two batteries on one alternator

i have a 98 dodge neon and i am upgrading all the wires i have an optima red top in the trunk and some random honda battery that was left in the shop. i have 0gauge wire running back to the red top and grounding it out i also have 4 0gauge engine grounds thats 3 more than it had from stock. i am using the honda battery under the hood to turn the starter only. what i am wondering if there is a way to block out the staretr battery after it is charged without manualy switching the wire. i know that i could put a voltage gauge in the dash and use a relay to switch it out but i want it to do ti on its own when it gets charged. to avoid people telling me what i allready know i am going to put an irragi alternator on it a 300a or 2 200a.

You must have some major power coming from your amplifiers if you need 400 amps of charging power. You could always just go the easy way and daisy chain them and just forget buying an expensive auto-battery switcharoo machine (if they make them).

If they do that would be pretty cool.

I've always wanted to leave my stock battery/charging system like it is, strap on another alternator going to a separate battery to charge my audio. It has turned out to be much more difficult than expected, but good luck friend.

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Sasquatch...
We know your legend's real...

Wire the batteries together in parallel.  Use a 200a relay to disconnect the batteries when the vehicle turns off. 

You don't need to worry about volt gauges and charging one battery then disconnecting it or whatever hyper complexity you have in mind.

If you purchased two identical batteries, I'd recommend Yellow Tops, you wouldn't even need the relay.

https://caraudiosecurity.com/shop/product/currency/EUR/products_id/5273.html

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"I'm finished!" - Daniel Plainview

thanks for the suggestoin sedate but the thing that i am worried about with haveing the batteries connected when the car is running is that i am still running a stock alternator and i dont want to burn it up untill i can afford to ger the iraggi. but that might work for now but when i get my iraggi i am going to try to have it made with 2 positive terminals. that dominic is pretty much a bad *** and he can do just about anything you ask him to do for the right money.

If you are adding a system that demands THAT kind of power, then running a second battery on a stock alternator is the LEAST of your worries. Once charged, an SLA battery will only demand a couple of amps, WORST CASE. I also recommend strongly AGAINST disparate batteries. With the two different kinds of batteries you have right now, you won't be replacing the alternator as often as you are replacing one or both batteries.

WHATEVER kind of battery you choose, (I say red-top, others here will say Kinetik, other still... yellow-top) if you are using multiple copies, you will ALWAYS want to use identical ones, even down to the age of them. DO NOT MIX BATTERY TYPES/CAPACITIES/AGES, EVER.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

98neon wrote:

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thanks for the suggestoin sedate but the thing that i am worried about with haveing the batteries connected when the car is running is that i am still running a stock alternator and i dont want to burn it up untill i can afford to ger the iraggi

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It doesn't work that way unless you hook them up discharged - which you would never do.  You would find that a pair paralleled deep cycles would be time-consuming to discharge with something as pedestrian as a car amplifier.  Regardless - what all are you trying to hook up anyway?  You haven't really specified what ur running so recommendations here are kinda blind at best.

haemph wrote:

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Once charged, an SLA battery will only demand a couple of amps, WORST CASE.

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Exactly.

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"I'm finished!" - Daniel Plainview

this setup is mostly to get the car on the road i will have 2 2000 kinetik's in tha trunk with a red top under the hood before too long thats after the alternator ('s)

as far as mixing the batterys the under hood battery will be locked out of the system unless the car is being started

BAD idea. BAD. The relay "solution" will ONLY be useful when listening in the parking lot. Under normal use, it is GOING to cause batteries to wear out faster, even the Kintetiks, but especially the red-top. Example: Front battery, used to start the car. Immediately, the back battery switches the alternator back to it, because you just finished a marathon listening session. UNTIL THOSE BATTERIES ARE CHARGED FULLY, the front battery will be powering everything in the car BY ITSELF - lights, A/C, the engine... This can and will, inevitably and repeatedly, drag the front battery to a low charge state, drastically reducing it's life. Hello $150.00 bill, once a year to replace that Optima... again. FORGET THE ISOLATION!!! I mean no relays, no diodes, no solenoids... NOTHING.

Also forget the idea of disparate batteries, completely. IDENTICAL batteries, front and rear, wired in parallel, a fuse appropriately within 18 inches of each one (so, yes, TWO fuses in the main power lead). Install power cable of sufficient capacity, based on the alternator's current rating - i.e. 150A alternator will require a #4, minimum.

Unless you are building a competition car, isolation (one) and disparate batteries (two) are a VERY bad ideas. Stack 'em on top of each other? Forget it.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

you hit the nail on the head right there it is going to be a comp car DB drag specifically who needs 5000 watts to two subs to listen to. i am planning on about 155 at the windsheald and ablut 160 at the headrest and the way that i have my fuse box wired it will only draw off the trunk battery

See... Now all of a sudden we have new information. Had you SAID it was gonna be an SPL/comp car from the get-go, I never would have even bothered to post.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."