Help with trojans please!

[benjammin5150]

So I picked up 2 brand new Trojan SCS150 100AH Deep cycles in october of 2014. When I got them home the voltage measured 12.5 on both, so I charged them with an auto charger to 13.2 but the SG only read 1.225 in both of them. Long story short, after many hours of equalizing Ive finally got the SG of all the cells to 1.275 on both at 12.8v. so thats good. Heres my problem...I have them wired in parallel and when I pull a small load of about 8amps the voltage will drop from 12.8 to 12.4 and stay there. I have them on a victron energy battery monitor and when it says they are at 70% SOC the SG will show 30% SOC(1.120). Ive taken them to a battery shop for testing and they said the batteries are really strong and there isnt anything wrong with them and suggested my hydrometer was bad...i doubt it .

Is it abnormal for the voltage to quickly drop from 12.8 to 12.4 with such a small load? again, they are wired in parallel so its 200 AH.

Im wondering if my wiring could be to blame so Ill explain it. Im running a 600 watt pure sine inverter. The cables to the inverter are 4awg and 5ft long. The battery interconnect cables are 4awg and 3ft long. Im only drawing 8-10 amps through the inverter so the cable should be plenty big for that right?

What would cause the battery monitor to say 70% SOC but the SG to say 30% SOC(1.120)?...The SG read 1.275 when I started drawing the load

Trojan says they need to be cycled about 50 times to reach full capacity...I have not done anywhere close to 50 cycles on them, could this be the cause?

I hope this doesnt sound confusing and I thank anyone in advance for trying to help me out.

[Sunking]

There is nothing wrong. Where are you measuring the voltage?

Let's start with SOC. There is only onw-way to measure SOC and that is with a hydrometer period. You cannot use voltage except on a full rested battery with nothing connected or Open Circuit Voltage (OCV). So ignore your monitor it means nothing.

Open Circuit Voltage on an FLA battery at 100% SOC is 12.6 volts. As soon as you put a load on a battery, the voltage is going to drop due to Internal Resistance and you can measure the Internal Resistance to determine if it is OK or not.

Let the battery discharge a bit, you do not want to test it fully charged 70 to 90% SOC is good.. You will need a way to measure current and voltage accurately at the same time.

Put a light load on the battery, say 1 amp and record the voltage directly on the battery term post.Record both the voltage and current. Call the Voltage V1, and Current I1.

Now put a heavy load on the battery say 10, 20, 300 amps. Then record the voltage and current again. Call the voltage V2, and the current I2.

Now get out your calculator.

Find the Delta Voltage Dv = V1 - V2
Find Delta Current Iv = I2 - I1
Now find the Internal resistance Ri = Dv/Iv

Should be .01 or lower.