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palpale2
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hello, sorry for the translation but I'm Italian. I expose you my problem, I have a 3200w 24 volt inverter I noticed that the battery voltage reading is wrong. When I am taking 1kw the difference in reading with the tester also reaches 2v. Is there any advice or any component to replace? thanks to all cordial greetings

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1 hour ago, palpale2 said:

I'm Italian.

Welcome to the forum.

1 hour ago, palpale2 said:

I have a 3200w 24 volt inverter

Can you give the exact model number, please? If it's a rebranded Axpert (they can have many names), it is possible to re-calibrate the battery voltage reading using special commands. But you may not need to.

1 hour ago, palpale2 said:

When I am taking 1kw the difference in reading with the tester also reaches 2v.

With higher loads, there is a higher voltage drop across the battery cables.

Are you measuring the battery voltage directly at the battery terminals?

Is your multimeter trustworthy?

1 hour ago, palpale2 said:

any component to replace?

If the reading drifts with time, temperature, or moisture, then there are specific tiny resistors inside that can be replaced to stabilise the reading. Then you can perform battery voltage measurement calibration. But if it's a fixed error percentage (e.g. always reads 7% high or 4% low), then this can be adjusted by calibration and you likely don't need to replace the resistors. All the above assumes that it's an Axpert; if not, you'd need to find a schematic diagram or service manual for your brand and model of inverter.

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thanks for your attention. as far as the measurement is concerned, I did it directly on the inverter input pins. The measurement was done with 2 different testers who read the same results. the reading varies with the load applied, for example with 20A I have a reading error of almost 1V with 50A almost 2 V. it must be said that they are not always constant as values. thanks again for your time

inverter verde.jpeg

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17 hours ago, palpale2 said:

where can i find some guide for both calibration and resistor replacement?

As per PM, for other readers:

Replacement of resistors (photo in a link): https://forums.aeva.asn.au/viewtopic.php?p=53951#post

Voltage calibration: https://forums.aeva.asn.au/viewtopic.php?p=71631#p71631

 

I see your inverter is an Axpert VM II clone. You can tell from the 15 digit serial number and the barcode sticker-on-sticker. It should still calibrate OK, though the way that the measurement depends on load suggests internal resistance from too-thin cables, and of course that can't be calibrated out. If the measurement is good at very low loads, then there is nothing that calibration can do to improve things.

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good morning, I renew my thanks. Continuing my tests I also noticed that it immediately recharges the batteries, I did the test with 2 new batteries. Is this reading always part of the resistances? As far as the section of the cables is concerned, I think it is right because my measurements are made directly on the terminals of the inverter. is there any firmware i can try?

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good afternoon everybody. I am writing to thank you thanks to your advice I was able to have an inverter that perfectly marks the voltage. I also tried with 60A everything seems regular. the only thing I didn't understand is how to save the calibration in memory. you would be kind enough to explain it to me. thanks again everyone

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10 hours ago, palpale2 said:

the only thing I didn't understand is how to save the calibration in memory. you would be kind enough to explain it to me.

It's all in the paragraph at the end of the voltage calibration post. Basically, you need to either send the PSAVE command (see the index on how to do that if you don't know), or change a setting that saves the battery calibration along with that setting. For example, changing the output voltage and back again.

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2 hours ago, palpale2 said:

where do I enter the PSAVE command? and this is not clear to me

Ah. I assumed that if you were able to calibrate your battery voltage readings, then you already were entering commands. Or if your calibration is good, then there is no need to save the changes.

To enter the PSAVE command, you need a third party product, a communications program. There are plenty of free versions about. But the complication is that you also need to send two CRC characters at the end of each command, and often these have the "sign bit" set, if so they need special treatment.

In the specific case of PSAVE, however, the CRC characters turn out to be easily typeable, so all you need to send is "PSAVEm0" (without the quotes) and enter. Case has to be exactly as shown, and the last character is a numeric zero, not an upper case 'O'.

I tried to quickly find an easy to use communications program, and found that Putty can talk serial, but it did not work for me. Personally I use TeraTerm, as linked in my battery calibration post. Unfortunately, this is not an easy thing to explain to someone whose never done it. You should not have to configure TeraTerm for the specific case of sending the PSAVE command. You will need a USB to serial adapter and the RJ-45 to serlal cable that came with your inverter. You will have to use Device Manager to find out what com port your USB to serial adapter appears on. All this is can be found in posts linked from the index of this large post. I wish there was a way of making it easier.

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15 hours ago, palpale2 said:

did the calibration with accessport and the commands all worked

Ah, good, so that's all set up. Did you add the "m0" to the end of the PSAVE command? Lower case em, digit zero, command in all upper case, enter at the end. Those are the two CRC characters, and are required.

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