Batteries only charging to 70%?

Re: Batteries only charging to 70%?

Welcome to the forum Robyn!

I will give it a shot... you have 14*230 Watt panels.

The rough typical maximum current I would expect to see from your solar array through a MPPT charge controller on a very nice day with batteries that need charging would be:

14*230 Watts * 0.77 panel+controller derating * 1/58 volts = 42.7 amps

Do you see this level of current from your solar array?

Next, how do you know your battery bank's state of charge?

If it is a flooded cell bank (sounds like it is), a hydrometer to log the temperature corrected specific gravity of each cell... What are you seeing at the end of a sunny day for each cell (yea--72 cells).

Bad cells (shorted or open) and bad cabling can cause strings to be "out of balance".

Do you have a DC Current Clamp DMM (digital multi-meter)? If not, I would suggest this one from Sears is pretty cheap and "good enough" for our needs here.

With an accurate DMM (and good batteries in meter), can you measure the voltage across each battery and record it (and tell us when the voltage was taken, morning before sun up, middle of day, night just as sun went down).

Next--using the DMM, can you measure the voltage at the 48 volt battery bus at different times of the day (i.e., 49 volts in the morning, 58-59 volts during mid-day, towards 52 volts float charging later in afternoon, etc.)? Ideally, we should see the battery voltage rise to ~58-59 volts and be held there for ~2-4+ hours per day, then reduced to 51 volts (or below 50.4 volts as the charging falls off).

When the sun is up in the mid-morning (and your batteries need charging, or you can even turn on some AC loads to get a power drain), you can use the DC current clamp meter to measure the current in each solar panel string. You are looking for "differences"--It all is well, each string should have about the same current flowing--If one is very low, or they are all over the place, there may be some wiring/panel issues (note: the Sears DC Current Clamp meter has a strange "zero" function--Read the instructions carefully, and try it on your car battery first to make sure you understand how it works--or ask here--It is not difficult, just different than you would expect).

You can also use the DC Current Clamp meter to measure current through each parallel battery string (ideally under heavy charging and discharging currents)--You are looking that the strings a sharing the current--If you see one string with 50% more or 50% less current than its neighbors, need to investigate.

Is this an On-Grid System? Do you have a backup genset? etc...

In general, we try to understand the condition of the battery bank and get it recharged--Batteries sitting round at less than ~75% state of charge for days/weeks/etc. is not good for them.

Did anything change recently--Have you confirmed that the system is not charging correctly, etc.?

How I would start.

-Bill