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ksmith avatar image

MPPT 100/30 float issue

Hi all,

I've had a look through the masses of previous questions and unfortunately couldn't find any that were quite the same as mine.

Recently I have noticed that my SmartSolar 100/30 completes it's bulk and absorption stages and enters float mode. When in float it will match any current draw from the battery for roughly an hour and then will suddenly no longer keep matching the battery and it will then start dropping down from 100%.
It says it is in float mode, there is plenty of sunlight and panel voltage present, however it doesn't output any charge to the battery. No other chargers connected to the battery.

I have the float voltage set to 15.8V and even when the loads connected to the battery increases it does not kick it back into bulk.

I then have to reset the controller by disconnecting the solar, then battery and reconnecting, which it will then it go back into bulk mode, absorption mode and then eventually into float again.

Has anyone else experienced this issue? Is it potentially a firmware issue?

Thanksvictron-smartsolar-100-30-float-stuck.pngimage0.pngimage2.pngimage1.png

MPPT - Solar Charge Controllerfloat
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8 Answers
marc-de-montreal avatar image
marc-de-montreal answered ·

hi, the idea that come automatically to me is have you upgraded the firmware? ..what kind of 12v battery you have for this high voltage setting? ..have you found something since your question?

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Hi Marc,

Yes, I update the firmware at each release. It has improved, but is still occasionally getting stuck in Float when there is only a small load.

I am using Lithium NMC LG Chem N2.1 battery cells in a 4S configuration. Max charge is 4.2V per cell but I limit it to 3.95V for safety/longevity.
Unfortunately I have not found any further information on this issue since asking this question. However as it only seems to occur when there is a low load and after the sun has gone down overnight it seems to reset and will work correctly the next day until reaches float mode again. When a larger load is running then it appears to function correctly.

Thanks, Kieren

marc-de-montreal avatar image
marc-de-montreal answered ·

your wiring is good confirmed?

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b918f71f-edcd-4278-a031-9bdacf04e051.pngConfirmed. The issue is only apparent when the MPPT enters float mode.8ed191b3-4b77-4c62-a8f5-a59dd7cd02d2.png

This is a snapshot from VRM of yesterday’s SOC vs Battery voltage.
You can see that the state of charge is dropping throughout the day until 18:00 when it suddenly releases itself from being stuck and tries to begin charging again but there is minimal sun at this time of day.
There is sufficient sun throughout the day here (Perth, Western Australia) and the panel is in full sun throughout the day.

marc-de-montreal avatar image
marc-de-montreal answered ·

hi, i has tried the simulation for my lithium batteries bank with lithium selected for the type of battery and the floating stage was disabled automatically.. have you selected, in your setting type of batt, the lithium?

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These are my current settings.

I will look to try as you said and see if that makes a difference.
Thank you for the suggestion.

daveychristie avatar image
daveychristie answered ·

I am trouble-shooting the same or similar issue. I have a Battleboard 100A battery, and an MPPT100/30 set to Battleborn's settings, with current firmware. I found recently that my battery was not recharging, and due to occasional loads, had dropped to ~80%. The charger was in float, and per BBs settings, float was 13.6V, less than the 13.8V in the battery, so no charging was happening. I pushed the float setting to 14.6V, which I confirmed with BB was okay, since the battery will be able to "rest" at night, and it's charging again. But I haven't gotten a good answer yet on how it gets into this state, and why BB's recommended settings seem to work for at least most of their customers, but not for me.

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alham avatar image
alham answered ·

Have you resolved your issue? If not, your float and absorption voltages are set at the same, when for most systems float is a few V lower.

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farnja avatar image
farnja answered ·

Hi @KSmith - I am having the same issue. Did you resolve this ever?


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kevin-b avatar image
kevin-b answered ·

did all this start after the update/

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I believe I was having the same issue, maybe to a lesser extent, previously.
patrickvanneck avatar image
patrickvanneck answered ·

Hi, I have exactly the same problem with my 100/20 charger very annoying and no solution.

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