Voltage drop very fast on load

[acdoctor]

0.2 volts less at inverter is discharging the battery. Is that voltage difference measured with same meter? When inverter is doing what? Surely that is not the case when charging. If so that won’t charge at all. Current flows because of difference in voltage.
Are you attempting to use this during your outages now, like yesterday, or the day before? I don’t think you will be able to get to a conclusion if you are. If you do it will take far longer.

 

[Montanat]

0.2 volts less at inverter is discharging the battery. Is that voltage difference measured with same meter? When inverter is doing what? Surely that is not the case when charging. If so that won’t charge at all. Current flows because of difference in voltage.
Are you attempting to use this during your outages now, like yesterday, or the day before? I don’t think you will be able to get to a conclusion if you are. If you do it will take far longer.

Yes when discharging.
Eg: invreter shows 48v. Multimeter shows 48.2v
This difference is always like that, yes same voltmeter I'm using.

 

[acdoctor]

So 0.2 volt difference between the meter in the inverter and the one in your hand?
What about difference from inverter to main battery connections( at the batteries) while charging and at what amperage ?

 

[Montanat]

So 0.2 volt difference between the meter in the inverter and the one in your hand?
What about difference from inverter to main battery connections( at the batteries) while charging and at what amperage ?

Yes it's 0.02v not 0.2v on discharge (load)
Eg: inverter 48v / multimeter 48.2v

On charging its the same value (sometimes 0.01v)
Charging at 30amps.

I try test again today when main power came:

Batteries DOD = 10.5v (42v)
Inverter Bulk setup = 61v (I gave the maximum voltage to try)
Inverter Charge = 30a

Maximum charging voltage shown on both ivnerter & multimeter reached 57.3V.
Batteries = 14,35 / 14,28 / 14, 38 / 14,37

Total Charging time = 4 hours

 

[acdoctor]

Why did you stop? It sounds like you were getting somewhere. I am not sure lead acid is going to work for you with out some solar. You need most of the 4 hours to bulk and then a couple of more to absorb at least every 3 days or they will sulfate up on you. Bulk don’t need to be any higher than is required to see maximum amps of 30 for your inverter.

 

[Montanat]

In

Why did you stop? It sounds like you were getting somewhere. I am not sure lead acid is going to work for you with out some solar. You need most of the 4 hours to bulk and then a couple of more to absorb at least every 3 days or they will sulfate up on you. Bulk don’t need to be any higher than is required to see maximum amps of 30 for your inverter.

Didn't stop. The inverter did when float reached 54.4.
And it was not continuous 30 amps charging for 4 hours . It went down slowly untill reached 1amp then charging stopped / completed.

 

[acdoctor]

If bulk was sent to 61 volts and batteries never reached 61 volts charge cycle was not completed. When where and how did you observe battery voltage at 57.3 volts?
I don’t think you are getting full inverter voltage at batteries. If you were amperage should not taper off to 1 amp before batteries reached 61 volts.
After they stopped and had a chance to settle some I could see them being 57.3 volts.

 

[Montanat]

If bulk was sent to 61 volts and batteries never reached 61 volts charge cycle was not completed. When where and how did you observe battery voltage at 57.3 volts?
I don’t think you are getting full inverter voltage at batteries. If you were amperage should not taper off to 1 amp before batteries reached 61 volts.
After they stopped and had a chance to settle some I could see them being 57.3 volts.

I was Observing voltage and current charge every 10-15 minutes.
Charging reached 57.3v after around 2 hours with 27 amps charge . It Stayed on 57.3v for 1 hour and a half with 27 - 25amps , Then both voltage & amps started to drop until 54.4v / 1 amp.

I will do the same test again but this time starting from 48v not 42v, I won't go down to 42v again. And with 57.6v bulk setting.

What Will happen if I set both bulk and float to 57.6v? Maybe if I do that I will force the inverter to reach this point. Just wondering if it doable for 4 hours.

 

[acdoctor]

Nothing wrong with that for the short term. You wouldn’t want to do it all the time though. Be sure to check voltage at battery while charging at the 25 to 30 amps. If that is greater than 0.1 volt difference the inverter will under charge the battery. Battery Voltage rising to the set voltage is how it interprets the SOC.
I am not talking about the difference in the display and the meter. I am saying meter it at battery and inverter.

 

[Montanat]

Took voltage now :
Inverter screen = 47.6
Inverter pins = 47.7
Multimeter on battery = 47.8

 

[acdoctor]

I would like to know those while charging at 25 to 30 amps?

 

[Montanat]

I would like to know those while charging at 25 to 30 amps?

I did recharge again today.
Please note we have 2 types of electricity power here... Private generator for the city, and main grid from the government.
When main grid cuts, generator gives power to the city and vise versa.
.......................................

Setup = Bulk 61v / float 57.6v / charge 30amps

Results are .
Charging Starting from 47v.

Grid voltage 225v (private generator power):
From 47v to 55.8v @27amps = 1 hour.

Grid voltage became 240v (government main power):
From 55.8v to 56.4v @25amps = 20 minutes

From 56.4v to 57.2v @24amps trickling down to @7amps = 2 hours

Government Power went off, generator power came (230v):
From 57.2v to 57.4v @8amps trickling down to @3amps = 1:40 hours

From 57.4v to 57.5v @1amp = 30 minutes

From 57.5v to 57.6v @*zero amps * (inverter shows zero amps charging) = 1:45 hours.

Charging stopped at 57.6v (charging light not blinking anymore)
...................................................

Note: Charging never reached 61v as per bulk setup (61v).

During the charging process, i decreased the float to 54.4v and the charging voltage started to go down very fast to follow the float setup and not the bulk setup. (I increased it again to 57.6v to keep the charge going).

Voltage of inveter screen and inverter pins where the same, batteries were lower by 0.01v (from 47v till 57v)
Eg: inverter 56.1 / pins 56.1 / batteries 56
From 57v till 57.6v all 3 readings were exactly the same.

PS: from 57 to 57.6 I could hear the batteries Boiling.

This procedure took 8 hours, while replying to you here I decreased the float from 57.6v to 54.4v after those 8 hours, inverter went down very fast to 54.4v

 

[acdoctor]

I don’t see where you specifically compared ( pins ) and battery voltage while charging at 30 amps?
It look like to me you have a 3 volt difference from pins to battery and everything else is working as it is supposed to. The larger the current on the battery lines the higher the voltage discrepancy will be. The lower the amps the smaller discrepancy.

 

[Montanat]

I don’t see where you specifically compared ( pins ) and battery voltage while charging at 30 amps?
It look like to me you have a 3 volt difference from pins to battery and everything else is working as it is supposed to. The larger the current on the battery lines the higher the voltage discrepancy will be. The lower the amps the smaller discrepancy.

Charging started from 27amps not 30 (setup was 30 amps yes)

Charging from 27amps down to 13amps the voltage difference was + 0.01 on the battery.
Example : screen 55v / pin 55v / battery 55.1v.
Or 56 / 56 / 56.1
Etc...

The voltage on all 3 (screen, pins, battery) was exactly the same when the charging amps reached 12amps and decreased till zero amps.

I tried to equalize the batteries 2 hours ago, setup was 61v for 2 hours, voltage didn't reach more than 57.6v for 2 hours it just sit there and charging amps was zero all the time.

 

[acdoctor]

I don’t suppose you have a 0 to 30 volt power supply do you? If you did you could break them up and charge individually to verify the problem is in the inverter. It should bring voltage to the set voltage.

 

[acdoctor]

You are barely getting to the proper charging point by setting to 61 volts. You can’t ever equalize.

 

[acdoctor]

57.6 volts is the target voltage. Are you getting better results from the batteries now that you are charging them?

 

[Montanat]

57.6 volts is the target voltage. Are you getting better results from the batteries now that you are charging them?

I am Testing tonight. Now I'm on batteries since 2 hours with 20amps load.

I have a new inverter I bought before this one but it Doenst have equalizing feature and fan stays on all the time, I will switch inverters and see if it charges more before I go and buy a 30amps charger and try to charge the batteries one by one.

And I have this step-up voltage boost module (input 3v to output 26v maximum) will it work? Attached is a pic and feature.

 

[acdoctor]

I would definitely give the other one a try. See if you have the same anomaly with it.

 

[Montanat]

I would definitely give the other one a try. See if you have the same anomaly with it.

Ok I will.

Inverter shut down now.
Cutoff set at 48v as it was before charging today.

It lasted 2 hours on14amps load and 45 minutes on 25amps load. I don't think it improved.
How much will it last if it was 20amps load with those values above ? Im not good in math...