Dual battery system
02-15-02, 07:04 PM
#1
Senior Member
Thread Starter
Join Date: Oct 2001
Location: Chicago area
Posts: 690
Likes: 0
Received 0 Likes
on
0 Posts
Dual battery system
Keeping one battery in the engine compartment, I also have a deep cycle one in my trunk. I want to link the two together so the rear one can also be charged by an alternator instead of my solar cell. Do I do this in a parallel or series setup? And should I use four gauge cable? Any recomendations for a pair (negative and positive) of four gauge wiring through the cabin?
Also/or: Any suggestions for an auxiliary power system?
Also/or: Any suggestions for an auxiliary power system?
02-15-02, 07:26 PM
#2
They would have to be in parallel, if they were in series it would be a 24 volt power system and then kaboom for your electronics most likely. What is the reasoning behind all this btw? And I don't know if the alternator and voltage regulator are up to this task...
02-15-02, 08:12 PM
#3
Lives on the Forum
It's gotta be in parallel.  The length of the install means it really needs some 2-gauge wire; 4-gauge is barely adequate for the 10 foot length you're going to need.
-Ted
-Ted
02-16-02, 12:52 AM
#4
Senior Member
Thread Starter
Join Date: Oct 2001
Location: Chicago area
Posts: 690
Likes: 0
Received 0 Likes
on
0 Posts
2 gauge, thanks. That's what I figured.
The deep cycle powers my lighting, high wattage stereo, screens, and etc. I'm looking for an FD 150 amp alternator. The deep cycle charges itself, also, but not very fast. And it has a solar cell.
The deep cycle powers my lighting, high wattage stereo, screens, and etc. I'm looking for an FD 150 amp alternator. The deep cycle charges itself, also, but not very fast. And it has a solar cell.
02-16-02, 02:12 AM
#6
Rotary Enthusiast
well technically doesn't matter how many batteries you have, if your alternator is say 70amp, it will be 70 amp while the car is on with 1 battery or with 10batteries. So the higher the current on the alternator, the better. Couple of batteries will be able to run your electronics longer if your engine is turned off.
Trending Topics
02-16-02, 10:11 AM
#8
Lives on the Forum
Originally posted by Gene
The batteries also act as a cushion, so to speak, if a very big hit on the subwoofers demands more current than the alternator is up to delivering.
The batteries also act as a cushion, so to speak, if a very big hit on the subwoofers demands more current than the alternator is up to delivering.
-Ted
02-16-02, 05:33 PM
#9
Passenger
Posts: n/a
NO NO NO!!!!
DON'T wire two different kinds of batteries in parallel. If anything, use a dual battery isolator. Either way, you are INCREASING the load on the alternator-- especially with the deep cycle.
I relocated my battery (yellow top Optima) to the compartment behind the passenger seat, and installed a cut-off switch, followed by an 150 amp fuse. I then discovered something interesting. After I start the car, I can cut-off the battery from the electrical system, and run off the alternator only. The voltage is HIGHER by about .3 volts with the battery disconnected. So, adding a second battery will definately lower your operating voltage, and will shorten the life of your alternator. Your sound system will probably sound worse overall, even though it may be unnoticeable. To take care of any peak power demands, capacitors are the only way to go. If you have a really high powered sound system, you should consider one of those monstrous cap modules such as the ones offered by Audiobahn.
PJHrad
DON'T wire two different kinds of batteries in parallel. If anything, use a dual battery isolator. Either way, you are INCREASING the load on the alternator-- especially with the deep cycle.
I relocated my battery (yellow top Optima) to the compartment behind the passenger seat, and installed a cut-off switch, followed by an 150 amp fuse. I then discovered something interesting. After I start the car, I can cut-off the battery from the electrical system, and run off the alternator only. The voltage is HIGHER by about .3 volts with the battery disconnected. So, adding a second battery will definately lower your operating voltage, and will shorten the life of your alternator. Your sound system will probably sound worse overall, even though it may be unnoticeable. To take care of any peak power demands, capacitors are the only way to go. If you have a really high powered sound system, you should consider one of those monstrous cap modules such as the ones offered by Audiobahn.
PJHrad
02-16-02, 07:13 PM
#12
Senior Member
Thread Starter
Join Date: Oct 2001
Location: Chicago area
Posts: 690
Likes: 0
Received 0 Likes
on
0 Posts
Oh yeah, one other thing. About the batteries being different--my other battery is an Optima red top starter. Think that will help things a bit? I know I'm increasing my load on the alternator, just don't really know how. Either way, I'm looking for a new high output alternator. 100 amp should be fine, I think. Please elaborate on a battery isolator, what is that?
02-17-02, 10:15 PM
#13
Passenger
Posts: n/a
If the batteries are different at all, you're not supposed to hook them up in straight parallel configuration. The absolute, safest way of hooking up two batteries so that they both stay charged is with a dual battery isolator. There are isolators with different current capacities. You can find an appropriate isolator at Autozone or Batteries Plus. Essentially, they are just electrical devices that distribute the charge to the battery that needs it the most-- keeping both charged.
I really don't have a technical explanation, but I know that it's the only safe way to hook up two batteries in a car with one alternator.
PJ
I really don't have a technical explanation, but I know that it's the only safe way to hook up two batteries in a car with one alternator.
PJ
02-18-02, 02:42 AM
#14
Lives on the Forum
Actually, I prefer a switching solenoid to connect the two batteries in parallel.  Battery isolators work, but there's a voltage drop (sometimes up to 2.0V!) over the battery isolator itself due to it's inherent design; a switching solenoid has almost zero voltage drop.  The switching solenoid would connect only when cranking/running but would disconnect when the ignition is off, preventing unwanted drain on the back-up battery.
-Ted
-Ted
02-18-02, 12:13 PM
#15
Passenger
Posts: n/a
How does it charge? I've heard of dual battery relays, but every time you switch in the second battery, you damage both-- decreasing the life of the batteries. The battery isolators do waste a lot of energy in the form of heat, though. Solenoids sound like a neat concept, but if it is only momentary, I don't see how they'd allow the backup to charge. I'm guessing this would be good if you have the battery for just that purpose: backup. But for a sound system, I've always prefered to have only ONE battery near the amps with as short of length of power cable as possible + a capacitor (size depending on demands). The reason I'm skeptical of dual batts is because I've blown 6 (SIX!) 130 amp alternators in my Thunderbird with my system. And seeing that a second battery increases the charging load, I never considered it a good idea unless you have a GREAT alternator.
BTW, what is the stock amperage for a '86 alt?
PJ
BTW, what is the stock amperage for a '86 alt?
PJ
02-18-02, 01:01 PM
#16
Senior Member
Join Date: Jul 2001
Location: Northern California
Posts: 595
Likes: 0
Received 0 Likes
on
0 Posts
OK here is some interesting information i found out regarding capicitors from the Phoniex Gold rep.
They did some testing on caps and found out that if the cap isnt within about a 10" cable run to your sub amp, its pretty much worthless. Caps farther away than that dont discharge energy fast enough to make the difference when your base hits. My local shop is changing how they install all their caps in cars now, putting them as close as possible to the subwoofer amplifier. Just though everyone might be interested in knowing that. Im going to rewire my caps soon, they are currently 24 inches away from my sub amp, and by what Phoenix Golds rep told me, that aint going to do **** for my system.
Graham
They did some testing on caps and found out that if the cap isnt within about a 10" cable run to your sub amp, its pretty much worthless. Caps farther away than that dont discharge energy fast enough to make the difference when your base hits. My local shop is changing how they install all their caps in cars now, putting them as close as possible to the subwoofer amplifier. Just though everyone might be interested in knowing that. Im going to rewire my caps soon, they are currently 24 inches away from my sub amp, and by what Phoenix Golds rep told me, that aint going to do **** for my system.
Graham
02-18-02, 01:12 PM
#17
Full Member
Join Date: Sep 2001
Location: Victoria B.C. Canada
Posts: 126
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by pjhrad
The voltage is HIGHER by about .3 volts with the battery disconnected.
PJHrad
The voltage is HIGHER by about .3 volts with the battery disconnected.
PJHrad
02-18-02, 01:20 PM
#18
Round&Round not Up&Down
Join Date: Aug 2001
Location: West Bloomfield, MI
Posts: 2,805
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by pjhrad
I've blown 6 (SIX!) 130 amp alternators in my Thunderbird with my system.
PJ
I've blown 6 (SIX!) 130 amp alternators in my Thunderbird with my system.
PJ
02-18-02, 03:19 PM
#19
Passenger
Posts: n/a
Originally posted by Mazdarules
This is because the alternator is charging the battery.
This is because the alternator is charging the battery.
Jimmy, yeah.. there was something wrong. Runnin 1800 watt amps on refurbished duralast alts. Lol. Yeah, I'd love to have a powermaster or wrangler in my T-Bird, but once I got the Duralast from Autozone, I had unconditional warranties... So, I figured, might as well spend the free alternators, and when I'm rich (yeah, right) I'll buy myself a good alt. Also, I DID buy a custom-wound alt once. That was the worst experience of my automotive life. It was a shoddy build, the bearings failed twice, and the whole thing rattled.
Powermaster or Wrangler is the way to go (at least for domestics). Something else that is strange... the alt that's in the Rex right now was rebuilt by Red Dog Alternators in Tucson, AZ... But I have no idea about what's been done to it (done by first owner). It could be custom-wound for all I know.
PJHrad
02-18-02, 03:37 PM
#21
Round&Round not Up&Down
Join Date: Aug 2001
Location: West Bloomfield, MI
Posts: 2,805
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by pjhrad
REALLY?!?!? My point exactly. A second batt will drain even more.
Jimmy, yeah.. there was something wrong. Runnin 1800 watt amps on refurbished duralast alts. Lol.
REALLY?!?!? My point exactly. A second batt will drain even more.
Jimmy, yeah.. there was something wrong. Runnin 1800 watt amps on refurbished duralast alts. Lol.
Yeah, I'd love to have a powermaster or wrangler in my T-Bird, but once I got the Duralast from Autozone, I had unconditional warranties... So, I figured, might as well spend the free alternators, and when I'm rich (yeah, right) I'll buy myself a good alt. Also, I DID buy a custom-wound alt once. That was the worst experience of my automotive life. It was a shoddy build, the bearings failed twice, and the whole thing rattled.
Powermaster or Wrangler is the way to go (at least for domestics). Something else that is strange... the alt that's in the Rex right now was rebuilt by Red Dog Alternators in Tucson, AZ... But I have no idea about what's been done to it (done by first owner). It could be custom-wound for all I know.
PJHrad
02-18-02, 09:00 PM
#22
Passenger
Posts: n/a
Sonicrat... Do you mean a set-up of the sound system or my battery relocation? I've got some old pics of my sound setup... Doesn't show much. Let me see if I can find it. Honestly, the 1800 watt# is ballpark peak power. RMS I'm probably only around 800. I don't have a digital anymore, so getting any other pics up would be difficult. :/
PJHrad
PJHrad
02-18-02, 09:03 PM
#23
Lives on the Forum
Originally posted by pjhrad
but once I got the Duralast from Autozone, I had unconditional warranties...
but once I got the Duralast from Autozone, I had unconditional warranties...
PAC used to make 100A to 200A battery switching solenoids.  If your alternator cannot handle charging a pair of batteries, something is wrong - every measured the internal resistance on an automotive battery?  It's only a few ohms.  With any dual-battery system, it is always recommended to change BOTH of the at the same time; this gives you pretty similar internal resistance rates as to not cause weird draining and charging problems due to widely differing internal resistances...
-Ted
02-18-02, 09:10 PM
#24
Passenger
Posts: n/a
Here is a pic of my crude setup (the whole car is undergoing reconstruction). I'm not particularly proud of it, but it pounded hard enough... I built the box. It's a bandpass/horn design with two 600wrms 10" Audiobahns (hit harder than my 3-10" sealed box).