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Old 07-06-2019, 02:18 PM   #1
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Victron BMV-712 Inaccuracy - Need 1A Fuse

Today I investigated what I believe to be a slight difference in the metered voltage of my GC2 battery bank and what the BMV-712 battery monitor reports. Granted, it is only a couple of mV, but (being somewhat OCD) the difference between the BMV-712 and the Fluke were puzzling.

Before I did anything radical, I searched the intertubes for "BMV-712 Accuracy" and received some interesting hits. The first was a BMV-712 Accuracy Article posted to the Victron Energy Community Forum documenting the discrepancy. Interestingly, the author solved the problem by replacing his unit's 100mA fuse with a 1A fuse to reduce the resistance.

Then, I came across a response by a Victron staff member (mvader) to a similar accuracy post indicating that a whole batch of 712's were sent out with an incorrect (100mA) inline fuse for the shunt's power. In his/her comments, the suggested fix is to replace the incorrect fuse with a 1A one.

Well, I checked the fuse for my 712 and it was indeed a 100mA fuse which was quickly replaced by a 1A. So now I have disconnected all power in the RV and am waiting for things to settle to see if this has solved this (admittedly OCD) issue.

Perhaps those with the BMV-712 battery monitor should check your inline shunt's power fuse. Or not.
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Old 07-06-2019, 10:30 PM   #2
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Any idea if it applies to the older 701s?
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Old 07-06-2019, 11:42 PM   #3
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Since I rarely use the display of my 712(bluetooth only) I doubt I would notice much difference. I am going to check the fuse though.
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Old 07-06-2019, 11:53 PM   #4
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Thx for the info. I use the Bluetooth also but did notice the voltage reading was lower than my connected dvm. I will check the fuse.

It seems the SOC is correct though based on accumulated amps drawn.
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Old 07-07-2019, 08:07 AM   #5
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Update:

Checked the 712 with the Fluke this morning and the situation is corrected! Looks like the 1A fuse did the trick. One less mystery in life.

Also, I should note that my fuse was removed for about 5 to 7-minutes and the 712 retained all its previous settings. However, I had taken the precaution of saving all the settings to a file and archiving them (via that facility in the Victron app).

aeblank - I'm not sure if the 701 may have shipped with the wrong fuse. There may be some more info in the Victron Community Forum or you can just check it. If you aren't getting difference between the Victron and your DVM reading (usually in the hundredths of a volt), then I'd think you're all set.

babock - I, too, rely on my phone to read the info. However, the data sent by BT is, of course, dependent on the BMV-712 signal processing. My sense is to make sure all the incoming data to the 712 is as accurate as possible to allow its algorithms to work properly. Since I can't see the 712's code, I'm not sure what the "downstream" effect produced by slightly inaccurate signals will be. But then, there's my OCD .

dalford - I think for the most part the SOC was fairly accurate, though it seemed that my (temperature-compensated) voltages strayed a bit from what I might expect from tables to which I have been referring. Not much, but some.
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