Absorption End Amp setting

Discussion about the FM100 AFCI Charge Controller
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Lara2023
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Absorption End Amp setting

Post by Lara2023 »

Hello, my current Flexmax allows me 50 amp max setting. Based on the capacity of my new battery bank, I needed about 68 amp. Is there a work around or does the FM80 allow a higher setting? I'm currently running about 1 1/2h absorption. Thanks
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Re: Absorption End Amp setting

Post by raysun »

The FM80 Current Limit parameter can be set to any value between 5A and 80A. In this case, it sounds like it's set to 50A. It can be reset to 68A.
Lara2023
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Re: Absorption End Amp setting

Post by Lara2023 »

Thanks, it seems the Flexmax 100 only allows 50. So I can setup my FM80 to trigger global float at 68 amp.
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SandyP
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Re: Absorption End Amp setting

Post by SandyP »

Lara2023 wrote: Sun May 12, 2024 1:13 pm Hello, my current Flexmax allows me 50 amp max setting. Based on the capacity of my new battery bank, I needed about 68 amp. Is there a work around or does the FM80 allow a higher setting? I'm currently running about 1 1/2h absorption. Thanks
End amps is usually a % of total battery bank Ah capacity and I thought around 2% was common. For your battery bank that would be around 35amps and at 3% would be ~53 amps. So if you have it currently set at 50 amps and are happy with the 1.5hrs absorb time then keep it at that (unless the Rolls documentation says otherwise)
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raysun
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Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
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Re: Absorption End Amp setting

Post by raysun »

Lara2023 wrote: Sun May 12, 2024 3:03 pm Thanks, it seems the Flexmax 100 only allows 50. So I can setup my FM80 to trigger global float at 68 amp.
We may be confused by parameter names, their purpose, and values.
The Flexmax charge controller has two optional settings:
• Current Limit
Thus parameter "throttles" the charger output current to a value less than its maximum. It's purpose is to set the maximum current, during the Bulk charge phase, to a value the battery can safely accept.
For example, if the array and controller are capable of producing 80A (FM80) of charge current, but the battery can only accept 45A, then Current Limit would be set to 45.

• End Amps
This is the value of charge current, in amps, that triggers Absorb Charging to stop. The End Amps value is typically set to 1% - 5% of the battery capacity.
End Amps is only useful in special cases. The controller only knows how much charge current its putting on the battery bus. It doesn't know what portion of that current is flowing into the battery v.s. the portion that flows to loads. Unless loads are well-known, and constant, End Amps will end up being too high or too low. If too high, charging ends before it should, if too low, End Amps doesn't stop charging as it might, the Absorb Timer takes over to end the charge phase.
End Amps should be set to 0, unless a special case exists.
Lara2023
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Re: Absorption End Amp setting

Post by Lara2023 »

Thank you, I will stick with my absorption for about 1.5h and will check my SG reader.
raysun
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Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
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Re: Absorption End Amp setting

Post by raysun »

Lara2023 wrote: Sun May 12, 2024 7:55 pm Thank you, I will stick with my absorption for about 1.5h and will check my SG reader.
Old School, and a good method for flooded lead acid batteries.

Are there other Outback components? A Hub? A FlexNetDC battery monitor?
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SandyP
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12 x 2V Hoppecke GEL 612 Ah C24 - 24V System (June 2011)
Outback VFX3024 Inverter/Charger
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Re: Absorption End Amp setting

Post by SandyP »

Lara2023 wrote: Sun May 12, 2024 7:55 pm Thank you, I will stick with my absorption for about 1.5h and will check my SG reader.
The battery manual for your new batteries specifies 2 hour absorb so maybe lower the end amps until you get that absorb time?
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raysun
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Posts: 11402
Joined: Tue Jul 26, 2016 5:57 am
My RE system: Flexpower Two: (2) FXR3048A-01 - Series Stacked, (2) FM80, MATE3s, FlexNetDC
6 SimpliPhi 3.8-48 (48v @ 75AH. 450AH total)
Outback IBR3 battery enclosure
REC Alpha 440W panels - 2 arrays: each of 4 strings of 2 in series
2 Midnite Solar MNPV6 combiners w/20A DC disconnects.
Honda EU7000is gas fuel generator
Off-Grid

Re: Absorption End Amp setting

Post by raysun »

SandyP wrote: Mon May 13, 2024 1:03 am
Lara2023 wrote: Sun May 12, 2024 7:55 pm Thank you, I will stick with my absorption for about 1.5h and will check my SG reader.
The battery manual for your new batteries specifies 2 hour absorb so maybe lower the end amps until you get that absorb time?
Or just set End Amps to 0
and Absorb Time to 2H.
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SandyP
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Posts: 573
Joined: Tue Jun 21, 2011 4:44 am
My RE system: 8 x 190W 24V Suntech panels (4 strings of 2) July 2011
4 x 325W 24V Suntech panels (2 strings of 2) added Sept2018
Mate2
Outback FM60 MPPT (max output lowered to 55amps)
12 x 2V Hoppecke GEL 612 Ah C24 - 24V System (June 2011)
Outback VFX3024 Inverter/Charger
Victron BMV-602s
Honda 5.5kW Genset
Location: Victoria, Australia

Re: Absorption End Amp setting

Post by SandyP »

raysun wrote: Mon May 13, 2024 8:25 am Or just set End Amps to 0
and Absorb Time to 2H.
Yes, I am probably over fixated on not 'over' absorbing my GEL batteries and have both an End Amps setting as well as a max absorb time set.
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