question

didgenero avatar image
didgenero asked

Premature Phase Change

I have a catamaran with Mastervolt system and Mastervolt Lithium Batteries to 720AH. I have 2 solar arrays with separate Victron controllers for charging. The smaller array is 2 x 125W panels on the bimini that run through a SmartSolar Charger MPPT 100/30. The larger array has 4 x 350W panels on the davits running through a Smart Solar Charger MPPT 250/100.

I am having an issue where the larger controller switches to Absorption and Float much earlier than I would expect while the smaller one continues on Bulk. The result is that the batteries are not charged by the end of the day.

The configuration for both controllers is the same using the preset Rotary Switch - Lithium batteries settings.

Images below show the controller in Absorption phase with 71% battery charge and Float phase with 75%. This is during the day with ample direct sunlight on the panels. Any advise to resolve this issue is appreciated.

MPPT SmartSolar
absorption.png (701.1 KiB)
float.png (878.8 KiB)
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klim8skeptic avatar image klim8skeptic ♦ commented ·

Hi,

You seem to have a lot of voltage drop on the cable between your mppt and battery.

Normally this is caused by thin cables, Long cables or bad joints/connections.



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didgenero avatar image didgenero klim8skeptic ♦ commented ·

Thanks for your thoughts. The Volts x Amps is not that different. I'm not seeing a big issue there - it is more the more the controller dropping down to Absorption and Float too early that concerns me.

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klim8skeptic avatar image klim8skeptic ♦ didgenero commented ·

Perhaps you should measure the battery voltage at the mppt terminals with a DVM to ensure accuracy against mppt battery voltage reporting.

Repeat voltage readings at the batteries terminals.

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1 Answer
Paul B avatar image
Paul B answered ·

as the battery voltage is at 14.2 volts as far as that unit is concerned its switching to absobtion then float., so you need to find out why there is this LARGE voltage diferance,

and as the others have said . with a volt meter check the reading at the REG and at the batteries. they should be basically the same voltage

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