diy solar

diy solar

Battery remains at Bulk Charge Voltage

M

Mohsin Ali

New Member
Joined
Aug 30, 2023
Messages
41
Location
Karachi
Hello Everyone
I have an off grid solar setup with 145 Ah lead acid battery , the issue is that the mppt charge controller does not switches to float charging mode if I run somewhat heavier load like a small fridge which draws around 12 amp dc and the battery stays at bulk charging volts throughout the day i.e. 14 volts despite in 100% charge state and if I remove the fridge then mppt switches to float charge mode and "battery charged" message appears.
 
Likely your battery is on its last legs. Any load drops the voltage so that float can only be achieved when unloaded.

You could try using an equalization charge after checking the SG and liquid level.
 
Not enough battery, not enough panel, or both of the above. Need enough system capacity to sustain the Float setpoint plus run the fridge and whatever else needing power at the time.
 
  • Like
Reactions: JRH
Mattb4 said:
Likely your battery is on its last legs. Any load drops the voltage so that float can only be achieved when unloaded.

You could try using an equalization charge after checking the SG and liquid level.
Click to expand...
Battery is new, purchased 2 weeks ago, the float voltage mode remains if I run light load like 2 ceiling fan or 2-3 bulbs but on heavier load the voltage increases to bulk voltage settings
 
can you share more detailed information about the rest of the system? All you’ve mentioned was an Ah capacity of the battery.

How much PV is connected to that battery?
What sort of method is controlling the battery charge, solar charge controller?
Are you running an inverter? 24/7? What is its idle consumption?
 
Mohsin Ali said:
Battery is new, purchased 2 weeks ago, the float voltage mode remains if I run light load like 2 ceiling fan or 2-3 bulbs but on heavier load the voltage increases to bulk voltage settings
Click to expand...

normal behavior

when the load turns off you should see it return to absorption/float. if you're seeing a large voltage drop while heavy loads are present it is also likely that the battery is not big enough :)

Ideally, one would size their PV to help cover day-time loads to keep battery floating until the sun sets.
 
Last edited:
  • Like
Reactions: JRH
With 800 watts of solar, a 12 to 15 amp load, and a 145Ah battery it's possible the battery has been damaged.
Discharging fully to 11.6 volts will, reduce battery life, as will excessive charge current. Even though the battery self limits to some degree, if its in a low state of charge it will accept a higher current than recomended.
145 Ah battery is too small to power a 12 to 15 amp load overnight.
 
mikefitz said:
With 800 watts of solar, a 12 to 15 amp load, and a 145Ah battery it's possible the battery has been damaged.
Discharging fully to 11.6 volts will, reduce battery life, as will excessive charge current. Even though the battery self limits to some degree, if its in a low state of charge it will accept a higher current than recomended.
145 Ah battery is too small to power a 12 to 15 amp load overnight.
Click to expand...

This:

"With 800 watts of solar"

has never been stated. Without knowing for sure, we are all making somewhat educated guesses.

If his battery is indeed new, then his panels are insufficient. And if the fridge draws 12A constantly and does not cycle while it's on (thermoelectric type - not compressor based - also never stated), his battery is also insufficient.

I regularly run a Haier 2.7 c/f AC compressor fridge (50W run) 24/7 off of a 100aH LFP and a used 250W Trina panel. But it cycles off and on, with apx. a 40% duty cycle.
 
v_green57 said:
"With 800 watts of solar"

has never been stated
Click to expand...
Read the previous posts the OP made,
diysolarforum.com

Upgrade Solar Wire Guage for better

Hello Everyone I have used 12awg wire from solar panels to charge controller the total length of wire is 70 feet but I am not getting good result so I want to increase wire guage. Now can I attach another 12awg wire of same length with this wire in parallel? Will it work or I have to install...
diysolarforum.com diysolarforum.com
 
You must log in or register to reply here.

Similar threads

M
MPPT - Battery Voltage Fluctuation
Replies
4
Views
220
Mohsin Ali
M
S
MPP Solar 3024 AIO not going into bulk charge
Replies
3
Views
240
Sparktastic
S
M
Does MPPT charge controller damages a battery ?
2
Replies
36
Views
1K
Q-Dog
Q-Dog
A
PowMr 60a MPPT voltage spikes in boost mode?
Replies
4
Views
287
WattSecond
W
S
Confused about Grid support battery charge priority
Replies
5
Views
285
DVD
D
Back
Top