Right, inverter off. BMV shows zero current.

Measuring on the batteries themselves, 25.1.
Before Shunt, 25.1
After shunt, 25.1
At inverter, 25.1

BMV volts 25.44

@The Terrible Triplett, and at that point, what did the inverter show? EDIT: (Sorry, just saw you wrote Inverter OFF)

You are using the same tester on all of these measuring points, if the tester is inaccurate, the reading will be the same everywhere.

Just for interest sake, did you fiddle with the BMV recently....... perhaps saw some smoke in the vicinity of the BMV?,, I recall reading about a certain forum member in your area who is famous for letting the smoke out of electronic components...

Inverter is off, the measurement was taken at the inverter cable connectors, to check the volts all over the system.

Nope, that person who lets the smoke out, has been forbidden the house, but he lurks around. 

Nope, no fiddling.

Inverter is on again showing 24.6v. BMV says 25v.

Just teasing ,

Its strange, dont know what to think, I found the BMV to be very accurate, but I use a fluke to check it. The V-series is normally within  0.1volt from the other 2. If it is the BMV that is out and you find the reason, I would love to know what caused it.

I will. It will be valuable knowledge shared on the forum.

Lets see what Victron says. 

TTT just off on a tangent. The BMV comes with about 10m of cable. If this cable's excess  is coiled up tightly you end up making a inductor which would then influence readings.

10 hours ago, Chris Hobson said:

• Tail current is a matter of trial and error. The 4% default is a bit high.  I steadily reduced it and my current setting is 2.8% with a charged detection time of 30 minutes. It is still not 100% with the Axpert showing fully charged marginally before the BMV shows 100% but I am happy with the setting.
• Never - with the Axpert showing fully charged marginally before the BMV I am happy for it to sync about 5 minutes later.

Chris, I have a question for you on these two point above. Asking for I have not tampered with these settings myself and now I am wondering why you are doing it? EDIT: Am I missing something and need to do the same?

How do you know the inverter's charging is accurate?

BMV Manual says: For a reliable readout, the state of charge as displayed by the battery monitor has to be synchronized regularly with the true state of charge of the battery. This is accomplished by fully charging the battery. In case of a 12 V battery, the BMV resets to “fully charged” when the following “charged parameters” are met: the voltage exceeds 13.2 V and simultaneously the (tail-) charge current is less than 4.0 % of the total battery capacity (e.g. 8 A for a 200 Ah battery) during 4 minutes.

 

9 minutes ago, Chris Hobson said:

BMV comes with about 10m of cable. If this cable's excess is coiled up tightly you end up making a inductor which would then influence readings.

I have always had the cables rolled up in a bundle. 

So I pulled the entire cable out. No difference on the volts on the BMV. 

 

15 minutes ago, The Terrible Triplett said:

BMV Manual says: This is accomplished by fully charging the battery.

I do this nearly on a daily basis. There have been probably ½ dozen times in the last year where we have not achieved 100% SOC. 

At 4% I was finding that the BMV registered 100% SOC but patently from the behaviour of the SCC the batteries were still in late absorb.

Dockarl made me aware of the issue in this video

https://www.youtube.com/watch?v=YXbjJzyIFgg

 

I see. Let me ponder on this a bit.

The Victron shunt is 50mV/500A. 500nV per ampere. That's so low that you'd have to put a serious load on it before I'd even be able to pick it up on the oscilloscope. So testing the shunt is going to be rather hard. The only other thing I can think of would be that the voltage is measured on the same connection that powers the device, including the backlight, so on long cable runs it will sometimes read low. Yours reads high though.

It shouldn't really affect state of charge figures. That's supposed to count amp-hours... not watt-hours (which would involve volts). Some readings will be out of course, but I would expect it to work perfectly in the SoC dept.

I switched off the feature on the inverter where it can accommodate high loads and volts dropping. Now the low battery warning is gone.

Will see what V responds with, if there is no solution, it is maar tough. 

The 600 is nearly 5 years old, and it has been around some mad scientist experiments.

So if the SOC is not affected, it will serve its purpose for many years still.

Here another question on the BMV 702 settings.

With the summer getting here slowly but surely I noticed that my SOC jumps from 97 - 100% and some times even lower on days that there is very little load. From what I understand its got to do with your tail current and charged detection time. So my obvious concern would be is 100% soc 100% when it "jumps" like this?

Here is a screen on the charge volts vs the soc

 

and here is the settings of the BMV

Lastly the batts specks.

Any and all thought?

 

Regards

Paul

The BMV has an auto-sync feature. It is possible for it to go out of sync. Batteries do degrade over time and might not accept exactly the same amount of charge, you may have been off a tiny bit the previous time, and so on... it's not a precise science. So if the batteries aren't accepting much charge for a prolonged period (the so called tail current) and it's close enough to 100%... it will jump. I would not be too concerned about it. I think you can do a manual sync if you want to, then it should stop jumping... for a while.

Cool thanks! @plonkster

I am looking to get a BMV-702 and have found an local online source at R2800, does that seem reasonable or should I keep on looking?

@Camel is a member of this forum and was cheaper than that.

Thanks, will do.

Hi Camel,

I am also looking for a BMV 702 ,can you please help.

Thanks,

 

hi! seems to be the bmv702 'fountain of wisdom' - or maybe the mother lode? any case, i am interested in getting one - question is, with my setup where the monitoring pc is 15m away from the axpert and batteries [i test icc at present] the question is how do i hook it up in order to have it communicate with the pc? there is a cat5e running from the axpert to the pc at present.

in Christ

gabriel

Hi @gabriel,

I am not sure that the BMV702 is intended to communicate with the PC - others will know more.

The BMV has 2 components - the shunt which is mounted next to your battery bank and the monitor where you read the information which can be mounted remotely (so it could be installed next to your PC).

Communication between shunt and monitor is via a 6wire UTP cable with with RJ11 (6 pin) plug on each end. The RJ11 is the same size as a telephone jack, and comes in 2/4/6 pin versions, very similar to the RJ45 which is the 8pin version used for LAN cables.

The system comes with a 10m UTP cable in the box, you will need to find an extension cable or make a new cable to suit your installation.

tx a lot @pilotfish, so after all there was a reason for me schlepping all those telephone cables along for all those years...

oh yes, how would icc 'see' the bmv?

 

1 hour ago, gabriel said:

oh yes, how would icc 'see' the bmv?

The BMV has a little 4-pin socket on the back into which you plug a vedirect->usb cable. That shows up as a standard serial port on the PC and/or Pi, and far as I know ICC knows how to read that.

In other words, you also need a vedirect->usb cable.

On 6/30/2017 at 7:06 PM, plonkster said:

The BMV has a little 4-pin socket on the back into which you plug a vedirect->usb cable

indeed it has, see image.

the question is why is the vedirect>usb conversion cable so pricey? the present euro price is 29 [zar462, their official 2017 price list] whilst we pay > zar600. question, is there something proprietary about it and why can it not be made up for far less?

8 minutes ago, gabriel said:

indeed it has, see image.

the question is why is the vedirect>usb conversion cable so pricey? the present euro price is 29 [zar462, their official 2017 price list] whilst we pay > zar600. question, is there something proprietary about it and why can it not be made up for far less?

@edmundp taught me a trick. One can connect a CP2102 USB chip to the output of a BMV and leave of the power connection and one can communicate  with the BMV. The normal cable is isolated so the is no risk in frying you BMV or PC. I eventually discontinued using a CP2102 since ripple from my gennie starting/stopping was causing ICC/SolarMon to malfunction.

I know one of the Cape based Solar suppliers had them fairly cheap on a Black Friday special a couple of years back.