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Batrium Shunt inaccurate current measurment
#31
Did you find high frequency noise across the shunt in your system as well?
I think the fix is to separate the board from the shunt part & put a capacitor (approx 0.1uF) across the board terminals then a resistor from each board terminal to the each shunt terminal (approx 10ohm should do it). You could also replace one resistor with a copper link. This makes a low pass filter that stops high frequency noise.
Hopefully Madsci1016 can confirm values he used, etc.
It could probably be built like a "daughter board" or similar with some PCB offcuts, etc
The noise isn't caused by the batrium gear, it's caused by the charger or inverter's high frequency switching & likely wiring inductance.
The 120mV of noise found is a lot when you're trying to read eg 50 or 100mV DC....
It's just that the Batrium circuit as is apparently doesn't read accurately when there is high noise levels.
Running off solar, DIY & electronics fan :-)
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#32
(01-24-2020, 12:13 PM)Redpacket Wrote: Did you find high frequency noise across the shunt in your system as well?
I think the fix is to separate the board from the shunt part & put a capacitor (approx 0.1uF) across the board terminals then a resistor from each board terminal to the each shunt terminal (approx 10ohm should do it). You could also replace one resistor with a copper link. This makes a low pass filter that stops high frequency noise.
Hopefully Madsci1016 can confirm values he used, etc.
It could probably be built like a "daughter board" or similar with some PCB offcuts, etc
The noise isn't caused by the batrium gear, it's caused by the charger or inverter's high frequency switching & likely wiring inductance.
The 120mV of noise found is a lot when you're trying to read eg 50 or 100mV DC....
It's just that the Batrium circuit as is apparently doesn't read accurately when there is high noise levels.

Ah - yeah I see now..  

Yes my charger does send high frequencies..   When I charge at really high levels above 180 amps I can actually feel / hear them in the steel server rack I have the batteries in.  At certain charging amps the whole thing resonates

There is a low 120hz frequency when charging from the grid and a much higher one when charging from my solar charge controllers

I'll make these changes when I have time and report back

Thanks
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#33
Very interesting (technical) thread.   I don't use shunt info 'precisely' - just as a background eye-candy.  When I said (earlier in this thread) that my Whizbang Jr (Midnite Classic 150s reporting) was < 1% different than Batrium - this is what I typically see in the amp range we're focusing on here.    These values 'twitch' second to second on the screen and I've never graphed them side-by-side to compare.

So I would not have noticed anything was off until this thread.   And... they could *both* be off in a similar way? As I said, very interesting...  Smile
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#34
So I did a drawing of a possible build for a low pass filter mod.
You'd need some room around the shunt.
It could be made pretty easily.
Running off solar, DIY & electronics fan :-)
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#35
Wow, sorry was on travel for a week, just catching up.

Yes I've talked to a handful of people now that all report the same type of issue. It's not just me (thankfully).

Yes, I used an RC low pass filter. Don't remember the values I used but it calculated to a 30Hz cutoff frequency. I though about designing and fabing a PCB like Redpacket, but Batrium seems confident in their solution. Which is a select-able "averaging" window for shunt measurements. They insist some types of loads require high sampling rates, so a hardware RC filter isn't an option. I don't understand that, but i don't have the experience they do to back that up.

Here's the problem noise that is so sever in my case.


[Image: -mtmDLQBiY0cWraSpIaGndaxKOSZ6o-sOyqCq3cx...51-h713-no]

(01-23-2020, 08:47 PM)farmerjohn Wrote: Thanks

John


Argh, they didn't make you pay return shipping for the first shunt?

(01-23-2020, 08:47 PM)farmerjohn Wrote:
(01-15-2020, 11:04 PM)madsci1016 Wrote: These are Sunny Islands I'm using to charge. If it's a noise issue I'd still fault Batrium EE design for insufficient filtering in the shunt. I am tempted to open one and look at their design to rule this out, but risk voiding my warranty and they don't take it back. Also them may have potted the PCB anyway. I don't have another 56V 120A charger laying around to prove that theory, and there's not much we can do in the way of filtering external to the shunt, without some major capacitors.

Well Maybe I can wait for a really sunny day and verify the 80-90A range as that is what my solar system max should be. But that's a month or so away probably.


I have the exact same issue with my shunt - even had it replaced last year from Batrium (for free)

The replacement was slightly better, but when charging over 100 amps - its way off.  I have a Conext XW system and a decent amp meter.  My meter and the conext agree within 1% while batrium is way off.   I gave up and just settled with the way it is

Glad they are going to fix it in software but would you be able to share more details on your hardware fix?

Thanks

John

Argh, they didn't make you pay to return the first shunt?
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