# Mismatch Smartshunt 500A and specifications **URL:** \ **Category:** Q&A and troubleshooting\ **Tags:** expert, marine, smartshunt\ **Created:** [12 December 2025 22:00 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145 "2025-12-12T22:00:47Z")\ **Posts on this page:** 16\ **Page:** 3
**Author:** ![UpCycleElectric](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/upcycleelectric/32/36895_2.png) [@UpCycleElectric](https://community.victronenergy.com/u/UpCycleElectric)\ **Post date:** [19 January 2026 09:31 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/41 "2026-01-19T09:31:25Z")
> [@dmitrych](#): > > # Proof of concept > > I’ve attached a proof of Thanks, very interesting. I ran into the same serialstarter issues when writing a custom USB-GPS filter in Node-RED. ---
**Author:** ![mystudio](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/mystudio/32/38041_2.png) [@mystudio](https://community.victronenergy.com/u/mystudio)\ **Post date:** [19 January 2026 23:11 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/42 "2026-01-19T23:11:06Z")
Nice! Regarding accuracy; the thing is more accurate than man might think. Did some quick tests today, now it has been tuned and it is SPOT ON. First impression it’s accurate upto 10mA. Tested with very small currents and even 10 mA and 20mA are visible and spot on. And going up it gets easier, and for now I think the resolution indeed is in the 0.01A or 10 mA. So, earlier posts about that that would not be feasible with a shunt which can go to 500A are not true; it’s perfectly capable of catching small currents. So, conclusion right now, if the resistor is right, the electronics are more than capable of doing their thing. Curious if you’re able to go to the 1mA domain/resolution. Keep us posted. ---
**Author:** ![dmitrych](https://avatars.discourse-cdn.com/v4/letter/d/c67d28/32.png) [@dmitrych](https://community.victronenergy.com/u/dmitrych)\ **Post date:** [20 January 2026 00:42 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/43 "2026-01-20T00:42:26Z")
> [@mystudio](#): > > Curious if you’re able to go to the 1mA domain/resolution I do see that the shunt returns numbers that differ by 1 mA from each other (either noise or real), so at least ADC resolution appears to be good enough, but unfortunately I don’t have lab grade equipment to ensure an outcome that could be relied on, and my wife might not approve buying it 😅 (I’m tempted though, not only for this project). In either case it’s great to hear that at 10 mA resolution it’s accurate, thank you for confirming that! ---
**Author:** ![lxonline](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/lxonline/32/25567_2.png) [@lxonline](https://community.victronenergy.com/u/lxonline)\ **Post date:** [20 January 2026 04:38 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/44 "2026-01-20T04:38:00Z")
> [@mystudio](#): > > do you see those weird SOC changes only on the BMS The soc jumps and sometimes it doesn’t register an soc drop even though there has been a draw. Yes. > [@mystudio](#): > > 5/1: SOC 63% Consumed Ah: 121.0 Ah > 3/1: SOC 64% Consumed Ah: 120,5 Ah > 2/1: SOC 64% Consumed Ah: 120,3 Ah > 31/12: SOC 64% Consumed Ah: 120.0Ah Sometimes the rounding on percentage can be an issue. But it seems pretty close. > [@MondeoMan](#): > > think JK BMS current readings are seriously affected by the local temperature in the BMS. Agreed. The SOC calc does need to take temps into account. And then its own pesky inefficiencies. Which also make losses due to heat. Then the percentage loss is relative to how hard the system is being used. ---
**Author:** ![ron\_h](https://avatars.discourse-cdn.com/v4/letter/r/ed8c4c/32.png) [@ron\_h](https://community.victronenergy.com/u/ron_h)\ **Post date:** [20 January 2026 11:34 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/45 "2026-01-20T11:34:11Z")
JK BMS is measuring peak current and not average. A Multiplus II with AC IN active, induced peak DC current on the batteries, and this is why the BMS never sees 0A current and always jumps between plus an minus amps. This is why JK BMS is inaccurate in the low current range. ---
**Author:** ![alexpescaru](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/alexpescaru/32/270_2.png) [@alexpescaru](https://community.victronenergy.com/u/alexpescaru)\ **Post date:** [20 January 2026 12:30 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/46 "2026-01-20T12:30:56Z")
> [@mystudio](#): > > I think the resolution indeed is in the 0.01A or 10 mA Do any of you open it and see which microcontroller a shunt is using? To know which resolution its ADC has? Because if the resolution is the usual 12bits, the current quanta will be 500A/2^12 = 122mA, for 16bit the resolution will be 7.6mA and only for 19 bits and above will be under 1mA. Again for 500A. Double that for 1000A variant. The usual microcontrollers are too noisy for a high-bit ADC and for sure you’ll get 2-3 LSBs of pure noise. Maybe the best we can hope is probably a 16bit sigma-delta and then don’t expect less than 10mA… ---
**Author:** ![UpCycleElectric](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/upcycleelectric/32/36895_2.png) [@UpCycleElectric](https://community.victronenergy.com/u/UpCycleElectric)\ **Post date:** [20 January 2026 13:21 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/47 "2026-01-20T13:21:17Z")
> [@alexpescaru](#): > > 19 bits and above will be under 1mA I’m pretty sure the ADC is 20bits or higher even. Reason being the roundtrip accuracy of the coulomb counter. ---
**Author:** ![dmitrych](https://avatars.discourse-cdn.com/v4/letter/d/c67d28/32.png) [@dmitrych](https://community.victronenergy.com/u/dmitrych)\ **Post date:** [20 January 2026 20:59 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/48 "2026-01-20T20:59:34Z")
> [@alexpescaru](#): > > Do any of you open it I wish I did, but right now it’s already installed and is difficult to access. I agree with Jan, looking at the actual data returned by my 300A shunt, I don’t think the ADC can be lower than 19 bits. I couldn’t find reliable sources for SmartShunt, but here in another thread someone confirmed that the BMV shunt, which has the exact same resolution, accuracy and voltage range specs according to its datasheet, is using [MSP430F6733A](https://www.ti.com/lit/ds/symlink/msp430f6733a.pdf) that has 24-bit Sigma-Delta ADCs: [Victron BMV Shunt - what internal a/d converter used? - VictronEnergy](https://communityarchive.victronenergy.com/questions/154494/victron-bmv-shunt-what-internal-ad-converter-used.html) ---
**Author:** ![UpCycleElectric](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/upcycleelectric/32/36895_2.png) [@UpCycleElectric](https://community.victronenergy.com/u/UpCycleElectric)\ **Post date:** [21 January 2026 00:55 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/49 "2026-01-21T00:55:21Z")
> [@dmitrych](#): > > [MSP430F6733A](https://www.ti.com/lit/ds/symlink/msp430f6733a.pdf) that has 24-bit Sigma-Delta ADCs: [Victron BMV Shunt - what internal a/d converter used? - VictronEnergy](https://communityarchive.victronenergy.com/questions/154494/victron-bmv-shunt-what-internal-ad-converter-used.html) Good find ![Screenshot_2026-01-21-01-53-52-902](https://europe1.discourse-cdn.com/victron/original/3X/4/a/4a4ce7d2b18a385d5c95665733f7bda04950eccd.jpeg) ---
**Author:** ![alexpescaru](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/alexpescaru/32/270_2.png) [@alexpescaru](https://community.victronenergy.com/u/alexpescaru)\ **Post date:** [21 January 2026 04:38 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/50 "2026-01-21T04:38:49Z")
Thank you both for finding the relevant information! 👍 I’ve opened a shunt the other night but the PCB and microcontroller were covered with some resin against moisture. Not to mention that exactly on top of the micro was a label with the shunt’s serial number and company’s name also covered in resin… That confirms that even with 4 bits of pure noise, still 20 bits remains which gives it a 0.5mA resolution for 500A and 1mA for 1000A. For 300A version the resolution could even be better than 0.3mA. ---
**Author:** ![UpCycleElectric](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/upcycleelectric/32/36895_2.png) [@UpCycleElectric](https://community.victronenergy.com/u/UpCycleElectric)\ **Post date:** [21 January 2026 11:03 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/51 "2026-01-21T11:03:50Z")
> [@dmitrych](#): > > They’re open source, so instead of the current value they use, the code can be edited to pass the high-resolution shunt current (and SOC or other values if needed) Can you please check/confirm the availability of **high-resolution** SoC% and other values such as Voltage and consumedAh? ---
**Author:** ![dmitrych](https://avatars.discourse-cdn.com/v4/letter/d/c67d28/32.png) [@dmitrych](https://community.victronenergy.com/u/dmitrych)\ **Post date:** [21 January 2026 12:24 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/52 "2026-01-21T12:24:45Z")
Voltage is in millivolts and Consumed Energy is in mAh. Power is in watts, and SOC is only provided with the same resolution it’s displayed (e.g. 99.9%), but they’re redundant since higher resolution power and SOC can be calculated from current, voltage, consumed energy, and your battery capacity. Assuming your battery capacity is at least 100Ah, you can get SOC with resolution better than 0.001%! (The proof of concept script output in output.txt from my post above has a sample of how all this data is represented). ---
**Author:** ![UpCycleElectric](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/upcycleelectric/32/36895_2.png) [@UpCycleElectric](https://community.victronenergy.com/u/UpCycleElectric)\ **Post date:** [21 January 2026 12:29 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/53 "2026-01-21T12:29:19Z")
> [@dmitrych](#): > > Consumed Energy is in mAh This is great. I have published an experimental Node-RED flow to detect / reverse engineer the capacity from SoC% and consumedAh. I’t needs some work still but that will get a whole lot easier with high-resolution consumedAh values. > [@How to fetch the battery capacity as defined in smartshunt-settings?](https://community.victronenergy.com/t/how-to-fetch-the-battery-capacity-as-defined-in-smartshunt-settings/48346/29): > > Version 1.3, very small change on line 93, increased testwindow: “Match = absDelta \< 0.055555;” Surely there are opportunities to improve on the rounding and selection mechanism (that discards ‘unfitting’ capacity candidates) but this works perfectly for us. The correct capacity is found within a handful of value updates and when I change the capacity in the BMV manually, it automatically re-aligns with the new values as well. // Battery Capacity Estimator: Async SoC and ConsumedAh to Bound I… ---
**Author:** ![Marc\_HD](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/marc_hd/32/9108_2.png) [@Marc\_HD](https://community.victronenergy.com/u/Marc_HD)\ **Post date:** [22 January 2026 08:47 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/54 "2026-01-22T08:47:34Z")
mAh is not the energy. Ah are the unit of the (transfered) charge. 1A = 1C/1s In Words: 1 Ampere = 1 Coulomb divided by 1 second Electric current ist the charge per second. So 1 Ah = 1 A \* 3600s = 3600 As = 3600 C or the example above 1mAh = 3.6 C ---
**Author:** ![dmitrych](https://avatars.discourse-cdn.com/v4/letter/d/c67d28/32.png) [@dmitrych](https://community.victronenergy.com/u/dmitrych)\ **Post date:** [22 January 2026 17:49 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/55 "2026-01-22T17:49:02Z")
> [@Marc\_HD](#): > > mAh is not the energy Right. It’s a bit confusingly called “CE“ in the protocol and I didn’t think much of it when writing the post, but [Victron documentation](https://www.victronenergy.com/upload/documents/VE.Direct-Protocol-3.34.pdf) does describe this field as “Consumed Amp Hours” “in mAh units”. So everything else in my post stays true. ---
**Author:** ![Marc\_HD](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/marc_hd/32/9108_2.png) [@Marc\_HD](https://community.victronenergy.com/u/Marc_HD)\ **Post date:** [22 January 2026 19:07 UTC](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145/56 "2026-01-22T19:07:48Z")
absolutely. You are right. [Previous page](https://community.victronenergy.com/t/mismatch-smartshunt-500a-and-specifications/50145.md?page=2)