Gel battery charge atate

[wpmaura]

I have 4 gel batteries in series to make 48v. What I am trying to figure out is at what level is 50 percent. If the in inverter is reading 48v are they about to die is 51v 100 percent etc.

These are donated chinese generic batteries so no documentation and bi english on side except gel 12v 100amh

 

[RandyB]

This should help.....

 

[wpmaura]

I have 4 12v 100amp chinese gel batteries had them charged up good made only load on them was charge controller for 4hrs. When I turned on inverter it states 51.5v. The only real thing that draws power on inverter from 9pm to 7am is a fridge which averages 90w an hr according to kill a watt meter. By this time it's usually down to 49v. So am I am trying to figure out whether my batteries are discharging to fast or what's 50 percent etc.

 

[RandyB]

Okay....so I have a bank of 6 volt GEL batteries in series/parallel configuration for a 12 volt system.
GEL batteries when charging to a complete charge when charger goes into float is around 14.1 volts.
This doesn't mean my batteries are over charged as they will eventually level out to 12.7 volts when charger is disconnected.
This would be a full charge.

So I am only assuming that your batteries should top off charging at anything above the 100 percent mark of 50.92 volts. (depending on your charging system a.k.a. charger and set up) I would guess you are in the correct range at 51.5 volts I would find the specs for your particular battery to see what they recommend for charging is. After charging your batteries they will level out and 50.92 volts is a full charge thus as 48.4 volts is at 50% percent for a 48 volt system no matter the type of battery.

My charger is capable of charging any battery type and is user settable, it has two GEL settings. I selected the charging voltage/method as my battery spec sheet specified.

By the way....That's not bad to be 70% charge after 10 hours of use on a 48v/100 amp hour system.

 

[RandyB]

Your usage @ 90W/hour for 10 hours is 900 watts....
48 volts x 100 amps = 4800 watts (total capacity)
4800 watts - 900 watts = 3900 watts (left after 10 hours)

50% is 2400 watts

60% is 2880 watts

70% is 3360 watts (your usage total is 3420 watts). <-------you are here (3900 watts after fridge runs for 10 hours) Yet.....your inverter will also consume some amount of wattage. (Inverters can consume roughly 1 to 2 amps/hour.)

So in your case we will call it 1 amp/hour. So 48volts x 1amp = 48 watts/hour. That's another 480 watts of usage for the 10 hours of use. That would drop you to 70% range easily.....then you actually would have 3420 watts left after calculating inverters usage. (amps left is 71.25)

75% is 3900 watts

 

[wpmaura]

Thanks

 

[nosys70]

to know where is the 50%, you kneed to know the minimum voltage , the maximum voltage and the discharging curve (that is certainly not linear)
so with min and max, you get the range (and 50% should be around min+range/2), but since the non linearity of the curve (battery discharge faster at the end) you can expect 50% will be more like 60%)

counting watts or Amps could be a solution, but unfortunately, you will not get same power from a battery if you discharge slow or fast, so again, the 50% could be a different value than the calculated one.
The easiest is to make a real life test, drain the battery from top to bottom once, then you get the time it takes with real use.
then you know that that if you get 6 hours of capacity, 50% will be 3 hours.
then you charge battery again, run then for 3 hours in same condition and measure voltage in the battery.