FM 80 shows "Charged" but won't go to float

RanchoPacifico · March 2021

I recently changed my battery bank to LiFepo 4 batteries and ever since then I have been noticing that my fm80 will sometimes work fine and go to float after the batteries finish absorb at 58v and float at 56v. But about every 3 days after absorb the CC shows "charged" and won't go to float. Anyone else seeing anything like this?

wellbuilt · March 2021

Aaaaa I don’t think the liFepo battery’s go thru absorb when charging with a fm 80 you need to really check that out .

Charged pops up when my battery’s time out of absorb and the controler says charged until the battery get down to float voltage then changes to float

RanchoPacifico · March 2021

I know not to absorb lifepo batteries but since the fm80 started acting up I thought that maybe the fm80 needed a little absorb time to go to float so I set absorb time to .1 hour hoping it would go to float but so far it works sometimes and not others. After thinking about it for a day I'm wondering if my bms is shutting my batteries off and the fm80 doesn't know what to do so next I'll try lowering the absorb voltage a .1 lower to 57.9v for .1 hour. and see what happens.

BB. · March 2021

If your battery bus "goes away" because of BMS shutdown... Review the battery specs and BMS logs (if present/accessable) and see why the BMS made that decision.

BMS shutdowns should be a a very rare event and I don't like to cut the battery bank out of a DC system/circuit. The battery bank is what actually "regulates" the Battery Bus voltage (holding it between ~42 and ~60 volts). Solar charge controllers, alternators, etc. are not usually designed to actually output regulated 5x.x volts and with the battery gone, the charging sources can frequently over voltage in a fraction of a second and possibly damage other loads/charging sources on the battery bus (car alternators/wind turbines can easily exceed 100 volts, and solar charge controllers can spike to near Vmp-array voltage).

And if you do "lose the battery", you should shut down the solar array(s) to your solar charge controllers, and turn off the DC battery connection... Wait a minute, then FIRST connect the DC bus and let the charge controller boot and stabilize, then connect the solar array next. If the charge controller is powered by the array first, it can get confused and not boot correctly (or even damage itself).

-Bill

wellbuilt · March 2021

Charged is a product of your voltage
when I hit my 3 hour absorb the fm80 go to charged when the voltage gets to my float voltage 54volt the controler go’s to float .
I think the lipo battery’s get 2 stage charging at first you have x amp till you get to x volt then constant volts till you hit the charged voltage number .

I’m sure one of the wizards on the board will chime on soon I wish I could be of more help

wellbuilt · March 2021

This has a really good Explanation as to how to
set the fm80 up to charge you just need to in put your voltages

mcgivor · March 2021

This has come up before, it's the transitional period between when the absorption ends and the time it takes for that voltage value to drop to the float value. Because LFP battery voltage dose not drop rapidly once the charging is terminated, unlike LA dose, the length of time the display reads charged will be extended in comparison.

To verify this, apply a load to reduce the battery voltage to the float value, whereupon the display will change to read float.

RanchoPacifico · March 2021

I agree, that seems to be exactly what is happening but on a few occasions I have not noticed the "Charged" notification until late in the afternoon and by then the voltage is down below the float voltage by about 4 volts (52v) and the fm80 didn't switch to float at 56v as it should have. As I said previously this "charged" notification doesn't happen everyday only once every 2 or 3 days. I've been using this fm80 for about 8 years and an mx60 for 10 years before that so I am not new to the Outback CC and have never seen my charge controllers do that. I still have my mx60 so maybe I'll try removing the fm80 and putting the 60 in its place and see if the problem goes away.

wellbuilt · March 2021

Are you running the fm80 thru a mate ?

My system started getting freaky last year at this time . For no reason the controller stoped
Absorb after a hour ?

Then I would see charged with out float
then the next day it would work ?

I never updated the firm wear .

Once I did the up dates and reprogrammed it
The system has been working real good
Maybe you need up dates ?

RanchoPacifico · March 2021

Yes I am running through a mate2 the older mate. I'll check on if there are updates available. I did some changes today and it went from absorb to float as it should. We'll see what happens tomorrow.

wellbuilt · March 2021

My system went screwy
I’m not the kind of guy that pushes buttons
My system changed buy it self , very strange since I’m not connected to internet
I did a update on my inverter and that fooled with my genarator charging ?

I’m getting less charging 1700watts vs 1900watts and don’t know why .

But it works it just take a little longer to charge.

My system is 4 years old and there where
4 updates

FM 80 shows "Charged" but won't go to float

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