how to run a second batt

[AxT4430 10+ year member]

isolators aren't a bad idea - when they isolate the battery when the car is off. that prevents the two from draining each other, but puts strain when they are eventually connected. ideally, you'd have an isolator and two voltage gauges at the dash. you'd verify they were close in resting voltage before you start and have a switch to prevent parallel if you had an issue. that's how i would do it anyway.
you need the alternator to charge both. so they have to be connected when the car is running.

you don't want the diode based isolators because they introduce a voltage drop and waste heat. the relay style of isolator is fine if properly installed.

and yes, fusing on every wire leaving the positive terminal of a battery.

^ what he said.. got most of it.. what is this magical circuit switch you speak of?//content.invisioncic.com/y282845/emoticons/uhoh.gif.c07307dd22ee7e63e22fc8e9c614d1fd.gif

 

[keep_hope_alive Premium Member]

^ what he said.. got most of it.. what is this magical circuit switch you speak of?//content.invisioncic.com/y282845/emoticons/uhoh.gif.c07307dd22ee7e63e22fc8e9c614d1fd.gif

Ha. Just a toggle switch in-line with the ignition power to the isolator. So you could prevent the two from paralleling

 

[jockhater2 10+ year member]

A. No, im neither. B. WHY did you think so?

C.Thanks, didnt know that, I was told wrong by a shop then.. fml

D. I love you now //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

yeah. your smitty/bob saget for dang sure.

I was told the same thing by a shop when I first got into car audio. That I needed a battery isolator. Then I later found out. Ummm. No I don't. why would I play my system when my car is off.

 

[AxT4430 10+ year member]

yeah. your smitty/bob saget for dang sure.
I was told the same thing by a shop when I first got into car audio. That I needed a battery isolator. Then I later found out. Ummm. No I don't. why would I play my system when my car is off.

No, im not ***

 

[jockhater2 10+ year member]

No, im not ***

keep it to PM's or the Dome

 

[Fi-brations 10+ year member]

can you wire the secondary battery to the alternator and not the 1st battery. I want to put in my big deka and use the stock battery as well, i dont want to wire them together since they arent the same type of battery, what should i do? i cant fit the deka under my hood

 

[OmegaBunny 10+ year member]

Get a different car.

 

[OmegaBunny 10+ year member]

I wouldn't see why you can't do that but I will let someone else chime in.

 

[jockhater2 10+ year member]

can you wire the secondary battery to the alternator and not the 1st battery. I want to put in my big deka and use the stock battery as well, i dont want to wire them together since they arent the same type of battery, what should i do? i cant fit the deka under my hood

You can wire 2 batteries of different size together. But from what I heard. If they are not of similar age. It was shorten the life of the newer one.

And as long as the size is kinda close. You will be fine.

You wouldn't want to wire the 2nd one to the alternator especially if its going to be in your trunk. That's a 15+ foot charging cable. Just wire them together. Probably upgrade the front battery as well.

 

[hispls 5,000+ posts]

do ineed a fuse for the back ? or atleast can i do without for a few and how many watts can a 250 a fuse use cause i wanna upgrade my aq2200 to a 3500 soon

Fuse next to both batteries or don't bother fusing at all. Doing only 1 defeats the purpose.

You may or may not pop 250A depending how hard you run that amp. I'd over-fuse between batteries since if the fuse pops your voltage will drop fast without alt and primary battery connected to the amp.

 

[Fi-brations 10+ year member]

the front is just a red top idk how old, the other is a couple year old deka 105ah, i dont want to upgrade the front battery, i guess ill just wire them together and see what happens, i dont care if the red top dies, i would rather just run the deka for everything but i have to run it in the back

 

[jockhater2 10+ year member]

the front is just a red top idk how old, the other is a couple year old deka 105ah, i dont want to upgrade the front battery, i guess ill just wire them together and see what happens, i dont care if the red top dies, i would rather just run the deka for everything but i have to run it in the back

When I say shorten the life. I just mean that. If one of the batteries is 3 years old than the other. The newer one's life will be shortened.

But it sounds like you should be fine.

When you are wiring 2 batteries in parallel. you are doubling your reserve and your amp hours. The reason why. Is because you are essentially make those 2 batteries 1.

That is why most recommend that they be similar in size and age.