FJ Cruisers of Northern California
Need help with those with dual battery setups
HI All.
I'm in the middle of doing a dual battery setup, but need some help from those that have done this project with either the dirty parts kit, DIY, etc.
I think i've figured out how I want to setup everything, but never the less, i'm still curious how the majority is doing this.
1.- Switch..
How is your switch setup? Is it mearly working as jumper? Do you have the system setup so the isolator turns on (conects the batteries) with the ignition?
2.- Isolator...
Where are you placing your isolator? Any pictures?
Thanks for any help guys.
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Replies to This Discussion
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Permalink Reply by Back in Black (FJ4 Tahoe) on
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Nester is that next to your Flux Capacitor?
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Permalink Reply by Red Leader aka DaveF2 on
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yeah, and I think his Mr Fusion is in the back luggage area
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Permalink Reply by manoweb on
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Wouldn't that create a complicated ground loop? What is the advantage?
I see many people use this dual battery setup, but I think one also needs to upgrade the alternator right? Otherwise I do not fully understand how it works...
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It's extra energy storage, that is why you use an isolator, so if one battery drains down, like you leave the stereo on too long or the fridge plugged in without the engine running, you can self jump start yourself with the isolated battery by just the flick of a switch.
Also the stock alternator puts out around 100 -120 amps, when you winch something heavy, and more than likely stuck in something sticky, you are drawing up to 150 amps, so the battery is the reservoir that keeps the winch going full power, with a second battery you have a twice the reservoir. On my old 4WD I only had one battery, I got stuck and really had to use the winch, then I made the mistake of turning off the engine too soon, I then needed to wait for someone to come by and give me a jump.
Charging two batteries doesn't require a larger alternator, they just take in and store what ever juice is left over from running all the normal items that require 12v, engine, fan, lights, ECU...
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Well when winching I think it's more that 400A. So I see, a dual battery may be useful in those situations, but many times I've read: "I have a lot of accessories so I put a dual battery system"
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Permalink Reply by 5150 Cruiser on
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First off no, having dual grounds does not make any "complicated ground loop". Not even sure what your getting at.
Second, no alternator upgrade is needed when adding a second battery. Like dave said, a second battery is mearly a way of storing more energy. Depending on what accesories are being ran while the vehicle is running is when an alternator upgrade might be needed. Police cars and other emergency vehicles comonly have larger alternators due to the extra equipment being ran at any given time. Lightbars, computers, camera systems, all draw aditional power that stock alternators were never designed to handle.
IN my case I'm installing a second battery for a few reasons..
1.- I plan on running all my electrical accesories on my second battery and have most of them "hot". (but will be on a timed out relay that is voltage protected) This way when my rig is off, i can still have all my equipent on. If for whatever reason my equipment drains my second battery, the first will still be able to start my rig.
2.- extra capacity when winching. This was already explained by Dave.
3.- Cost. This whole project is costing me less than $100 since most of the equipment i've been able to design myself, or recieve for a discounted price.
NOw i will admit that in my aplication, i don't need a second battery. but again, for the cost i couldn't pass up the equipment.
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Ground loops are intrinsically complex matter, it mainly manifests itself when having to do with RF or audio related equipment. How can you exclude ground loops problems in that configuration? Or, in other words, why a double ground to engine and chassis is better?
I always have all the accessories I have added (3 extra cigarette adapters, fog lights) always hot. I hate when things turn off when the engine is stopped. So far I've never had a problem, and I was curious why so many people have a dual battery system...
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I know what ground loops are. But by your explanation you seem to be taking the term a little to litterly. Ground loops mainly accour when there isn't a sufficient ground for any given component. (to small a wire, not a good conection to the chassis.) By adding a second ground wire from the engine to the chassis you helping eliminate any electrical interferance that may be caused by other electrcial componets such as UHF radios and the sort. Remember the chassis and engine block are one big ground plane. Now wether a dual ground is acctually needed may depend on the type of equipment your running. If you have alot of radio and comunications equipment then running dual grounds might be benificial. One would just need to do an OHLM reading before and after running a secondary ground wire. In my experiance build emergency vehicles, one can never run to big of a ground wire and its best to use factory ground points when you can.
Like i said, i don't really need a dual battery setup, but for the cost and piece of mind, its worth it. (for me at least). I can't speak for others, but between Dave and myself should give you an idea of different reason for wanting and/or feeling the need for a Dual Battery setup.
IN your case a dual bettery setup would not be benifical. Your factory battery can handle your compents just fine and unless you have your cig. adapter filled to the brim with accesory adaptors an you fogs running when the vehicle is off then there should be any draw on your battery when your truck is off.
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I disagree with your explanation. The problem you mention is quite the opposite of the ground loop, that is a "poor ground" problem. Adding a second wire causes the ground loop, where parts of the system that are in theory at the same potential, in fact are not. A general rule that many people (including me) observe when doing circuits is that everything in the system should have one and only one ground path to every other thing in the system. Never zero, never two.
According to this theory, if the path between the block and the chassis is poor, it should be fixed by adding a heavy connection between the two, instead of adding a second one. In fact, the only current flowing from the engine block should be the starter current, so my question is: is that second cable meant for this?
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Permalink Reply by Boss73 on
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I mounted my switch on the left hand side below the gray blank plate, just out far enough that the door molding is snug when the door is closed .
I have two Sears platinums. I did not plan to do this as I just got one as my second battery and I noticed that my main battery was below 11.5 volts. So I got another just cuz sears was having a sale ..
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manoweb,
Go out to your FJ and look at the factory ground setup from the battery. You'll find two ground wires coming off the battery. One attached to the body, and another attached to the engine block. Yes, the main reason for having the ground on the engine block is the starter, but there are other electrical componets that can be grounded on the engine block (engine temp sensors for example) Regardless, by your reasoning there is already a "ground loop" in the system. This is a factory setup from Toyota and i believe 90% of cars are set up from the factory this way. (I just checked the Ford Crown Vics in my shop and all have wires running from the body and to engine block from the battery) So in a sence, your always going to have more than one ground path.
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