Victron bmv600 confusion

[Dod42]

I have fitted a victron BMV 600 battery monitor and I'm more confused now than before I had it. I have a 440 AH AGM house bank that I wanted to monitor. I have set it up as per the manual, a bank of 440AH and a floor of 50%. Out for the weekend and here is the problem. The monitors shows SOC of 98.5% a CE of 10.5ah, a current load of 2.72 but a voltage of 12.43 fridge kicks in every 5 minutes. That's why I'm confused.

The battery bank started at 100% we had been plugged in for over a week. Yes I know that the voltage measurement should be without load but does it alter it that much. The SOC shows 98.5% but from what I remember 12.43 volts is more like 60%. I don't worry at 98% but I do at 60%. I have check the voltage at the battery with a meter and it shows close enough to 12.4 volts. So from what I can tell 60% is closer to the mark. How come this thing shows 98.5%

Is the 98% of the 50% floor or to zero

[Ex-Calif]

Not an expert but sounds like you have ground wires on the battery side of the shunt.

Might turn off all DC loads and turn them on one at a time while monitoring the I page.

Read this very carefully if you have not done so before. This guy knows his stuff.

Installing A Battery Monitor Photo Gallery by Compass Marine How To at pbase.com

[Dulcesuenos]

12.1 v is 50% soc for a lead acid. http://www.trojanbattery.com/Battery...e/Testing.aspx


Sent from my LG-LS980 using Cruisers Sailing Forum mobile app

[Sailmonkey]

That's why you measure voltage with no load and allow it to stabilize for several hours

[DotDun]

Originally Posted by Dod42

I have fitted a victron BMV 600 battery monitor and I'm more confused now than before I had it. I have a 440 AH AGM house bank that I wanted to monitor. I have set it up as per the manual, a bank of 440AH and a floor of 50%. Out for the weekend and here is the problem. The monitors shows SOC of 98.5% a CE of 10.5ah, a current load of 2.72 but a voltage of 12.43 fridge kicks in every 5 minutes. That's why I'm confused.

The battery bank started at 100% we had been plugged in for over a week. Yes I know that the voltage measurement should be without load but does it alter it that much. The SOC shows 98.5% but from what I remember 12.43 volts is more like 60%. I don't worry at 98% but I do at 60%. I have check the voltage at the battery with a meter and it shows close enough to 12.4 volts. So from what I can tell 60% is closer to the mark. How come this thing shows 98.5%

Is the 98% of the 50% floor or to zero

It's counting amp hours to determine SOC. It assumes your batteries are performing as they did when new since you just installed it.

[Dod42]

Thanks all for the replies. I have worked out where I was wrong. It seems I had misread the wiring on the negative and so it was really only monitoring 1 of the 4 batteries so the shunt was very confused like me. Now moved and looking better. Will know more in a day or 2

[Ex-Calif]

Originally Posted by Dod42

Thanks all for the replies. I have worked out where I was wrong. It seems I had misread the wiring on the negative and so it was really only monitoring 1 of the 4 batteries so the shunt was very confused like me. Now moved and looking better. Will know more in a day or 2

Good on ya!

BTW - I am considering this monitor myself and have not found any real world description of the programming - Yes I can RTFM but I am interested to know if you found it confusing or daunting?

[Dulcesuenos]

Love ours, works great and easy to set up.

Sent from my LG-LS980 using Cruisers Sailing Forum mobile app

[Dockhead]

Originally Posted by Ex-Calif

Good on ya!

BTW - I am considering this monitor myself and have not found any real world description of the programming - Yes I can RTFM but I am interested to know if you found it confusing or daunting?

I have the Victron battery monitor and don't like it. The amp counting is not very useful for understanding SOC. I convinced myself of that when I cross checked with a hydrometer. It's better if you really fine tune it to your batteries' real (not nominal) capacity, and frequently zero it out. The first is a lot of trouble which never seemed worth it, particularly since real capacity changes constantly, and the last is impossible if you are cruising off the grid for extended periods as I do, but will work better for people who live on shore power and go off only occasionally.

Mine is now disconnected and I'm using a simple voltmeter and my own brain -- with much better results. When I redid all my electronics last winter I just didn't reinstall it -- couldn't find a good place for it in my revamped instrument panel and ended up just leaving it out.

What I do now is just watch system voltage with no big loads on, and where there haven't been any big loads in a couple of hours, and compare that to Trojan's open circuit voltage versus SOC chart, which I printed and laminated and stuck up on my instrument panel. I have a fairly large battery bank (420a/h @ 24v) and so small loads look to it almost like no loads, and any error is going to be on the conservative side, so this actually works really well. I charge when I see 24.5 volts, or at worst, 24.2, and I know that the real state of charge will be at least slightly above, and by no means below, the 60% or 50% shown on the Trojan chart. I think this technique is much more accurate than any amp-counting device can calculate, and best of all, this technique cannot indicate a higher SOC than what is real -- that is to say, all error is on the conservative side.

If I need to know how much current some item of equipment draws, I just use a DC clamp meter.

Next I'm going to try the SmartGauge, which does not count amps, but analyzes voltage patterns, and is supposed to give much better results. We shall see. When I get around to it. I don't feel any pressing need for anything other than what I've got now.

[Maine Sail]

Originally Posted by Ex-Calif

Good on ya!

BTW - I am considering this monitor myself and have not found any real world description of the programming - Yes I can RTFM but I am interested to know if you found it confusing or daunting?

For an Ah counter to be accurate, you will need to know:

*Your banks ACTUAL PHYSICAL 20 hour Ah capacity at this current time. This requires a controlled 20 hour capacity test.

*Your banks average temperature (the BMV does not have a temp sensor)

*Your banks Peukert

*Your banks charge efficiency (how many Ah's out vs. in to get back to 100% SOC)...


For an Ah counter to be a good guide you need:

* The closest approximation to your banks current physical capacity. (It will not be the rating for very long) Programing for less than you assume you actually have will always be safer..

* Your banks average temp

*Peukert (factory number fine)



With any Ah counter please do yourself a favor and dial out "auto reset".. I have not seen a single one that works well and there are far too many variables that can trick them into resetting to 100% SOC well before the bank is actually at 100% SOC... These devices DO NOT reset on Ah's they reset on voltage, % current and time at both..

"Know full resets" are the best way of keeping them in-line and should be done as often as possible when the bank is known full..

How do you determine known full?

Is the bank accepting less than 1.5% of its Ah capacity at 14.4V+ (ABSORPTION VOLTAGE)? (14.1V for GEL) If yes, reset....

DO NOT do a known full reset at float voltage! The batteries must be accepting less than 1.5% - 2% of Ah capacity at absorption voltage.


Ah counters are NOT plug & play they are like dead reckoning and require human intervention to give accurate results. Far too many owners try and plug and play with them, and for a couple of years it works to their advantage, then it tends to fall off the cliff......


Do not expect Ah's consummed to relate to SOC. It NEVER WILL!!!! Only the SOC screen, with a PROPERLY programmed monitor, can do this because it takes Peukert, temp and other factors into consideration that the Ah's consumed screen does not.



20 Hour Capacity Test (an Ah counter can be used to count the Ah's delivered):

#1 Charge battery to 100% full

#2 Let sit at 75-80F until the battery is at that temp

#3 Apply a load = to the 20 hour rating tested load. This is Ah Capacity divided by 20. Eg:

100Ah / 20 = 5A
150Ah / 20 = 6.5A
225Ah / 20 = 11.25A

#4 Hold load steady, adjust as needed, as voltage decays. Current will change as voltage falls. It needs to be held steady for the capacity test to be accurate.

#5 Discontinue test as soon as battery terminals hit 10.5V

#6 Count Ah's or count time. If less than 20 hours before hitting 10.5V what percentage of 20 hours did the bank deliver. If using an Ah counter how many Ah's before hitting 10.5V?

#7 Recharge battery immediately at the 20 hour rate. Do not "fast charge it"...

[T1 Terry]

For lead acid batteries I can see one of these being a major headache and relying on regular zeroing to 100% SOC. For lithium batteries they are the ants pants, absolutely magic and hassle free. I have even moved away from my much loved Plasmatronics with the shunt kit to the stand alone Victron BMV and I recommend them with every system I have a hand in setting up, you know exactly where you are with these monitors.

T1 Terry

[Maine Sail]

Originally Posted by T1 Terry

For lead acid batteries I can see one of these being a major headache and relying on regular zeroing to 100% SOC. For lithium batteries they are the ants pants, absolutely magic and hassle free. I have even moved away from my much loved Plasmatronics with the shunt kit to the stand alone Victron BMV and I recommend them with every system I have a hand in setting up, you know exactly where you are with these monitors.

T1 Terry

I agree, for LiFePO4! For lead acid the Smart Gauge is absolutely simple and works very well but is more expensive. The Smart Gauge however does not work on LFP.....

I am sitting next to my Link-Pro right now showing me at 24% SOC. Almost time to re-charge..... Have not run the motor or solar for charging in 4 days!!!! Ah the beauty of LiFePO4!!!

Today there is supposed to be less than 5 knots so we will be motoring and our alt will get the bank back up quickly..........

[Dockhead]

Originally Posted by Maine Sail

For an Ah counter to be accurate, you will need to know:

*Your banks ACTUAL PHYSICAL 20 hour Ah capacity at this current time. This requires a controlled 20 hour capacity test.

*Your banks average temperature (the BMV does not have a temp sensor)

*Your banks Peukert

*Your banks charge efficiency (how many Ah's out vs. in to get back to 100% SOC)...


For an Ah counter to be a good guide you need:

* The closest approximation to your banks current physical capacity. (It will not be the rating for very long) Programing for less than you assume you actually have will always be safer..

* Your banks average temp

*Peukert (factory number fine)



With any Ah counter please do yourself a favor and dial out "auto reset".. I have not seen a single one that works well and there are far too many variables that can trick them into resetting to 100% SOC well before the bank is actually at 100% SOC... These devices DO NOT reset on Ah's they reset on voltage, % current and time at both..

"Know full resets" are the best way of keeping them in-line and should be done as often as possible when the bank is known full..

How do you determine known full?

Is the bank accepting less than 1.5% of its Ah capacity at 14.4V+ (ABSORPTION VOLTAGE)? (14.1V for GEL) If yes, reset....

DO NOT do a known full reset at float voltage! The batteries must be accepting less than 1.5% - 2% of Ah capacity at absorption voltage.


Ah counters are NOT plug & play they are like dead reckoning and require human intervention to give accurate results. Far too many owners try and plug and play with them, and for a couple of years it works to their advantage, then it tends to fall off the cliff......


Do not expect Ah's consummed to relate to SOC. It NEVER WILL!!!! Only the SOC screen, with a PROPERLY programmed monitor, can do this because it takes Peukert, temp and other factors into consideration that the Ah's consumed screen does not.



20 Hour Capacity Test (an Ah counter can be used to count the Ah's delivered):

#1 Charge battery to 100% full

#2 Let sit at 75-80F until the battery is at that temp

#3 Apply a load = to the 20 hour rating tested load. This is Ah Capacity divided by 20. Eg:

100Ah / 20 = 5A
150Ah / 20 = 6.5A
225Ah / 20 = 11.25A

#4 Hold load steady, adjust as needed, as voltage decays. Current will change as voltage falls. It needs to be held steady for the capacity test to be accurate.

#5 Discontinue test as soon as battery terminals hit 10.5V

#6 Count Ah's or count time. If less than 20 hours before hitting 10.5V what percentage of 20 hours did the bank deliver. If using an Ah counter how many Ah's before hitting 10.5V?

#7 Recharge battery immediately at the 20 hour rate. Do not "fast charge it"...

Bleh! That's just what I was talking about. Now does anyone actually do all of this? I bet exactly 0.0% of cruisers actually use amp-counting battery monitors correctly.

For lead-acid batteries, I think intelligent watching of voltage is far more practical and gives a better sense of SOC and battery condition.

By the way, if you buy the SmartGauge from the manufacturer in the UK, it costs about half of what you pay to Balmar with their egregious markup. I don't think it is more expensive than the Victron monitor, and far easier/cheaper to install.

[Maine Sail]

Originally Posted by Dockhead

Bleh! That's just what I was talking about. Now does anyone actually do all of this? I bet exactly 0.0% of cruisers actually use amp-counting battery monitors correctly.

For lead-acid batteries, I think intelligent watching of voltage is far more practical and gives a better sense of SOC and battery condition.

By the way, if you buy the SmartGauge from the manufacturer in the UK, it costs about half of what you pay to Balmar with their egregious markup. I don't think it is more expensive than the Victron monitor, and far easier/cheaper to install.

I actually have a number of my customers who do a very good job at keeping their Ah counters accurate. This was not easy though.

I think the best part of them is they create more attention to the bank and CHARGING performance, thus perhaps 98% of my customers have improved battery life with an Ah counter regardless of whether it is actually pin point accurate or not. Know full re-sets have been the biggest help....

[Ex-Calif]

Originally Posted by Dockhead

I have the Victron battery monitor and don't like it. The amp counting is not very useful for understanding SOC.

As I get ready to actually open the wallet I am getting serious about reading. Mainesails articles and your advice and others basically point out that one absolutely has to understand

- how the calibration works and the data it needs
- You batteries deteriorate and calibration needs to be redone
- If you are not interactive and active eventually the soh will be useless

To be honest - when there was nothing else a/h counting could be made to work well but I think I am going to go with the Smartgauge. Over the life of the gauge the ~$100 bucks difference is not a big deal I think.

Originally Posted by Maine Sail

For an Ah counter to be accurate, you will need to know:

*Your banks ACTUAL PHYSICAL 20 hour Ah capacity at this current time. This requires a controlled 20 hour capacity test.

*Your banks average temperature (the BMV does not have a temp sensor)

*Your banks Peukert

*Your banks charge efficiency (how many Ah's out vs. in to get back to 100% SOC)...

I guess the average person "guesses" at some of this stuff and that to me is a big downside.

I think (based on your testing) I am going to go with the SmartGauge - It appears to be the next gen.

I understand the Smartgauge does not have a a/h counter or amp gauge - I understand why but it is a disappointment.

I have been Goggling and searching for an amp gauge but have not found anything that is suitable or if suitable really expensive.

Any recommendation for a digital ammeter or preferably ammeter/voltmeter combo?

As always thanks for your advice around here!