upgraded alternator, dual parallel batteries. Fuse ?

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mikez71

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I have installed second battery (parallel dual) with the factory cables.
Also installed a 220A alternator. Stock setup is a 145/160 amp alternator, with a 175A fuse.
Sounds like I'm supposed to add a larger fuse (250A?) but am worried the battery and alternator cables maybe too small?

What if I wire a SECOND CABLE from the alternator to AUX battery with ANOTHER 175A fuse?
The batteries (+) would then be connected through both the starter and alternator cables.
Alternator could output full power if needed going through two 175A fuses.

I know many upgrade the battery cables, but with two batteries/cables, I'd prefer to leave it stock if one or two extra cables can achieve the same thing. (I like the stock battery terminals)

Or will this create radio noise or other problems, or just not work like I am thinking?
 
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Doubeleive

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I wouldn't change the fuse the amperage is based on a safe amperage to keep other attached equipment from getting fried, so the fuse will blow before wires melt and/or over amping a module, etc
i have dual battery's also parallel for years now and run a amp and sub's and HID lights and etc. no issue's
 
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mikez71

mikez71

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I wasn't planning to uprate fuse on stock wiring (unless people tell me stock is large enough, but all the Big3 upgrades make me think stock wiring is borderline)

I just don't think you can get the full 220A potential on a 175A fuse.?
Therefore I am thinking about adding a second alternator cable to the aux battery.
Worried there will be some negative side-effects I don't know or understand..
I would like the ability to power a 2000W or larger inverter if possible. Sounds like they can draw around 170A, and a 3000W around 250A..
 
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Joseph Garcia

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I'm assuming that the larger capacity alternator is for a sound system or some other large energy user. If that is the case, the power amp main power wire for this accessory should be directly wired to the main battery with its own separate fuse. Therefore, there is no reason to change the existing in fuse on the firewall.
 
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mikez71

mikez71

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I'm assuming that the larger capacity alternator is for a sound system or some other large energy user.
A power inverter, but I am worried about the fuse limiting the alternator power. I want to hookup accessories to aux battery because it's more convenient to access, and if I ever install an isolator, I want the accessories on the aux battery. Not sure if adding a secondary alternator cable to aux battery would work or cause issues. Trying to read up on battery hookups, ground loops etc. now my head hurts!
 
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Doubeleive

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A power inverter, but I am worried about the fuse limiting the alternator power. I want to hookup accessories to aux battery because it's more convenient to access, and if I ever install an isolator, I want the accessories on the aux battery. Not sure if adding a secondary alternator cable to aux battery would work or cause issues. Trying to read up on battery hookups, ground loops etc. now my head hurts!
it's for protection only, it can pass a lot more watts, like 2000 or something around there
 
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iamdub

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I have installed second battery (parallel dual) with the factory cables.
Also installed a 220A alternator. Stock setup is a 145/160 amp alternator, with a 175A fuse.
Sounds like I'm supposed to add a larger fuse (250A?) but am worried the battery and alternator cables maybe too small?

What if I wire a SECOND CABLE from the alternator to AUX battery with ANOTHER 175A fuse?
The batteries (+) would then be connected through both the starter and alternator cables.
Alternator could output full power if needed going through two 175A fuses.

I know many upgrade the battery cables, but with two batteries/cables, I'd prefer to leave it stock if one or two extra cables can achieve the same thing. (I like the stock battery terminals)

Or will this create radio noise or other problems, or just not work like I am thinking?

I wasn't planning to uprate fuse on stock wiring (unless people tell me stock is large enough, but all the Big3 upgrades make me think stock wiring is borderline)

I just don't think you can get the full 220A potential on a 175A fuse.?
Therefore I am thinking about adding a second alternator cable to the aux battery.
Worried there will be some negative side-effects I don't know or understand..
I would like the ability to power a 2000W or larger inverter if possible. Sounds like they can draw around 170A, and a 3000W around 250A..

A power inverter, but I am worried about the fuse limiting the alternator power. I want to hookup accessories to aux battery because it's more convenient to access, and if I ever install an isolator, I want the accessories on the aux battery. Not sure if adding a secondary alternator cable to aux battery would work or cause issues. Trying to read up on battery hookups, ground loops etc. now my head hurts!

The fuse is to protect the load. It is to fail to cut power should the load exceed a set amperage. A higher amperage fuse won't blow as "easily", meaning the load (everything downstream of it) will be subject to the higher amperage and it, in turn, will act as the fuse.

Just like a higher amperage battery, a higher amperage alternator doesn't "push" amps into a system. It's just the amount that's available should the system (load) need it. So, the 175A fuse isn't choking down 45A of your 220A alternator. Your system is still drawing the same amperage it was before. With the 220A alt, you now have 60A more headroom for loads if you previously had the DR44 160A.

The stock wiring is barely adequate at best in a stock setup. You'll have twice (or more) the power requirements so upgraded wiring is absolutely necessary or you'll be having even worse voltage fluctuations and deficiencies than you have now (and might not even realize). Rather than adding a bunch of extra wires, I think upgrading what's there would be simpler and cleaner. But, yes, "doubling up" on power and ground wires would technically double the conductivity. A circuit is only as strong as its weakest link. You can have all the 1-, 2- or even 4/0 power cables you can cram under the hood but they won't do any better than stock if the ground isn't as good.

Honestly, a 2000W inverter needs its own battery bank. I think you'll be okay since you have that second battery. But, the batteries will be doing most of the work. It'll come down to the factor of time. If you're not using all 2,000 watts for more than a few minutes, then that 220A alt might keep up just fine if you're not running a lot of other high-amperage devices.

The inverter, or any other high-amp load should be connected directly to the battery(ies) with their own fused power cable, just like how an aftermarket audio amplifier is done. They do not go on the factory circuit downstream of that 175A main fuse. That is strictly for protecting the factory original equipment. Any other high-amp device you add should get its own power cable with its own appropriately-sized fuse.
 
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mikez71

mikez71

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Thanks Iamdub. Yep, not planning to run 2000W for long, mostly thinking it'd be nice to be able to run power tools/cooktops if needed. Will have to upgrade grounds. Other thought was, since inverter would be connected to aux battery, it might be more efficient with the alternator charging it directly rather than pulling through the 175 amp fuse and 2 starter wires.

Also wondering if running two cables to the back would be easier/acceptable compared to 1 larger cable.. And if a separate ground cable needs to be run. Looking at PPV/SSV wiring diagrams, they seem to run a big "blunt cut" ground to the inside passenger, but not to the back cargo area. 4 guage wires in back with 50A circuit breakers and 8 gauge fusible links.

Here's some info about wiring up dual batteries so they charge more evenly, not sure how it applies to my setup. https://caravanchronicles.com/guides/how-to-connect-two-batteries-in-parallel/
 
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mikez71

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Just like a higher amperage battery, a higher amperage alternator doesn't "push" amps into a system. It's just the amount that's available should the system (load) need it.
Right, so when running an inverter that can pull 175A, all that juice has to go through the 175A fuse? I keep reading that it's good to have a larger fuse than your alternator can provide (assuming you have adequate wiring I guess)

In reality, I doubt I will need it, but just like planning for 'what if'. Also the car uses some juice while running, but that is hooked up to the same side of the fuse as the alternator.
 

iamdub

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Thanks Iamdub. Yep, not planning to run 2000W for long, mostly thinking it'd be nice to be able to run power tools/cooktops if needed. Will have to upgrade grounds. Other thought was, since inverter would be connected to aux battery, it might be more efficient with the alternator charging it directly rather than pulling through the 175 amp fuse and 2 starter wires.

You mean that 175A main fuse on the firewall? DO NOT connect the inverter "downstream" of this fuse. Don't even connect the inverter to the fuse holder block. Connect the power wire that feeds the inverter directly to the positive post of either battery, whichever is more convenient for routing. Have an inline fuse or breaker with a fuse rating of whatever the inverter's manufacturer specifies. The inverter will be fed by both batteries simultaneously since they're paralleled together. In fact, just look at it as having one big battery that's split into two locations with the convenience of two positive terminals and two negative terminals. As such, the alternator is charging both batteries simultaneously. The charge wire from the alt doesn't need to be on the same terminal that the inverter power wire is on.


Also wondering if running two cables to the back would be easier/acceptable compared to 1 larger cable..

Physically, it's easier, simpler, cleaner and almost always cheaper to run one wire- less attachments/straps, terminals, fuses, etc. It's often a few bucks cheaper, depending on the single- versus dual wire sizes. It also depends on what you're gonna do with it. If you have the inverter in the back and that's all, you'd run one power wire that meets or exceeds the ampacity (factor amperage and circuit length plus a little headroom) required by the inverter. If you have the inverter plus some other high-amp device, you'd need a separate power wire for each device ran from the battery. Or, one large power wire that'll support the amperage of both devices ran to a fused distribution block, then a power wire of proper gauge, connected downstream of each fuse and routed to its respective device. The one large wire ran from the battery will have a large fuse that supports and protects the load of both devices as well as that circuit as it's routed along the frame.


And if a separate ground cable needs to be run. Looking at PPV/SSV wiring diagrams, they seem to run a big "blunt cut" ground to the inside passenger, but not to the back cargo area. 4 guage wires in back with circuit breakers and 6 guage fusible links (50A per wire)

However big your power wire is, the ground needs to be the same. This is why the Big 3 Upgrade should be the first step. Your grounds should be as short as possible. If you have a large ground from the battery(ies) to the frame, then you'd only need to run a ground from the inverter/device to the frame. The frame is the most convenient large-gauge conductor on the vehicle and, also conveniently, it runs from front to back and side to side of the vehicle.
 

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