Voltage drop with Hybrid Gel

[Off Gridin' It]

I need the help of my peers on a Voltage Drop problem.

Here is a run down of my system.
1200 watts of solar on the roof.
4000 watt AIMS inverter/charger
800ah (400 usable) of Renogy Deep Cycle Hybrid Gel batteries. (4800 usable wh) - Eight 100ah Batteries connected in parallel.
12 volt system. (Please lets not get into a whole debate over 12 volt vs 24 volt vs 48 volt and focus on the problem)

The inverter is connected to the bank with 4/0 (ought) cable.
The battery interconnects are also 4/0.

The problem.
In the past I have been able to run my air-conditioning for about 3 hours on a full charge at night. (Longer in daylight hours)
It is a roof mounted air conditioner and it is pulling about 130 amps when in use. 130amps x 12 volts = 1560 watts.
This is far below the limits of the 4000 watt AIMS inverter.

I have my ideas about what it is but I am going to tell you what I have tried and what I have narrowed it down to and I want to see if you agree or if you have other ideas.

WHAT I HAVE TRIED
- I have checked all crimps, connection, breakers and grounds and they are strong and tight
- I have done load tests on both the AIMS inverter/charger and a GIANDEL 4000 watt inverter.
- I have pulled the AIMS inverter out and put in a GIANDEL 4000 watt inverter that I had sitting around to check and see if it was an inverter problem. (It wasn't and the problem persisted.)
- I charged up the batteries to a full state of charge and then I disconnected all the batteries from the system and from themselves and let them get to a resting voltage and monitored the voltage over 3 days. Below are the results.
-I tested the pass through mode on the AIMS inverter/charger to see if shore power would work under load and it operated properly charging the batteries and powering all AC appliance.

SO, take a look at my test results below and tell me what you think this voltage drop problem could be.
I should be able to run my air for 3 hours. But the surface voltage is dropping so fast the best I can get is 30 to 35 minutes before the low voltage disconnects shut off both inverters. Even with the low the SOC of the batteries has never dropped below 88% in any of the tests.
I believe it might be a battery problem but the resting battery test doesn't support this theory.


_________________________
BATTERY VOLTAGE STATE OF REST TEST

Batteries disconnected and sitting idle by themselves not connected to anything or themselves and no loads.
I just wanted to monitor the voltage drop over time.

7-24-21
11am
1. 13.87
2. 13.85
3. 13.85
4. 13.85
5. 13.86
6. 13.86
7. 13.86
8. 13.86

7-25-21
9am
1. 13.1
2. 13.03
3. 13.06
4. 13.06
5. 13.06
6. 13.05
7. 13.04
8. 13.04

7-26-21
10:45am
1. 13.05
2. 12.97
3. 13.0
4. 13.02
5. 13.01
6. 13.0
7. 12.99
8. 13.0

___________________________________________________
Load test of AIMS 4000 watt inverter/charger.

Hook the batteries back up and started a load test with the air conditioning.
Air conditioner is pulling 130 amps.

Batteries voltage immediately dropped from 12.99 volts down to 12.22 volts.
Batteries at 99.5 SOC.

Air conditioning test started at 8 PM.
Positive terminal read 80.7° negative terminal read 79.8°.
At 8:07 PM positive terminal reads 81.1° and negative terminal read 81.1°.
Voltage stable at 12.23 volts.

——————-

8:20 PM
Battery bank state of charge is down to 93.7% the voltage on the battery bank is reading 12.09 volts.
The positive battery terminal is reading 81.1° the negative battery terminal is reading 84.9°

8:32pm
Voltage is now down to 11.46 volts and the lights are starting to flicker.
State of charge is at 90.1%

With Air conditioning and lights running is 145.4 amps
That is only 1,744.8 watts at 12volts



Load test of GIANDEL 4000 watt inverter.
Solar panels are disconnected at the DC breaker.

7:50pm
Test starting at 7:50 PM voltage is 13.05 V state of charge is 99.9% with 798.6 amp hours.

The voltage began to drop immediately as the surface charge comes off.
No dimming of lights was observed when roof mounted air conditioning was started.

Voltage at 12.37%
Positive battery terminal reading 83.8° negative battery terminal reading 86.7°

It should be noted that it is pretty warm inside the camper because the air-conditioning wasn’t running and it is in the middle of summer with a high in the 90s today.


7:57 PM
Voltage at 12.38 volts with a 98.2% state of charge the air conditioner is pulling 121 amps

28 min
8:17pm
Voltage at 12.03 Volts
air conditioner is pulling 125.9 Amps
State of charge is 92.9%
Positive battery terminal is 86.7% and negative battery terminal is 87.2%

32 min
8:22pm
Voltage is at 11.25 Volts and dropping fast. Lights have began to Flicker
State of charge is 91.5%

 

[Substrate]

Need more about your SCC. Are you using temp-comp, and if so are you doing the *right* thing by running the temp comp sensor to the battery terminals of the hybrid-gels, rather than relying solely upon the SCC -ambient- sensor?

Another trick question: What is the CV voltage you are using with the hybrid-gel?

 

[mikefitz]

You state in the past performance was acceptable, what is the age and cycle life of the batteries? How are you monitoring state of charge?

My immediate suggestion is the batteries have very much reduces capacity compared to the 100Ah .

The cause could be,
higher discharge/charge currents than the batteries can tolerate.
never fully charged leading to a walk down in effective capacity.
accelerated ageing due to temperature.
underestimate of daily capacity use.
Renogy exaggerated claims on performance and use.

Mike

 

[Off Gridin' It]

Need more about your SCC. Are you using temp-comp, and if so are you doing the *right* thing by running the temp comp sensor to the battery terminals of the hybrid-gels, rather than relying solely upon the SCC -ambient- sensor?

Another trick question: What is the CV voltage you are using with the hybrid-gel?

I have a 100amp Rover solar charge controller. There are temp sensors on the the batteries from both the charge controller and the Inverter. The temp of the batteries is normal. They typically stay around 77 degrees.

Both the charge controller and the inverter have settings for GEL batteries.

AIMS inverter sets the "Fast Charge" at 14.0 volts and "Float Charge" at 13.7 volts.
The Renogy Rover 100 amp charge controller is set to "Boost" at 14.2 volts and "Float" at 13.8 volts.

Boost and Fast charge both being absorption.

 

[Off Gridin' It]

You state in the past performance was acceptable, what is the age and cycle life of the batteries? How are you monitoring state of charge?

My immediate suggestion is the batteries have very much reduces capacity compared to the 100Ah .

The cause could be,
higher discharge/charge currents than the batteries can tolerate.
never fully charged leading to a walk down in effective capacity.
accelerated ageing due to temperature.
underestimate of daily capacity use.
Renogy exaggerated claims on performance and use.

Mike

The batteries are only 8 months old and under warranty.
They have very few cycles on them. Certainly no where near the amount of cycles that these batteries can handle as they have only been in service since November 2020. Then after it went into service the camper only saw weekend use until I took a 7 week trip around the country where I never had to hook to shore power or generator. At that point the solar system operated great and I could run air for about 3.5 to 4 hours depending on the outside temp.

I am using a battery monitor with a 300amp shunt to monitor State of Charge.
With eight batteries in parallel they will have discharge rate of 240 amps and I have not exceeded that.

The solar keeps them fully charged everyday. I have 1200 watts on the roof so no problem there.
The temp has always been in the manufacturers range.

Normal usage the batteries usually don't go below 80% unless I run the air which I actually rarely do for more then an hour at a time just to take the edge off the heat. But I have always been able to run it for 3.5 to 4 hours at night if it is really hot. (Until now)