VFX2812 Restart Bulk

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feudalkaos
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VFX2812 Restart Bulk

Post by feudalkaos » Fri Feb 14, 2020 10:51 am

I have a VFX2812 connected to a 400Ah LiFePO4 bank at 12V. I have configured charging as such:
Absorb Voltage: 14.0 Time: 0.1
Float Voltage: 12.0 Time: 0.0
Re-Float Voltage: 11.0

I am trying to understand at what point the inverter will restart the Bulk charging stage. I can see that it has a re-float stage but since I am using Lithium cells I am turning off the floating stages (setting them as low as possible). These cells do not like float charging.

Is there a lower voltage point at which the inverter will automatically restart Bulk?

raysun
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My RE system: Flexpower One: FX3048T, (2) FM80, MATE3s, FlexNetDC
Outback 200NC batteries (8 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: VFX2812 Restart Bulk

Post by raysun » Fri Feb 14, 2020 11:28 am

I don't think the inverter charger is "smart" enough to concern itself with REBULK. IIRC, REBULK is principally a trigger point to increment the ABSORB timer on the FlexMax charge controllers. It does however also trigger a new charge cycle.

If you press the CHARGER button on the Mate for example, and select Bulk Charge, you will see the Absorb Time is whatever is set in the parameters. It will run that Absorb cycle irrespective of the calculations done by the charge controller.

Auto Charge Tedmination on the Mate will stop the inverter and charge controller charge cycles in accordance with the Battery Charged parameters in the FNDC.

raysun
Forum Emperor
Posts: 1686
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower One: FX3048T, (2) FM80, MATE3s, FlexNetDC
Outback 200NC batteries (8 @ 48v)
Outback IBR3 battery enclosure
Suniva 330 watt panels (12 - 6 strings of 2 in series)
Hyundai 355 watt panels (6 - 3 strings of 2 in series)
Honda EU7000is gas fuel generator

Re: VFX2812 Restart Bulk

Post by raysun » Fri Feb 14, 2020 3:03 pm

So this system is aboard your boat, yes? There's nada in your profile so I'm just guessing about capabilities and usage.

I'm guessing the issue with a solar charge controller(?) is one of battery charge maintenance, and after full charge is reached, continued PV harvest to run house loads. Is that correct?

The problem is not wanting to hold the battery at 100% SoC in the process - good for lead acid, bad for lithium.

There's no problem holding lithium at a partial state of charge and adding small amounts of additional charge - as long SoC < 100%. Is that a proper concept?

Perhaps, instead of bulk charging to 100%, can the battery be charged to 90% and the headroom left for the occasional Bulk charge interval that may sneak it's way in during times the PV harvest is primarily serving house loads.

A nominal 360AH battery is still a buttload of charge, and the headroom de-stresses the cells from the full SoC issue.

feudalkaos
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Posts: 22
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Re: VFX2812 Restart Bulk

Post by feudalkaos » Fri Feb 14, 2020 7:54 pm

raysun wrote:
Fri Feb 14, 2020 3:03 pm
So this system is aboard your boat, yes? There's nada in your profile so I'm just guessing about capabilities and usage.

I'm guessing the issue with a solar charge controller(?) is one of battery charge maintenance, and after full charge is reached, continued PV harvest to run house loads. Is that correct?

The problem is not wanting to hold the battery at 100% SoC in the process - good for lead acid, bad for lithium.

There's no problem holding lithium at a partial state of charge and adding small amounts of additional charge - as long SoC < 100%. Is that a proper concept?

Perhaps, instead of bulk charging to 100%, can the battery be charged to 90% and the headroom left for the occasional Bulk charge interval that may sneak it's way in during times the PV harvest is primarily serving house loads.

A nominal 360AH battery is still a buttload of charge, and the headroom de-stresses the cells from the full SoC issue.
Yes on a boat.

This issue is separate from the FlexMax 60 issue that you commented on also. I have taken each of these things in isolation and tested them that way so as to be sure they are not related.

For this question I am just trying to understand what events cause a restart of the Bulk stage. As far as I can tell so far it only appears to happen when AC power is lost then regained or the Bulk On command is turned on. I was hoping that it would restart after a lower level voltage.

This issue is also not related to solar harvesting. I am only charging up to about 90% on the cells and considering that 100% already so as to get the best performance out of them. I will squeeze more out of them as times goes on but I want to get the system to a stable state before pushing the limits.

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