Charge Times and Voltages

ForeverHomestead · January 2021

I have been working at getting my battery bank brought back to a healthy state. I have done some big repair EQ's and have a couple more to go, but now that I am in a battery place capacity wise I want to revisit my charge times and voltages.

I have it set based on what the manufacture says, but I think the times need to be extended.

I have 48 S-1450 batteries. Two string of 25 batteries in parallel for a total AH capacity of 2248

My voltages according to Rolls is:
Bulk/Absorb = 60V
Float = 52.56V
EQ 64V

Based on this info, what would your think my times should be?

Vic · January 2021

Hi Forever..,

Have read all of your comments, and have wondered, just where is all of the power that your system supplies, GOING ??

You have a large system, what are the power demands, and when do these occur?
Also, forget, just where you are located(?).

The Absorb time depends upon the depth of discharge that the battery has experienced in the previous discharge.

If you Skip charge Days, the accuracy of the SOC, and Net AH, as shown from the WbJr Status/LAPP, will drift.

Also, if you use Follow Me for the three Classics, Skip Days cannot be used (should you be thinking of Skipping Days).

Also, thought that the recent Guidance from Surrette is to use a Float voltage, around 54 V.

Personally use an Float Voltage (Vflt) of 52.4, for the Surrette FLAs, here. IMO, though, Vflt should the lowest voltage that will just barely, keep a fully-charged battery, fully-charged.

SGs measurement IS the Gold-Standard for SOC, of course.

FWIW, Thanks for added info, Vic

ForeverHomestead · January 2021

Vic said:

Hi Forever..,

Have read all of your comments, and have wondered, just where is all of the power that your system supplies, GOING ??

You have a large system, what are the power demands, and when do these occur?
Also, forget, just where you are located(?).

Hello Vic. I am on The Bruce Peninsula in Ontario Canada. pretty much at the 45th Parallel

We sized our system based on what we were using when connected to the grid. That was 21kw a day. On average we are using about 700 to 800 watts an hour. This of course goes up and down. One of the biggest draws is a saltwater aquarium. the heater on this is a killer. Based on my tracking over the last couple of weeks is uses almost half of the power in the winter months. This is crazy and I have just completed designing a heat system for it that uses our return from the infloor heat that will heat it instead of power from our bank,.

I wanted to get rid of the tank but it has been with us for over 8 years and the family would have no part of it.

Once I get that installed our hourly usage should be down to around 400 to 500 watts an hour.

Vic said:

If you Skip charge Days, the accuracy of the SOC, and Net AH, as shown from the WbJr Status/LAPP, will drift.

I do not put allot of faith in the SOC that the system shows. I am not sure if it is because my bank needed some work to get back to a better state our what, but I never found it to be very accurate.

Vic said:

Also, if you use Follow Me for the three Classics, Skip Days cannot be used (should you be thinking of Skipping Days).

Also, thought that the recent Guidance from Surrette is to use a Float voltage, around 54 V.

Personally use an Float Voltage (Vflt) of 52.4, for the Surrette FLAs, here. IMO, though, Vflt should the lowest voltage that will just barely, keep a fully-charged battery, fully-charged.

I am getting my voltages from the side of the battery. I wonder if I should be raising it up.

I do not see myself skipping days, as they are to hard to recover from. In the summer things are obviously easy. This is my 2nd winter living off grid full time and I usually feel a bit like a power Nazi with my family trying to get usage cut down. The more I learn, the more I realize I still have allot to learn about batteries and off grid living.

Vic · January 2021

Hi Forever..,

Thanks for the info, thought you lived in the far North, but thought that is might have been in AK.

Even 400 W/hr, in Winter, in a far North location is quite a bit.

Suppose that you PV module elevation angle/s favor Winter production. Anyway, seems that you are making progress getting the SGs, closer to spec.

Have tried using End Amps (Finishing current), to end Absorb, but on the FLAs here, this Ending current seems to vary, by about 10%, depending upon the DOD of the battery in the previous cycle. Although, the main banks of Surrette 4KS25s, are now in their 16th year of service. Perhaps this can account for the EA variation.

IMO, ideally, the Finishing Current really needs to measure the Rate of Change in the battery charge current, in Absorb, not a fixed current. As a result of this, we have ceased using WbJr battery charge current, in favor of the fixed Absorb time setting.

FWIW, Thanks, keep warm, Vic

Charge Times and Voltages

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