question

kaypea avatar image
kaypea asked

Anyway to calibrate voltage readings?

Victron Easysolar 2 GX system, 130a/h lead calcium batteries (24v). Short 50mm cables to batteries.

Are there any settings/adjustments to be able to bring the solar and system voltages closer to the real battery voltage?

I have a calibrated fluke multimeter on the battery which measures 26.01v - I have a chart recorder connected to the battery which also says 26.01v - I have a cheap ebay KG140 meter which reads 25.96v (50mV error) and then the Victron VRM remote console which measures 26.3v (299mV error).

I would have expected the Victron to be fairly accurate, but when the batteries are getting low at night, the battery voltage reads 24.1v and the victron system reads 24.4v. These measurements are when loads are quite light on the system.

Yes, I have connected the remote sensor terminals to the battery, but ithe Victron system always reads 300mV too high.

In a system where 300mV error is a big deal for a lead/calcium battery, I could do with being able to calibrate to account for the difference. Is this possible? Have I missed something?

EasySolar All-in-One
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

3 Answers
nickdb avatar image
nickdb answered ·

What your post doesn't clarify is, whether or not you did meter readings at the mppt/inverter terminals at the same time and if they agreed with the battery readings?

Differences are not uncommon but usually related to cabling losses, though these should be measurable, especially under load.

As mentioned elsewhere, you can use vsense inputs on the inverter or configure SVS on DVCC so an external reference is used for charging.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

kaypea avatar image
kaypea answered ·

The readings were taken at the battery under a very light load. Cables are a combination of 35mm and 50mm but very short. The readings were the same at the MPPT terminals.

The vsense inputs are connected, but you said about configuring them on DVCC - Maybe thats the issue - I will have to check if that bit is configured correctly. EDIT - Just checked and all the DVCC settings for SCS, SVS, and STS are turned on...

The load on the system was only 3amps when the voltage checks were done - battery system is 12v lead/calcium (two in series - three sets in parallel for 520a/h capacity).

Thanks for your reply.


3 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

nickdb avatar image nickdb ♦♦ commented ·

It's challenging when you can't see how a system is setup, if you're using a shunt and that is configured for DVCC with SVS, if your devices are physically connected to the GX and under external control then that is what will be used for charging, irrespective of what they independently report.

If you are using the ports on the multi, the following from the manual applies:


4.4.5. Voltage sense (connection terminal J, see appendix A)

For compensating possible cable losses during charging, two sense wires can be connected with which the voltage directly on the battery or on the positive and negative distribution points can be measured. Use wire with a cross-section of 0,75mm².

During battery charging, the MultiPlus-II will compensate the voltage drop over the DC cables up to a maximum of 1 Volt (i.e. 1V over the positive connection and 1V over the negative connection). If the voltage drop threatens to become larger than 1V, the charging current is limited in such a way that the voltage drop remains limited to 1V.

0 Likes 0 ·
Show more comments
kaypea avatar image
kaypea answered ·

I have an update to my question from over a year ago. My original problem with the system was about the voltage readings being 300mV too high from the MPPT charger... Today I expanded my system with a 2nd MPPT charger and guess what? The voltage reads correct from that one, but the original MPPT reads 300mV too high even though they are connected to the same battery. So it looks as though my orginal MPPT has a fault giving the voltage reading 300mV higher than it should be.!!!!

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.