I have had problems with my Smartshunt sometimes displaying phantom currents. For instance I recently found it had recorded a 22 amp draw for 48 straight hours from my 100 AH battery (while also recording a steady 13.3V from the battery). All while our trailer sat idle with the battery cutoff engaged.
The battery and Smartshunt are mounted on the rear bumper of our 17 foot travel trailer. The trailer is parked in our yard next to the electric transformer supplying electricity to our house. Our electric service is provided by a buried cable and the transformer is a large steel box sitting on the ground.
Is it possible that the fluctuating magnetic field emanating from the transformer or the service lines connected to it could affect the Smartshunt? I am not clear on how the Smartshunt senses current flow, but those stacked metal bars look to me like they would be an excellent antenna.
Interesting theory. But less plausible than a wiring problem.
The smart shunt is not a hall effect sensor but a resistive one. Maybe possibly the alternating magnetic field from the transformer could affect the electronicsnbut certain not to the extent of a steady 22a draw.
If the battery was cut off and wired correctly, then a zero current calibration is in order.
Thanks for the reply. And for the opportunity to learn about the Hall effect, which I was not familiar with but Dr Google explained nicely. As you suggest, it seems unlikely a magnetic field would explain these anomalies.
I have experienced a number of bizarre readings with this Smartshunt over time. In the interest of brevity I only outlined a salient example in my post. I realize that my description suggests a wiring problem but for the life of me I cannot identify what it could be. I have a simple setup- my only connections on the load minus side are a wire to the chassis ground and the negative side of a pigtail to a plug for charging the battery. One would think if the 20 amp drain was real it would be glaringly obvious by heat, smell, or worse.
In the past I have tried the zero calibration function several times, but has not had a lasting effect. The shunt will revert to reporting wild swings in current.
A puzzling aspect here is that these episodes of bizarre readings are intermittent. Most of the time my Smartshunt works fine. Especially, I cannot remember it ever misbehaving while we were camping, only while parked at home or while towing.
I had similar problems a year ago or so. At that time I noticed that the battery and shunt were covered with road dust, so I blew the dust off with an air compressor. I also better secured the chassis ground, insuring good metal-to-metal contact between the chassis and the cable connecting to the shunt. These steps seemed to address the problems at that time. But they have popped up again in the last two weeks.
My first step this week was to again blow the dust off the battery and shunt. When I did this, the amp reading from the shunt dropped from -22 amps to -5 amps as I blew dust out of the vanes of the shunt. Why did this happen and does it point to any possible causes of these problems?
I could go on, but I do not want to try anyone’s patience. I would be most interested in any comments you or anyone else in the community has regarding the above.
These are the hardest and most frustrating ones to find. And worse yet if you do solve them there is always that thing at the back of your mind wondering if you didn’t.
Slightly damp dust is conducive. So that is also plausible as well.
Corrosion would also change readings; so would loose connections and corrosion there.
Being in a trailer, chassis connection check regularly to make sure that is a clean connection and of course from vibration thing can work loose so that should be a regular maintenance check as well and would affect reading with air blowing over them.
Roger that regarding intermittent problems. Responsible for a lot of sleepless nights. What a relief now that such problems are confined to our little trailer rather than a college campus.
Inspecting the chassis ground requires sliding my 75 year old body under the trailer and then scraping off the liquid electrical tape I had carefully applied last year. Nevertheless I see that I need to get it done.
My current curiosity- (pun intended)- I found that reported current fluctuated greatly as I tightened the load minus terminal bolt. With the bolt snug the shunt reported 0 amps, as expected. As I tighten it the report climbs to 5 or 10 amps. As I have said, these reports appear to be phantom because the battery does not actually drain when I leave it overnight or longer in this state.
So I it appears that anything that affects the electrical resistance across the shunt will lead to erratic readings, and I need to be especially attentive to dust or moisture that gets in the battery case. This is my lesson here.