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ben-frobig avatar image
ben-frobig asked

Using SmartShunt 500A with starter battery on car

Forgive me for being a novice here, but I'm trying to find an easy to install, safe Amp and volt meter to monitor the battery on my car that has an intermittent draw. I need to have something permanently installed that will give me the voltage on the battery as well as the amp draw so I can see 1) if the draw is active so I can trace it, and 2) how long I have before the battery dies. The battery is under the passenger seat, so it is basically impossible to check this with a handheld meter without taking the seat out. Thus the advantage of the bluetooth permanent install here. Can the bluetooth SmartShunt be installed on the starter battery or just a house battery on an RV, or does it even make a difference? And, it looks like I can get all the data I need from this device, am I missing something? Any help would be very much appreciated.

starter battery
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cameron-bennier avatar image cameron-bennier commented ·

I have one installed....yes it works fine....untill the alternator kicks in then its useless as the current is coming from the alternator.

It wont show the cranking current either...no fast enough to display it...

Just tested it again...and yes if you go to the trends tab and log the startup it will log what you need.screenshot-20210924-152824.png

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ejrossouw avatar image
ejrossouw answered ·

Hello @Ben Frobig Below are some usage scenarios. https://www.victronenergy.com/upload/documents/Datasheet-SmartShunt-EN-.pdf I don't fully understand. Do you wan't to use it standalone in your car or in a system where there is a house battery too e.g. RV?

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ben-frobig avatar image ben-frobig commented ·

Thanks for the quick reply. It would be used stand alone on the starter batter for my car, No house battery installed.

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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

Should be working but I'm not sure if the shunt can handle/recognize the cranking current properly.
I think is also depends on the car model and the temperature, a bigger engine/at low temperatures you will have a higher/longer cranking current.

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ben-frobig avatar image ben-frobig commented ·

Thanks for the quick reply. The cranking amps is really my concern. The auto parts store tells me a starter in good working order should only draw about 120-150 amps, but I'm not sure what to trust. The car is a 5 liter V8, so it's a big engine. I also have concerns about how much power the monitor itself will draw when the car is off. I want to be sure that if I try to install something, it can handle the amps at startup, wont mess up the electronics in my car, and wont add to my problem of the battery draining when parked overnight. Thanks again, for any additional feedback.

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mrhappy avatar image mrhappy ben-frobig commented ·

If you have access to a DC clamp meter you could measure the actual cranking amps to make sure. Maybe pay a car workshop to measure it for you if you don't have a clamp meter.

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edwin-earthcruiser avatar image edwin-earthcruiser commented ·

I have a doubt, does shunt affect the cranking if I added a smart shunt to monitor start battery current?

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Nev avatar image
Nev answered ·

Our motorhome has a single 4 cell 300Ah LiFePO4 battery to both start the 3.9l turbo diesel motor and power the house.

It is monitored by 2 500A shunts is series with it all.

The battery has started the truck probably thousands of times over the last 7 years of full-time travel. No problems so far.

The Victron 500A Smartshunt and Juntek battery monitors have both registered a peak current of c730A during startup. The mean is obviously much less. The typical 0.3Ah required to start the truck is replaced by the alternator in about 20 seconds.


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