Tricked-Out-Toy

iTrader: (1)

Ok ive got door poppers and sometimes they need an extra kick ive already got a red top dry cell in the car and that isnt enough I have another red top just sitting around and want to throw that in and wire them in parallel. does anyone know if I can do this without causing damage to the starter? the combined CCA of both batteries would be 1440amps @ 12 volts. I also have an incar computer so I was planning on having two batteries anyway.

NEEDAZ

Really should use an isolator. The problem is not "will it damage the starter?", it's the potential for what they call 'dueling battery syndrome'. With two batteries directly in parallel it one start to get weak (the voltage drop below the others) the other battery will try to charge the weaker one. This will leave you with two dead batteries instead of one weak one. Some people 'get away with it' for some time, but if it leaves you stuck, you're stuck.

Tricked-Out-Toy

iTrader: (1)

Well the problem with the isolator is it doesnt switch on the second battery until AFTER I start the car. which doesnt do me any good when im trying to get into my car and need two batteries to pop the doors. unless there is another way wire the isolator??

NEEDAZ

If the battery has enough to start the car it should be more then enough to pop the doors. What do you have for wiring to the solenoids? B+ and ground? Think we should be able to get you straight without the extra money for the battery.

Tricked-Out-Toy

iTrader: (1)

I already have an extra dry cell just sitting there so its a freebee. I ussually dont have a problem popping the doors but sometimes I need just a little extra. sometimes ill have the car running and the doors will pop fine but if i turn the car off and try to pop them they hang up a little bit. so the extra battery is more of insurance than anything. and on top of that id like to be able to run my computer and screen longer without having to start the car. so for free I dont see any reason not to put it in. I just need to make sure nothing will catch fire or burn out with 1440 CCA vs. the 720CCA the single battery has

GTA_IN_T.O

i have been using 2 batteries for years.....make sure they are identical batteries and start of with 2 brand new ones, i run 2 optima yellow tops

Tricked-Out-Toy

iTrader: (1)

I have two red top which were both bought 3 months ago so thats fine. how do you have them wired? do you have a sketch diagram you could post? thanks

firebirdjosh

iTrader: (1)

A running car has higher voltages than a battery does- it's probably not an amperage problem.

NEEDAZ

^^^ I really think all you doing here is covering up a bigger problem. I think what's happening is a voltage drop to the solenoids problem. With the car running you start with a higher voltage so dropping 2 or 3V will not have as big an impact. Adding the extra battery will not help with this if that is in fact the problem. The second battery is a good idea with the carputer. But if we can get the poppers working right, then you can do it right and use an isolator.
Again

Tricked-Out-Toy

iTrader: (1)

ya I know the voltage is higher when the car is running 14.4 vs 12 im trying to get more amps. when the car is running it puts out plenty of amps and can hold the amps when a load is applied but whent he car is off the battery has to provide enough amps to pull the popper but sometimes it doesnt have enough. im not trying to debate wether a single battery has enough juice to pop the doors im trying to add two batteries for multiple uses and reassurance.
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im running 8 gage to the relay and then to the selonoid

Tricked-Out-Toy

iTrader: (1)

Im not sure I understand, I thought voltage didnt matter in this case it was the amperage which determined the load you could apply. I have 50lb selonoids but they arent mounted so the pull is directly straight up and down, there is some lateral loading which I think is the problem but due to space issues its the best way I could have mounted them. so please explain how It wont make a difference to have 1440 CCA vs 720CCA? Cause the way I understand it is similar to why you would need an extra battery in a car with a multiple large amps and big subs. when the subs hit the amps draw amperage from the batteries there for having two batteries lessens the sudden impact loading and voltage drop on the alternator and the demand is distrubuted accross the two batteries. Am i wrong?

NEEDAZ

You'll really close, but a little off in the theory end, which I think is confusing you more then helping you. I'm going to use a lot of quote to try and pull thing together for you.
First ohms law, E=IR
To get "more amps" or more current (amps is a unit of measure for current) you need to increase the voltage or decrees the resistance. The resistance of the coils is, for the most part, going to stay the same. So you would need to increase the voltage. Adding two batteries is not going to increase the standing voltage at the batteries, but it adds to the potential for more current to be 'pulled' from the electrical system before the voltage at the terminal of the batteries drops below a given point. Now, when you pull a large amount of current from a battery, the voltage at the terminal may drop some, but if your battery is able to supply the current needed to start the car, it should be able to supply more then enough current to pull in the coils on the door poppers.

When the car is running and the alternator is putting out a given voltage, the current 'pulled' for the system is determined by the load (resistance) on the system. But what is being "held" is the voltage.

The voltage should stay more less consistent at 12V, but the load determines the current based off of voltage.
Some examples:I'm going to change the 'R', this would be the DC Resistance of the coils.
E=IR (E is voltage, I is current measured in amp, R is resistance measured in ohms), so I=E/R or E/R=I

12/10=1.2
So if you have a 10ohm coil on a 12V system it will 'pull' 1.2amps
12/100=0.12
So a 100ohm coil on the same system would 'pull' 0.12A The only way to get more current flow with the 100ohm coil would be to increase the voltage.
20/100=0.2
So that 100ohm coil on a 20V system would 'pull' 0.2A. Starting to see the relation ship between voltage and current?

You have 8gage to the coils. Is that right from the battery? How are things grounded? Do the coils say how much current they 'pull'? (note the quotes around 'pull' throughout the post)
You can confirm my hypotheses by checking the voltage at the battery with the coils held in (not for to long) then check the voltage at the coils when they are held in. I think you'll see a volt or two less at the coils, and this indicate excessive resistance in the B+ line OR in the ground path.

Tricked-Out-Toy

iTrader: (1)

So if I have a sizable drop in voltage accross the 8 gage from the battery to the coil I should get larger cable to reduce the resitance in the line? the manufacture recomended the 8 gage and it is run straight to the battery the groun is the door itself which probly isnt the best but I dont think its causing my issue since my door locks and power window utilize the same ground. at 8 gage i think I have a resistance of .004 or 5 ohms/ft and my length is about 15 foot. do you think that could be giving me these occasional problems with the poppers? I thought it was just the way it was pulling since it isnt straight up and down it was prolly hanging up a little. to help the solenoid I added a helper spring which seams to work well but once in a while still hangs up.

back to the two battery option do i need to fuse the second battery if ran in parallel without an isolator?

NEEDAZ

I bet the stock ground for the door is OK for the small low current solenoid for the door lock, but not enough for the poppers. We are talking about door pop solenoids here right? Any way, If the manufacture recommends 8 gage for the power wire that thing must pull some current. Take another * gage wire from the solenoid ground though the door and to a GOOD chassis ground. I BET that will help.
Typically if the batteries are right next to each other there is no fuse used. But remember I DON'T recommend NOT using the isolator, so thats all I'll say about that. I don't like it. Now, that all I'll say about that.
But still more then willing to help with the popper problem.

Tricked-Out-Toy

iTrader: (1)

Thanks for the help with the poppers, yes they are solenoid style. you say you dont recommend using two batteries without a isolator but doesnt diesel trucks and some cars have twin batteries without isolators? they just wire them in parallel. ne who again thanks for the help on the poppers im going to try different grounds and even a larger cable (4gage) to see if that makes a difference.

nameinuse

I had three batteries paralelled in a van I used to own,ran it that way for over three years with no ill effects.
One was in the original spot,the other two were mounted about six feet rearward in a compartment in the subwoofer box.
All batteries were of different sizes,but they were all new when put in.

Tricked-Out-Toy

iTrader: (1)

you just ran them parrallel without any isolator or fuses?

NEEDAZ

They do it that way because it cheaper, not better. If you go back through old post of my you'll see that if there is a OKish way to do something and a better way, I will away PUSH for doing it the better way, just me. Running them in parallel doesn't mean you will have problems, but if you do have problems (even if it's just leaving the lights on) BOTH batteries will be out. With an isolator you can hit the switch, use the other battery and be on you're way. As you go down the road your re-charging the dead battery. Can't do that with them just in parallel.

nameinuse

Yes,the + wire was pretty fat and drawn in an electrical conduit hose giving it some extra insulation and the hose was in turn isolated from the chassi.
Had a battery separator and fuses,but never got around to install them.
I`m an electrician by profession,you see.

Tricked-Out-Toy

iTrader: (1)

I see what your saying now. since the dual batteries wont help my door pop any bettter than the one there is no reason not to run an isolator. now what do you recomend for an isolator from what ive found there is two option, 1) diode style and 2) solenoid style. now with a isolator when I turn the car off it switches to just one battery right? what I want to be able to do is still run both batteries at tiimes when im surfing the internet or watching a movie on my hard wired computer of course with the car off.

hey Name what did you need three batteries for??

NEEDAZ

For what you want to do I would use a solenoid isolator and run all the "extra" stuff off of the second battery. That way if you wanted you could flip a switch and have both batteries linked. But really by running all the "extra" stuff off the second battery if you use a yellow top, you could run it dead and still be able to start the car. Or run it with some kind of volt meter or audible alarm that would signal you when the second battery drops below a given point, then start the car. The advantage is if you are sitting for a long time with both batteries linked, you still run the rick of running them low enough that they wouldn't start the car. With them isolated you run all the extra stuff, kill the second battery, and still start off the battery in the stock location. That lets the second battery charge right back up.

Tricked-Out-Toy

iTrader: (1)

now for the final question, who makes a GOOD solenoid kit?

nameinuse

Wanted an extra for the stereo,but since there was room beside the subwoofer box for two batteries why not fill it?

NEEDAZ

If you are looking for a kit, Painless wiring has two. I would go for the non-water resistance design for you. I got the water resistant one for my truck, but it's a truck. The instructions make it vary easy to install. To save some bill you can check E-Bay for the solenoids and make your own kit.