I agree with the Guys talking about cable. Sorry. Put a digital multimeter on the starter lug and have a friend start the car. Watch the voltage drop on the meter. You'll be shocked. The correct way to do a trunk mounted battery is to jump out the starter mounted solenoid and use a Ford style solenoid in the cable. I used to drive a 440 Dodge Charger every day. The battery was in the trunk and I never had a starting issue. I used a 900 amp group 24 battery. I think you'll be wasting time and money adding another battery.
Dual batteries or single larger battery?
- Thread starter sifan
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sifan- I sincerely mean this. You've earned the highly coveted
for unparalleled efforts toward achieving automotive lubrication perfection.
for unparalleled efforts toward achieving automotive lubrication perfection.
I'm curious as to why the starter mounted solenoid needs to be "jumped out"? With the proper cables and connections (meaning the return path has to be taken in account), everything should operate just as if the battery is mounted in the engine compartment.
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Sorry, couldn't help it, carry on.
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If I had to do this, being the cheap 'tard that I am, I'd just get cheaper cable and run it along side the current installed cable. the investment may be a new lug for the starter connection.
I'm unsure how the priming pump is wired, but sifan may consider wiring it to something other then the ignition switch. He energizes a bunch of other stuff when he turns on the key (fuel pump, ECM, etc.). Not that these draw a whole lot of current on their own, but add the oil pump and then whammy the battery with the starter draw after its done the nasty ..
I'm unsure how the priming pump is wired, but sifan may consider wiring it to something other then the ignition switch. He energizes a bunch of other stuff when he turns on the key (fuel pump, ECM, etc.). Not that these draw a whole lot of current on their own, but add the oil pump and then whammy the battery with the starter draw after its done the nasty ..
The reason for adding the remote solenoid and jumping out the starter mounted one is so the starter solenoid gets full battery voltage during cranking. It helps. Also- the cable is only evergized during cranking, a great safety feature. And, yes.. The charging wire needs to be relocated to the battery side of the Ford solenoid.
JHZR2
Staff member
Ill just give my 2C from the E30 BMW world.. and my personal experience.
SOmetime in the life cycle of the E30 product line (a past model 3-series), BMW re-mounted the battery from underhood to the trunk, in order to achieve better weight distribution.
In doing this, they also routed a "double aught" (2/0 is the official name, IIRC) wire from the battery lug to a main jumper lug under the hood, that everything else moves from. They had to have done this for good reason, and it should be noted that from this lug under the hood, the starter gets a smaller (4 ga IIRC) line that is maybe a foot long.
Now, my anecdotal evidence is that more than once in sub freezing temperatures (25-28, however), I have left on my lights on. Now, the BMW turns off the headlights and just leaves the parking lights on, but they were on for two hours or so each time... this is on a battery that a year prior had experienced total discharge when the diode on my alternator went bad.
The car cranked and started just fine. I don't think that you should have an issue with your battery being too small or weak - do you know how much power the preluber takes? How much time between when it runs and when you crank? Sometimes a battery likes to recover a bit.
What size pipeline (connector wire between the battery and the starter or terminal lug under the hood) do you have? I know youre not keen on going there, but just humor me... is it a double aught? triple? single?
Thanks,
JMH
SOmetime in the life cycle of the E30 product line (a past model 3-series), BMW re-mounted the battery from underhood to the trunk, in order to achieve better weight distribution.
In doing this, they also routed a "double aught" (2/0 is the official name, IIRC) wire from the battery lug to a main jumper lug under the hood, that everything else moves from. They had to have done this for good reason, and it should be noted that from this lug under the hood, the starter gets a smaller (4 ga IIRC) line that is maybe a foot long.
Now, my anecdotal evidence is that more than once in sub freezing temperatures (25-28, however), I have left on my lights on. Now, the BMW turns off the headlights and just leaves the parking lights on, but they were on for two hours or so each time... this is on a battery that a year prior had experienced total discharge when the diode on my alternator went bad.
The car cranked and started just fine. I don't think that you should have an issue with your battery being too small or weak - do you know how much power the preluber takes? How much time between when it runs and when you crank? Sometimes a battery likes to recover a bit.
What size pipeline (connector wire between the battery and the starter or terminal lug under the hood) do you have? I know youre not keen on going there, but just humor me... is it a double aught? triple? single?
Thanks,
JMH
I guess if your on the ragged edge it might help. The solenoid doesn't use that much current.
You still need power for everything else: headlights, AC, CPU, RW defroster, windows, wipers, seats, sound system, etc, etc. Then you sometimes need to send much of the alternator current in the other direction to charge the battery. I still don't see it.
I could demonstrate it a thousand times easier than I can describe it. I drove my car with trunk mounted battery for years and all my electrical accessories worked fine. I'm building another now. Check out painlesswiring.com for diagrams.
It isn't about how much current thestarter solenoid draws. You have the battery in the trunk, now the dc power has the entire length of the car to travel, it goes through the key switch and the pull in wire. It draws a lot more than the slave solenoid I'm talking about. A Fluke meter probing a few key locations will uncover a ton of information.
Huh? What does the keyswitch have to do with it? If the battery current is brought to the front of the car with sufficiently little resistance then all the other wiring requirements are roughly the same.
While I won't dispute that a trunk mounted selonoid has it's advantages, it's not the only way it can be done and have it work effectively. After all, these are pretty basic DC circuits that once properly defined as far as requirements, can be put together without being a rocket scientist.
In any event, here a website calculator that will give some idea of AWG requirements:
http://www.powerstream.com/Wire_Size.htm (scroll down)
427Z06, You and I are on the same page but different paragraphs. I'm already assuming he has 2/0 wire. I'm also assuming his engine is worked to some degree, so the load on the starter is increased. The mod that I'm talking about came about when I used to assemble offshore speed boats. The batteries were 6-8 feet from the starter motors and the engines started MUCH easier when I set them up this way. The key switch absolutely comes into play here. If he's starting an ice cold engine with a battery that just took a hit operating the prelube pump, the amp draw through the switch will be increased. As I stated earlier, I drove a 440 Chrysler and later, a 493" engine every day. I never had cranking issues whatever the temperature. I wish I was computer savvy enough to post a diagram. It's painfully simple and everyone who sees it agrees it works flawlessly.
Sounds to me like you had it wired incorrectly if there was increased current through the key switch just because the battery was in the trunk.
Yes Yes. Absolutely. I had it wired wrong.
The old VW Beetles were notorious for having starting problems due to the starter solenoid receiving inadquate power. The wiring runs were too long and the wire was too small. Add a few years for corrosion, etc. and the solenoid wouldn't engage. The common fix was to add a small relay under the back seat that energized the starter solenoid. The new relay didn't require as much power to activate, problem solved.
Joe
In other words, it was wired incorrectly (inadequately) to begin with or the original wiring/connections were defective.
Sifan, I'm not going to continue to go back and forth here. If you're interested in what I'm saying, let me know and I'll give you my e mail address so I can send you a schematic. This isn't relaxing anymore.
Relaxing? Well it won't be for the guy that follows instructions to create a Rube Goldberg remote battery installation.
Ya know, I know you don't understand what I'm saying because it isn't complicated and you seem to be the only one that has a problem with it. What do you know about making anything yourself with a handle like that, anyway? Are we supposed to be impressed?
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