Absorb end amps

Discussion about the FM100, FM80, and FM60 Charge Controllers

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1madtrapper
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Absorb end amps

Post by 1madtrapper » Wed May 25, 2016 5:32 pm

Hello all , I am running 6x48vbanks of 100ah gm batts what should my absorb ends amps be? Today one charge controller abs for 8 mins the other for 10 seems like very lil amount of time the ends amps is set to 12.Thanks for any info

Kent Osterberg
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Re: Absorb end amps

Post by Kent Osterberg » Wed May 25, 2016 7:58 pm

In most systems, in fact almost all systems, the absorb end amps should be set to zero; effectively defeating it. If there are loads in the system that can change during the day, the charge controller output will have to increase or decrease to accommodate them. This makes it impossible to choose an appropriate value for the absorb end amps. Absorb end amps is an unnecessary feature, just make sure that the absorb time in the advanced menu is set long enough that your batteries can get fully charged, but not so long that they spend hours hydrolyzing water unnecessarily. That is the only charge termination necessary for lead acid batteries.

If the batteries have little or no load, it is possible that the battery voltage will not drop below the re-bulk setting over night. In this case, I believe that the charge controller goes directly (or almost directly) to float mode. That may be the reason you were seeing a really short absorption time.

1madtrapper
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Re: Absorb end amps

Post by 1madtrapper » Thu May 26, 2016 2:57 am

I am running glass matts , do you set the absorb end time for 0 on GM batts aswell? I am running about 1500watts steady for the day and more when we need it.
I seem to be avrg about 25 kwh a day from the system I expected it to make a lil more..

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Re: Absorb end amps

Post by ralphday224 » Thu May 26, 2016 5:01 am

I've always avoided absorb end amps for an absorb ending setpoint. I have a wind turbine as well as pv. Sometimes (when I flirted with absorb end amps) there would be enough wind that the solar was cut way back, to the absorb end point, shutting the MX60 out of absorb and into float...with only a short time in absorb being completed. Set to zero at least 10 years ago and never played with again.

Ralph

1madtrapper
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Re: Absorb end amps

Post by 1madtrapper » Thu May 26, 2016 5:29 am

Thanks very much for the reply's I have set my absorb end amps to 0 ,and my max absorb time is set to 3 hrs. I will see how much time it stays in absorb today ,I am running 2 flexmax 80's and 28, 225 watt panels series/parallel hoping this will run my whole house eventually for now my storage is 24 100mah telcom batts running 48v. Seems to be working ok although I expected more power out of this system.

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Re: Absorb end amps

Post by SandyP » Thu May 26, 2016 5:29 am

Kent Osterberg wrote:I.....If there are loads in the system that can change during the day, the charge controller output will have to increase or decrease to accommodate them. This makes it impossible to choose an appropriate value for the absorb end amps. Absorb end amps is an unnecessary feature, just make sure that the absorb time in the advanced menu is set long enough that your batteries can get fully charged, but not so long that they spend hours hydrolyzing water unnecessarily. ....
I understood that end amps allows for early termination of your max absorb time if the criteria is met thus preventing the battery staying at an elevated voltage longer than required.
Yes, base loads will mean that the charge controller will continue to produce the amps when these are going to loads and not the battery - one should be able to allow for this if they are constant - if not then absorb will end when it reaches the maximum allowed time.

So, is the worst case scenario the equivalent of having end amps set to zero anyway?

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Re: Absorb end amps

Post by larrywa » Thu May 26, 2016 6:27 am

Yes, read the manual.

Absorb End current is another setting for the system to cut the Absorb time shorter.

It is which ever comes first, your timer at 3 hr, or the end amps setting, held for the time you set.

You could set your end amps to 1000 and it wouldn't change your 3 hr timer, but set properly, can shortcut your Absorb timers to get you more grid-tie production time and/or less unnecessary boiling of your battery bank.

The manual describes the percentage of you battery bank recommended for the setting and the automatic battery setup in the Mate3 will also set it for you.

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