Victron Smart Shunt

[Sewdhull]

To a customer it only matters if it works properly or not.

 

[Sewdhull]

To put that in perspective, a 500A current from a 12V battery is transferring 500 x 12 = 6000W. If the cables carrying that current had a voltage drop of 3% (the usual guideline loss) then the power lost in the cables will be 180W. So a shunt losing 25W in that situation is not too significant. And shunts are usually made of constantan, a metal alloy which has a constant resistance value as the temperature changes, so it will remain accurate anyway.

It's only relevant because it heats up, shunts are compact can be out of air flow.
Anyone held a 25w incandescent light bulb?
It's only 2ah each hour, but that's at 500A. Hopefully no one's going to run at 500A

 

[autorouter]

High current shunts are likely to be Manganin rather than Constantin (seen all the time in PSUs)

You are right, manganin is an improvement on constantan, so its resistance varies even less than constantan as the temperature varies. That means the shunt remains accurate even when it gets hot.

A 500A Victron SmartShunt can measure a current of 0.1A, so I assume the A-to-D converter has a resolution of 12 bits, ie 4096 steps in a 500A scale.

If a BMS can measure a minimum current of 1A with a maximum current of 200A, then it presumably has an 8-bit A-to-D converter with 256 steps.

 

[Lenny HB]

The points about the amps limit and the battery capacity limit are valid.
But, for many of us those limits are way outside our requirements. Nothing on the motorhome gets anywhere near 150 amps.

The lack of adjustments is part of the advantage. The meter just works out-of-the box.
(after you tell it the battery capacity - which is all it needs)

We occasionally draw more than 150 amps. Also if you can't even adjust just the charged voltage how can you set it up for different batteries, not all Lithiums are the same, you need to be able to set it to make sure the cells get balanced.

OK if it works for you but not for me.

 

[LithiumConvert]

You need to be able to set it to make sure the cells get balanced.

The BMS in my Sterling Power batteries does that job.

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[Raul]

It's only relevant because it heats up, shunts are compact can be out of air flow.
Anyone held a 25w incandescent light bulb?
It's only 2ah each hour, but that's at 500A. Hopefully no one's going to run at 500A

To be honest, in the off grid house, I have 500A victron shunt, but running at 48v nominal, most of the time at 52v plus. Occasionally we have loads as big as 8000w, but most of the time with house chores 2-4KW. The shunt is enclosed in 100x 100mm trunking, with the associated cabling, and never dawned on me the heat it may produce. I may relocate it, or, insert some openings at top/ bottom for a bit of air flow.

 

[mikash]

You are right, manganin is an improvement on constantan, so its resistance varies even less than constantan as the temperature varies. That means the shunt remains accurate even when it gets hot.

A 500A Victron SmartShunt can measure a current of 0.1A, so I assume the A-to-D converter has a resolution of 12 bits, ie 4096 steps in a 500A scale.

If a BMS can measure a minimum current of 1A with a maximum current of 200A, then it presumably has an 8-bit A-to-D converter with 256 steps.

The datasheet actually claims 0.01A resolution so that'd be ˜16 bits. The ADC is probably 24bit like on the older BMV series, so getting 16 -bit effective resolution with very little noise would be trivial.

 

[Sewdhull]

To be honest, in the off grid house, I have 500A victron shunt, but running at 48v nominal, most of the time at 52v plus. Occasionally we have loads as big as 8000w, but most of the time with house chores 2-4KW. The shunt is enclosed in 100x 100mm trunking, with the associated cabling, and never dawned on me the heat it may produce. I may relocate it, or, insert some openings at top/ bottom for a bit of air flow.

I used an IR camera to find drivers in trunking for some LED lights. But they are rated at 60C and weren't near that, but were easy to find in the trunking.
8kW is only 8W dissipation on that shunt but if it's enclosed...

 

[autorouter]

The datasheet actually claims 0.01A resolution so that'd be ˜16 bits. The ADC is probably 24bit like on the older BMV series, so getting 16 -bit effective resolution with very little noise would be trivial.

I was looking at an old version of the SmartShunt data sheet, which states a resolution of +/- 0.1A. However the latest datasheet on the website shows the resolution as +/-0.01A, the same as the BMV series shunts. Maybe they changed the A-to-D, or just got the datasheet wrong and have now corrected it.

A shunt that drops 50mV for a current of 500A has about the same resistance as 16mm² copper cable that is the same length (8cm) as the shunt. The power dissipation will also be the same.

 

[autorouter]

8kW is only 8W dissipation on that shunt but if it's enclosed...

If it's a 48V system it's only 1/4 the power dissipation of the same shunt in a 12V system.

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