Voltage drop under load...what is normal?

[overdoc]

Hello,
Still in the process of building my off-grid system. I bought 8 6V deep cycle batteries (230Ah each) that were used. Age and state unknown (initial voltage between 6.15-6.30V). They are wired in series/parallel to provide 12V 960Ah. I proceeded to charge and equalize them until the entire bank reads 12.93 and individual batteries read between 6.45 and 6.47V. Specific gravities are all above 1.255 with highest at 1.265 @10 celsius/50 fahrenheit. My concern is that once i apply load to batteries the voltage immediately drops to 12.3-12.4V. It will stay there for hours. When i remove load and allow batteries to rest they gradually rise again to 12.5-12.6V. Is this normal or a sign that the batteries are not as strong as my readings indicate? Do others see a significant drop when load is applied? Thanks for the help in advance.
Happy New Year to all!

[NCmountainsOffgrid]

it seems normal that a 'load' will certainly show a lower overall VOLTAGE to your readout, as the batteries are 'at work', of course. What is this 'load' you speak of?

Our Inverter's panel readout of battery bank VOLTAGE will certainly drop when running the microwave, the residential fridge kicks it's compressor on, etc., and the 12.8 initial reading may drop to 12 or even down to 11.5 during the microwave run, but when it's off, the voltage reading will jump back up to 12.7 or 12.8, depending on how 'long' the microwave ran.

2014 Thor Palazzo Diesel Pusher motorcoach, Magnum ME2012 inverter, 4 - 6v Duracell deep discharge battery bank.

[overdoc]

I had a light load. A 40w light bulb and a clock radio.

[Mike90250]

I had a light load. A 40w light bulb and a clock radio.

What size is the inverter that powers them ? What's the self-consumption of the inverter - that could be consuming a lot of power in itself.

[overdoc]

The inverter/charger is a Renogy 3000w. Specs say the consumption is 30w in normal and 20W in eco mode. I believe it is in eco mode currently. Is it possible that the voltage readings differ while load is applied and that voltage readings underrepresent the no-load capacity?

[Mike90250]

Voltage higher than 12.8V is generally surface charge that will quickly dissipate with a small load. After that point, you should you need to be able to check the voltage with a known load applied, and after an hour, recheck the voltage. Then you can compare your power consumed calculation and battery level, to a reference chart:battery-state-of-charge LeadAcid.jpg

PV_BatteryCycleTestTrojan.pdf