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Nas Escobar

Anyone here running a battery in the trunk?

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Out of curiosity, is anyone here running a battery in the trunk? I'm debating whether or not this is a worthwhile mod for me since I am planning on rewiring my car for amplifiers, and I also want to do a CAI, but I'm not wholly convinced.

 

If anyone has pics, I'd like to see that as well.

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one of my favorite topics but I remember being discussed and argued about to the point of closed threads in the past. I still have not tried the best configuration, but it is so nice that I have not needed it so far. it involves a capacitor where the stock battery is and deep cycle in the trunk.

 

Is it worth messing with? I have found that it is.

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I hope now that we are a smaller community, we wouldn't have to face heated arguments; but I digress.

 

I've heard about capacitors, but I've also been told they're not worth it and that a high output alternator is more efficient than a capacitor that can drain the battery.

 

Regardless, if I relocated, I'd probably get a big BMW type battery since BMW's usually have em in the trunk.

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I hope now that we are a smaller community, we wouldn't have to face heated arguments; but I digress.

 

I've heard about capacitors, but I've also been told they're not worth it and that a high output alternator is more efficient than a capacitor that can drain the battery.

 

 

This. A capacitor will only help you if you have enough output from the cars charging system in the first place. A cap can only store power, not generate it. A high output alternator and deep cycle battery is the way to go. But it's really only necessary if you are running a rather large system. A capacitor can be useful if you compete is bass offs and whatnot, otherwise they are pretty much a waste of money.

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Initially, trunk mounting was a way of moving weight from the heavy front to the rear. Ideally it should be located to the right rear to offset some of the weight of the driver by that school of thought. The biggest problem I see is with people not grounding them to something solid.

Since W-Body fuel pump wires can become less than adequate with age you may consider putting a new fuel pump relay in the trunk too so there's just a short run to the pump.

I'm eyeing up the rocker panel as a conduit between the front and rear for mine. And you don't need a special BMW battery, there are relocation kits all over E-bay, Summitt and such. It would be nice if there was a box that could be sealed and run a vent tube out of the trunk though since they release small amounts of hydrogen when they charge.

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If the cap made a difference, there is another problem the cap helps cover up, IMO.

 

 

I agree with this. it covers up is a real big problem. a 1000 watt amp that hits the alternator with every bass note until it doesn't keep up the battery.

 

I can see how this IS the problem.

 

 

I have another $200 capacitor on the way. The same one I bought for my white car. and that car already has the cs144 alternator. It's the 10 farad hybrid capacitor from rockford fosgate. I really like how powerful and compact it is compared to the old one that was in my red car. I had the old, I think, 3? farad one in that car and it was nice, but just WAY too big and heavy as shit. like a boat anchor and just took up too much room in the trunk.

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This. A capacitor will only help you if you have enough output from the cars charging system in the first place. A cap can only store power, not generate it. A high output alternator and deep cycle battery is the way to go. But it's really only necessary if you are running a rather large system. A capacitor can be useful if you compete is bass offs and whatnot, otherwise they are pretty much a waste of money.

 

 

I agree that a capacitor can not generate power, but it should not be expected to. All it can do is like you said, store power, however is also useful, as it will triangulate your grounds, and create a web of power by installing one. Also another battery will do the same, so I basically agree with you.

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Initially, trunk mounting was a way of moving weight from the heavy front to the rear. Ideally it should be located to the right rear to offset some of the weight of the driver by that school of thought. The biggest problem I see is with people not grounding them to something solid.

Since W-Body fuel pump wires can become less than adequate with age you may consider putting a new fuel pump relay in the trunk too so there's just a short run to the pump.

I'm eyeing up the rocker panel as a conduit between the front and rear for mine. And you don't need a special BMW battery, there are relocation kits all over E-bay, Summitt and such. It would be nice if there was a box that could be sealed and run a vent tube out of the trunk though since they release small amounts of hydrogen when they charge.

 

 

the fuel pump wire should include a relay in the trunk in a trunk mounted battery car. very much in agreement.

 

 

however we do not have trunk mounted battery car here all-out obvious just to help us make a point. We do not have bmw's that were designed that way, they probably have a relay right there and a short wire to the fuel pump. Our cars have a longer one so it's either modify the wiring of a *bunch* of stuff to make it "right" or... leave it all the same and still be right. only way I can see that happening is to install a capacitor in the stock battery location. then you should be good. long as you block it from the heat but I don't know if that would be an issue...:shrug:

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just like a battery, a hot cap needs to be able to vent, otherwise they would build pressure and become a safety hazard.

 

the hotter it gets, the faster the cap loses its rated capacitance due to electrolyte evaporation/loss.

 

rule of thumb is that for every 10*C(18*F) a capacitor is subjected to, its useful life is cut in half.

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the fuel pump wire should include a relay in the trunk in a trunk mounted battery car. very much in agreement.

 

 

however we do not have trunk mounted battery car here all-out obvious just to help us make a point. We do not have bmw's that were designed that way, they probably have a relay right there and a short wire to the fuel pump. Our cars have a longer one so it's either modify the wiring of a *bunch* of stuff to make it "right" or... leave it all the same and still be right. only way I can see that happening is to install a capacitor in the stock battery location. then you should be good. long as you block it from the heat but I don't know if that would be an issue...:shrug:

 

I'm not sure why there's talk of a cap like it's a necessity, all that's needed is a good guage wire run front to back and hook it up the same as factory. If there's some question about current carrying just run a bigger wire gauge and a larger battery than factory.

 

On the fuel pump relay it's as easy as soldering the Green/White wire to the Gray wire when eliminating the relay and then using the gray wire all the way in the trunk as the relay coil power wire.

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I've already run a 10 AWG wire directly from the stock relay (took the relay center apart, and soldered the 10AWG wire to the connector) back to the fuel pump, would I still need the relay in the trunk?

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SPECIFICATIONS

MODEL- 10 Farad Hybrid Capacitor RFC10HB

Rated Capacitance – 77°F (25°C) 10 Farad

(Constant Current Discharge (5A) 15.0v–>3.0v)

Capacitance Tolerance ±10%

Rated Voltage,VR 16.0 Volts

Surge Voltage 18.0 Volts

Maximum Internal Resistance (ESR): <6.5m

Operating Temperature Range* -40 to 140°F

(-40 to 60°C)

Storage Temperature Range -40 to 158°F

(-40 to 70°C)

Input/Output Connections (6) 1/0 AWG and/or 4 AWG

(AWG-American Wire Gauge)

Dimensions:

Height 2.25" (5.72cm)

Width 10.25" (26.04cm)

Length 6.5" (16.51cm)

Weight: 3.31 lbs. (1.5kg)

*Prolonged operation above the operating temperature limit of a cell will greatly reduce its useful life

span. Exposure to temperatures below the operating temperature will reduce the ability of the cell to

easily accept a charge.

Specifications subject to change without notice

 

 

 

this is from the owner's manual for my new cap.

 

 

RFC10HB_1_m.png

all those power inputs would be nice to have when you remove the stock battery though. gotta do something with the wires. on my tgp, it has 2 grounds to the negative, and 2 power cables. one to the AUX post, one to the starter. the 3rd port you could run one off it all the way to the trunk battery.

 

you would need to make sure the fender/battery tray is staying below 140 for it to work though.

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I've already run a 10 AWG wire directly from the stock relay (took the relay center apart, and soldered the 10AWG wire to the connector) back to the fuel pump, would I still need the relay in the trunk?

 

Good God! A GM fuel pump relay is typically rated for 15A, you've got a wee bit more wire than you need there. I run a 16, which is slightly bigger than the GM Gray wire. With my Trunk mount Relay that may get turned into a 14GA for mine since I don't mind wasting the heavier wire on a short run like that.

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Good God! A GM fuel pump relay is typically rated for 15A, you've got a wee bit more wire than you need there. I run a 16, which is slightly bigger than the GM Gray wire. With my Trunk mount Relay that may get turned into a 14GA for mine since I don't mind wasting the heavier wire on a short run like that.

Yea, I wanted to make sure it would never be a problem. The price difference between the 2 sizes was minimal, so why not go big?

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Initially, trunk mounting was a way of moving weight from the heavy front to the rear. Ideally it should be located to the right rear to offset some of the weight of the driver by that school of thought. The biggest problem I see is with people not grounding them to something solid.

Since W-Body fuel pump wires can become less than adequate with age you may consider putting a new fuel pump relay in the trunk too so there's just a short run to the pump.

I'm eyeing up the rocker panel as a conduit between the front and rear for mine. And you don't need a special BMW battery, there are relocation kits all over E-bay, Summitt and such. It would be nice if there was a box that could be sealed and run a vent tube out of the trunk though since they release small amounts of hydrogen when they charge.

 

I've read up about this on the 240SX forums, but my logic isn't to move the battery to the trunk for weight distribution. Our chassis will forever be nose heavy thanks to its drive power going to the wrong wheels. If it was RWD and still the G body that the W replaced, then I can see this benefit, but with our cars, they will always be nose heavy since everything is up there.

 

I've seen the relocation kits, but I'm on a budget, and if I can score a BMW battery for $100 or so and find a cheap battery housing I assume I'd be fine since BMW's come with a battery stock in the trunk. My theory is that those batteries wouldn't vent into the trunk.

 

If the cap made a difference, there is another problem the cap helps cover up, IMO.

 

 

I was reserving my real opinion on caps since I had just started the thread at the time it was brought up, but me personally, unless it's a known brand and there is a real need to "store" energy, I don't see a real need for a cap. If a cap is there and it's helping the alternator because it's weak, then the problem is the alternator itself. I personally wouldn't get a cap unless I had a bass competition car. At the moment, all I want is something nice and loud, so if I felt the power drain quick, I would just get a beefier alterantor and do the big 3. I've done this before (although I really didn't need to) to a stock alternator, and I noticed that doing the big 3 helps in start times and other random electronics. For example, my windows would go down faster after I did the big 3. This was done on a Pontiac Grand Am with the Ecotec though, and those alternators put out 105 amps. In all honesty, I've ran 900 watts RMS with a stock alt and just the big 3 and I had no drain or charge issues, so I think I should be safe if I do the same to my Cutlass. Although I am very worried about the alt on the LQ1 since I could not find a way to upgrade it.

 

I have another $200 capacitor on the way. The same one I bought for my white car. and that car already has the cs144 alternator. It's the 10 farad hybrid capacitor from rockford fosgate. I really like how powerful and compact it is compared to the old one that was in my red car. I had the old, I think, 3? farad one in that car and it was nice, but just WAY too big and heavy as shit. like a boat anchor and just took up too much room in the trunk.

 

While on this subject, has anyone fit a CS144 on the LQ1? I think I asked a similar question last year about the alternator thing and it seemed that the answer was that there was no upgrade for the LQ1 and my only option was to rebuild my alternator for more amps, but it wasn't an option since we all know where that alternator resides. That was one of the few jobs I paid to have done.

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