 2020 2:40 pm
you have have 24V system , 0.2V should be fine as long the inverters and charges are well calibrated.
for 48V is 0.4V.

the difference is needed to prioritize charging from solar over grid.
not sure why is your inverter staying on to charge in absorb with the timer set. did you tried to have the inverters charging only when is no solar charging? maybe if there is solar charging in the same time might not respect the timer.
When it is supposed to kick on is when the voltage drops below 24v for 6 minutes as I currently have it set. That happens in the middle of the night based off the battery draw during consumption. It goes to absorb voltage and immediately drops to float voltage most of the time. Although last night, it completely ignored the mini grid voltage and almost killed my batteries. I've tried HBX which is marginal, but I really liked the "idea" of mini grid in that it shares the load as necessary to charge the batteries, either at night or in low PV production which is the case currently as I only have (4) 325w panels. I will be upgrading to 9 panels soon. That will solve the daytime PV issue on a sunny day, but still doesn't fix the issue that the charger doesn't respect timers.
I'd be willing to bet the charger is respecting timers, just not in the way you think (or would like). I can explain the charge cycle for the FM series pretty well, but the complexities of the Inverter charger must be studied in the docs. It does a bunch of stuff to maintain continuity across multiple, possibly interrupted, charge cycles. There's a section on it in the Inverter manual. It is not as simple as "wake up and start at Bulk".

Again, I'd highly suggest putting the grid interactive and HBX modes on the back burner until the nuances of charging are understood and can be consistently managed.

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Re: Absorb/Bulk switching back and forth

Post by EA6LE-ONE » Mon Aug 03, 2020 5:04 am

raysun wrote:
Sun Aug 02, 2020 3:42 pm

This value is tricky, as it does more that what appears in its name. Re-Bulk is, of course, the battery voltage that triggers another Bulk charge cycle. If the battery is not drawn down to the Re-Bulk voltage, the FM80 may wake up the next day, start a charge cycle, and proceed quickly to Float. There is a second, related function to Re-Bulk. For every minute the battery stays above Re-Bulk, one minute is subtracted from the Absorb Time internal counter (ChgT). For every minute below Re-Bulk, one minute is added to the counter. There's another level, but I forget the value, below Re-Bulk where every minute adds four minutes to the counter.
This is something new I just learned. always good to read every post here :)

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Re: Absorb/Bulk switching back and forth

Post by jstone » Mon Aug 03, 2020 7:31 am

Thanks for that explanation. Why on earth anyone would design one counter to affect is another is beyond me, but I guess we are stuck with it. I'm going to run a day with Re-Bulk on both the inverter and CC at 27.2, which is 0.2 less than float. Fingers crossed for a normal night. I switched to grid use mode because I can no longer trust mini grid to kick on at the prescribed voltage.

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Re: Absorb/Bulk switching back and forth

Post by raysun » Mon Aug 03, 2020 4:04 pm

jstone wrote:
Mon Aug 03, 2020 7:31 am
Thanks for that explanation. Why on earth anyone would design one counter to affect is another is beyond me, but I guess we are stuck with it. I'm going to run a day with Re-Bulk on both the inverter and CC at 27.2, which is 0.2 less than float. Fingers crossed for a normal night. I switched to grid use mode because I can no longer trust mini grid to kick on at the prescribed voltage.
When less occupied by other system concerns, come back to this question. It seems counterproductive but in truth is quite important - especially in one vital aspect - battery health.

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Re: Absorb/Bulk switching back and forth

Post by jstone » Tue Aug 04, 2020 11:19 pm

So here is the updated event history after adjusting re bulk settings. This was with the FM60 in time of RE. The VFX inverter was in AC Drop.
Attachments
Screenshot from 2020-08-04 22-52-39.png
Screenshot from 2020-08-04 22-53-32.png

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Re: Absorb/Bulk switching back and forth

Post by pss » Wed Aug 05, 2020 9:10 am

My comment here may or may not be helpful. But I am now in my 4th Summer with my system and am always trying to achieve nirvana of settings. Now, I have no proof of this, I just know it to be true. In my system, which is grid tied sell enabled, I have my charge controller's voltages set 0.4 above that of my inverter's charger. And since I am in sunny So Cal, I almost always keep my inverter charger off. In the hot weather days, my PV output is lower, but also the charge controllers cycle beginning around noontime between no PV (sleeping/silent) to BULK or ABSORB and FLOAT and repeat this behavior. Then along with these charger state changes, the PV harvest will go down in like 3-5 steps over a couple of minutes until 0 is reached and then the cycle repeats. Now, if I drop the grid connection through the grid use timer or drop AC button on Mate 3S, the PV will go up and the chargers will stabilize and the total PV harvest will be greater in the day than if I stayed connected to the grid and did not sell, but was trying to sell. It apparently has something to do with "grid resistance or grid impedance" in the inverter which tells the charge controllers to even go to sleep so the inverter can cool down and not have to work so hard trying to sell to the grid. But the result is a net negative.

So I am not sure if your behavior is like mine, but if it is, try dropping the grid in early morning and see if chargers then normal behavior in the rest of the day. You can stay in grid tied mode.

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Re: Absorb/Bulk switching back and forth

Post by raysun » Wed Aug 05, 2020 9:55 am

pss wrote:
Wed Aug 05, 2020 9:10 am
My comment here may or may not be helpful. But I am now in my 4th Summer with my system and am always trying to achieve nirvana of settings. Now, I have no proof of this, I just know it to be true. In my system, which is grid tied sell enabled, I have my charge controller's voltages set 0.4 above that of my inverter's charger. And since I am in sunny So Cal, I almost always keep my inverter charger off. In the hot weather days, my PV output is lower, but also the charge controllers cycle beginning around noontime between no PV (sleeping/silent) to BULK or ABSORB and FLOAT and repeat this behavior. Then along with these charger state changes, the PV harvest will go down in like 3-5 steps over a couple of minutes until 0 is reached and then the cycle repeats. Now, if I drop the grid connection through the grid use timer or drop AC button on Mate 3S, the PV will go up and the chargers will stabilize and the total PV harvest will be greater in the day than if I stayed connected to the grid and did not sell, but was trying to sell. It apparently has something to do with "grid resistance or grid impedance" in the inverter which tells the charge controllers to even go to sleep so the inverter can cool down and not have to work so hard trying to sell to the grid. But the result is a net negative.

So I am not sure if your behavior is like mine, but if it is, try dropping the grid in early morning and see if chargers then normal behavior in the rest of the day. You can stay in grid tied mode.
That whole "grid interactive" thing has some complex interactions it would appear. (Makes my simple minded brain happy I'm off-grid.)

If as @pss described, the charge controllers certainly would appear to behave strangely, until the behavior is understood.

To understand the behavior of the charge controller, simplifying its behavior to off-grid conditions will be an informative first step. If, the Absorb/Bulk cycling is happening then, there are only three potential causes:

#1 PV harvest conditions are not supplying enough charge to maintain the Absorb voltage. This is typical of partly cloudy days, when the sun's effective irradiance can be rapidly changing. Watch the display on the controller for a hint about In voltage and current.

#2 The voltage calibration on the charge controller is off. Set the system to Grid power, so the battery is "quiet". Disconnect the PV array from the charge controller.
Measure the voltage at the battery terminals, then at the Bat +/- terminals in the wiring compartment of the charge controller. The two values should agree. Next, compare the measured voltage at the Bat +/- terminals to the Out voltage on the charge controller display. The two values should agree.

#3 The charge controller is damaged. With the PV array disconnected, compare the In and Out voltages on the charge controller display. The In voltage should measure roughly 75% of the Out voltage. If the In voltage = 0, the controller is damaged. If the In voltage = Out voltage, the controller is damaged.

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