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bradraut avatar image
bradraut asked

SmartShunt Accuracy with AGM vs Lithium

Good Day

I am looking at purchasing a SmartShunt to monitor a Dual Battery System with a 100Ah Lithium Auxillary Battery and a Lead Acid Starter Battery. Today I was told by someone that the SmartShunt is great with AGM however it is inaccurate with Lithium Batteries due to a linear voltage. Does this make sense?


Kind Regards

Bradley

Lithium BatterySmartShuntAGM Batteryorion dc-dc
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4 Answers
kevgermany avatar image
kevgermany answered ·

The shunts measure current and use this to calculate state of charge etc. To prevent drift building up they automatically reset 100% when fully charged parameters are met.

So just as good for both chemistries. But no meter is 100% accurate.

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wildebus avatar image
wildebus answered ·

As Kev says, they work with both chemistries, but you do need to tweak the settings to get as accurate a result as possible regardless of what type of battery you have, and the correct settings also depend on if you have a Solar Controller in the system as well (to prevent a premature jump to 100% SOC in certain circumstances).

Victron have some very useful video guides on their YouTube channel on how to configure the BMV/SmartShunts for Lithium and if you have solar also.

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l00semarble avatar image
l00semarble answered ·

Keep in mind that the entire point of a shunt is to measure current, not to measure voltage. The primary function of a shunt based battery monitor such as the smartshunt is to count amp-hours which of course is done by measuring current and time and doing a little math.

it can/will count amp-hours for Lithium just as well as AGM/FLA. Yes there are some nuances in the settings for when it will synchronize to 100% charge but it is very configurable and can be customized to the needs of the batteries.

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bradraut avatar image
bradraut answered ·

Excellent, thank you for this. I will go ahead and order myself a SmartShunt. I might just need some assistance in sorting out those tweaking issues. I will have a look at their videos as well. What settings do you adjust to prevent the premature jump to 100%? I have the VictronConnect App in Demo mode.

I definitely plan to have both DC DC charging as well as Solar Charging.

One last thing, if you have a non-isolated DC DC charger, I assume you can still wire this in just from the battery to the smart shunt and then to a negative block with the charger, solar MPPT and the Starter battery connected there? Would that work?

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wildebus avatar image wildebus commented ·
The key parameter to change is the "charged voltage".


Victron recommends when you have a Solar setup that this parameter is set just below the absorption voltage, whereas with no solar it would be at the float voltage.

Ref wiring, however you connect the negative from the B2B - be it to vehicle chassis, to starter battery or to a -ve busbar - it must not be connected directly to the -ve post of the Leisure Battery.

If you connect to the Shunt, that is ok as long as it is on the LOAD stud and NOT on the BAT stud. The only thing that should be connected to the -ve post of the battery you are monitoring with the SmartShunt is the Smartshunt itself.


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