Second Battery Questions

[Frostedflakejake 148]

So i bought a Shuriken bt-120 and i just have a few basic hook up questions. I have the 0 gauge and the HO alternator ready.

so should i just replace my starter battery with the shuriken? if not, how do i hook up the two? and if i do stick the shuriken in the back, i need a battery isolater correct???

thanks

[altoncustomtech 773]

I didn't use an isolator in the van. As long as all the batteries are the same type and you're starting it, driving and charging the vehicle on a regular basis most people don't have problems simply running the batteries in parallel. So if it's your daily driver then you shouldn't have any issues.

Perhaps some of these guys with more experience running miltiple batteries can elaborate some more though, as my experience thus far is limited in this area.

Edited February 6, 2010 by Alton

[jcarter1885 995]

There are two ways I would do it, first I would install it in the main battery location if it can fit and then monitor your voltage. If your voltage is fine during full tilt then you wont have to worry about two batteries. If your voltage drops then put the stock battery back in and run the Shuriken in parallel, positive of starting battery to positive on shuriken battery, negative of shuriken battery to cars frame.

An isolator is not needed unless your playing with your system with the car off a lot.

[emh9009 199]

running in parallel like that, should a run on 0 gauge be run from the front battery to the rear? or would grounding both to the frame work well enough?

[jcarter1885 995]

I would just ground each individually to the frame unless you want to run a wire from the front of the car to the back just for a ground wire, either way would work fine.

[Dammed 12]

If you want to keep the starting battery in the front and use the Shuriken in the back then you should use a isolator since the resting voltage is much lower on your starter battery. What will happen is that Shuriken battery in the back will start charging the starting battery until it's discharged to the resting voltage of the starter battery when your car is off. Now this will be a problem in the long run, since AGM batteries don't like resting at a low voltage.

If you replace your starting battery with the Shuriken BT-120 you bought, then I think you'll get a bit low voltage at the amplifiers int he back. And you will loose some AH since you're not using the battery in the front.

The best thing you can do is to buy another Shuriken battery to replace the one in the front and use the BT-120 in the back close to the amplifiers. This way your ESR will be about the same and the batteries will not charge each other (to some extent). You will get a higher Ah rating in the system, and your voltage at the amplifiers will be higher.

[Frostedflakejake 148]

The best thing you can do is to buy another Shuriken battery to replace the one in the front and use the BT-120 in the back close to the amplifiers

Yeah i figured this was the case since on most of the build logs on here people always buy one big battery then a smaller one of the same company. So if i were to buy another shuriken, what would i have to look for? could i just go and buy the smallest one? or should i get one closest to the bt-120? (if thats the case i'm just going to stick the stick the bt-120 under the hood for now because i can't afford to drop another couple hundred dollars. not after valentines day, ha)

thanks! all great advice!

[Dammed 12]

If you have very little money, buy the smallest one.

if you have a ok amount of money, buy a battery with the same ore more AH rating as the starting battery you are using now.

if you want the best, buy the biggest battery you have room for under the hood.

[Julian 641]

i never used an isolator. As Jay-Cee said if you're regularly driving your vehicle and it isn't sitting around for insane amounts of time. You should be ok i had 140+AH in my trunk and i could always start.

[shizzzon 461]

this is what i do, it's cheap and effective-

Isolators cause a voltage drop for one so scrap that idea.

Solenoids(big ass relays) is what you would want.

www.oznium.com sells them for cheap cheap. Go to teh relay section and get you a 200A relay.

This is how it works-

For one, solenoids don't cause voltage drop so that's good.

When the car is off, the batteries are "isolated".

When in ignition mode(or started), the batteries are joined together.

They cant fight each other because the alternator has the higher voltage level and will disperse charge to anything that needs it.

Once car is off, they become "isolated" again.

Now, if you replace ur front batt with a shuriken then u wouldnt need this but these things are a lot cheaper than a battery.

I have used my stock battery for 3.5 years now and out of that, 1 of those years i've got over 10,000w of power in the car with xs power batts in the back separated with a solenoid.

My stock batt nor my xs power batts have ever had problems and won't unless the solenoid dies... if that happens, the alt can't charge the back batts but that's what a voltmeter is for too.

[Frostedflakejake 148]

thank-you shizzon =]

you're a huge help

[Kanaworm$ 292]

this is what i do, it's cheap and effective-

Isolators cause a voltage drop for one so scrap that idea.

Solenoids(big ass relays) is what you would want.

www.oznium.com sells them for cheap cheap. Go to teh relay section and get you a 200A relay.

This is how it works-

For one, solenoids don't cause voltage drop so that's good.

When the car is off, the batteries are "isolated".

When in ignition mode(or started), the batteries are joined together.

They cant fight each other because the alternator has the higher voltage level and will disperse charge to anything that needs it.

Once car is off, they become "isolated" again.

Now, if you replace ur front batt with a shuriken then u wouldnt need this but these things are a lot cheaper than a battery.

I have used my stock battery for 3.5 years now and out of that, 1 of those years i've got over 10,000w of power in the car with xs power batts in the back separated with a solenoid.

My stock batt nor my xs power batts have ever had problems and won't unless the solenoid dies... if that happens, the alt can't charge the back batts but that's what a voltmeter is for too.

Good real world results! Very helpful, thanks!

[Frostedflakejake 148]

okay. so i'm not doubting Shizzon or anyone on here, i'm sure he is right. Along with Dammed and Jay-Cee

but here is my question.

So the alternator monitors the batteries right? and sends out the appropriate current to charge them right? and this works flawlessly in a stock system because your starter (and only) battery runs low and the alternator sends out current to charge it. So when you hook up two batteries, the big one in back, and when a heavy bass moment requires lots of power from your after market battery, the alternator sees that it needs to send a lot of current to that second battery right? Well, as my car is and as any car is without some modding, the alternator will send out the current necessary to re-charge the monster after-market battery but it will charge the starter battery with the same amount of current. and of course that starter battery can't take that much current and it will boil over.

so, that's my trouble. I'll let you know that this isn't my question. For better or for worse i completely trust Shizzon and would do what he says, however, i'm only 17 and although my vehicle and everything in the system is mine, it still has to be approved father. And if you guys know Mechanical Engineers you probably noticed that most of them are stubborn as hell and even when facing something they don't know a whole lot about, they are always "right". Its very frustrating. If anyone can give me a good answer it would be greatly appreciated. I've been working towards my system since August and i finally have everything i need, just this one issue is slowing the install process. Thanks!!

[Don Ganso 13]

Yeah dude, my dad's like that too...

[jcarter1885 995]

Well you can talk to a lot of guys on here as they have been doing it for years with no problem, not sure on the theory your stating above but I do understand the father thing. You could also call Kinetik, XS Power or other battery companies and ask them to explain it better to you to see if it is a real danger. I would just buy a battery charger to relieve all worries so you can charge the secondary battery every now and then to take some work off your alternator. Just my .02 but I personally dont think it will be a problem but when you find out share with me so I will know for the future.

[Dammed 12]

Tell your father this, if he's a mechanical engineer he should feel a little bit embarrassed by stating that question. No hard feelings. I'm also studying to be one actually.

When your bass starts hitting really hard the amplifiers in the back will take power from the battery in the back, the alternator does not see this at the moment. Your front battery starts to charge the battery in the back becuase the battery in the back has a lower voltage since it's discharged. The alternator sees this and starts charging the front battery. This happens in a fracture of a second.

Since the cables on the front battery are contacted to the top, the electricity can flow around the front battery, in a way it will almost bypass the front battery and it will charge the battery in the back. Meaning after the first discharge of the back battery, the alternator will charge it almost directly.

You can compare electricity to water. The batteries are buckets and the wires are pipes, the alternator is a pump.

When you take out some water in the back "bucket" the water pressure gets lower here, the front "bucket" will then send some water back in an atempt to equalize the water pressure, the pump will then notice the loss in water pressure and starts pumping more water into the system.

This is really simplified, but in a way it's how it works.

And no you will not destroy your front battery, but you will over time (very long time) damage it if it's a normal OEM battery, becuase those can't handle the abuse of the car stereo. That's why I recommend you to buy a Shuriken front battery since this is meant for daily car stereo abuse.

edit: And if he does not believe the "punk ass teen" on the forum, ask him to ask a car electrician. They will probably say this: Your car stereo system will use more power then the alternator can replace, this may damage the alternator over time becuase it runs at 100% almost all the time, but your alternator will not damage your front battery. This is a fact, that's why people buy HO alternators so that the alternator can charge the batteries back up. For you the cheapest way to solve this is to buy a good INTELLIGENT battery charger that can charge AGM batteries, and then you plug the charger in to charge your batteries when your car is off. Maybe you don't need to do this, but it is advised.

Edited February 16, 2010 by Dammed

[Frostedflakejake 148]

For you the cheapest way to solve this is to buy a good INTELLIGENT battery charger that can charge AGM batteries, and then you plug the charger in to charge your batteries when your car is off. Maybe you don't need to do this, but it is advised.

woah woah woah, even if i have a 260 amp alternator, i should still do what you stated above? sorry i'm just not sure if you're aware of my alternator or not.

and thanks a bunch, i'll run it by him and despite his "opinion" i'm going to hook it up anyways. See his motto is that everything i'm doing just isn't necessary. and i'm like... well yeah, but its fun

[Dammed 12]

mm have heard that one before. My father says normally, why do you do this, can't you hear the music, doesn't your factory speakers work?....

Sorry I didn't notice you had a HO alternator... To be honest you should get one, since a HO alternator cannot fully charge your batteries. I have a 180A (biggest that fits my car) alternator and I bought myself a Ctek XS 25000, it can handle batteries up to 500Ah and it charges with a 25A current, it's a really good charger.

Np mate, good choice, a electrical system is the foundation of a car stereo. Nobody likes a foundation with cracks in it.

[shizzzon 461]

there is one thing i disagree with and that's when the rear battery(ies) discharge power to the amps the front battery will try n charge the rear and then the alt will charge the front in a fraction of a second...

that's wrong.

Whoever has the highest voltage level is in control so let's start with that first-

The alternator supplies power to the stereo all the time. that's why when a user is jamming, his voltage still remains above the battery's rest voltage.

Now, let's say a quick bass note happened and the voltage regulator couldnt respond quick enough. the rear battery would compensate for the drag and the alternator will still continue to power the car stereo and immediately give the rear battery a small charge back. The front battery has VERY little to do with the stereo system.

I tested that one time wanting to know how much current the front battery sends to the back when the car is off.

I had a consistent 235A current draw when the car was off from 2 amps so i clamped the link cable that combines the front and rear battery bank...

the front battery only dispersed about 23A of current to the back... that's nothing.

The amps will get power from the point(s) of least resistance first.

The batteries closest to the amps will get worked more than the front battery will.

That's why when using mult batts, buss bars are nice to have. You can attach amp power points on the bars in between batteries so you can attempt to evenly distribute battery drain.

Understanding when an alt is stressing is good to know too.

The lower your voltage is when driving, the more the alt is being worked.

If you have a low or no aftermarket load on the alt and it's still sagging some on the voltage, it's because it's hot.

If the alt typically runs around 15v and it's running around 14v flat with low load... let it cool down!

I don't know what a threshold is from one alt to another but heat kills alts.

[Dammed 12]

hmm, I think you misunderstood me mate. I meant that front battery will charge the rear in only a fraction of the second, before the alt/alts notice the current draw from the rear. After that the alternator will increase it's current supply. Current and voltage ain't the same thing, so the volt should be able to stay stable with a little variation as long as the current drawn from the amplifiers is lower then the current supply from the alternator.

How do you let it cool down, you stop pushing the amplifiers right?

[shizzzon 461]

yea u let it cool down by removing the load.

I dont think that information should be posted because i don't see how it could be proven that the front battery could ever attempt to charge the back bank for a split second.

Even if it could be proven, it's so fast, the information is irrelevant for safe practices.

[Dammed 12]

Ahh ok, do you have like a temp feeler mounted on the alternator or do you just stop pushing the amplifiers after certain amount of time?

yeah I know it's pointless information if you view it from a practical point of view, that's why i wrote: "This happens in a fracture of a second."

[Frostedflakejake 148]

"if the two batteries are connected and the alternator has to send a big load of current to the back battery, it will go through the front battery. and the front battery is not made to hold that kind of current."

his thought is two voltage regulators. one for each battery.

thoughts? comments? he just thinks the high current required by my shuriken in the back will also be going through/to the starter battery. and that amount of current will be too much for starter.

i apologize if this is frustrating for "dammed" and "shizzon" and anyone else who has made a good response. But understand how frustrating it is for me. working to get my setup and six months later i have everything and already installed some wires only to have the vehicle "owner" say "no".

[shizzzon 461]

tell him devices only receive current when they need it. just because cuttrrent runs over something doesnt mean it receives it too

[viper167 1]

this is all a lot of good info. its good to know.

learn something new everyday