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-   -   Installing Battery Monitor - cable gauge (http://www.cruisersforum.com/forums/f14/installing-battery-monitor-cable-gauge-202412.html)

gauvins 10-06-2018 05:37

Installing Battery Monitor - cable gauge
 
I am in the process of replacing my battery bank and installing a battery monitor.

All would be fine and dandy, with the exception of the windlass (1500W, powered by the house bank). Cables are 000 AWG.

My understanding is that all negative should be captured by the shunt. Would be easy to bring the panel's and windlass' negative to a post and connect the post to the shunt.

My question is whether I should (must) use 000 cables to connect the battery monitor's shunt, or if I can use smaller gauge, since the shunt is a few inches from the battery (ex. AWG 3).

In other words, gauge calculators assume constant wire diameter to compute the expected voltage drop. If a very short section of relatively smaller gauge is inserted in the circuit, what happens?

Sorry if this is a simplistic question.

svlamorocha 10-06-2018 07:02

re: Installing Battery Monitor - cable gauge
 
ok to have a short section of smaller gauge. In order to calculate drop add up the drop in volts for each segment. If you want to use American tables that dont give drop in volts you can " adjust" the length of the piece of different gauge to use the table. Example: If you will use 1 foot of wire that has half the cross section (circ mils or mm2) of the main wire, then count that as 2 more feet of main wire.

CharlieJ 10-06-2018 07:10

re: Installing Battery Monitor - cable gauge
 
Why would you want to do this? What is the advantage?

gauvins 10-06-2018 07:10

re: Installing Battery Monitor - cable gauge
 
Ok. Thanks

Cadence 10-06-2018 10:26

re: Installing Battery Monitor - cable gauge
 
The current leaving a load is the same as entering the load. Down sizing wire gauge?

gauvins 10-06-2018 11:01

re: Installing Battery Monitor - cable gauge
 
Quote:

Originally Posted by CharlieJ (Post 2648748)
Why would you want to do this? What is the advantage?

I'll have to run a 1 foot cable from the shunt to the battery. AWG 000 is stiff and would complicate things.

AWG 2 can handle close to 200A and voltage drop is insignificant.

a64pilot 10-06-2018 11:09

re: Installing Battery Monitor - cable gauge
 
The OOO is Iím sure to prevent voltage drop, due to wire run length.
Surely it isnít there cause it needs to be that size to keep from overheating, or he has Godís own battery bank.
We ran smaller wire than that to start a Honeywell (Garrett) G-10 engine, that drew a sustained 1000 amps at 24 V for likely 30sec during starting.

roverhi 10-06-2018 11:11

re: Installing Battery Monitor - cable gauge
 
Thought the PO was looking for input on laxatives from the title. Sometimes better to spell out what you are looking for in the title.

Pete7 10-06-2018 11:17

Re: Installing Battery Monitor - cable gauge
 
Quote:

Originally Posted by roverhi (Post 2648923)
Thought the PO was looking for input on laxatives from the title. Sometimes better to spell out what you are looking for in the title.

Second one today, I have edited the title for him.

gauvins 10-06-2018 11:43

Re: Installing Battery Monitor - cable gauge
 
Quote:

Originally Posted by a64pilot (Post 2648920)
The OOO is Iím sure to prevent voltage drop, due to wire run length.

yes yes, I understand this and do not question the size of the main cable.

Again, my question was whether it is OK to insert a short length (1 foot / 30cms or so) of smaller cable in the circuit. Turns out that it is perfectly possible. I am set on a short length of AWG 2 (50mm2) to connect the battery to the shunt.

thanks for your input

Cadence 10-06-2018 14:04

Re: Installing Battery Monitor - cable gauge
 
Just remember the radius of the wire size is a squared function when it comes to circular mill area and current carrying capacity.

gauvins 10-06-2018 15:31

Re: Installing Battery Monitor - cable gauge
 
Yes. I am in Europe at the moment. The metric is the cable cross section, expressed in square mm. Actually easier to understand and work with.

a64pilot 10-06-2018 17:01

Installing Battery Monitor - cable gauge
 
Iíd still fit as large a wire as will fit without undue stress.
Just canít hurt having large cabling, and we are talking about a short run, so cost isnít likely an issue either.

hzcruiser 10-06-2018 20:45

Re: Installing Battery Monitor - cable gauge
 
Quote:

Originally Posted by gauvins (Post 2648674)
I am in the process of replacing my battery bank and installing a battery monitor.

All would be fine and dandy, with the exception of the windlass (1500W, powered by the house bank). Cables are 000 AWG.

My understanding is that all negative should be captured by the shunt. Would be easy to bring the panel's and windlass' negative to a post and connect the post to the shunt.

[...]


Correct, you should capture all current with the shunt, but you don't have to. The simplest option would be to leave the windlass out of the "BM picture", if it causes undue efforts and costs to include it.


Compared to other consumers, the windlass only runs on rare occasions for short periods anyway. It all depends on what you really want to achieve with and expect from the BM.

Cadence 11-06-2018 06:37

Re: Installing Battery Monitor - cable gauge
 
Quote:

Originally Posted by gauvins (Post 2649086)
Yes. I am in Europe at the moment. The metric is the cable cross section, expressed in square mm. Actually easier to understand and work with.

It makes more sense than AWG.


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