charging and voltage

[abdelrahman mubarak]

i installed a UPS system using felicity solar hybrid inverter and 2x12v 200ah blue carbon lifepo4 batteries for a 24v system,
because we have daily power outages and i can't afford solar panels right now.
my question is
i charge my batteries with 28.2v bulk and 27v float. utility charging current 25a
once i introduce a 800w load the voltage drops to 25.6
and it stayed for 5 hours using this 800w load
until it reached 24v my inverter disconnect setting.. the inverter cutoff out of the box set to 21v
is this normal?
can i increase my charging current?
batteries set to 100amp input current

 

[abdelrahman mubarak]

images from my system

 

[acdoctor]

800 Watts x 5 hours is 4000 watts or 167 Amp hours. If this is output measurement I would say it is good. You have inverter losses. If it is input measurement probably not so good. Maybe not fully charged. The battery info says to charge at 50 amps and 15 volts. So in series that would be 50 amps at 30 volts. 15 volts seems a bit high to me but my be correct for pouch cells if that is what they are I am not familiar with them. Also 24 volts is not fully discharged? 20 volts is fully discharged. I wouldn’t recommend going to 20 volts the BMS will disconnect when the first cell gets to 2.5 volts. You didn’t say how long the outages are. But adding 2 more batteries will get you 10 hours maybe more if you can find ways to reduce the consumption wattage during outages.

 

[Bud Martin]

800W AC load on the output of the inverter, that means the input power to the inverter will be about 800W/0.85 = 941W of power draw from your batteries due to conversion loss.
Charging at 25A @28V = 700W, but you load is drawing 941W, that means the charger and the batteries are providing the power to run your load and you are not charging the batteries, so if you want to charge the batteries and run the 941W load at the same time you will need larger charger.

 

[abdelrahman mubarak]

800 Watts x 5 hours is 4000 watts or 167 Amp hours. If this is output measurement I would say it is good. You have inverter losses. If it is input measurement probably not so good. Maybe not fully charged. The battery info says to charge at 50 amps and 15 volts. So in series that would be 50 amps at 30 volts. 15 volts seems a bit high to me but my be correct for pouch cells if that is what they are I am not familiar with them. Also 24 volts is not fully discharged? 20 volts is fully discharged. I wouldn’t recommend going to 20 volts the BMS will disconnect when the first cell gets to 2.5 volts. You didn’t say how long the outages are. But adding 2 more batteries will get you 10 hours maybe more if you can find ways to reduce the consumption wattage during outages.

the outages around 7 to 8 hours daily,
i reduce the consumption to 450w
and i go through it every day when the grid comes back the voltage is around 25.4v
i reduced the bulk charging to 27.4 because i don't want to fully charge it
and increased the amps to 30a because it was taking to long to charge, and float it at 26.4
are these settings OK?

 

[acdoctor]

Yes they are fine, but you can increase to 50 amps if you have the grid capacity.

 

[abdelrahman mubarak]

thank you so much