Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
 


Reply
 
Thread Tools Search this Thread Display Modes
 
Old 09-26-2019, 09:55 AM   #1
4 Rivet Member
 
2019 23' International
Portland , Oregon
Join Date: May 2015
Posts: 454
Victron Disrepancy

I really like the Victron, as Iíve said in other posts itís a complete game changer. But... camping over the past few days, woke up and the Victron said ďbattery 86%.Ē

It also said I used 33 Ah. That calculates to 80% remaining of my two 81 Ah batteries. I checked the settings on the Victron and itís set at 162Ah.

Any thoughts on how the Victron arrives at the 86% number?
__________________
2019 International Signature 23FB "Cecil"
2020 RAM 1500 Laramie
Former coach: 2015 Bambi 16 "Beanie"
leedav is online now   Reply With Quote
Old 09-26-2019, 10:30 AM   #2
The Aluminum Tent 3
 
pcskier's Avatar
 
2014 23' Flying Cloud
Park City , Utah
Join Date: Aug 2015
Posts: 2,031
Victron Disrepancy

I have given up on the percentage readout. 80 percent calculated vs 86 displayed is actually pretty good compared to my results. Iím sure Bob will weigh in here with a technical answer on how it works and how itís really just a guess at any moment in time. Iíve learned to ignore it and just monitor voltage instead. Thatís the number that matters to me. Same way I look down the toilet to see black tank status rather than rely on the tank monitor :-)
pcskier is offline   Reply With Quote
Old 09-26-2019, 11:41 AM   #3
4 Rivet Member
 
2019 23' International
Portland , Oregon
Join Date: May 2015
Posts: 454
Right now if I had to choose I'd rely on the Ah reading. The voltage, in my view, is just more precise but no more accurate
__________________
2019 International Signature 23FB "Cecil"
2020 RAM 1500 Laramie
Former coach: 2015 Bambi 16 "Beanie"
leedav is online now   Reply With Quote
Old 09-26-2019, 11:42 AM   #4
Site Team
 
wulfraat's Avatar

 
2017 30' International
Broomfield , Colorado
Join Date: Apr 2009
Posts: 3,552
Images: 1
Without getting too crazy on the math, this is the basic gist of it:

% Available = 1-(AH Usage / Total AH Available)

This value is calculated and updated every second or so, time-wise, and the resulting value is made available on the BMV monitor and VE.Bus devices such as CCGX.

AH Usage value is dynamic based on energy flowing in and out of the batteries as measured by the shunt. AH Usage will increase if you are discharging, or decrease if you are charging. Current (amps) flow in/out is measured at the shunt, and then calculated based on a 60 minutes to get amp hours. Can go further on the math but not needed for explanation purposes.

For example, if you have discharged 25AH of energy from a battery bank over some period of time (5 minutes, 30 minutes, 2 hours, whatever) with 200AH total (as set in the BMV), usage % would be:

1-25/200 = 87.5%

AH is a much better and more precise measure of battery usage vs. voltage. Many elements can affect voltage to give you false measurement of how much energy has actually been depleted from the batteries.

For instance you may read 12.6v for a fully charged battery in the day, sitting on the ground with nothing attached to it. At night, with temperature drop, voltage might read 12.4v, even through no energy has been depleted from the battery.
wulfraat is offline   Reply With Quote
Old 09-26-2019, 11:54 AM   #5
Site Team
 
wulfraat's Avatar

 
2017 30' International
Broomfield , Colorado
Join Date: Apr 2009
Posts: 3,552
Images: 1
Quote:
Originally Posted by leedav View Post
I really like the Victron, as I’ve said in other posts it’s a complete game changer. But... camping over the past few days, woke up and the Victron said “battery 86%.”

It also said I used 33 Ah. That calculates to 80% remaining of my two 81 Ah batteries. I checked the settings on the Victron and it’s set at 162Ah.

Any thoughts on how the Victron arrives at the 86% number?
One of two things:

1. You did not set 162Ah on your BMV as battery capacity and so BMV is not displaying correct %.
2. You have set battery bank capacity correctly, but there was some energy in-flow into the batteries from solar or what have you that slightly offset the 33ah used.

Victron will not show you NET in the AH used value - they will show you GROSS AH used.... AH added back via charging sources is a different value. You need to know both to obtain NET AH.

In your example, your numbers tell me that your NET was likely ~23AH used. (33AH depleted - 10AH charged). (1-23/162) = ~86%
wulfraat is offline   Reply With Quote
Old 09-26-2019, 12:11 PM   #6
Rivet Master
 
AirMiles's Avatar
 
2018 27' Globetrotter
Apollo Beach , Florida
Join Date: Feb 2017
Posts: 1,401
I am not a fan of battery monitors. They precisely measure the AH output from an unknowable pool of AHs. This article goes in depth on why I feel this way about battery monitors: https://marinehowto.com/programming-a-battery-monitor/ . Its a great read for those with battery monitors.

Its not that battery monitors are inaccurate, its just that nobody knows the actual number of Amphours in their battery bank. Just like voltage is inaccurate when the temperature changes, your battery bank's available AH change too. Sure we know the lab rated, 77 degree number of Amp hours. Are your batteries new? Is it 77 degrees outside? How abused were your batteries in the past . . .

I use my batteries like propane exchange tanks, when they run out of juice I'll just replace them. I buy a cheap pair ($250 total) of golf cart batteries, run the furnace all night, fantastic fans all day, use the inverter to watch Nascar races and Dancing with the Stars, play the radio all day, use lights and pumps as needed. When my batteries can no longer do these things, I'll just run over to the nearest Sam's Club that sells 6V golf cart batteries with $250 and install a new set.

I get it if you have an expensive bank of Lithiums. I'd sweat the details too if my replacement cost was thousands of dollars. That's why I choose to use a $250 battery bank. A senior moment that kills my batteries and costs me $250 is just a bad day.
__________________
2021 Northern-Lite 10-2 & F350 DRW PSD, 600W Solar/Victron/600A BattleBorn
146 nights 31,000 miles (first 10 months!)
Sold: 2018 GT27Q, 74 nights 12,777 miles
Sold: 2017 FC25FB, 316 nights 40,150 miles
Sold: 2013 Casita SD17 89 nights 16,200 miles
AirMiles is offline   Reply With Quote
Old 09-26-2019, 12:17 PM   #7
Rivet Master

 
2007 22' International CCD
Corona , California
Join Date: Jul 2013
Posts: 9,098
Yeah to that. Missed a switch setting on my MPPT solar controller and boiled out a set of GC-2 batteries in a few months from excess charging voltage. Lesson learned. Cleaned up the mess, installed new batteries and drove on.

I will use a shunt-based monitor, but voltage is my fast check.

Installed a battery watering system and just make sure I schedule a visit to the trailer once a month in storage to add a few ounces of distilled water to top them off.
__________________
Rich, KE4GNK/AE, Overkill Engineering Dept.
'The Silver HamShack' ('07 International 22FB CCD 75th Anniversary)
Multiple Yaesu Ham Radios inside and many antennae sprouting from roof, ProPride hitch, Prodigy P2 controller.
2012 shortbed CrewMax 4x4 Toyota Tacoma TV with more antennae on it.
rmkrum is offline   Reply With Quote
Old 09-26-2019, 12:41 PM   #8
4 Rivet Member
 
2019 23' International
Portland , Oregon
Join Date: May 2015
Posts: 454
Wulfraat more math please. The formula you cite is the same as I used to get the 80 percent. The part I don't understand is the 86 percent. I double checked the battery size setting, I have no solar, and nothing is connected outside the shunt except the unused Zamp connector. I would expect the meter to do a simple integral of Idi/dt and plug it into your formula above. But there's apparently some spin on it.
Oops edit minus peukert losses
__________________
2019 International Signature 23FB "Cecil"
2020 RAM 1500 Laramie
Former coach: 2015 Bambi 16 "Beanie"
leedav is online now   Reply With Quote
Old 09-26-2019, 12:47 PM   #9
4 Rivet Member
 
2019 23' International
Portland , Oregon
Join Date: May 2015
Posts: 454
Maybe some other setting is wrong?Click image for larger version

Name:	Screenshot_20190926-114626.jpeg
Views:	32
Size:	40.7 KB
ID:	353016
__________________
2019 International Signature 23FB "Cecil"
2020 RAM 1500 Laramie
Former coach: 2015 Bambi 16 "Beanie"
leedav is online now   Reply With Quote
Old 09-26-2019, 12:50 PM   #10
Rivet Master
 
sgschwend's Avatar
 
1986 25' Sovereign
2008 F350, 6.4L diesel , Oak Harbor, WA
Join Date: Sep 2015
Posts: 605
Images: 13
Not sure if anyone has suggested that AH is not a accurate way of describing energy. Which is often defined as one amp delivered for one hour (the actual battery voltage is not taken into consideration).

If possible try using watt hours which is actual voltage times current delivered over time. I would guess that Victron graphs both voltage and current then multiplies the two to determine wattage per a short time period, for example one minute. The sums after 60 minute and divides by 60 to come up with the energy in watt hours.
sgschwend is offline   Reply With Quote
Old 09-26-2019, 12:55 PM   #11
4 Rivet Member
 
2019 23' International
Portland , Oregon
Join Date: May 2015
Posts: 454
Quote:
Originally Posted by sgschwend View Post
Not sure if anyone has suggested that AH is not a accurate way of describing energy. I
f possible try using watt hours which is actual voltage times current delivered over time.
Maybe... But power is also i≤R across the shunt, and R does not change appreciably. BTW please I'm not trying to be a butt. (wife says I don't have to).
__________________
2019 International Signature 23FB "Cecil"
2020 RAM 1500 Laramie
Former coach: 2015 Bambi 16 "Beanie"
leedav is online now   Reply With Quote
Old 09-26-2019, 01:12 PM   #12
Rivet Master
 
sgschwend's Avatar
 
1986 25' Sovereign
2008 F350, 6.4L diesel , Oak Harbor, WA
Join Date: Sep 2015
Posts: 605
Images: 13
It is still related to the voltage and in a lead acid battery that can range nearly 8 percent.

Good luck to you.
sgschwend is offline   Reply With Quote
Old 09-26-2019, 01:25 PM   #13
Site Team
 
wulfraat's Avatar

 
2017 30' International
Broomfield , Colorado
Join Date: Apr 2009
Posts: 3,552
Images: 1
Quote:
Originally Posted by leedav View Post
Wulfraat more math please. The formula you cite is the same as I used to get the 80 percent. The part I don't understand is the 86 percent. I double checked the battery size setting, I have no solar, and nothing is connected outside the shunt except the unused Zamp connector. I would expect the meter to do a simple integral of Idi/dt and plug it into your formula above. But there's apparently some spin on it.
Oops edit minus peukert losses
Peukert Exponent is coming into play in terms of efficiency of energy delivery to the load as it relates to stored capacity. Given that you have the correct battery AH entered in BMV and no source of charging, assuming other items are not coming into play, it sounds like you had a relatively low current draw down of those 33ah, which helps to preserve battery capacity, vs. a heavy current, shorter timespan of the draw-down.

Here is a good thread:

https://community.victronenergy.com/...sumed-off.html

If you care about the formula that BMV uses in addition to other calcs:

T = C / In (or C = T * In), where C is theoretical capacity (in amp-hours, equal to actual capacity at one amp), I is current (in amps), T is time (in hours), and n is the Peukert number for the battery.
wulfraat is offline   Reply With Quote
Old 09-26-2019, 01:31 PM   #14
4 Rivet Member
 
2019 23' International
Portland , Oregon
Join Date: May 2015
Posts: 454
Thank you! That's even better news for the Victron!

Quote:
Originally Posted by wulfraat View Post
Peukert Exponent is coming into play in terms of efficiency of energy delivery to the load as it relates to stored capacity. Given that you have the correct battery AH entered in BMV and no source of charging, assuming other items are not coming into play, it sounds like you had a relatively low current draw down of those 33ah, which helps to preserve battery capacity, vs. a heavy current, shorter timespan of the draw-down.

Here is a good thread:

https://community.victronenergy.com/...sumed-off.html

If you care about the formula that BMV uses in addition to other calcs:

T = C / In (or C = T * In), where C is theoretical capacity (in amp-hours, equal to actual capacity at one amp), I is current (in amps), T is time (in hours), and n is the Peukert number for the battery.
__________________
2019 International Signature 23FB "Cecil"
2020 RAM 1500 Laramie
Former coach: 2015 Bambi 16 "Beanie"
leedav is online now   Reply With Quote
Old 09-28-2019, 03:58 PM   #15
The Warthog
 
GSansoucie's Avatar
 
2019 28' Flying Cloud
Portsmouth , New Hampshire
Join Date: Aug 2018
Posts: 75
Quote:
Originally Posted by wulfraat View Post
That thread was very helpful. I have the same setup as the OP and am testing it right now, the % value didnít seem to be dropping fast enough, but now I know why (I donít have a huge load on it for my test).
GSansoucie is offline   Reply With Quote
Old 09-28-2019, 05:10 PM   #16
Half a Rivet Short
 
2017 30' Classic
2022 Interstate 24X
Carlisle , Pennsylvania
Join Date: May 2017
Posts: 15,033
Hi

Everything on the 712 is programable. If you want as accurate a readout as possible, you need to carefully match up the settings on the 712 to *your* battery. It also helps (a lot) if you have a temperature probe on your battery (hooked to the 712 .... ).

The default settings on the 712 (just like on the MPPT) make some assumptions based on Victron made batteries. Often these are a bit wide of the mark for something you just got from Costco. Key settings are:

1) Temperature coefficient - ( under "misc" on the menu ). This is a pretty big deal. Your batteries can change capacity by +/- 30% (or more ...) over a normal camping temperature range. For +/- 40 degree (F) change from 70F that would be 0.75%/F (if the 30% applied to your batteries).

2) Charged Voltage - (under "battery settings"). This is the voltage at which the monitor resets to 100%. What this is set to depends both on your battery and your charger. 14.2V is not much use if your converter / charger only gets to 13.6V. (See the next to as well, they *also* must be true to reset).

3) Charged Detection time. ( under "battery settings" ). How long does the battery have to be at or above the magic voltage (and below magic current) to be fully charged? A spike in the voltage (or fast dip in current) should not reset things to zero. Anything under 10 minutes is probably nonsense, but it does depend on your setup and settings.

4) Tail Current (under "battery voltage"). (under "battery settings"). If the current into the battery falls below this level the battery is considered full. What you set this to very much depends on your charger and the various loads in your system. All of the conditions need to be met (time, voltage *and* current) in order for "full" to happen. When all three come true, the past current history is cleared and the display goes to 100%.

5) Charge efficiency (same) How much of the current put into the battery *actually* turns into stored energy? It's never going to be 100%. The number is going to depend on battery type, battery resistance, battery condition, and charge current. If indeed things seem to be heading out of whack, this and 8 below are what you play with).

6) Current threshold (same) If the current is below this level, ignore it. The shunt is only just so accurate. As you get to very low currents, errors mount up. Ignoring small currents is a way to get these out of the calculation.

7) Time to go averaging: (same) How many minutes does it average over to come up with your "hours left". I don't see much use for this function ....

8) Peukert Exponent: (same) The ever popular elf in your battery As you discharge a battery heavily, it may not have the same capacity as at lower discharge rates. Lead acid's have a lot of this, lithium's not so much. To be even more nutty, different electrode alloys / constructions / chemistries all get into the act as well. You can set this from the data in your battery spec sheet (if you bought a good battery brand) or you can guess ....

9) Zero Current Calibration (same) The magic brain in the unit can have a slight offset in it's current measurement. For the highest accuracy, make sure there is no current in the shunt and do a zero cal.

And no, that's not everything but it's plenty to deal with.

=====

So how does this work in practice?

Assuming you charge up to full every day, the reset stuff happily puts you back to 100% each day. Welcome to living on shore power.

If you put a big hit on the battery (lots of current for a short while) number 8 comes in and fiddles things. The amp hours and the percentage now are out a bit. Same thing with very low currents, except it's out the other direction. It's not *wrong* it simply does not add up in terms of current used vs percentage left.

If the temperature changes from 31 degrees this morning to 72 degrees right now, the capacity is going to change a bit. The basic amp hours of battery capacity has changed ( from maybe 70AH to 100AH). 10AH of usage this morning took down a bigger percentage than 10AH of usage this afternoon. It shows 20AH used, but half of that took a bigger bite.
If it had been hot this morning, it would have taken a smaller bite.

To the degree the numbers match up with your battery, the results can be very accurate. Even with a few guesses here or there you will do well. Even with the defaults, you will be doing much better than the stock display that you get with the solar package. The only exception to all that is if you set 2 to a voltage the charge system does not get to (so it never resets to 100%).

Bob
uncle_bob is offline   Reply With Quote
Old 09-28-2019, 07:31 PM   #17
The Aluminum Tent 3
 
pcskier's Avatar
 
2014 23' Flying Cloud
Park City , Utah
Join Date: Aug 2015
Posts: 2,031
Outstanding post as always Bob!
pcskier is offline   Reply With Quote
Old 09-29-2019, 07:18 AM   #18
Half a Rivet Short
 
2017 30' Classic
2022 Interstate 24X
Carlisle , Pennsylvania
Join Date: May 2017
Posts: 15,033
Quote:
Originally Posted by pcskier View Post
Outstanding post as always Bob!
Hi

Now lets hope I didn't make yet another typo and get something backwards

Bottom line still is, there are a couple ways the percentage and amps get so you don't think they are right (but they are indeed correct).

Bob
uncle_bob is offline   Reply With Quote
Old 09-29-2019, 09:36 AM   #19
The Aluminum Tent 3
 
pcskier's Avatar
 
2014 23' Flying Cloud
Park City , Utah
Join Date: Aug 2015
Posts: 2,031
My 712 is showing 88 percent SOC this morning in rested state, 12.4V. Thatís at 39 degrees but I do have the temp monitor. Clearly not accurate. Iíll play with settings as per your post but really, Iím worrying less and less about all this. Itís been a good Ďlearningí trip. I mainly like the monitor to keep track of powers usage Ďasí Iím using it, particularly after the panels have gone to sleep for the night. Helps make decisions on how liberal to be with furnace, inverter tv/dvd) etc.
pcskier is offline   Reply With Quote
Old 09-30-2019, 08:59 AM   #20
Half a Rivet Short
 
2017 30' Classic
2022 Interstate 24X
Carlisle , Pennsylvania
Join Date: May 2017
Posts: 15,033
Hi

That does indeed seem a bit weird.

Bob
uncle_bob is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Victron Battery Monitor Install NoResults Batteries, Univolts, Converters & Inverters 82 01-23-2017 10:02 AM
Victron Energy BMV-702 Battery Monitor TinVenture Electrical - Systems, Generators, Batteries & Solar 5 10-15-2016 08:49 AM
Victron 702 Placement stephenb Electrical - Systems, Generators, Batteries & Solar 8 09-13-2016 11:33 AM
Victron Battery Monitor with Bluetooth connection to smart phone jhart657 Electrical - Systems, Generators, Batteries & Solar 23 07-27-2016 01:56 PM
Victron Multiplus Hybrid/Boosting Inverter/Charger Install CA_Tallguy Electrical - Systems, Generators, Batteries & Solar 7 03-15-2016 11:03 PM


Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by the Airstream, Inc. or any of its affiliates. Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.



All times are GMT -6. The time now is 05:57 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2023, Jelsoft Enterprises Ltd.