question

reno avatar image
reno asked

Circuit breaker vs Smartshunt

Hello,

I'm about to add a Smartshunt on my installation in my campervan. I'd also like to add a general circuit breaker to be able to easily isolate the battery if necessary (i.e. working on the installation, winterizing, etc...)

So here is my question : is it ok/safe to place this circuit breaker between the battery and the Smartshunt ? Or should it be placed after the smartshunt (but in that case, the smartshunt is still powered) ?


Thanks !

SmartShunt
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2 Answers
Alexandra avatar image
Alexandra answered ·

@Reno

Ideally nothing should be between the negative and the shunt.

The answer depends on if your battery can take the drain of the smart shunt over the expected time you are leaving it unattended.

You could always disconnect the positive power cable anyway if it is on the battery side.

If it is a good lithium it will likely go to sleep and stop the parasite draw. If lead acid you might return to a dead undercoverable battery.

Don't forget there is also battery self discharge as well.

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reno avatar image reno commented ·

Thanks for your answer. Ideally, it's to leave no consumer at all (it's a Gel Battery).

My concern - assuming I place it between the battery and the shunt - is the fact that in case of shut off/shut on, the smartshunt will be "wired" in the inverse order of the manual indications, i.e first battery minus, and last positive wire. Could it damage the shunt ?


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cybermaus avatar image cybermaus reno commented ·
It would not be connected *inverse*. The left side would still go to your chassis or negative binding post. And the right side would still go to the actual battery minus. Just with a switch inbetween.


I cannot speak for Victron of course, but I would be highly surprised if the Smartshunt could not handle that. Worst that could happen is it losses the time of day until you connect a phone again, so your history is off.


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reno avatar image reno cybermaus commented ·
Yes, I misspoke, it would of course not be inverse in the wiring itself, but in the sequence of pluging it.

I agree with you, and after all, that is what would occur if I had to unplug the battery negative.

I guess the most careful way to switch off would be to first unplug the positive cable of the smartshunt, and then switch off the system.


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regman54 avatar image regman54 reno commented ·
@Reno Hi reno. I've owned various campers since the 70s. For winter storage I would just remove the batteries and store them indoors in a dry, somewhat warm location if you can. Batteries will self-discharge over time anyway so an inexpensive solution to keep them fully charged is to keep them hooked up to a small motorcycle battery charger. Battery Tender is one brand as an example. That's all I've been using over the past 25 years or so.


I also use a Victron SmartShunt (IP65 version). Over the camping season I don't disconnect it as it only uses a few millivolts. If I do want to disconnect the shunt I just remove its fuse.


Just a suggestion but if all you need is a way to disconnect the battery a disconnect switch such as this might be easier to install.

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reno avatar image reno regman54 commented ·

Thanks for your answer. I do not need to fully remove the battery : worst case scenario, I have an IP67 Victron charger onboard, and I can get the van near my appartment to plug it on 220v.

About the switch, that's exactly the kind I intend to install, although smaller because my circuit is simple and at low-power.

For instance :
Battery switch

So, you think it would be ok to place it between the shunt and the battery ?

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reno avatar image
reno answered ·

Hi again !

So, on your advice - and my doubts - I went with the recommended solution, that is placing the smartshunt between the battery and the switch (reminder : negative circuit breaker in my case).
So far so good, I can live with that... BUT !! I then plugged the V.aux cable to monitor the main battery (starter battery), and I'm facing a new problem : when I switch off the circuit breaker, the Shunt is no longer connected to the common negative, and so the V.aux is something erratic (23v in the present case).


Do you think it's something to worry about ?


I wonder if the best solution was to place the switch between the battery and the Shunt actually...

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cybermaus avatar image cybermaus commented ·

Well, lets first remark that I was giving observations rather than advise. For a negative disconnect, I think I would have done it like you did, but I also did not think it would matter much.


But yes, it means you cannot read the aux battery (mine has a temp sensor). But had you place the shunt on the other side of the disconnect, you could read the aux, but not the main battery.


I guess if you want them both readable, you'd have to move the disconnect to the positive side. Like is more common nowadays, rather than the tractor example.

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reno avatar image reno cybermaus commented ·
Yes you're right, and no worries about observations vs advice, I thank you all for those ! ;-)

Next step is to add a switch before the loads on the positive side, so I won't have to use the main negative switch except for maintenance/emergency.

So far, I'm ok with this installation, but I just would like to be sure that keeping the Aux plugged while switching off is safe and harmless for the Smartshunt.



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regman54 avatar image regman54 reno commented ·
Even the smallest SmartShunt can handle up to 500 amps (current) so from what I can tell you should be good.
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