how long is to long of battery cable?

twofourdee

Seaman Apprentice
Joined
Dec 21, 2009
Messages
48
Hi I just added a 2nd battery and switch and was just wondering how long is to long of cable to run from the betteries to the switch? The motor is a 4.3 L and both batteries are group 24's the longest cables i installed are the 2 pos. going to the switch and they are about 50'' i just wanted to make sure that was fine before i take the boat out... Would have asked prior to install but i just ran across a post saying to go as short as possible and this is about as short as i could go.. I would think this length sould be fine but im not an expert by any means with this size of cables and what not.. Thanks for any in put
 

saildan

Petty Officer 1st Class
Joined
Mar 7, 2009
Messages
264
Re: how long is to long of battery cable?

Hi I just added a 2nd battery and switch and was just wondering how long is to long of cable to run from the betteries to the switch?
The issue is this:

Excessive voltage drop impairs the starting and the operation of electrical equipment. Undervoltage can result in inefficient operation of heating, lighting, and motor loads. An applied voltage of 10 percent below rating can result in a decrease in efficiency of substantially more than 10 percent ? for example, fluorescent light output would be reduced by 15 percent, and incandescent light output would be reduced by 30 percent. Induction motors would run hotter and produce less torque. With an applied voltage of 10 percent below rating, the running current would increase 11 percent, and the operating temperature would increase 12 percent. At the same time, torque would be reduced 19 percent.
PowerStream Technology​
Distance becomes a factor in the equation since as distance grows so does resistance. The longer the wire the larger gauge it needs to be to deliver the same required volts and amps.

You can find tables like this on the net to aid you in matching wire gauge to load.

http://www.powerstream.com/Wire_Size.htm

Perhaps a little intimidating at first glance. Worth studying and figuring out how to use.

There's a plug-n-play calculator below the table. Enter the wire type, wire size you installed, system voltage, length, max load the cable needs to be able to carry.

Now see where you stand with the loss limit(s) allowed by the manufacturer(s) for your equipment.
 

twofourdee

Seaman Apprentice
Joined
Dec 21, 2009
Messages
48
Re: how long is to long of battery cable?

wow thats all pretty much greek to me but from what i can make of it i should be fine as my loss is not that great.. Thanks guys
 
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