2 batteries

[MYSHO1]

I have an optimum and a new battery that I am adding, the optimum is going in the trunk. What would be the best way to wire it all together?

 

[Frankiek3]

well in parallel of course, but I'll let some one else chime in on placement

 

[SHOZ123]

If I were to use two batteries I would want two identical ones. the Optima and a regular car start battery are not the same design. The internal resistance will be different and you will burn one up and never fully charge the other leading to sulfation.

But the real point is there is no need for two batteries.

 

[SHOOFF13]

I have had my optima yellow top in my trunk for about a year now powering all my entire system which consists of a pioneer indash screen, 2 icon tv headrest monitors, 2 amps, 2 subwoofers, a cd changer, my 4 infinity speakers, and tweeters. I will adding 4 more monitors soon also. I have had no problem with my car running two different batteries. Theres no way you could power all that stuff and still get the power you need for the car with one battery. My friend has an audi with 4 subs and 2 amps and needed an extra battery because his car was powerless because off all the audio equipment and tvs. He runs an optima red top under his hood and a yellow top in his trunk and he has no problem now with two batteries. I am running the yellow top in my trunk for the entire system and an interstate battery under the hood and my car still had all of its performance like new. If you have one battery with a big system you will have such problems as the headlights dimming or sometimes flashing. The extra battery is just for added power. I have had no problem with it Pat. So go for it.

 

[SHOZ123]

When your car is running it is the alternator that is powering the vehicle. The battery is just a load or buffer if you will for the alternator. No way will more than one battery give you more power when the car is running. No more so than caps.

 

[Frankiek3]

I agree with using two of the same batteries although the same problem can happen it is less likely.(You basically making one battery with more internal cells)

Two batteries is usually not necessary, but will aid more than a high capacitance capacitor. (Since they are load an alternator down more, when they charge, IMO they are worthless in the way many use them)

 

[NiNeTy Fo SHO]

Its not meant to give "more power", its meant more balance the power out. When the bass hits, your lights dim b/c you are needing more than the alternator can provide for those few seconds. Then they come back on bright and your not using all the power the alternator can provide in the next few seconds.

Using 2 batteries, when the bass hits, power from the battery gives the amp (other electrical sutff) power for those few seconds and then recharges the next few seconds between bass hits, etc.

A battery acts almost exactly like a cap but better in my opinion.

I used 2 different batteries for over a year to power all of my equipment with no problems. I ran a 2 gauge power wire between the batteries with large fuses at both ends for protection. I also ran a 2 gauge ground wire to the body in the trunk and upgraded the wire that goes to the body from the battery under the hook to a 2 gauge wire. 2 gauge is bigger than what is coming from the alternator, but you are pulling power at 12 volts, whereas the alternator charges at 13-14 volts (whatever), more than 12.

Yes, 2 batteries will not last forever if you are constantly using more than the alternator can provide. But thats the key, you arent using more than it can provide most of the time. Running a big power wire between batteries helps, but wont solve the problem. Answer, another battery with shorter distance runs to the objects being powers helps mucho.

I believe they dont have to be the same battery, as long as they are both the same voltage of batteries (both being 12 volts). If you have one 12 volt and one 9 volt, then the situation you mentioned would occur. All the power from the 12 volt battery would try to travel to the 9 volt because its a lower voltage. (think of volts being degrees F, a higher degree will travel to a lower degree to balance out) If you have a large mass thats 70 degrees F and a piece of paper 70 degrees F, energy will not travel into the paper as they are the same temp....it doesnt matter that one has more total energy, just that they are the same.

I try to get technical and explain things, but sometimes it just doesnt work out right.

Anyway, I have done it and so have other for extended periods of time (1-2 years) without either battery dieing. I removed me 2nd one just because I removed my large amplifier and was not needed anymore. It actually still works and have used it to jump start a car before. The one in my car still works too, as I start it almost everyday.

 

[SHOOFF13]

Ya I knew those things. The person who posted below this comment couldn't have said it better. I agree with using 2 batteries.

 

[SHOZ123]

Battery voltage at 12V nominal is less than what the alternator will provide at 14 volts nominal. If you are dropping below the alternator voltage you will always have dimming. The voltage drop usually is caused by a restriction in wiring due to too small of size or poor connections.

If your lights don't dim it is not because you have two batteries but rather that your alternator can deliver the nominal 14V the car's electrical system runs on to the amps.

Batteries do not make power, only store power. Seeing as a car's fully charged battery is 12.5 v without load and the car's electrical system runs at ~14 volts any time you are depending on the battery for power over the alternator you will be at a reduced voltage and the lights will dim.

If adding the extra battery solved the problem of the lights dimming it is because there is less voltage drop between the power source and the power being used. This can just as easily be solved with the correct size wire and proper connections.

Anytime you have two batteries with different internal resistance the battery with the lower resistance will over charge and the battery with the higher resistance will undercharge. It may take a while but eventually both batteries will have their lifespan shortened.

 

[Frankiek3]

SHOZ123 is correct

I would recommend using two of the same batterys (both new, so they are the "same" and will more likely to age the same) or just one

you CAN use your two batterys no one is stopping you, but I wouldn't recommend it

my die hard should have died years ago, its still running fine, some batterys just get lucky, yours might too