MorningStar TriStar MMPT-45 Overcharging

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Heli_av8tor

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Mar 3, 2017
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NW Illinois
My controller is set for Absorb = 14.7v and Float at 13.5v. (Switches 4-5-6 = on-off-on). The remote verifies this setting.

However, the controller routinely runs in Absorb mode in the morning running the battery voltage to 15.0 to 15.1 before switching to Float mode.
This voltage is reported both by the Morningstar remote and my Trimetric battery monitor. This is with minimal overnight battery draw and/or on shore power (Xantrex Freedom XC 2000).

Batteries: 2 - FullRiver DC260-12

Why would it be doing this and how do I correct it?

Thanks,
Tom
 

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AStravelers

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San Antonio, TX
You could contact Morningstar support.  It looks like you would have to go online and describe the problem and they will get back to you.  I didn't see a phone number listed in the support contact page.
 

PJ Stough

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Sep 20, 2009
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Central Iowa
Mine will do the same when the weather is cooler, as I have mine set for 14.7 volts temperature corrected, and have seen as high as 15.3 volts when the outside temperature is down in the 40s or 30s.
 

Kevin Means

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Lakeside, California
We have a different controller Tom, and unfortunately I'm not familiar with how to program Morningstar controllers. However, I would recommend that you keep your battery compartment a little cleaner. I saw two grains of dust on top of one of your batteries. See ya at KOFA! ;)

Kev
 

AStravelers

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San Antonio, TX
Heli_av8tor said:
Thanks Al and Paul.

My battery temperature was 55 this morning.

See you both in KOFA or Q this year?

Tom
Our winter travel plans are still up in the air so I don't know if we will be in the Q area or even if we will travel this winter.
 

Gary RV_Wizard

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Feb 2, 2005
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West Palm Beach, FL
The most obvious reason for those readings is a battery that is getting weak, perhaps just one cell in the entire battery bank.  A modest amp draw knocks the voltage down substantially, so the charge control reacts by going into absorb mode and staying there until it gets the SOC up again.
 
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