mechmain

iTrader: (4)

When hooking up two (or more) batteries, is it necessary to have a fuse in between the batteries on the power cable?

If so, what size?

Thanks,

Reekor

Yes, size depends on your alternator output. You should also use an isolator......

BIG UNIT

iTrader: (2)

x 2 on the battery isolator. If you're gonna do it, do it right the first time, not the second, after your insurance won't pay for fire damage from your "mistake"

JohnVroom

you put a fuse where you want to protect the upstream (supply) side of the system it is not there to protect the down stream stereo. If you have your amps, or any extra batteries in your car a fuse is a good idea in the front of your car to protect your car and its electronics from your stereo system faults. The need for this is inversely proportional to the quality of your install (if you did your own install you probably NEED a fuse, if you had the install done by a MECP certified installer it is still a good idea).

I would think a fuse in the engine bay is a good minimum, maybe another after the second battery

Reekor

What are you talking about?, your post is ill'in. Fuses should be installed within 12 inches of the battery. Most 2nd batteries get installed after the engine firewall (trunk). With that said, you get into a collision or your wire shorts out after the engine bay fuse (12 inches), if all goes well the engine bay fuse will blow and the 2nd battery will start feeding the short (now your power stream is flowing the other way). I don’t care who installed it. If you don’t install another fuse before the 2nd battery then you don’t need to install a fuse at the main battery because in the event of a short in the main power line you're S.O.L just the same with or without an engine bay fuse. There should be a fuse after the main battery and a fuse before and after the 2nd battery.

Sound_Deamon

To begin with ... any true SPL freak will not run any fuse whatsoever on any of the 0awg lines (some of us run 4x 0awg power and 4x 0awg ground) from one battery to the one in the back !!
if it's a daily music for fun style system you are running and don't want to run any risks (wich i have yet to see when installed professionaly) then yes the way it's stated is to have a fuse within 6" to 12" of your front batt. to the rear one and then the same from the line heading out from your second batt. to the next batt. or to your amp.
Personnaly i have ran a daily system and spl too and in neither case did i ever see the use of the fuse! as long as it's done right ....

Reekor

As long as its done right? Is that someting like, as long as doesn't happen?

Sound_Deamon

in the sense of .... ex: getting positive and ground leads to touch .... you know stuff like that (misshabs) .... stuff that a pro won't or at least has less chances of doing!

JohnVroom

Illin is that a word?
A fuse is sized to blow at a specific point where the current being drawn is greater than the amount of current that is possible in a properly operating system. So that means the downstream component has failed and is on its way to becoming an electrical fire. The fuse blows to protect the rest of the system (in this case the car) not the load. And I would agree with your additional fuse between the 1st and 2nd battery as a good idea, maybe overkill... but sound.

So put a fuse in the engine bay from the primary starting battery (12 inches from the battery if you want but it doesn't have to be) and my point was to consider a second fuse after the second (or however many batteries you have) because if you have a fault (the most likely fault would be speaker shorting or amplifier meltdown) the additional batteries will continue to feed the fault. So I dont get your Illin thing since you agreed with me...

power systems in a car are relatively simple adding extra batteries only adds a little complexity. I would do fusing with a minimum of two fuses to protect for the most likely failure (the amp shorting or a power wire going to the amp coming loose or the speaker wires shorting) though the third isn't a bad idea.

As mentioned competition SPLers dont do fuses because it wont make you louder... just safer (unless it is in the rule book). I have seen thousands of SPL installs some were just plain dangerous some were exceptionally well done. So you can get by with no fusing but there is risk, I will always have a fuse in the engine bay to my stereo.

Every SQ sanctioning body insists on a fuse at least within 18 inches from the battery in the engine bay, several SPL sanctioning bodies are insisting on fusing too (but to identify power class though it does have the fault interupt benifit too).

What does MECP recomend?

Reekor

You totally avoided my point. In a dual battery install using just one fuse in the engine bay at the main battery is totally pointless. We all know, well other then Sound_Deamon that most cars have a negative body ground. All you need is a collision and have something cut into the power cable and there is your short. Now with no fuse before the rear battery the rear battery will feed the short and there is your fire. No if's or but's that's just how it is. The fact that competition SPLers don't use fuses is besides the point, they know what the risks are and they dont need to ask how to fuse a battery. With that said, I personally don't need to give some 18 year old kid (for all I know, not sure who it is that asked the question) ill (bullshit) advice on how to turn his/her car into a bomb fire with him/her in it. Who in there right mind uses their main power cable fuse to protect their amplifiers. There is nothing wrong with ignorance, as long as it's not passed onto others.