Stark 533 AGM charge parameters

TEG · February 6

Hi All,

What a great site, there is a wealth of knowledge here.

I have an Outback VFX3648 inverter with FNDC / Mate3, Midnite Classic 150 CC, 8 x Stark 533 6V AGM batteries, 4080W of solar and a 6kW Generac Ecogen with autostart.

I've been having capacity issues with the batteries so have been digging in to the charge parameters and anything else I can think of, today i came across what might be a major issue. I have conflicting information on the data sheet and sticker for the batteries, I just noticed today that the batteries actually had charge parameters on them. The data sheet calls for "constant voltage" of 7.3 - 7.4V, I've assumed that to be absorb, and a "float use" of 6.8 - 6.9V, these are the parameters I have been using to charge the batteries. While testing today, I noticed fine print charge parameters on the batteries themselves, "standby use" 7.3 - 7.4V and "cyclic use" 6.8 - 6.9V.

I am now worried that I've been overcharging the batteries using the standby setting rather than the cyclic setting for absorb charging. I've attached the data sheet and a picture of the battery parameters.

I need to do some math and testing for capacity, as it sits I don't believe i'm getting anywhere near capacity that I could form the batteries. After a full day of sun, and the batteries being topped up to 8.4A end amp setting from the FNDC / Mate3 module, I am right back to 50% SOC (48.2VDC) by 730am the next morning. Sun goes down about 6pm here right now and i'm averaging about 400Wh drawn over that 13 hour period, 5200W, 108A @ 48VDC.

What do you all believe those voltage parameters to specify? If the "float use" setting on the data sheet is actually my "cyclic use" absorb setting, not a float setting, have I damaged the batteries irreversibly by applying to high a voltage? The temperature compensation is set up in the Mate3 parameters.

Any help is greatly appreciated, if there is anymore info needed to push this train down the tracks, please let me know.

TEG · February 8

Forgot to add: I would normally go back to the supplier with these questions, I cannot find a direct line to Stark Energy anywhere. They are / were a Canadian company, I believe. I think they may have been bought semi recently. I can find the batteries at small distributors, not the actual company itself.

Marc Kurth · February 9

These appear to be one of many OEM-labeled batteries made by Vision, a large battery manufacturer in China. The specs carry the fingerprint for these batteries designed for UPS/Backup duty. Note that they do not even publish cycle life for normal off grid shallow DOD levels - only 50% down to 100% depth of discharge. Batteries designed for UPS type duty need to spend most of their life in Float. This is not easy (impossible) with offgrid.

- The amp hour rating of 533 amp hours is based on a 1 amp draw, and the C/20 rating is 424 AH.

- Based on the datasheet, the optimal charge voltage is 7.3v to 7.4v for cyclic duty.They do not publish the "end amps" or current draw at 100% SOC. I would recommend staying in Absorb until the current draw drops to around 2% of the C/20 rating.

- Their cycle life ratings are based on 60% of original capacity being end of life, instead of the normal 80%

In general, I would not use these in an off-grid cyclic system, but since you have them already - be sure that the battery bank has 4-5 hours per day in Float on average.

Does this make sense?

Marc

BB. · February 9

It appears that the "owner" of Stark eventually changed the company name to "Charge Solar" a few years ago:

https://www.chargesolar.com/products/energy-storage/?yith_wcan=1&brands=stark-energy
https://www.chargesolar.com/brands/stark-energy/

https://www.chargesolar.com/about-us/contact-us/

No idea if this is correct/current "owner" of Stark--But it is a starting point.

https://www.dropbox.com/s/7n9o7nbnye7pb06/SRK-533.pdf?e=1&dl=0 (Stark Battery Data Sheet)

-Bill

Marc Kurth · February 9

I grabbed this datasheet for you - it's the only thing that was readily available when I looked.

https://centexbatteries.com/personal/SRK-533.pdf

TEG · February 9

Hi Guys! Was going to write up a post today, I got in touch with Charge Solar yesterday, @BB. , you are correct, they were "absorbed" (hehe) a few years back by Charge. They have the market cornered around here, used to be HES PV. The technical service manager from Charge put me in touch with the tech service manager from Rolls, the Stark batteries are to be treated identically to the Rolls S6-460AGM's, he says they are basically identical other than the plate. They were both extremely helpful and quick to respond, even though I am not a customer. I was sent the user manual for Rolls AGM's, have everything setup now, I was not over charging the batteries. They recommend 3% tail current in the manual, I am trying to sort out how long I should sit there before going to float. The manual calls for an hour for the FLA's but doesn't mention a time for AGM's.

I am still trying to wrap my head around whether or not I have lost capacity in my battery bank, I need to do some math. I have been reading a bunch of both of your posts to try and determine the best course of action to test capacity. I am getting about 13 hrs of autonomy right now, will be enough that we don't need the genny from spring through fall but its run daily through the winter. We've added to the house load since we purchase the house, I am slowly building the system up as we go, would like to get as much out of these batteries as I can.

TEG · February 9

Rolls user manual for anyone else that may need it in the future.

Marc Kurth · February 9

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Stark 533 AGM charge parameters

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