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Old 01-12-2018, 22:17   #1
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Victron 100/30 voltage measurement

I've recently upgraded my solar system with a couple of 42 V 200 W panels in parallel, plus a Victron 100/30 MPPT controller. It is all working quite well, and putting in some useful power.

I'm using their Bluetooth app to monitor the system... a neat and handy tool. However, I've noted that the battery voltage that is posted there is around 0.2 volts higher than that measured with a good DVM. This is measured right at the output terminals of the controller, so voltage drop is not the issue. The differential remains fairly constant over a wide range of output currents.

This, of course, means that the set Absorption, Float and Equalize voltage points are incorrect. I'm charging 4x T105s and have used the user defined protocol to set Absorption at 14.8, etc. So, when the reg thinks it is outputting the 14.8 volts, the batteries are only getting around 14.6. I have set the voltage higher to compensate for this, but don't really like that as a work around.

So, has anyone else seen a similar issue? And, is there a way to calibrate the voltmeter in the regulator? If no one here on CF has wisdom to offer, I'll try going to Victron directly, but am not optimistic that I will be able to reach a real competent human being.

Ideas?

Jim
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Old 01-12-2018, 22:19   #2
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Re: Victron 100/30 voltage measurement

I would try a 2nd DMM to confirm
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Old 01-12-2018, 22:21   #3
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Re: Victron 100/30 voltage measurement

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I would try a 2nd DMM to confirm
Have done so.

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Old 02-12-2018, 01:20   #4
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Re: Victron 100/30 voltage measurement

Unless you have access to a properly calibrated meter, you have no way of knowing which of the 2 measurements is correct - if either....

It’s not uncommon for consumer grade meters and electronic devices to be several tenths of a volt away from the correct value, I have seen many boat MFD’s and volt meters that were half a volt out.
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Old 02-12-2018, 01:23   #5
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Re: Victron 100/30 voltage measurement

I don't know of any way to calibrate the voltage of the MPPT.

Some options:

Install a BMV-712 with the optional battery temperature sensor. Then Bluetooth network the BMV and the MPPT together using the app. This will share the battery voltage and temperature with the MPPT. Otherwise you are relying on the charging device to provide accurate voltage. Without the BMV the temperature is only measured before the charging starts each day. Inevitably batteries heat up as they charge and so does outside ambient temps during the day when solar is producing power. With the BMV the temperature is constantly updated to the MPPT.

Victron Battery sense will also provide the voltage you are looking for. But I would just install the BMV-712. It's easy to install and works well.

You may also search your issue on the support forums: https://community.victronenergy.com/index.html

Also research the accuracy of the meter you are using. I purchased a pricey meter with NIST to verify what the BMV reads is correct. I'll know early this week just how accurate my BMV-712 is.

Please let us know what you find.
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Old 02-12-2018, 02:27   #6
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Re: Victron 100/30 voltage measurement

It is important to get the charging voltages correct. Even a small (0.1v) error will make a practical difference to charging times and ultimate battery health.

You are doing exactly the right thing checking the calibration of the controller. Many have a significant error. However, I have three Victron controllers and all read close to correct voltage.

There is no provision for adjusting the voltage display, but you can adjust the set points so the actual voltage used is correct. The Victrons allow for a fine (0.01v) adjustment, which is a great feature.

You need to be sure that your multimeter is accurate. There are some simple high precision voltage reference devices available for $10-15 which are ideal for checking multimeters.
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Old 02-12-2018, 03:00   #7
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Re: Victron 100/30 voltage measurement

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I.....
You need to be sure that your multimeter is accurate. There are some simple high precision voltage reference devices available for $10-15 which are ideal for checking multimeters.
Got one you could recommend? I saw a bunch on Aliexpres from $3 to $15.
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Old 02-12-2018, 03:32   #8
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Re: Victron 100/30 voltage measurement

I have a new 75/15 Victron smartmppt regulator and a Victron BVM. The reg. shows higher Voltage and Amperage than the BVM. I haven’t worked out what’s going on yet!
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Old 02-12-2018, 03:54   #9
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Re: Victron 100/30 voltage measurement

I have a few mppt controllers from Victron aswell. They have been pretty much spot on voltage wise.
When I have wondered about stuff regarding victron equioment, and sendt mails to Victron, they have always responded with good answers.
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Old 02-12-2018, 04:28   #10
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Re: Victron 100/30 voltage measurement

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Got one you could recommend? I saw a bunch on Aliexpres from $3 to $15.
I think they are all likely to be fine in terms of accuracy for our purposes. It is usually only worthwhile to calibrate voltage rather than current etc so the simpler models should be OK.

Something that will verify the accuracy close to 12v (at least on the same scale as the multimeter uses to read 12v) is better.

It is a shame to buy something for the boat that will in practice only be used very infrequently, but it is important to get the voltages correct. Some meters in multimeters, battery monitors, solar regulators etc can be long way out of calibration.

You can open up most multimeters and adjust the calibration, but a simpler method is to simply note the error and add this to the reading. Some of the cheaper multimeters drift with time and temperature and this simplified method encourages more frequent checks.

When you have checked the calibration you can have confidence in the reading, but don’t forget about voltage drop. This will mean the voltage reading at some points in the circuit will not necessarily be the true battery voltage.
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Old 02-12-2018, 04:31   #11
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Re: Victron 100/30 voltage measurement

I have a 75/15 Victron Controller also and when I monitor the voltage with my lap top it's always off by a few tens of volts as compared to my DVM or my PWM Controller which is sometime hooked up also.

I don't worry about the differences though since it could be so many different things. I go with the DVM and the PWM Controller Voltage since they are usually the same. Plus I only have two 12 volt batteries in parallel which cost less than $175 for both so it's not a big risk.

I believe it's lower on the monitor/computer but it's disconnected now and removed from the boat as are all my panels except one 20 watt panel with a PWM Controller set at 13.2 Float while the boat is in the yard
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Old 02-12-2018, 06:33   #12
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Re: Victron 100/30 voltage measurement

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I'll try going to Victron directly, but am not optimistic that I will be able to reach a real competent human being.
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Old 02-12-2018, 10:19   #13
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Re: Victron 100/30 voltage measurement

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Originally Posted by FlyingScot View Post
...
Install a BMV-712 with the optional battery temperature sensor. Then Bluetooth network the BMV and the MPPT together using the app. This will share the battery voltage and temperature with the MPPT. Otherwise you are relying on the charging device to provide accurate voltage. Without the BMV the temperature is only measured before the charging starts each day. Inevitably batteries heat up as they charge and so does outside ambient temps during the day when solar is producing power. With the BMV the temperature is constantly updated to the MPPT.

Victron Battery sense will also provide the voltage you are looking for. But I would just install the BMV-712. It's easy to install and works well.
...
Jim, I don't have an answer about adjusting your Victron controller.

I wanted to mention that we did as FlyingScot suggests, and with excellent results.

Each of our 3 solar panels has its own Victron SmartSolar Charge Controller with Built-In Bluetooth – MPPT 75/15. Each displays within ~.1V of another when reading individual controller voltages from the VictronConnect app.

We installed one BMV-712 [initially for temperature compensation because our controllers are all in different temperature zones than the battery bank.]

However, since the BMV-712 reads voltage at the battery bank, it also provides that value to the controllers. Now they all read the same voltage since the source is the same for all 3 controllers.

You only need one BMV-712 even if you have multiple controllers. [~US$50] The VE Smart Networking choice you see under settings for the each controller in your VictronConnect app allows all of our controllers to connect [via Bluetooth] to a single BMV-712 voltage and temp sensor.

I wish all the other charging devices that need direct sensing at the battery bank were as easy to wire...

Best wishes resolving this issue.

Cheers! Bill
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Old 02-12-2018, 10:39   #14
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Re: Victron 100/30 voltage measurement

I have noticed similar issues with our Victron solar controller. But put it down to not having an accurate voltage meter.

I wasn't planning on spending more $$ to buy another piece of equipment to have flown in and pay duty on (BMV-712) just because the unit I have installed is "possibly" not accurate.

Jim I would be most interested in what Victron rep says about this. I also have had very quick response from them when sent questions

Cheers

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Old 02-12-2018, 10:48   #15
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Re: Victron 100/30 voltage measurement

There are patterns, and then patterns of patterns. The brain is a pattern discovery machine.

I've learned a tremendous amount from this site, and much from posters on this thread. On ocassion I've wondered how those without the necessary resources of time and understanding manage to go boating at all.

To be clear, this discussion has helped me. I've just spent two days hanging from my arch, putting up 1.08 kw of panels (3 x 360 watt). I plan two more for the bimini. I have three Victons with Bluetooth, am contemplating wiring them so I have port-side panels on one (similar shading and insolation), starboard panels on another, and of course a back-up.

Then along the dock comes a guy to tell me he is thrilled with his 200 watts of flexible panels he lays on top of his bimini, sliding from one side to the other with a piece of line. I don't know if I want to spear him or copy him.

Point is, aside from the fun and challenge of understanding details to the nth degree, how much will we save in real dollars (Euros or PoundS) compared the those who DON'T know their Victron is .1V off? And will adjusting for that be significant when compared to all the other factors beyond our control?

I am not trying to be a smart-ass, here. As I said, I've learned and made changes as a result of the forums and received signficant help from those more knowledgeable than me. But I wonder at times about the cost of the greater understanding, as well as the difficulty in measuring gain, proving again I can be a bit compulsive.
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