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Current draw with Smart Shunt using battery cutoff


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battery switch.pdfI am planning to install a Blue Sea  battery cutoff switch. I am also installing a Victron Smart Shunt.  I don't have solar or lithium but do plan to add them down the road. 

If I install the cutoff on the  (+) lead as indicated in the attached sketch, will the two small wires that serve as the temperature probe allow any current flow while the cutoff switch is open? (in the battery cutoff position)?

Thanks, 

Steve #512

,battery switch.pdf

 

 

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That would be a good question for Victron to verify.  But their spec sheet says that the shunt draws less than 1 mA, so even if that's continuous even with battery power cut off, that would be less than 9 Ah a year, if my math is correct.

Snowball • The world's only spherical Ollie

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I'm not familiar enough with lead acid batteries to know how long they can be left without a charge.  They'll lose charge on their own over time even without a draw, and how quickly they do so depends on the battery type, temperature, and probably other things as well.  But I don't think that the draw from the shunt would be much of a factor.  Trojan says that the best practice for their batteries is to not allow them to go below 70% while stored, so I think if you don't have a battery maintainer on them that you'd probably want to check them every few weeks regardless.

Edited by Overland

Snowball • The world's only spherical Ollie

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I agree with Overland on this and I do have the Trojan T-105's (lead acid batteries).  During storage I check mine every 6 to 8 weeks.  Normally all I do is add water - they don't take much but since I'm at the storage yard I do it anyway.

Bill

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2017 Ford F150 Lariat 3.5EB FX4 Max Towing 2016 Oliver Elite II - Hull #117 "Twist"

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The Victron temp probe should be just like the Zamp solar one, it is just a variable resistor. With power removed from the system, it won’t do anything at all in terms of current. You could actually move the small red power wire for the SS to the other (switched) side of your cutoff switch. Then the SS will be powered off entirely. But leaving it attached as drawn, you should be able to connect with the app and read battery state, even with the battery bank disconnected. I think.....

John Davies
Spokane  WA

Edited by John E Davies
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"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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I considered starting a new topic, but since my question is similar I will piggyback on carnivore's existing topic. Please let me know if it is better to start new topics instead of reusing older ones. 

I want to be able to isolate the batteries, solar and house 12V appliances from each other.  I purchased the Blue Sea 5510e (dual circuit) switch and plan on wiring it such that one source is a bank of lithium batteries and the other source is the positive terminal from the solar charger (new MMPT).  I will connect both outputs from the switch to the positive bus bar. 

Any thoughts on this approach?

 

image.png.55475c89d293c6cee43c1bd1cd2091b5.png

Edited by mjrendon
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One thought is that there may be times when you want to disconnect either the batteries or the solar, but not both.  For example, when I was recently trying to diagnose my bad batteries, I had to disconnect the solar in order to get an accurate voltage reading.  Or you may want to cut the solar in freezing temps to prevent charging LFP batteries, but don't want to completely cut power to the trailer.

Edited by Overland

Snowball • The world's only spherical Ollie

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I'd recommend two separate disconnects, one for the solar and one for the batteries.  Only because it's an idiot proof solution, and I'm often an idiot.

 

Edited by Overland
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Snowball • The world's only spherical Ollie

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A really simple way to provide a manual disconnect feature for a single source is to use one of the very nice Bussmann circuit breakers, these are available from 25 amps to 150 amps. There is a bigger model that goes higher. You should already have one or more, my Hull 218 has one for the “house bus”. You just push the red Test button and it opens the circuit, simply swing the yellow bar back into place to close it. I plan to use at least two more in various applications like a MPPT solar controller and a DC to DC Redarc charger. They are better than a single massive switch because you get individual control over each circuit as Overland mentioned, plus they allow you to throw away either a fuse or a stupid automotive style auto reset circuit breaker. Don’t pay over about $30 for one, they are easy to source. Several of them located in a neat row will look way better than the odd mix of electrical parts Oliver installs.

B03783AA-F9F0-42E9-BB81-088748F70796.thumb.jpeg.c9bca30aa5b8098877c155e9ade1161a.jpeg

If you are determined to buy a Blue Sea switch (and they are most excellent) I personally would choose a pair of their mini switches, with their switched sides going together at a positive bus. You could even add more, for other stuff like a portable solar charger, and make a pretty marine style panel. It can be mounted in a number of ways, I am not sure if that applies to the big switches...? I think a master power control panel with flush mounted switches below the rear dinette seat would be quite cool, if you have room there. 

56518F15-C934-4644-9844-656673A8D3C9.thumb.jpeg.4627ef8e885dc13c980ee3d753ba8ad1.jpeg

https://www.bluesea.com/products/6005/m-Series_Mini_On-Off_Battery_Switch_with_Key_-_Red

They are quite dainty, about 3” square. .... http://assets.bluesea.com/files/resources/dimensioned_drawing/M_Switch_Key.pdf


John Davies

Spokane WA

Edited by John E Davies
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"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags.

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