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Re: Debating moving battery to trunk , advantages?
[Re: 383man]
#1683440
10/09/14 02:24 AM
10/09/14 02:24 AM
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Joined: Jul 2006
Posts: 4,319
Puyallup, WA
StealthWedge67
master
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master
Joined: Jul 2006
Posts: 4,319
Puyallup, WA
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I moved my battery to the trunk a while back and I'm glad I did it. I like extra room and clean look under the hood, and it lends some weight to the "strip" side of the "street / strip" vibe I'm going for. I used 1g cable on the hot side, and 2g on the neg. side, with a heavy duty waterproof Summit rotary switch at the bumper just to the right of the license plate. I also used a Taylor vented stainless battery box so I'll never have issues at tech.
I don't know that I needed the weight transfer advantage in an 11-second car, but it does hook with no issues.
LemonWedge - Street heavy / Strip ready - 11.07 @ 120
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Re: Debating moving battery to trunk , advantages?
[Re: B3422W5]
#1683444
10/10/14 09:54 PM
10/10/14 09:54 PM
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Joined: Oct 2007
Posts: 4,206
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,206
New York
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The physics of moving the battery are more dramatic than they appear.
The front location is forward of the front axle, which means that the 70 lb. battery exerts more than 70 lbs. on the nose - by cantilevering, it removes weight from the rear axle.
The change to trunk mount is exactly the reverse: since the weight is behind the axle (and probably far more distant than the front location) it adds more than 70 lbs. to the rear axle weight since it removes weight from the nose.
The actual numbers can be had by measuring the distance from the center of the battery to the front axle, divided by the wheelbase, and multiplied by the battery (and tray) weight.
Example: if the battery center is 11" ahead of the axle and the wheelbase is 110", the ratio is 10%, so you get an extra 7 lbs. on the nose.
Do it the same way for the rear. The battery center is 20" behind the axle, the ratio is 18.2%, so the change includes:
1. the 70 lb. battery
2. the extra 7 lbs. on the nose
3. the extra 12.7 lbs. on the rear
totaling almost 90 lbs.
The rearward distance also helps prevent weight transfer slightly by increasing the polar moment - the leverage makes the tail end harder to rotate around the axle center.
Boffin Emeritus
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Re: Debating moving battery to trunk , advantages?
[Re: Leigh]
#1683445
10/10/14 10:55 PM
10/10/14 10:55 PM
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Joined: Jan 2003
Posts: 27,421
Balt. Md
383man
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,421
Balt. Md
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Quote:
Beautiful pic of your car, Ron.
Thank you.  Ron
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Re: Debating moving battery to trunk , advantages?
[Re: B3422W5]
#1683447
10/11/14 06:20 AM
10/11/14 06:20 AM
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Joined: Aug 2003
Posts: 3,245
Between a rock & a hard place
cudadoug
master
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master
Joined: Aug 2003
Posts: 3,245
Between a rock & a hard place
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Quote:
Quote:
I'd lose those 002/003 springs and have the Caltrac/spring deal going on. Yes, taller front tires will help and you'll gain rollout and thus a gain in ET.
About the battery? Here's what I'm going to do in my street/stripper rather than move it to the trunk:
http://performancedistributors.com/product/dyna-batt/
I am old school, my old car ran 9's on 002/003 leafs with a small tire and I could dial the car blindfolded. Not a big cal trac fan. At this current cars power level these leafs are well more than adequate( and I just put them on it) ....lol
Old school is cool, just making a suggestion. But...I can tell you that once upon a time I gained .07 in 60 by adding 2" lowering blocks to the same same springs and going to a 27" front tire from a 25" version.
I wasn't smart enough to know what I was doing ET wise. I just didn't want the John Deere look...
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Re: Debating moving battery to trunk , advantages?
[Re: polyspheric]
#1683448
10/11/14 01:21 PM
10/11/14 01:21 PM
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Joined: Dec 2003
Posts: 22,696
Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
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Quote:
The physics of moving the battery are more dramatic than they appear.
The front location is forward of the front axle, which means that the 70 lb. battery exerts more than 70 lbs. on the nose - by cantilevering, it removes weight from the rear axle.
The change to trunk mount is exactly the reverse: since the weight is behind the axle (and probably far more distant than the front location) it adds more than 70 lbs. to the rear axle weight since it removes weight from the nose.
The actual numbers can be had by measuring the distance from the center of the battery to the front axle, divided by the wheelbase, and multiplied by the battery (and tray) weight.
Example: if the battery center is 11" ahead of the axle and the wheelbase is 110", the ratio is 10%, so you get an extra 7 lbs. on the nose.
Do it the same way for the rear. The battery center is 20" behind the axle, the ratio is 18.2%, so the change includes:
1. the 70 lb. battery
2. the extra 7 lbs. on the nose
3. the extra 12.7 lbs. on the rear
totaling almost 90 lbs.
The rearward distance also helps prevent weight transfer slightly by increasing the polar moment - the leverage makes the tail end harder to rotate around the axle center.
Assuming your numbers/calcs are correct and they seem to be and I agree with the conclusions, there is another impact to consider besides just a straight line forces one might consider in moving a battery, a rear mounted battery can be mounted often lower, lowering the COG, and if any cornering/handling goals are desired, there are some benefits to be found having a battery in front of rear axle, closer to f/r COG regarding yaw forces. 
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Re: Debating moving battery to trunk , advantages?
[Re: jcc]
#1683449
10/11/14 02:31 PM
10/11/14 02:31 PM
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Joined: Oct 2008
Posts: 506
Utah, USA
1964superstock
mopar
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mopar
Joined: Oct 2008
Posts: 506
Utah, USA
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Quote:
Quote:
The physics of moving the battery are more dramatic than they appear.
The front location is forward of the front axle, which means that the 70 lb. battery exerts more than 70 lbs. on the nose - by cantilevering, it removes weight from the rear axle.
The change to trunk mount is exactly the reverse: since the weight is behind the axle (and probably far more distant than the front location) it adds more than 70 lbs. to the rear axle weight since it removes weight from the nose.
The actual numbers can be had by measuring the distance from the center of the battery to the front axle, divided by the wheelbase, and multiplied by the battery (and tray) weight.
Example: if the battery center is 11" ahead of the axle and the wheelbase is 110", the ratio is 10%, so you get an extra 7 lbs. on the nose.
Do it the same way for the rear. The battery center is 20" behind the axle, the ratio is 18.2%, so the change includes:
1. the 70 lb. battery
2. the extra 7 lbs. on the nose
3. the extra 12.7 lbs. on the rear
totaling almost 90 lbs.
The rearward distance also helps prevent weight transfer slightly by increasing the polar moment - the leverage makes the tail end harder to rotate around the axle center.
Assuming your numbers/calcs are correct and they seem to be and I agree with the conclusions, there is another impact to consider besides just a straight line forces one might consider in moving a battery, a rear mounted battery can be mounted often lower, lowering the COG, and if any cornering/handling goals are desired, there are some benefits to be found having a battery in front of rear axle, closer to f/r COG regarding yaw forces.
This all my be true, but if you do it the safest correct way to install a battery in the trunk, it is a ton of work and expensive. I just finished installing a battery in the trunk job, and will NEVER do it again. Unless you are building a drag only car looking for a slight gain in traction, or whatever, I would forget about it. Just install a lightweight battery up front. The actual performance gains with the battery in the trunk for a street/strip car are very little in my opinion, mostly for looks, but a huge PITA. My opinion since you asked.
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Re: Debating moving battery to trunk , advantages?
[Re: B3422W5]
#1683451
10/11/14 04:38 PM
10/11/14 04:38 PM
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Joined: Sep 2007
Posts: 1,890
Spahn Ranch
RMCHRGR
top fuel
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top fuel
Joined: Sep 2007
Posts: 1,890
Spahn Ranch
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Street/strip car here, my battery is in the trunk. Taylor 4 pole switch under the r/s bumper. Bought the car with it like this but completely rewired it after I went to an internally regulated Denso 60a alternator.
Went through a lot of jive to get it wired right with a cut off switch and alternator. Ended up using two solenoids, one for the long positive cable so it's 'only hot when cranking' and one continuous duty solenoid for the alternator so the switch turns it off. All my dash wiring goes through the disconnect too.
Ran my big B+ wire through the wiring trough on the driver's side and under the carpet. Goes through a grommet in the firewall and to the starter. I used a second relay up front to activate the starter with the ignition switch. Was a little complicated but it works.
I used a 'buss bar' from Mad Electrical on the firewall to tie things together that go from the front to the back. Works good and provides a spot for B+ when the system is on. Things like test equipment, timing light etc.
I have a couple #4 ground wires too, one bolted from the back of the r/s head that goes to the front sub frame and one from the battery to the rear chassis.
I have a few pics if needed.
'71 Duster
'17 Ram 1500
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Re: Debating moving battery to trunk , advantages?
[Re: RMCHRGR]
#1683452
10/11/14 05:14 PM
10/11/14 05:14 PM
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Joined: Mar 2009
Posts: 1,058
bigfork mn
dragram440
super stock
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super stock
Joined: Mar 2009
Posts: 1,058
bigfork mn
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I would do all those mods and not even think twice. The weight of the cable isnt that much and being towards the back doesnt hurt. I also wouldnt hesitate on the elctric water pump, There is nothing better in my opinion. They cool the car good and when you shut it off at the ice cream shop you dont have to get back in with 230 degree temps. As far as cal tracs I think people tend to use them on applications that dont really need them. My car makes pretty good torque and horspower and I just have a set of the xhd springs and a pinion snubber and it hooks on wet grass with 275 drag radials.
67' charger 499 RB
10.57 at 127
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Re: Debating moving battery to trunk , advantages?
[Re: forphorty]
#1683454
10/14/14 08:20 AM
10/14/14 08:20 AM
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Joined: Mar 2006
Posts: 9,835
MI, usa
dvw
master
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master
Joined: Mar 2006
Posts: 9,835
MI, usa
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Quote:
I would be interested in how much all that extra cable weighs.
My Optimas weigh 45lbs each. 0/2 copper, not 2/0 was used in my build, it weighed a total of 7lbs. Minus what ever the stock stuff was. Obviously mine is over twice as thick as factory stuff.
Doug
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Re: Debating moving battery to trunk , advantages?
[Re: jcc]
#1683455
10/14/14 08:56 AM
10/14/14 08:56 AM
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Joined: Jan 2003
Posts: 3,943
Melbourne.....Oz-land
Moparmal
master
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master
Joined: Jan 2003
Posts: 3,943
Melbourne.....Oz-land
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Quote:
Quote:
The physics of moving the battery are more dramatic than they appear.
The front location is forward of the front axle, which means that the 70 lb. battery exerts more than 70 lbs. on the nose - by cantilevering, it removes weight from the rear axle.
The change to trunk mount is exactly the reverse: since the weight is behind the axle (and probably far more distant than the front location) it adds more than 70 lbs. to the rear axle weight since it removes weight from the nose.
The actual numbers can be had by measuring the distance from the center of the battery to the front axle, divided by the wheelbase, and multiplied by the battery (and tray) weight.
Example: if the battery center is 11" ahead of the axle and the wheelbase is 110", the ratio is 10%, so you get an extra 7 lbs. on the nose.
Do it the same way for the rear. The battery center is 20" behind the axle, the ratio is 18.2%, so the change includes:
1. the 70 lb. battery
2. the extra 7 lbs. on the nose
3. the extra 12.7 lbs. on the rear
totaling almost 90 lbs.
The rearward distance also helps prevent weight transfer slightly by increasing the polar moment - the leverage makes the tail end harder to rotate around the axle center.
Assuming your numbers/calcs are correct and they seem to be and I agree with the conclusions, there is another impact to consider besides just a straight line forces one might consider in moving a battery, a rear mounted battery can be mounted often lower, lowering the COG, and if any cornering/handling goals are desired, there are some benefits to be found having a battery in front of rear axle, closer to f/r COG regarding yaw forces.
And of course its not just about fore/aft distribution or COG
Placing a heavy battery over or behind the right rear wheel adds ballast where it's most needed - because its the RIGHT side wheel that tries to " pick up" due to the inertial counterforce of the pinion against the crown wheel.
(Same reason a single spinner always breaks the right tyre loose....)
Placing it over the left rear wheel CAN cause more potential loss of traction due to the existing imbalance of downward force between the left and right wheels....but this is when the car is on the ragged edge of tractibility.....
Generally the battery re-location is one of many mods like a snubber, stiffer right side spring, spring clamps and rated shocks that go towards correct weight distribution and achieving separation which the Mopar leaf spring system was designed to do.
Bare in mind...a lot of these adjustments work because the super stockers ran serious overhang behind the wheel arch - a short assed car like our aussie Chargers usually needs some sort of traction bar or Caltrack.
Squatting is for chicks and Chebby owners 
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You can see the shut-off switch rod sticking out of the left rear taillite. To bad it could not be off when pushed in where it looks better but who ever saw a cut-off switch that says.......pull to cut-off ? 
Ron
