Adding a Second battery

Discussion in 'Automotive Electrical' started by TheViking, Nov 19, 2006.

  1. TheViking

    TheViking Well-Known Member

    Wel, Its time for another topic in this section......

    The addition of a second battery to your adio system.

    First, WHY would you need to install a second battery?????

    Welp, pretty simple really, It gives your amp the added capacity to produce its short term peaks, and allows for longer play times at reduced alternator output levels. (and if you do it right, you can jump start your car without ever leaving the cabin, or having another car, ask me later!!! )

    Lets start at the fornt of the car. You have your existing electrical sytem already upgraded and performing to its max by upgrading the big 3?/? Right??? Do this first before you go any further here!!!!!

    Now, what does it take to do a second battery? Just a few things, most of you are familiar with, and one you may not be. First find a location in the back of your vehicle to mount the battery. I suggest an enclosed type marine battery holder, they can be had for around 15 bucks and they contain the battery and prevent any spils into the interior. Find a location that allow for relatively easy access and servicability. Once you have your spot staked out, lets move on to the wire. the wire for this battery to maintain a charge does NOT have to be HUGE....4 AWG is more than adequate and will transfer all the power that is reguired of your amp and keeping the battery charged.... The Wire itself, that runs from the front of your car to the rear will need TWO fuses, each within 18 inches of each battery. One at the front, and one at the rear battery. These fuses prevent the wire from gong into thermal overload (BURN) if it ever get shorted out!!!!!! Use ANL type fuses, NOTHING ELSE!!!! The ANL type fuses handle the curent properly and are 100% reliable. Any other type of fuse holder is second rate at best.....PERIOD. 100 amp fuses will do just fine in most applications. but no bigger than 200 amp....

    Now, the next thing on the list is VERY important. A relay. A BIG relay. This is critical in allowing 2 batteries to co-exist in the same car without literally killing each other. If you put in 2 different batterys, of different size, CCA,age,reserve power, health, etc, you WILL kill them!!!!!!!!! BOTH of them!! What you want to do is allow both batteries to work in unison with each other to power up your amps, and still get a charge from the alternator, AND not let them die from setting hooked up together when NO charge current is available (when you shut the car off an let it set for 2 weeks when your off on a vacation nailing your best freinds sister when he is drunk passed out on the floor)........

    the KEY to allowing both batteies to live with one another is to install a RELAY. The relay serves a simple purpose in life. It allows both batts. to be connected in parallel when the car is running and the aternator is charging, and allows the amps to pull current from both batteries. It also DISCONNECTS both batteies when the car is off and the alternator is NOT charging, thereby preventing the batteris form killing each other. With this method, you can use ANY 2 batteries......Its simple, and it WORKS

    The realy i am reffering to is a 200 amp unit.

    This one has been around for years and is fairly reliable ( seen a few failures)

    The relay can be mounted in front under the hood, or in back , does not matter, it is simply an electro mechanical switch, it dont care where its at. Just BE SURE it is mounted properly and securely, those 2 big terminals on top have ALOT of current to kick out if the thing shorts out and will blow the 2 fuses!!!!! From the front battery go to one side of the relay, from the back battery, go to the other one, simple. Now, one of the smaller terminals needs to go to a good ground, the OTHER small terminal needs to go to a switched power source. A few options on this one. i always hooked it up to a source of ignition voltage that was not LIVE when the car was being started. But was live when the car is running. Radio ignition lead would work fine, Be sure to fuse this lead also..(2 amp fuse)

    You COULD hook this lead up to a voltage source that is HOT while cranking the engine over, but I DONT reccomend it (hard on the relay).

    Oh yes, the ground for the secong battery, same rules apply, all paint cleaned off to shiny metal and a BOLT holding it down....NOT a seat bolt, NOT a seat belt bolt, and NOT a factory ground!!!!!!!!!!!!!!! If your gunna do this, do it RIGHT!!!!!!!

    Now, everything is installed, all hooked up and ready to go. when you turn on the cars iginition you should hear a "click" from the realy. GOOD!!!! when you shut off the car you should hear another "click" from the realy....GOOD!!! iIt is turning off and on as it should!

    Now start the car and measure battery voltage at EACH battery, they should be near IDENTICAL!!!! IIf not, you have issues!!!

    You are DONE!!!!!!!!!! You now are able to allow your amps to run off 2 batterys and yet allow neither nattery to kill the other!!!!!!

    The ONLY way other than this to hook up 2 batterys is to install 2 new batteies, BOTH of the same size and age.......THEN you could not worry about the installation of the realy....If you put in a new fangled yellow top. red tp. blue and green top, or even a carrot top with your existing battery without a relay, then you ae asking for problems....

    As always, i open this up to LOGICAL and REASONABLE discussion/questions....

    Thanks for listening folks, i am here to help you get the most out of your car audio!!!!!
  2. aznboi3644

    aznboi3644 Full Member

    Thanks Viking...exactly what I needed...also to clear it up...only one relay is needed correct???

    And I was thinking about using my relay I use for my remote 12 volt to turn on this a relay turning on a relay lol
  3. CadillacETC1997

    CadillacETC1997 Well-Known Member

    muy bueno
    just wish we could define what an alt/alternator is...
  4. Throttletune

    Throttletune Full Member

    It's a generator. Some silly manufacturer decided to call it an alternater for some odd reason. Probably because it makes A/C then converts it to DC or some such silliness.

    Course, if one ever has a drivability problem that makes one scratch their head, AC ripple seems to be the last thing people check. Any drivability problem I get, the battery/charging/starting system gets a check in many different ways. As far as those items go, they can pass nearly any test I throw at them. All it needs to do is fail just one to get any component in that group condemned.
  5. TheViking

    TheViking Well-Known Member

    Yes only one relay is required for this, and as far as using the remote turn on relay, sure, it would work, but It would be better to use an ignition source so the battery is always being charged as needed when the stereo is off... But either way will work!
  6. DREAMZmustang

    DREAMZmustang Full Member

    good thread, but you really must have a serious setup to need a second battery
  7. TheViking

    TheViking Well-Known Member

    I would like to add onto this section with a few more thoughts,

    I have seen on a few sites where folks are using "battery isolatoirs"....

    this is really not a good way to add a second battery. the reasons are simple. Using a battery isolator causes a voltage drop, it does not allow the second battery to be "seen" by the alternator (so it never really gets all the current it needs) and it does not allow the car audio system to draw from BOTH batteies during peak demands.

    I know many will argue this with me.....and thats OK, if you think a battey isolator works good for you, than by all means use. it does work. (at causing a voltage drop and limiting the current to your amps and limiting the charge portential to the second battery).

    I would also like to add another means of adding a second battery, the Orion MBR 70. They were made years ago and do an EXCELLENT job at regulating the the second battery, without ever letting your main battery run down. They may be hard to find, but they work, and work well

    thats all

    The Vikiing
  8. aznboi3644

    aznboi3644 Full Member

    Thanks Viking...I was just gonna ask that question about the isolators.

    But they cost too much and suck balls...I'm just gonna go with the PAC 200 amp relay unit.

    I am going to add another SLI battery...really no need for a deep cycle and they give out the power quicker and charge faster...what would you recommend for 100 bucks or less
  9. TheViking

    TheViking Well-Known Member

    Years ago I swore by the interstate batteries........

    in this day and age, i have bought all my truck and car batteis from orschelns farm and home supply (its like a tractor supply) ,for the past 8 years anyway, all have been good performers. I never liked sears..they seemed to be the shortest lived

    Any battery would probably do good. Even a cheap a$$ wally world. Just a good ol fashioned lead acid ....wont go wrong..........If you can afford it, a sealed gel cell does great. I have no personal expereince with the optimas. Hell a 13 galvinized nails, 13 pennies, and 13 lemons will make just over 12 volts for a LONG time !!!!!!!!
  10. aznboi3644

    aznboi3644 Full Member

    Well I was looking at some batteries from wal mart and some from rural king (farm and tractor supply store) but I'm not sure which batteries are sealed as the battery is going to be in the rear of my SUV
  11. TheViking

    TheViking Well-Known Member

    that brings up another topic, batteries that are sealed or not.........If you can, buy a battery that has removable covers!!!!!!!!!!! ALL battereis lose water over time.....the sealed ones cannot have the water replaced!!!

    So buy one with removable caps!!!!!!!!!!!!! And use ONLY distilled water, and ONLY fill them AFTER it has reached a full charge! Dont use beer, thats a LAST resort.......:D
  12. aznboi3644

    aznboi3644 Full Member

    Well my friend's Protege 5 came with a crappy lead acid battery that had a kind clear white casing and you could clearly see that one of the six cells had about an inch and a half less liquid in it...and it also read at 9 and it died about a week after he got it...i told him right when I saw it that he needed a new battery without even checking it with a meter.

    So would a Wal-Mart Everstart Maxx battery work inside the vehicle and no toxic gases would leak out?? because a lotta the normal batteries I see have these two rectangular looking caps on them
  13. TheViking

    TheViking Well-Known Member

    With ANY battery, during the charging/discharging process, tou will get hydrogen gas.....period. Just put it in a safe spot, secured down, and make sure that it get a little ventilation........ in the trunk your fine....... I have yet to see an explosion from he hydrogen build up in any any catastropuic failures...yes a wally world battery will work.
  14. aznboi3644

    aznboi3644 Full Member

    Damn this is hard finding the right battery for me lol.

    How would I have ventilation for my battery when it is in the cargo area of my Explorer??
  15. TheViking

    TheViking Well-Known Member

    the modern cars/truck s do have a natural airflow to a point. just put the sob in there, if yu smell rotton egg odar, get out and dont light up your pipe in the truck!
  16. aznboi3644

    aznboi3644 Full Member

    lol...alrighty...I'm get the Everstart Maxx from wal'mart

    1000 cranking amps and like 825 cold cranking...3 year warranty and replacement. I've read about people returning it after a few months for no reason but they have to replace it no questions asked lol

    Damn but I'll have to get the damn relay haha
  17. TheViking

    TheViking Well-Known Member

    Yep, get the realay!!! It works, and works BETTER than any othr method........If anyone tells you different, punch them in the head!
  18. 961kyle

    961kyle Full Member

    just a few questions on adding a second battery

    first ive been putting off uprading my big 3 and now have decided to add another battery, should i upgrade my big 3 or would i be alright with just the two batteries

    also what kind of strain will this put on my alternator, more?, less?, good?, bad? will adding it affect anything really?

    one more and probably the dumbest but i have to ask, i ground the isolator itself, and the second battery? or do i run a negative wire from the front battery to the one in the rear?

    ok i lied one more dumb one, does the isolator go between the fuses and does it matter where, could i have that under the hood?
  19. TheViking

    TheViking Well-Known Member

    You really need to upgrade the big 3 to realize the full potential of your stock eletrical system, So yes, you should do this step!

    The "strain" to the alternator is really not an issue. The only way the alternator could have its life shortened is if the batteries are run in a constant state of "discharge", thereby making the alternator work hard, for a longer period of time.

    DO NOT use an ISOLATOR!!!!!!!!!!!!!!! USe the relay I gave the link to earlier in this thread!!! Gounds for the second battery sghould be as close as possible to the battery itself. Dont run a ground from one battery to the other. Just ground them to the chassis of the vehicle. As far as the relay goes, it can be mounted virtually wherever you want, but yes, it should be between the 2 fuses on the power wire.
  20. aznboi3644

    aznboi3644 Full Member

    Ditched the wally worl everstart battery...gonna go with a Duralast red top...big ass one lol

    I like the batteries with side and top posts....just for your information