What is FLOAT CHARGING on Controller?

hmong2017

I have been using PWM controllers 60A for my 8  12V Solar Panels for 3 years now. My Controller stopped working suddenly. 
SO I ordered a MPPT 60A Charge COntroller off ebay called Y-SOLAR. 
It is a little heavier and the cover is metal. (Seems like things are going work better and last longer now)
I got it and hooked it up. The new controller goes to work immediately-charging LED is blinking. 

We resumed using the solar like normal. A sunny day- but it suddenly stopped and the inverter is making low voltage alarm sounds. 
I checked everything, inspected all wires & Cables. Everything seems to be in good condition. 
UNTIL, I realized the green charging LED light is not blinking. I pressed the button (UP ARROW) and the screen says "FLOAT CHARGING MODE" 

While it is on FLOAT CHARGING MODE, my batteries are entirely depleted & my inverter sounds an alarm instantly when turned on. 

I did a quick research but it didn't take me far. I ran into a goode search saying only PWM Charge controllers use Float Charging. 
SO WHAT IS FLOAT CHARGING? WHY ISN'T IT CHARGING MY BATTERIES EVEN IN FULL SUN? AND IS IT TRUE THAT ONLY PWM CONTROLLERS USE FLOAT CHARGING MODES? IF YES, I need to report this to Ebay instantly and get my money back. I spent over $200 on this controller. 

Thank you very much for your time. 

If it helps, this is my setup:
8 of 12v 100W SOLAR PANELS
Each panel puts out 5.55A
Panels are connected in parallel 
2500 WATT Power inverter
4 of 100Ah Deep Cycle Universal Acid Sealed Batteries
60A MPPT Charge Controller (The one I am describing above)

I never had problem with this setup before and used it for 3+ years until this new controller. 

Vic

It is NOT true that only PWM Charge Controllers (CCs) have and use the Float stage.

For depleted batteries,  quite a lot of charging can occur in Float.

It sounds like there is no metering on the CC,   or the inverter.  So use your Digital Multi-Meter (DMM) to measure the PV input voltage to the CC,   and the battery voltage,   at the battery terminals (that feed the CC and inverter,  AND the battery terminals on the new CC.

There should be some settings (usually small switches on smaller CCs),   that must be set correctly for your battery type,  etc.

Also, with parallel battery strings,   carefully check each battery cable for corrosion,   loose connections,   etc.  Measure each battery's voltage at each battery terminal.

Also check each connection on the PV Combiner (and check for tripped breakers or blown fuses).   Measure the voltage at the output of the Combiner.

If you are not using a combiner,   check each connection (connectors on the PVs),   and where these connections come together --  measure this voltage at the combination point.

Please DO report  the voltage readings at the PV Combiner,  the PV input terminals at the CC,   the battery terminal voltage,   and the reading on the CC battery terminals.

Please also report any additional observations that you have on the system.

Do you have the manual for the new CC?
Have you made the correct settings in the CC for your type of Sealed batteries?

Thanks for the added info. Vic

Photowhit

Float is one of the 3 basic charging modes, first is bulk where about 80% of the charging is done until the voltage starts to 'run away', then absorb which is where the charging is finished with the charge controller maintaining the voltage at a safe level so the battery doesn't 'boil out'/over heat about 14.5 on 12 volt flooded batteries, Perhaps a bit lower on AGM/sealed batteries, and then float which maintains the charge about 13.6 volts.

Since this is a MPPT type charge controller you should have the panels in pairs so it will have enough over head to work properly. Have you read through your instruction manual?

Did you hook up the batteries first? Most simple aren't settable, they simply read the battery voltage and use that info to setup. If you hooked up the panels first the Open circuit voltage is likely high enough for it to set a 24 volt system voltage.

I don't know this controller, I have suggested a Y-Solar PWM controller for a couple people the same 30 amp one for a 36 volt golf cart and one for a 48 volt system and have heard they both appear to be working fine.

I saw one on Amazon, and they suggest maximum input of 720 watts, which your 8 - 100 watt panels are unlikely to exceed but they fact that they don't allow over paneling suggests a poor design.

If you don't have instructions, you may be able to find them at Y-Solar's site;

http://www.y-solar.com/list.php?fid-77-page-1.htm

Vic

Will add,   that if the battery voltage is quite low,  many CCs will simply not charge batteries.   Most CCs get the voltage that they need for reliable operation, from the batteries. Below a certain voltage (varies from CC, to CC)  the CC simply cannot operate  --  and NO battery charge can happen.

FWIW,   Vic

mcgivor

@Photowhit said  Perhaps a bit lower on AGM/sealed batteries, and then float which maintains the charge about 17.2 volts.
I'm sure a typo, 17.2 volts should read 13.4V or thereabouts don't want the OP to get confused.

Photowhit

mcgivor said:

@Photowhit said  Perhaps a bit lower on AGM/sealed batteries, and then float which maintains the charge about 17.2 volts.
I'm sure a typo, 17.2 volts should read 13.4V or thereabouts don't want the OP to get confused.

I was thinking about my 24 volt system... Must have had a 'brain fart' as I was converting from 27.2 volts for a 24 volt system.