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Old 07-31-2020, 10:10 PM   #1
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Victron BMV help

I have a BMV700 that has gone funky. It's reporting 6-9v and some hundreds of amps being pulled (-793 at the moment). Simply put....no. wrong. Also the backlight sometimes stays on, sometimes flickers on and off.

I'm plugged in, for starters and my solar controller (victron also) reports 13.xx volts.

I have unplugged the little voltage feed wire and the data cable. I've *NOT* disconnected my battery cable yet, as we're camping and there hasn't been a good time to.

Thoughts? I'd have to re-pull my fridge to install a new one. Shunt is easy to get to. Maybe something shorted on the shunt control board and a cleaning would "do it"?
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Old 08-01-2020, 07:08 AM   #2
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I think I would remove all power and reboot to see if that gets it back to reading correctly
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Old 08-01-2020, 10:59 AM   #3
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Almost sounds like the wire going from the shunt to the positive post of the battery has a bad connection or the fuse holder is faulty.
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Old 08-01-2020, 12:03 PM   #4
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Almost sounds like the wire going from the shunt to the positive post of the battery has a bad connection or the fuse holder is faulty.
This^^^^^

I'd also check the screws that hold the small circuit board to the shunt and make sure they are tight. Better yet, remove them and clean the contact surfaces on both circuit board and shunt, where the screws pass through.

The shunt is only measuring milivolts and any imperfect connection can cause erratic readings.

This happened to my shunt when it got damp.
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Old 08-01-2020, 01:46 PM   #5
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I'll see about taking the shunt out. I figured it'd be that "end" of the system. Was hoping it was a common/known issue.
It's in a box on the frame. Haven't driven through rain in a while though, so sorta weird.
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Old 08-01-2020, 01:57 PM   #6
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I'll see about taking the shunt out. I figured it'd be that "end" of the system. Was hoping it was a common/known issue.
It's in a box on the frame. Haven't driven through rain in a while though, so sorta weird.

When I first installed my BMV I had it in a "Watertight" container outside the battery box. When I decided to move it inside with my new Battleborn batteries I found that "watertight" really didn't mean what I thought.

Just to make sure I removed the circuit board and found signs of corrosion beginning. Wasn't having a problem but I could see how it could become one if left to "marinate".

I'd start with babcock's suggestions, connection of shunt power wire at battery's positive terminal and the fuse holder. The wire is small and the fuse holder is rather fragile.
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Old 08-01-2020, 03:18 PM   #7
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Well, I took it out and cleaned things. It looked good, and sure enough, didn't fix it. The fuse/holder was a bit corroded, and I fixed that up too.

Guess the thing to do is check the mv and v across the shunt and at the voltage monitor "port" and see if I get good or nonsensical values. For what's on that PCB, I now assume my problem is the head unit. Bleah.

I want a 712, but not like this...

Any other/further thoughts?
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Old 08-01-2020, 04:09 PM   #8
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Well, I took it out and cleaned things. It looked good, and sure enough, didn't fix it. The fuse/holder was a bit corroded, and I fixed that up too.

Guess the thing to do is check the mv and v across the shunt and at the voltage monitor "port" and see if I get good or nonsensical values. For what's on that PCB, I now assume my problem is the head unit. Bleah.

I want a 712, but not like this...

Any other/further thoughts?
Don't overlook the wire connecting shunt and the Display unit (Head). It's essentially like old telephone wires and remember how we often had to unplug and re-plug a few times to get rid of static on the line? Sometimes even replace the wire itself?


You should be able to use a "straight through" patch cable with RJ-12 connectors.

Amazon has a 14 foot one for $7 and shorter ones too.Just make sure they are "straight" cables with RJ-12 connector, not "ethernet".

https://smile.amazon.com/Cables-Go-0...XV0XVMAWZTF0XR
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Old 08-01-2020, 06:47 PM   #9
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Hmm.
Very doubtful, but I can pop the cover back off and reconnect the cable a few times. I could also use my cheap-ass network cable continuity checker on my existing cable. If I got a new monitor, I'd use my existing cabling....

I mounted the monitor above the fridge... I wonder if I can reach it through the ceiling vent... But there's a wire mesh in there too, I think. Dangit dangit... Oh, maybe if I take my inverter control panel out I can get a hand in there.. hmmm. Off to experiment again. Thanks all (though none of it has helped)....
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Old 08-01-2020, 07:14 PM   #10
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Hmm.
Very doubtful, but I can pop the cover back off and reconnect the cable a few times. I could also use my cheap-ass network cable continuity checker on my existing cable. If I got a new monitor, I'd use my existing cabling....

I mounted the monitor above the fridge... I wonder if I can reach it through the ceiling vent... But there's a wire mesh in there too, I think. Dangit dangit... Oh, maybe if I take my inverter control panel out I can get a hand in there.. hmmm. Off to experiment again. Thanks all (though none of it has helped)....
You use nicer words than I seem to when running into problems. I've stopped throwing things though.
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Old 08-01-2020, 07:47 PM   #11
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an email to their support mail box might bring some help. i had some questions a few weeks ago about one of their products and they we most helpful!
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Old 08-01-2020, 07:49 PM   #12
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So, it isn't the cable. I don't have my tester here, but I replugged many times, both ends. Was easy to get to once I removed my inverter controller. Contacts looked perfect.

Annoys me to re-spend $200 on something that only lasted like 2 or 3 years... Options are pretty limited though. Probably just gonna Amazon one up, unless someone has any more bright ideas.
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Old 08-01-2020, 07:51 PM   #13
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an email to their support mail box might bring some help. i had some questions a few weeks ago about one of their products and they we most helpful!
What email? When I looked, they said they don't do direct support (contact reseller). I'd be more than happy to email them.
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Old 08-01-2020, 07:59 PM   #14
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sales@victronenergy.com

they were more than responsive and helpful to me.

i installed their smart shunt. only $130 and it does 99% of everything the bvm-712 does using a blue tooth connection to your smart phone.
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Old 08-01-2020, 08:45 PM   #15
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Hmm.
Very doubtful, but I can pop the cover back off and reconnect the cable a few times. I could also use my cheap-ass network cable continuity checker on my existing cable. If I got a new monitor, I'd use my existing cabling....

I mounted the monitor above the fridge... I wonder if I can reach it through the ceiling vent... But there's a wire mesh in there too, I think. Dangit dangit... Oh, maybe if I take my inverter control panel out I can get a hand in there.. hmmm. Off to experiment again. Thanks all (though none of it has helped)....
I was re-reading your post(s) and ran across the above hi-lighted statement.

Was earlier reading about heat surrounding refrigerators, especially in warm weather. How hot is it getting where you have your monitor mounted?

I don't know what Victron's recommended operating temps are for the monitor but if the refrigerator vent stack isn't baffled or insulated properly it could be getting quite warm in that area. Worth checking to make sure a new one isn't headed for an early failure. Most electronics don't like heat. How much? Victron should have specs online.

I know that earlier this week while boondocking in near 100 degree temps my refrigerator outside vent was having trouble shedding heat.through the roof.

Don't know but it might be possible that your unit got warm. Worth checking.
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Old 08-01-2020, 11:49 PM   #16
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I was re-reading your post(s) and ran across the above hi-lighted statement.



Was earlier reading about heat surrounding refrigerators, especially in warm weather. How hot is it getting where you have your monitor mounted?



I don't know what Victron's recommended operating temps are for the monitor but if the refrigerator vent stack isn't baffled or insulated properly it could be getting quite warm in that area. Worth checking to make sure a new one isn't headed for an early failure. Most electronics don't like heat. How much? Victron should have specs online.



I know that earlier this week while boondocking in near 100 degree temps my refrigerator outside vent was having trouble shedding heat.through the roof.



Don't know but it might be possible that your unit got warm. Worth checking.
No, it's not that warm up there. I don't have a thermocouple up there, but it's barely a few degrees above ambient, which has been in the 80s. Maybe 90 when this started.
As it so happens, I'm an engineer and worked a dozen+ years at a place that built PCBs (and 5 more that used them in extreme conditions). I more or less designed their enclosures. As such, I'm extra aware of things like that.... Anyway, the fridge enclosure is large and roof-vented. It just isn't hot. I'm confident there's no such thing as 20*C or 30*C components. More like 85*C and up.

Good thought though. I just can't see it.
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