Hi. I recently put a second battery in my car for the first time. I have a battery isolator installed, but it seems like my voltage doesn't stay at higher levels for as long as it used to.
Before this install, my voltage was normally around 13.8, even with a/c on and stereo at low volumes. Now I am seeing it regularly get down to around 13... Does the isolator draw that much extra power, or is this just a coincidence? I am contemplating taking the isolator out, since I don't know if I really need it.
Basically, what are the pros and cons of having a battery isolator?
Thanx guys.
-Ian-
Replies (10)
ttocs on 08/12/2006 20:15:07
if you didn't upgrade your alternator, you are probably not helping your system at all. By adding a 2nd battery you SIGNIFICANTLY increase the load that the alt has to support.......
cybersailor420 on 08/12/2006 21:28:35
hmm... interesting point. so should i take the 2nd battery out until I can get a bigger alternator? by the way, this setup is only temporary for a DB drag sound competition. I thought it might help me have a little extra power for the 10 seconds i have to test. Let me know what you think. Thanx.
-Ian-
swez on 08/13/2006 08:53:42
A 2nd battery and the isolator are both considered loads to the alternator. The isolator polls the charging state of each BAT it feeds and directs the ALT charging path to the BAT & its load that demand the most power.
In a cold start, the ALT will go as high as the voltage regulator will allow it to, until the primary starter BAT is fully charged. In most cars, this voltage is 13.8-14.4 volts. This lasts for just a few minutes until the BAT is fully charged. Then, the regulator tell the ALT to revert back to normal charging rates of 13.0-13.5 volts.
Isolators also draw power as they work. Depending on the type used, (diode or relays), the voltage drop can range from 0.4 -0.6 volts with a diode type Isolator. Couple that with power wire resistance that feeds the 2nd BAT and this accounts for the 0.8 volts drop you are seeing.
Now, depending on the amplifiers used in this application, a voltage drop to a highly regulated power supply type amp, (like JL's Slash or PG's Xenon series) this voltage drop is not going to effect amplifier output very much. However, in loosely regulated (Most amps) or un-regulated power supplies, (DB Drag, high SPL amps) amp outputs are greatly affected by voltage supplied.
Read this:
http://www.bcae1.com/battiso.htm
Swez
cybersailor420 on 08/13/2006 10:46:12
Thank you Swez, that website helped alot. So I am definitely going to take out my isolator. My main question for you guys now, is should I leave in the second battery, with no isolator, just for the purpose of a DB drag? Or will it not help anymore than just having the one battery up front?
I am using Optima Yellow Top 750CCA batteries, as they are the only Optima battery that you can get in the Virgin Islands. Thanx again for your help.
-Ian-
swez on 08/13/2006 11:14:21
Hummm, not sure what the rules are for DB drags in the VI's. However, the goal here, is to get your amplifier voltage as close to the amps max usable voltage for input.
The Yellow Top is a fine Gel Cell BAT. These are great for warm weather climates, have strong storage capacities and are sealed against leaking fluids or hydrogen gasses into the vehicle. They are also Deep Cycle BAT's. This allows more than 350 deep discharge cycles before the BAT's even shows any signs of pooping out. GREAT PRODUCT!!!
You can run dual BAT's w/o an isolator as long as they are matched pairs. In this case, you are good to go. However, to get max transfer of power from the ALT to your BAT's, consider the "Big 3 Upgrade" and using 1/0 wire from the ALT output terminal, to your rear BAT.
Warning: Always fuse this line between the ALT and 2nd BAT. Here,
use a fuse that is matched to the max output of your ALT. This fuse protects the ALT and main BAT against overloads and excess current draw that can damage your main electrical systems. See that link I provided for fusing details. This shows 3 main fuses plus a fused D-block that feeds your amps.
FYI: To insure maximum power to each amp, consider running the sub amp ONLY, off the rear BAT. Any full range amp(s) can be powered off the Primary Starter BAT. This allows all the stored current in BAT #2, to power the sub amp(s) only.
Got all that?
Swez
PS If you need a diagram to get all this done properly, shoot me a private e-mail and I can make one up for you using Power Point.
swezdp@juno.com
cybersailor420 on 08/13/2006 12:30:21
Swez, excellent details and instructions, as usual! I already have the big 3 and fuses, all with 1/0 wire. i think i will take your advice and branch the full range amps off before the 2nd battery. hadn't even thought of that... I have run my power wires from the alternator through the stock fuse (100A) for the same reasons you mentioned. I guess this is about all I can do to maximize my power for now. A local guy is working on a better alternator for me, but it's so rare that people need high output alternators for a Suzuki... sucks for me :(
Thanx once again for all your help. I think that's it from me.
-Ian-
swez on 08/13/2006 14:19:08
Great! I hope this all works as planned and if you do get a H.O. ALT, ask if they can put a higher voltage regulator in that ALT. Hopefully, they can get you a solid 13.8 -14.0 volts as this will provide more voltage and less current demand from the ALT used.
This may depend on the ECM installed in your Vitara. Some computers, (ECM's) need a well regulated supply voltage and don't tolerate excess voltage well. Your ALT guy should know that info before he does anything over factory specs. US made cars can tolerate almost 15.0 volts w/o much trouble. However, since this is an import, not sure what the top limits might be.
Swez
PS Care to make a modest donation to CK? This puts you as a CK site sponsor and you get a Gold Star next to your name in posts. This is a free site to be sure, but we rely on readers to support the sites' funding needs. We don't use annoying pop up ads for that very reason!
Thanks in advance.
cybersailor420 on 08/13/2006 14:25:07
Donation made! Thanx again.
-Ian-
swez on 08/13/2006 14:31:58
And THANK YOU as well. Look for your Gold Star to pop up in a few days. Your name will also be added to the Sponsor's list.
A Class Act is one that asks great questions, heeds recommendations and supports CK w/o griping... SMILE
Best regards,
Swez
ttocs on 08/14/2006 07:38:29
hey look at that, thanks fer the donation mang!!!
welcome to the forum, stick around and you will be suprised what you can pick up, and some of it is usefull too!
Before this install, my voltage was normally around 13.8, even with a/c on and stereo at low volumes. Now I am seeing it regularly get down to around 13... Does the isolator draw that much extra power, or is this just a coincidence? I am contemplating taking the isolator out, since I don't know if I really need it.
Basically, what are the pros and cons of having a battery isolator?
Thanx guys.
-Ian-
Replies (10)
ttocs on 08/12/2006 20:15:07
if you didn't upgrade your alternator, you are probably not helping your system at all. By adding a 2nd battery you SIGNIFICANTLY increase the load that the alt has to support.......
cybersailor420 on 08/12/2006 21:28:35
hmm... interesting point. so should i take the 2nd battery out until I can get a bigger alternator? by the way, this setup is only temporary for a DB drag sound competition. I thought it might help me have a little extra power for the 10 seconds i have to test. Let me know what you think. Thanx.
-Ian-
swez on 08/13/2006 08:53:42
A 2nd battery and the isolator are both considered loads to the alternator. The isolator polls the charging state of each BAT it feeds and directs the ALT charging path to the BAT & its load that demand the most power.
In a cold start, the ALT will go as high as the voltage regulator will allow it to, until the primary starter BAT is fully charged. In most cars, this voltage is 13.8-14.4 volts. This lasts for just a few minutes until the BAT is fully charged. Then, the regulator tell the ALT to revert back to normal charging rates of 13.0-13.5 volts.
Isolators also draw power as they work. Depending on the type used, (diode or relays), the voltage drop can range from 0.4 -0.6 volts with a diode type Isolator. Couple that with power wire resistance that feeds the 2nd BAT and this accounts for the 0.8 volts drop you are seeing.
Now, depending on the amplifiers used in this application, a voltage drop to a highly regulated power supply type amp, (like JL's Slash or PG's Xenon series) this voltage drop is not going to effect amplifier output very much. However, in loosely regulated (Most amps) or un-regulated power supplies, (DB Drag, high SPL amps) amp outputs are greatly affected by voltage supplied.
Read this:
http://www.bcae1.com/battiso.htm
Swez
cybersailor420 on 08/13/2006 10:46:12
Thank you Swez, that website helped alot. So I am definitely going to take out my isolator. My main question for you guys now, is should I leave in the second battery, with no isolator, just for the purpose of a DB drag? Or will it not help anymore than just having the one battery up front?
I am using Optima Yellow Top 750CCA batteries, as they are the only Optima battery that you can get in the Virgin Islands. Thanx again for your help.
-Ian-
swez on 08/13/2006 11:14:21
Hummm, not sure what the rules are for DB drags in the VI's. However, the goal here, is to get your amplifier voltage as close to the amps max usable voltage for input.
The Yellow Top is a fine Gel Cell BAT. These are great for warm weather climates, have strong storage capacities and are sealed against leaking fluids or hydrogen gasses into the vehicle. They are also Deep Cycle BAT's. This allows more than 350 deep discharge cycles before the BAT's even shows any signs of pooping out. GREAT PRODUCT!!!
You can run dual BAT's w/o an isolator as long as they are matched pairs. In this case, you are good to go. However, to get max transfer of power from the ALT to your BAT's, consider the "Big 3 Upgrade" and using 1/0 wire from the ALT output terminal, to your rear BAT.
Warning: Always fuse this line between the ALT and 2nd BAT. Here,
use a fuse that is matched to the max output of your ALT. This fuse protects the ALT and main BAT against overloads and excess current draw that can damage your main electrical systems. See that link I provided for fusing details. This shows 3 main fuses plus a fused D-block that feeds your amps.
FYI: To insure maximum power to each amp, consider running the sub amp ONLY, off the rear BAT. Any full range amp(s) can be powered off the Primary Starter BAT. This allows all the stored current in BAT #2, to power the sub amp(s) only.
Got all that?
Swez
PS If you need a diagram to get all this done properly, shoot me a private e-mail and I can make one up for you using Power Point.
swezdp@juno.com
cybersailor420 on 08/13/2006 12:30:21
Swez, excellent details and instructions, as usual! I already have the big 3 and fuses, all with 1/0 wire. i think i will take your advice and branch the full range amps off before the 2nd battery. hadn't even thought of that... I have run my power wires from the alternator through the stock fuse (100A) for the same reasons you mentioned. I guess this is about all I can do to maximize my power for now. A local guy is working on a better alternator for me, but it's so rare that people need high output alternators for a Suzuki... sucks for me :(
Thanx once again for all your help. I think that's it from me.
-Ian-
swez on 08/13/2006 14:19:08
Great! I hope this all works as planned and if you do get a H.O. ALT, ask if they can put a higher voltage regulator in that ALT. Hopefully, they can get you a solid 13.8 -14.0 volts as this will provide more voltage and less current demand from the ALT used.
This may depend on the ECM installed in your Vitara. Some computers, (ECM's) need a well regulated supply voltage and don't tolerate excess voltage well. Your ALT guy should know that info before he does anything over factory specs. US made cars can tolerate almost 15.0 volts w/o much trouble. However, since this is an import, not sure what the top limits might be.
Swez
PS Care to make a modest donation to CK? This puts you as a CK site sponsor and you get a Gold Star next to your name in posts. This is a free site to be sure, but we rely on readers to support the sites' funding needs. We don't use annoying pop up ads for that very reason!
Thanks in advance.
cybersailor420 on 08/13/2006 14:25:07
Donation made! Thanx again.
-Ian-
swez on 08/13/2006 14:31:58
And THANK YOU as well. Look for your Gold Star to pop up in a few days. Your name will also be added to the Sponsor's list.
A Class Act is one that asks great questions, heeds recommendations and supports CK w/o griping... SMILE
Best regards,
Swez
ttocs on 08/14/2006 07:38:29
hey look at that, thanks fer the donation mang!!!
welcome to the forum, stick around and you will be suprised what you can pick up, and some of it is usefull too!
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