How to stop false 100% battery status

[Elysium_Van_Isl]

I am trying to finish up with some upgrades to my electrical system and wanted to cast a few questions out to the group regarding charge parameters, battery health and overall setup of the system. It’s a bit of a long post but I wanted to try and put down as much info as possible so that people know what I’ve done and how the system is currently set up.. Essentially though – my question is how do I avoid false “Full” monitor status.
Components:

• 6 Costco GC-2 batteries wired in Series/Parallel for a 12V system
• 4 60W solar panels using 2 Victron MPPT 75/10 Smart Controllers
• Victron Smart Battery Sense
• Victron BMV-712
• Balmar 120A alternator with ARS-5 regulator and Electromaax serpentine.
• NO shore power AC charge system (boat on a mooring)

My efforts to find the complete specs on the “Kirkland” GC-2 batteries were not quite successful, as Costco did not get back to me on the original manufacturer information. I have seen online that some say they are made by Johnson Controls, others say Interstate. Without specifics I’ve obviously had to make some assumptions about charge parameters. I also have not yet been able to do a proper bench-test 20hr capacity… so again, have made assumptions.

BMV Settings –

• Battery Capacity (guessed at): 600Ah (sticker value is 624Ah)
• Auto-Sync: Off
• Charge Efficiency Factor (guessed at): 90%
• “Charged” Voltage: 13.8
• Peukert (guessed at): 1.25
• Absorption Voltage: 14.8
• Float Voltage: 13.8

Smart Solar Controllers –

• Obtain Battery temp & Voltage from SmartBatterySense
• Other values set to match BMV numbers

Balmar settings –

• High Voltage Limit: 14.8
• Batt temp voltage compensation limit: 14.92
• Bulk voltage limit: 14.8
• Absorption limit: 14.8
• Float Voltage Limit: 13.5
• Field threshold for Bulk to Absorption: default
• Field threshold for Absorption to Float: default
• Batt temp compensation slope: 5.0

So here is where I get confused – even though Auto-Sync is turned off, the monitor will still incorrectly classify the batteries as 100% if this scenario happens:
Voltage is > 13.8 and solar is putting out 5 Amps for 3 minutes or longer.
A 5 Amp solar output is super common for me and since this is way less than 4% of my Ah capacity won’t I constantly get a premature 100%?? Have I missed something here?!! Should I change the time setting to be way longer than 3 minutes? Maybe that would avoid false full? I feel like I have all the components to make for a healthy battery life, but there are just a few loose threads that need dealing with.

I am attaching my electrical schematic as well, just for interests sake.
Thanks all!

 

[colemj]

You have told your battery monitor that you consider the batteries charged when they reach 13.8V. Change that to 14.7V and see how it works. If it gets close after that, then play with the charge efficiency and/or bump the Peukert up to 1.35. 90% is a bit high for FLA. 80-85% is more normal for these when new.

Mark

 

[dlochner]

Battery manufacturers don't change their cases when different labels are slapped on. Look at the case and the cell covers and compare them to known brands. East Penn makes a lot of batteries brands other than their own, Dekka brand.

 

[Davidasailor26]

Does the BMV have a tail current option like the Smart Shunt? If so turn the tail current down and it should fix your problem. Also you should not need to have the charged voltage that high once you solve the tail current part. Mine is set to 13.1, below my float, bulk, and absorption voltages. My tail current is set to 0.90%, and my SOC seems to track very well.

 

[Stu Jackson]

So here is where I get confused – even though Auto-Sync is turned off, the monitor will still incorrectly classify the batteries as 100% if this scenario happens:

See these:

For everyone installing a battery monitor: The "Gotcha Algorithm" thread, a "MUST READ"

Link-series Charging Algorithms -- The "Gotcha" Factor!

DEFAULTS are factory settings that are made to be modified to suit your setup.

Also read this one:

Programming a Battery Monitor (by Maine Sail)

Making Your Battery Monitor More Accurate - Marine How To

 

[jssailem]

Starting out.

Battery Specs	Kirkland Signature GC2 Golf Battery
Amp Hour	190
BCI Group Number	GC2
Reserve Capacity	105 Minute
Voltage	6 Volt

two 6-volt 190 amp-hour batteries in series:
Voltage doubles: 6V + 6V = 12 volts
Amp-hours stay the same: 190 amp-hours

Now two sets in parallel
Voltage stays at 12 volts
Amp-hours increase to 190x2= 380 amp-hours

Because they are flood acid batteries you get (at 50% state of charge) 190 usable amp hours.

 

[jssailem]

If you did not buy the Kirkland GC2 battery then please attach a picture of the battery logo.

 

[jssailem]

Costco also sells an Interstate logo battery. Their GC2 battery reports 210amp-hour capacity. It will calculate out using the above same formula to roughly 210 usable amp hours.

 

[Davidasailor26]

Costco also sells an Interstate logo battery. Their GC2 battery reports 210amp-hour capacity. It will calculate out using the above same formula to roughly 210 usable amp hours.

The OP has three sets though, so 3*210 = 630 AH at 12V. That’s about 315 “usable” per the usual rule of thumb, but the amount you should program into the battery monitor is the total, not the usable.

 

[jssailem]

My bad counting @Davidasailor26.
The OP said "efforts to find the complete specs on the “Kirkland” GC-2 batteries".
I think that indicates 190 x 3 or 570 amp hours. with usable at 285 amp hours.
Certainly, adequate power for several days at anchor, unless he is running a lot of electronics.

 

[Elysium_Van_Isl]

AhHa!! OK first off, I see a mistake I made on my wiring diagram with respect to the battery capacity. I found a photo showing the tops of the batteries. So I should be using 3 pairs of 190Ah each, making for a total factory capacity of 570Ah. I guess if I take away roughly 30Ah again from that to account for decreased capacity with age that would give me about 160Ah.

From looking online, the Kirkland GC2's seem to come in a few different specifications. I see 190Ah, 208Ah and 205Ah all listed for the product. Even though all have the exact same item ID number (114723). Mine have 190Ah on the sticker. Attached is the pic I found from when I was recently checking the water levels.

 

[Elysium_Van_Isl]

See these:

For everyone installing a battery monitor: The "Gotcha Algorithm" thread, a "MUST READ"

Link-series Charging Algorithms -- The "Gotcha" Factor!

DEFAULTS are factory settings that are made to be modified to suit your setup.

Also read this one:

Programming a Battery Monitor (by Maine Sail)

Making Your Battery Monitor More Accurate - Marine How To

Thanks Stu, yes I read those a number of times through and have done my best to interpret!

 

[Davidasailor26]

AhHa!! OK first off, I see a mistake I made on my wiring diagram with respect to the battery capacity. I found a photo showing the tops of the batteries. So I should be using 3 pairs of 190Ah each, making for a total factory capacity of 570Ah. I guess if I take away roughly 30Ah again from that to account for decreased capacity with age that would give me about 160Ah.

From looking online, the Kirkland GC2's seem to come in a few different specifications. I see 190Ah, 208Ah and 205Ah all listed for the product. Even though all have the exact same item ID number (114723). Mine have 190Ah on the sticker. Attached is the pic I found from when I was recently checking the water levels.

Yes, sounds like 190*3 would be your more precise capacity for programming the monitor. That won’t affect your 100% sync issue though. The capacity will affect your state of charge percentage, time remaining, and to a small extent the peukert coefficient math. The syncing isn’t especially related to that though, at least not to a large extent. You’ll still need to figure out how to tailor the charged voltage, timing, and tail current to get the syncing right.

 

[Elysium_Van_Isl]

Does the BMV have a tail current option like the Smart Shunt? If so turn the tail current down and it should fix your problem. Also you should not need to have the charged voltage that high once you solve the tail current part. Mine is set to 13.1, below my float, bulk, and absorption voltages. My tail current is set to 0.90%, and my SOC seems to track very well.

Yes, I can set the Tail Current, so then I should change that from 4% to a much smaller number. Combine that with Mark's suggestion of increasing the 'Full' voltage and maybe I would get more accurate tracking....

 

[Elysium_Van_Isl]

Yes, sounds like 190*3 would be your more precise capacity for programming the monitor. That won’t affect your 100% sync issue though. The capacity will affect your state of charge percentage, time remaining, and to a small extent the peukert coefficient math. The syncing isn’t especially related to that though, at least not to a large extent. You’ll still need to figure out how to tailor the charged voltage, timing, and tail current to get the syncing right.

Exactly, yes that was my loose understanding, thanks!!

 

[Davidasailor26]

Yes, I can set the Tail Current, so then I should change that from 4% to a much smaller number. Combine that with Mark's suggestion of increasing the 'Full' voltage and maybe I would get more accurate tracking....

Yes, I can set the Tail Current, so then I should change that from 4% to a much smaller number. Combine that with Mark's suggestion of increasing the 'Full' voltage and maybe I would get more accurate tracking....

I would definitely dial down the tail current. I’d watch the solar output on a sunny day and see what it is when it really tails off - the amount you’re getting when the output is near zero and decreasing very slowly. I know my 300 amp hours of AGM tail off around 3A, so I set my tail current to just less than that, which is 0.90%. My monitor usually syncs to 100% with a small jump from 99.1%, which I figure is close enough. When I had my tail current at 4% the jump was from about 97%, so a little too soon.

I probably wouldn’t turn the charged voltage up any higher, since you’re already above Victron’s recommendation of being the float voltage.

 

[jssailem]

I looked. I did not find a charge profile that was specified by Kirkland or Clarios (formerly Johnson Controls)

I did find this for Trojan and Deka Flood acid batteries.

BRAND	Charging DC Voltage	Float DC Voltage
Trojan Flooded	14.8V	13.5V
Deka Flooded	14.7V	13.8V

 

[Elysium_Van_Isl]

Ah, OK I see. When I'm out next I will watch for a 'jump'. Good thought

 

[Elysium_Van_Isl]

I looked. I did not find a charge profile that was specified by Kirkland or Clarios (formerly Johnson Controls)

I did find this for Trojan and Deka Flood acid batteries.

BRAND	Charging DC Voltage	Float DC Voltage
Trojan Flooded	14.8V	13.5V
Deka Flooded	14.7V	13.8V

Thanks John. I'd be worried the Kirkland were thinner-plate batteries so other parameters would also be different. It's so frustrating that Costco can't tell me who makes them! But I guess that is why they are so much cheaper to buy....

 

[jssailem]

Yes, it is frustrating. One way to compare batteries is the weight of the battery.

In Seattle, there is a Manufacturer, Dyno. I have used them due to their defining the battery specifications and fair pricing.