2nd battery install

I was just wondering how exactly you would go about installing a 2nd battery.

Is it safe to run two batteries off the stock alternator of the 92 SVX?

If so;
-should I connect the batteries in series or hook them both to the alternator in parallel?
-what gauge wire should be used?

In case you're wondering... I was planning on putting the 2nd in my trunk to power the stereo. I've been having electrical problems ever since I installed it. Lights dim, and the car doesnt get enough electricity to start unless I turn every appliance off first. I know i could get a capacitor, but I'd rather know how to install another battery.

[Earthworm]

The batteries should be hooked in parallel (+ to + and - to -).

You could also hook the 2nd battery (neg) to ground and your amps.

[lee]

the very best stereo site I know of is:

http://www.bcae1.com/

scroll down the side bar until you get to a section titled battery isolators (or something close to that anyway). It addresses running two batteries with & without isolation.

[UberRoo]

Hooking the batteries up in series would be pretty, ummm, interesting. I don't think your car would cope well with a 24-volt electrical system.


Before you worry about adding a second battery, it'd be best to figure out what's wrong with the one you have. Adding a second battery will not fix the problem. At best it will bandage things, but most likely it will just make troubleshooting the problem more difficult.

First, check your charging voltage. If it's not charging with at least 13 volts, figure out why. It should be just a smidge over 14 volts.

Second, have your battery tested to see if it's up to par. If it's questionable, replace it. A failing battery will not only give you a headache, it can (and eventually will) also damage your alternator.

Last; remove, clean or replace, and reinstall the major battery cables. This means the ground cable and the starter cable at the minimum.

A capacitor will only take the edge off of massive current draw. It can discharge very rapidly, but it's capacity is far too small to help with the starting of a motor. The only good reason I know to add a second battery is to extend the time you can run the stereo without recharging the battery(ies).



In regards to the first questions though, the negative terminal of the second battery needs to be connected to ground somewhere on the chassis. The positive terminal needs to be connected to the positive terminal of the primary battery or another major device, such as the positive terminal of the starter motor relay.

The wire you must use should be fairly large, probably 4 gauge, and unless the second battery is located right next to the first battery, the positive cable should have a fuse or circuit breaker at each end, probably at least 50 watts. (I use a 90 watt fuse.)

The stock SVX alternator can easily charge two batteries. The one proviso is that alternators are designed to keep the batteries topped off and to run the car's electrical system. They are not designed to "charge" batteries - only to keep them charged. What this means is that if you greatly discharge your batteries and then use the alternator to recharge them, this puts quite a strain on your alternator. It will not necessarily cause problems, but the alternator will wear out faster and could potentially wear out very fast. ...all depending on how heavily loaded it is of course.



I use two batteries because I frequently leave my car's computer running overnight. (This allows me to upload files and such.) When I do this, my car is a little weak to start the next morning, but turns over nonetheless. If I drive to work with the stereo thumping, headlights, heater, defrost, and heated mirrors on, it will still be weak to start even after the drive to work. If I reduce the load on the alternator by turning all that stuff off, the alternator will almost completely charge the batteries and it will start effortlessly after the drive to work. If I leave the computer running especially long, it may take two day's commute to fully recharge the batteries. I avoid doing this because it's hard on the alternator.

I should also mention that my batteries are deep-cycle batteries. I have a couple thousand watts of amplifier, yet one battery is adequate for them. It's the small, continuous draw that requires the auxiliary supply. I don't need more output, just the same amount for a longer period of time.

[Landshark]

UberRoo,
you might want to check out the Battery Tender device. its a small battery charger/maintainer that i used a lot for my for my 928 when it sat in the garage all winter. it has a small connector that you can permanently attach to you battery for quick hookups (also comes with alligator clips.) it won't overcharge the battery, because it will go into float mode once its charged. in your case, maybe once a week charging might keep your batteries in top shape.

[UberRoo]

Actually, I have a couple of them. Well, they're cheap knock-offs that only have float mode, but they've definitely been worth owning. I agree. They're cool.

I don't use them on the SVX because the drain is marginal (which is why I added the extra battery) and because I'm too lazy to drag out an extension cord to hook one up (which is another reason why I added the extra battery. ) I do keep one on another car and a couple more on some spare batteries in my garage.

What I'd like to have is an inductive coil on the bottom of my car and the other coil in a floor mat on my parking spot. That way I could just park without having to hook up any wires. I'd never turn off my electronics then.

[RojoRocket]

UberRoo,

....probably at least 50 watts. (I use a 90 watt fuse.)

That would be amps not watts. Yeah, I know, picky picky.

Glenn

[UberRoo]

Bah! Watts, amps, volts. What's the difference?!?!

Umm, yeah. Amps. Good call R. Rocket. My brain was elsewhere during that part. Electrical systems are picky, picky.

ya uberoo you were so right....

before i even got to try to do anything you suggested... I was driving around at like midnight, and all of a sudden my lights start to get real dim...

dimmer and dimmer and suddenly i realize that im gonna lose all power...

so i had to turn off everything to just keep the engine from stalling, including the heat and headlights...

so im driving around at midnight with no headlights trying desperately just to get to a gas station where i might find help...

and then the car stalls in the middle of a dark, yet busy intersection, and i have no way of lighting up my car to let any passerby know that im even there

I cant beleive that i didnt get hit.

I had to get the car towed, and there's no doubt that I need a new alternator...

[oab_au]

Originally posted by UberRoo
Bah! Watts, amps, volts. What's the difference?!?!

Umm, yeah. Amps. Good call R. Rocket. My brain was elsewhere during that part. Electrical systems are picky, picky.

Whats the difference? get it wrong, and you let the smoke out. then you have to get one, with the smoke still inside.

Harvey.

[96redsvx]

man i dont no much but what i do no is car audio first of all you need to get your second batery

dont conect the bateries together while your alternator will hold up under normal loads ad an 1800 watt amp drawing 160 amps of curent with is almost double what your alternator puts out there is know way your knew alternator will lats

you neeed to get a device caled a batery isolater(it reads voltage from each batery and handles each of them on an indavidual basis to protect your alternator from overloading itself)
it should have 3 post on it one for the power from the alternator and the other two go to the positive of each batery.
if you are going to upgrade the wire from the alternator then you will need a 90amp fuse and 4gauge wire will be fine and the same for each batery to prevent the wire from cathing on fire
*the second batery dosnt need to be conedted to chasis ground either*
the rest is simple common sense

u could also use a seleniod but not as fail safe and a more complex install

[UberRoo]

I've never used a battery isolator, but I suppose that's an option. Some of the nicer, more sophisticated [read: more expensive] models have some pretty cool features. Some have smart management circuitry to prevent overcharge, undercharge, and way to balance loading between batteries. Some have neat indicators to tell you what's going on.

Unless you massively discharge your battery(ies) on a routine basis, I don't think a battery isolator would do you much good except for those who just like collecting fancy toys, which I fully support.

Using a relay (solenoid) for isolation is fairly simple, but it has a problem. If one battery becomes discharged, and then is connected to the other battery (via the relay,) you will have a huge current flow between the two batteries through the relay. This causes at least two problems. The first is that such a large current flow will blow your fuses (which you really should have) and if you don't have fuses, it'll fry your wires and/or relay. (Ask "Sparky" about that one.) The second problem is that rapidly charging and discharging batteries is not good for them. Yes, that means jump-starting a car isn't really such a good idea, but you can get away with it for brief periods on the rare occasions when it's necessary. Did-ja ever notice the size of the wires on jumper cables?

Alternators are capable keeping quite a number of batteries charged. Recharging batteries on the other hand, will eventually make your alternator cry. Even bringing one small battery up from a complete discharge can kill an alternator.

One way to keep the alternator happy is to use a small gauge wire to connect the second battery. The high resistance keeps the second battery from overdrawing current from the alternator during a recharge. The downside is that it prevents the second battery from supplementing the first battery during high-draw situations such as starting, or when a large amplifier is trying to produces lots of bass. This design only gives you longer battery life, not more peak output. It works well in RVs.

Ummm... The second batery does need to be conedted to chasis ground. I no of know other way.