I have 500 watts of solar going to my 24v battery bank but im not going over 25 volts.

Re: I have 500 watts of solar going to my 24v battery bank but im not going over 25 volt

Probably not normal or healthy for your battery bank.

Do you have some sort of solar charge controller--Or are the panels just connected directly to the battery bank?

Ideally, for a "cycling" deep cycle battery bank, you would want around 5% to 13% rate of charge. For your battery bank:

• 4* 12 volt * 105 AH * 1/0.77 panel+controller derating * 0.05 rate of charge = 327 Watt array minimum
• 4* 12 volt * 105 AH * 1/0.77 panel+controller derating * 0.10 rate of charge = 655 Watt array nominal
• 4* 12 volt * 105 AH * 1/0.77 panel+controller derating * 0.13 rate of charge = 851 Watt array "cost effective" maximum

So, your 540 watts of solar panels seem to be sufficient.

Ideally, your "resting voltage should be around 25.4 to 26.6 volts or so if fully charged (no loads, resting for ~3+ hours). If the battery is 1/2 full (resting), around 24.0 volts... You really do not want the battery to be operating too often at lower voltages (batteries will not last as long)... And you do not want battery at less than ~75% state of charge to sit around for days/weeks/months. They will sulfate and die.

Charging voltage, somewhere around 28.0 to 28.4 volts (if AGM) and around 29.0 to 29.5 volts (if flooded cell), usually held for ~2-6 hours (longer "absorb cycle if the batteries are more deeply discharged).

Float voltage is usually around 26.4 to 27.6 volts or so.

Then the questions... If this is a flooded cell type battery, have you measured (logged) the temperature corrected specific gravity of each cell? You need to understand where your batteries are at today--And (probably) get them recharged quickly.

Next, need to figure out how much current is going from the array to the battery bank in mid-day/under full sun... A 540 watt array on a PWM controller would expect to output (typical maximum):

• 540 watts * 1/35.0 Volt Vmp array = 15.4 amps or so (rough guess)

If you do not have any way to measure the current flow, I would get a DC Current Clamp DMM (like this one from Sears for ~$60 is "good enough").

Also, take an accurate volt meter and measure the voltage across each battery. Looking for differences (a battery with low voltage could have a shorted cell).

Take a quick read through the Battery FAQ.

-Bill