Reply
 
Thread Tools Display Modes
Old 02-13-2020, 03:43 PM   #1
Senior Member
 
GoneSouth10's Avatar
 
Join Date: Sep 2017
Location: Southern California
Posts: 578
Victron BMV-712 SOC Setting

Absolutely love my BMV-712 and all the data it provides, but I have a question on set up.
My battery set up is 4 Duracell Ultra 6V SLIGC125 (FLA) batteries in a 2P/2S configuration. Each battery is 235Ah, so at 12V, I'm at 470 Ah total. Using the 50% discharge rule of thumb, that gives me 235 "usable" Ahs.
In reading through the Victron manuals, it appears to employ this "50% discharge" rule of thumb as the default for FLA batteries (along with every other electrical variable imaginable, but that's another thread - who knew "Peukert Exponent" would ever come up while roasting marshmallows!), such that, I'm assuming, it would be built into the SOC calculation, given as a percentage of remaining battery life. The "Time remaining" calculation appears to use the "50% discharge" rule of thumb when I just eyeball out the current flowing versus the delta between 235 Ah and the displayed "Consumed Ah" number, but the SOC percentage seems way over stated. For example, if the "Consumed Ah" number is 100 Ah, then I should have 135 AH, or 57% of my "usable" 235 Ah, left. So I would think that the SOC should read 57% (if the denominator is 50% of my entered battery capacity of 470 Ah) OR the SOC should read 71% (if the denominator is my entered battery capacity of 470 Ah).
My question: Does the SOC measure the entire 470 Ah in my setup (such that I should be monitoring that down to 50% displayed SOC) or should I input the "usable Ah" of 235 Ah as the "battery capacity" in my BMV-712 settings, so that the SOC displays my "usable" battery charge left?
And they said there would be no math . . .!!!
__________________
2015 Berkshire 34QS
GoneSouth10 is offline   Reply With Quote
Old 02-13-2020, 04:57 PM   #2
Senior Member
 
Join Date: Jul 2017
Location: California
Posts: 7,451
You set the capacity of your batteries to the entire capacity of 470. In the time to go part you can put in the 50% if you want.

If you draw down the batteries 235AH at a fairly low current draw, you should be at 50%. As your batteries age, your capacity goes down so you will have to adjust the capacity setting at some point.

Set Peukert's constant to 1.25 or 1.30

Just so you know, because of the Peukert's constant, if you draw more power than the 20hr rate, your capacity goes down faster. The BMV will use the Peukert's constant to approximate that.
__________________
2017 Coachmen 233RBS
2018 Ford F150 Lariat 3.5 Eco
"Common sense is not very common"
babock is offline   Reply With Quote
Old 02-13-2020, 05:37 PM   #3
Senior Member
 
Join Date: Jan 2013
Location: Space Coast of Florida
Posts: 2,824
Quote:
Originally Posted by babock View Post
You set the capacity of your batteries to the entire capacity of 470. In the time to go part you can put in the 50% if you want.

If you draw down the batteries 235AH at a fairly low current draw, you should be at 50%. As your batteries age, your capacity goes down so you will have to adjust the capacity setting at some point.

Set Peukert's constant to 1.25 or 1.30

Just so you know, because of the Peukert's constant, if you draw more power than the 20hr rate, your capacity goes down faster. The BMV will use the Peukert's constant to approximate that.
Where is the time to go setting that you say can be set to 50% if you want? Is the the SOC in setting where it can be set manaually?
__________________
2016 Siverback 33IK, Towed 30K+ miles
2018 Ford F-350 Lariat 6.7L V8 Diesel 4WD Crew Cab
Andersen Ultimate Hitch
RadMini Stepthru eBikes

"If you don't know where you are going, any road will get you there."
dalford is offline   Reply With Quote
Old 02-13-2020, 05:52 PM   #4
Senior Member
 
GoneSouth10's Avatar
 
Join Date: Sep 2017
Location: Southern California
Posts: 578
The only SOC setting I could find (Manual Section 4.2.1 (16)) was for the "discharge floor" on the SOC relay.
From what I can tell, the "time-to-go" calculation is based on a trailing average of your current draw (you can set that trailing average to be anywhere from 1 to 12 minutes - Manual Section 4.2.1 (8)), relative to the Ah you have not yet consumed, with that calculation taking into account all the various variables, including Mr. Peukert's constant).
__________________
2015 Berkshire 34QS
GoneSouth10 is offline   Reply With Quote
Old 02-13-2020, 08:07 PM   #5
Senior Member
 
Join Date: Jul 2017
Location: California
Posts: 7,451
Quote:
Originally Posted by dalford View Post
Where is the time to go setting that you say can be set to 50% if you want? Is the the SOC in setting where it can be set manaually?
It's in a non intuitive area. Go to settings...Go to relay...Go to low SOC relay.

__________________
2017 Coachmen 233RBS
2018 Ford F150 Lariat 3.5 Eco
"Common sense is not very common"
babock is offline   Reply With Quote
Old 02-13-2020, 08:27 PM   #6
Senior Member
 
GoneSouth10's Avatar
 
Join Date: Sep 2017
Location: Southern California
Posts: 578
Quote:
Originally Posted by babock View Post
It's in a non intuitive area. Go to settings...Go to relay...Go to low SOC relay.

Yup, got that on the SOC relay setting, but I was wondering more about the displayed SOC value and whether that could be adjusted. I think the answer is "No" and that the SOC that is displayed is relative to your batteries' total capacity (so, in the case of FLAs, be alert to it hitting 50%).
__________________
2015 Berkshire 34QS
GoneSouth10 is offline   Reply With Quote
Old 02-13-2020, 08:31 PM   #7
Senior Member
 
Join Date: Jul 2017
Location: California
Posts: 7,451
Quote:
Originally Posted by GoneSouth10 View Post
Yup, got that on the SOC relay setting, but I was wondering more about the displayed SOC value and whether that could be adjusted. I think the answer is "No" and that the SOC that is displayed is relative to your batteries' total capacity (so, in the case of FLAs, be alert to it hitting 50%).
Yep...that's what you do.
__________________
2017 Coachmen 233RBS
2018 Ford F150 Lariat 3.5 Eco
"Common sense is not very common"
babock is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by Forest River, Inc. or any of its affiliates. This is an independent, unofficial site.



All times are GMT -5. The time now is 11:30 AM.