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not-a-hard-question-to-answer asked

Lets try a second time. Whats the Voltage accuracy of Victron products?

Disclaimer:

It seems questions often arise on this forum about the Voltage accuracy of Victron units and variances between voltages measured vs what's displayed on the app.

SINCE there is zero information about the accuracy of the Voltage meters in Victron products, it makes sense that some questions be answered on this community page, which is there to help Victron users!


Elvis, Kevgermany - You didn't like my replies to you and those who commented on my previous question, before you got offended and blocked my account - Maybe go back and read the "so called assistance" that was provided and understand I'm not some completely useless person "like you all suggested" and as a result I gave blunt responses in return showing my appreciation for the RUDE/little assistance and belittlement I received for you.

I fielt my replies were warranted, considering the attitude and belittlement I got from a number of you. All because I don't have access to a "very expensive" FLUKE DMM!


• My questions of how to confirm accuracy of a DMM, fell on deaf ears.

• My questions of the products number/model number of the voltage meters in Victron products, so I could answer the above question, fell on deaf ears.

• My question about how you can all guarantee the accuracy of Victron voltage meters when you all told me that unless a DMM is calibrated every year its not guarantee accurate, so I clearly asked how and why the Victron units can/are still considered accurate when they aren't calibrated every year? This fell on deaf ears.

• How can Victron products be guaranteed to have accurate Voltage if they're not regularly calibrated?

• Exactly what accuracy percentage does a Digital Multimeter need to have to be considered accurate enought to perform testing?


^^^These are SIMPLE QUESTIONS that will help MANY future Victron users and save them from having to create posts/questions when it's already been answered (the whole point of this community according to community guidelines)...


Let's watch you delete my account again for trying a second time to ask BASIC questions all because you assume I'll abuse you - The difference is that if you actually provide clear answers and don't provide VAGUE information, or try to waste my time asking for irrelevant information and/or imply I'm useless, then my replies will be respectful.

If you waste my time again, be rude or vague you will get blunt/rude replies in return - Not sure why you're surprised by this.


* I've been told I'm blunt due to my Autism, but that won't change the sour people who have been offended at my responses to them after they wasted my time, or implied I am useless (which in itself) is very insulting to me!

^^^ You offended me and/or wasted my time first before I gave it in return...

voltagebattery system voltageaccuracy
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2 Answers
jc2010 avatar image
jc2010 answered ·

How to confirm accuracy of a DMM?
Aside from returning the DMM to the manufacturer to perfrom calibration you can use another instrument that is known to be calibrated to calibrate your DMM.

The products number/model number of the voltage meters in Victron products?
You would have to email victron and ask, but they may not provide this information and just provide you with details of accuracy.

My question about how you can all guarantee the accuracy of Victron voltage meters when you all told me that unless a DMM is calibrated every year its not guarantee accurate, so I clearly asked how and why the Victron units can/are still considered accurate when they aren't calibrated every year?

DMMs can recieve a lot of accidental abuse when used for testing, and can be introduced to a lot of risks that can cause harm to the DMM. It is less of a concern for a static instrument that is not introduced to unknown environments and conditions.

• How can Victron products be guaranteed to have accurate Voltage if they're not regularly calibrated?

If we are talking about Shunts, they are quite accurate and generally quite stable over a wide temperature range, they achieve this by using manganese alloys for the resistive elements that you see as 'fins' of metal between the posts of a shunt. The fins also serve as extra surface area to help cool the shunt because as the shunt gets warmer it is less capable of carrying its rated current.
So this helps stabilize the temperature. In addition to those most shunts are remote from a BMS or monitor and you have to worry about voltage drop in the Kelvin wires that measure between the posts and can lead to inaccuracy, with the SmartShunt one advantage is that this concern is virtually eliminated because the measuring electronics are mounted directly at the Shunt.

In addition whilst they are manufacturing and calibrating the shunt a small amount of material from the fins will be milled out to make sure the voltage drop is as accurate as possible to their reference, this is because shunts are so sensitive these kind of discrepancies have to be accounted for in manufacturing.

Even with all of these provisions to retain accuracy even shunts can stray over time, that is why Victron have the option to perform a zero calibration of the shunt from within the app if you suspect a problem.

Of course I have only talked about SmartShunts here because any other type of voltage measurement from an MPPT or Charger, or Voltage sense is widely understood to be worthless, and is more an 'indicator' rather than a 'measure'.

• Exactly what accuracy percentage does a Digital Multimeter need to have to be considered accurate enought to perform testing?

For the SmartShunt the resoultion is +/- 0.01V with an accuracy of +/- 0.3%. So more accurate than that.

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Thank you for the clear and in depth information, that is extremely appreciated!
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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @Not a hard question to answer

Some Victron products such as the SmartShunt are intended as measuring equipment. These products have their accuracy listed in their data sheet, see this example for the SmartShunt, with a resolution of +-0.01V, and accuracy of +-0.3%

cleanshot-2022-06-29-at-191349.jpg


Other products make use of a built in voltage reading to serve their primary function, such as battery charging or inverting. The built in precision and accuracy of their measurements is sufficient for that task (which are intended to be functional, and not absolute), but will vary, and has additional installation dependant variables.


There is a quality of power called Ohms law, basically there is a relationship between voltage, current and resistance. The power electronics that draw, or push current will cause the voltage to drop, or rise.

If the product uses these same wires to sense the voltage, then it can appear that the voltage is higher or lower than it will appear at the battery terminals taken from a voltage sensing device that is not drawing or pushing any current.

Further to that, the size of the wires that are selected by the installer on site will also affect this current carrying voltage reading for these charging or load products. There is a lot more detail about these effects (and how significant they can be in certain circumstances) in the Ohms Law chapter of the Victron book Wiring Unlimited here.


For the most part our equipment will do it's best compensate for these variations to the amount that is required to perform the job reliably (such charging a battery, or turning off an inverter before a battery is totally flat). In some cases, users might want the extra accuracy that can be provided by a dedicated piece of measuring equipment, with a defined resolution at accuracy and we make that possible too.


This is not essential from Victron's perspective, and most users are happy to accept our design and some level of variation. It's a complex dynamic, but from our experience the variables and tolerances are acceptable as long as all the specifications in the product manuals are followed correctly. As an example, in a battery charger when the battery is full the charging current is reduced and the voltage reading will be more accurate.


For those that DO want the extra precision, there is a variety of ways to do so.

For example installing a SmartShunt and then setting up a VE.Smart Network, and then sharing the voltage from the battery terminals with a paired SmartSolar MPPT.

For the MultiPlus, you can wire in a dedicated voltage sensing wire connection (that doesn't carry any current, just the voltage, providing a more accurate reading).

Or enabling Distributed Voltage and Current Control (DVCC) with a Victron GX device, and connecting all the system components to that.

Again, all of these are optional improvements for those that want to improve the accuracy of things, but may or may not be necessary from Victron's perspective and dependant on the installer to assess. They may decide a very long wire run will cause sufficient issues to warrant additional equipment in one installation, while a very short and thick wire run in another does not.

In some regions these requirements are dictated by specific local standards that govern the acceptable amount of voltage drop between a source and an appliance - while in another region a different installer may choose to manage that variation in other ways.

We consider our equipment reliable and accurate enough to use as is out of the box, as long as it is installed by a suitably qualified and trained installer.


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Thank you for the clear information.


I notice there was no mention of the Smart Battery Sense, I assume since it hadn't been mentioned it's not as accurate as the smart shunts are and they're clearly not able to be calibrated from what I can see with the one I own?


I'm asking these questions because I (and it seems a number of others on this forum over the years) have noticed a variance of 0.2-0.3v (for me it varies) between two multimeters (yes they're cheap) but they both show a significant variance between Battery voltage and the Victron app - That is why I was asking for specifications/accuracy of the Voltage meters in these devices to gauge whether both my cheap multimeters are wrong (both read within 0.02v of each other when measuring voltage coming from my DEFA 10A smart charger) which had me concerned I may have been discharging my batteries a bit deeper than intended, due to using the voltage on the app as a rough gauge of battery health based off "voltages under load" and yes, I am aware this is not extremely accurate, however it's all I have to go off since I can not currently afford to buy a smart shunt (I will buy one as soon as I have money to spare).


Thanks again for the information, I'm certain your reply and the reply from jc2010 will help out other users who notice similar variances between their DMM and Victron app amd have similar questions as to why.


Thanks,

Glenn.

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