Victron negative cable

wolfnwillow

Senior Member
Joined
May 21, 2018
Messages
203
Location
Wisconsin
I plan on installing a Victron Battery Monitor Smart Shunt 500A. I understand a single negative cable must be installed from the negative terminal of the battery to the "battery minus" side of the shunt and that will be the only connection between those two points.
My question is, is there any limitation to the length of that one cable? In my application it may be up to 5 feet long. I will only be connecting one battery and wonder if the length of that cable has an impact on the monitors performance.
The monitor itself will not be that far from the battery (if that makes a difference). It's just that I would like to take advantage of some existing holes in the trailer for routing purposes.
I have exhausted the Victron Energy site but most of it is way over my head and often discussing loads, powers balance, etc when dealing with battery banks.. Not my situation...only one battery.
Thanks
 
There is a limitation for any cable's or wire's length based on the maximum current the cable needs to carry (and for how long in time). In other words, if you ever had even close to 500a of current, the length of the cable along with its thickness (awg size) comes into play much more so than with a fraction of that amount of current. The longer the cable is the larger it needs to be to reduce "line loss" and "voltage drop". However, I doubt you would ever pull more than 50a from the battery and likely wouldn't need a 500a shunt. Keep in mind I am just thinking about common low current RV usage from the battery but if you added something that required a lot of current like a high wattage inverter, then the cable size has to be much larger to handle the load and the shorter the cable the better.

Point being, you need to have an estimate of the maximum load (amps) and then determine the wire size (cable size AWG) that you already have and then the entire length of the cable in order to determine if the cable is large enough in size to handle the anticipated load. This is why most inverter installation manuals suggest to place the inverter as close as possible to the battery(s). ~CA
 
As craigav said the max load plus a little leeway is what you need. I google up 12 volt wiring amperage chart and came up with several. In my case the charging amperage is much more than the maximum draw amerage, lights, pump, TV, vent fans all running maybe 15 amps vs. converter output.
10 gauge might work, 8 would be better, but if you can get 6 gauge you would have a huge safety margin.
PS, what is your max charging amps? Do you have a heavy enough positive cable. Mine from the converter (maybe 15 feet long) was #10 which I think is a bit small but that is Jayco for you.
 
That's the whole problem. All I wanted was to switch to one 100 AH lithium battery but I have spent countless hours trying to get educated and become an amateur power engineer. So much info. I appreciate your replies but really don't understand them or know how to find the answers. It is a very basic set up now. This is what the converter shows if that helps: Output Power: 940 W
Output Current: 50 A, 55 A
Input Voltage/Hz: 105-130 VAC, 60 Hz
There is no inverter involved. 500 A is the smallest they carry and is a very simple shunt. Will never go near that many amps.
I am not sure if load is involved, possibly. Again not my area. In this application, a single negative cable goes to the shunt terminal coming from the battery negative. The other terminal on the shunt gets the original grounded negative.
The positive is as usual.
Does any of that help?
 
There are lithuim batteries with a bluetooth app that will display charge / discharge / percent charge remaining / temp, and many more parameters. With a single lithium battery, you wouldn't really need a shunt.

If you do decide to go with a shunt monitor, Victron does make good equipment.

There are alternatives that use a hall sensor which wouldn't need a additional cable, a sensor simply slips over the existing negative cable. There is no bluetooth app, they have their own wireless display which needs a USB power source, and it's a a bit of a learning curve as they have many other functions that you would likely never use. Another issue is this particular model has no case for the display, it's for a cutout mount, but there are similar ones that do have a case. I use a 500A version of this one-


Battery Monitor Meter Wireless DC 120V 100A VOLT AMP AH SOC Remaining Capacity

https://www.ebay.com/itm/132814863412?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D20200818143230%26meid%3Dfed92cc0d5824b9784e3d47cdf98cf06%26pid%3D101224%26rk%3D4%26rkt%3D5%26sd%3D175872609771%26itm%3D132814863412%26pmt%3D1%26noa%3D1%26pg%3D4429486%26algv%3DDefaultOrganicWebV9BertRefreshRanker%26brand%3DUnbranded&_trksid=p4429486.c101224.m-1
 
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I doubt that you need to be too concerned about the length on the cable. If you did not change the converter during the lithium battery upgrade, the wire is already sized for the converter output. This is most likely the high load on your 12v wiring system. Adding a bit of length (say less than 6 feet) to the run, assuming you keep the wire gauge the same, is unlikely to be an issue. Don't overthink this, install the shunt monitor and enjoy all your new data.
 
ARoamer got it right when he mentioned Bluetooth. Both my solar MPPT and my battery are from Renogy and have Bluetooth readouts on my phone app. Always have state of charge, rate of charge or discharge, how much solar is making, even battery temperature.
One of the reasons I went Renogy is the constant knowledge of what is happening with my battery and solar. As I have 200 watts of solar I shut off my converter as my solar has consistently kept my battery recharged during camping off grid.
 
I plan on installing a Victron Battery Monitor Smart Shunt 500A. I understand a single negative cable must be installed from the negative terminal of the battery to the "battery minus" side of the shunt and that will be the only connection between those two points.
My question is, is there any limitation to the length of that one cable? In my application it may be up to 5 feet long. I will only be connecting one battery and wonder if the length of that cable has an impact on the monitors performance.
The monitor itself will not be that far from the battery (if that makes a difference). It's just that I would like to take advantage of some existing holes in the trailer for routing purposes.
I have exhausted the Victron Energy site but most of it is way over my head and often discussing loads, powers balance, etc when dealing with battery banks.. Not my situation...only one battery.
Thanks
Your primary concern is to ensure that the cable leading from the battery negative terminal to the shunt is of the appropriate ampacity to carry the maximum current you can expect from your system.
DC wire_selection_chartlg.jpg

Don't worry about the minor losses of energy to resistance that will occur from an increasingly longer cable. That energy usage (loss) won't get measured by the shunt, but were at decimal points at that point.

My negative battery cable is about 3 feet to the shunt. Also note that particular length of cable doesn't include the total negative cable length used to make all of the parallel connections to each negative battery terminal. There are resistance losses along those lengths that aren't measured by the shunt. The resistance losses just aren't enough to worry about at these lengths.

20230910_030010-1.jpg
 
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