Seconary battery install for audio, little help/info needed

[AllLowd]

I am wanting to install a second battery for the audio system i am installing, so amps get all the power they want without robbing it from the cars system.
I have been seeing a lot of posts about the cars electronics monitoring the battery for different reasons, and I am wondering if hooking up a second battery will mess up the battery monitoring system, causing electrical problems?
Any help is greatly appreciated.
I have a 2015 allroad, and the second battery is a small 35 amp hour 12v duracell agm.

[Smac770]

Deep cycle battery useful if you want to run the audio with the engine off; still need a cap. Bigger alternator and a large cap better if you want to run the audio with the engine on.

https://js-alternators.com/product/2...mp-alternator/
I wonder why their listing ends at 2014; 2015 and 2016 were no different from 2013 and 2014. But you might inquire about it.

[AllLowd]

Thanks for the reply, i would only be running the audio with the car on, and will be adding a bigger alt sometime down the road, as the system increases in wattage, but for now 1200 watts, stock alt and 2 batteries should be sufficient.
I am mostly concerned if adding a second battery will have any negative effects on battery monitoring system. The car monitors the voltage of the stock battery, and ive read that a lot of people have to re-code if they change batteries, or charge the battery, since the car sometimes will go into a kind of reserve/limp power mode, and sometimes doesn't read the actual charge of the battery with out a re-code with vcds. Has anyone added a second battery without any issues?
Thanks again.

[Theiceman]

How do.you know existing setup will not be enough ?
The only reason you would get an extra battery is if because you dont have enough alt putput and depleted one. Adding one just delays that.
I dont think you are solving anything by adding batteries.

Sent from my SM-G973W using Audizine mobile app

[AllLowd]

Adding more amp hours will help the vehicle from dipping into the 12v range, so i can get the most out the amps. Ive ran the same wattage in a mk3, mk2, and had headlight dimming issues with the larger 165 amp vr6 alt, in a 2.0, until i added a second battery, and stayed at a constant 14v+ at the amp.
My neighbor does spl competitions, and just got a bigger amp and some new batteries and offered me his perfect 1 year old ones. He had 4000 watts on the stock alt with 2 of these batteries with no issues, they tested at 13.25 after sitting for a week out of the car. He told me adding one of these would guarantee my smaller system will have no problems with dimming or premature battery failure, HD600 jl mono block pushing a 12" w6v3, and a Audison AP8 with 600watts for the, focal 165ac and 165as, highs and mids.
So the batteries are free, and assurance.
So no one knows if this will effect the battery monitoring system?

[Smac770]

If the battery is having to provide fill for the generator shortage, when is that battery going to get recharged? A battery is a storage pool, not a generator. And a cap is a better storage pool for an audio system than a chemical battery.

I'd put a 1F cap in front of the amps and leave it at that. Monitor the alternator output and duty cycle and the battery state of charge with an OBD tool (measuring blocks in address 19) and see if things are not keeping up. If so, then go with a bigger alternator.

[Smac770]

One question would be are the batteries the same type? AGM vs non-AGM? They are different optimal charging profiles. The J519 is going to dictate terms to the generator based on the data from the BEM.

Beyond that, I have no experience with actual dual battery setups. They seem more normally used with an isolator and for engine off delivery. It sounds like you've used a battery as a substitute for a cap previously. If so, wire it as such and it should be fine. But a cap would be a better solution.

[AllLowd]

Yea, they are both agm batteries. I wanted to go lithium, 6 banks of Yinlong 40ah LTO cells, but id have to change the whole system to lithium, and that is just not feasible at the current $$$ of large lithium starter batteries, and would most definitely open a whole can of worms with the battery monitoring that the car does. As far as running multiple batteries, i have done it many times, as well as larger alts that add more parasitic drag to your engine, and it helps out a lot better than any cap i have ever ran, a cap store voltage for low bass hits, but takes too long too charge if your planning on playing your system for long periods, for something like quick constant hitting techno. An extra battery will add more amperage. Take a flashlight for example, the bigger and brighter the light the more batteries are needed to power it, not extra capacitors. A cap will rob the power from your amp as it charges, size for size a cap would be larger than the same amperage agm battery. Caps are more expensive, caps have to be charged every time you turn off your car before they are useful, while batteries store amps long term. An extra battery can also be used by the car, while a cap can not. A cap is defiantly a step up, but not as good as adding more store-able amps imo.
I should be fine with the stock alt for now. Our alts are 180amp alts, and our stock battery is 140ah, so adding a 35ah battery makes the total battery capacity 175ah on a 180amp alt.

[Smac770]

Looks like the B8.5 allroad has 180A Valeo; my B8.0 avant has only a 140A Bosch. I assume the refresh got larger alternators to cover the electric steering rack. Largest stock battery in a B8 is 110Ah (PR-J0Z). You probably upgraded the battery at some point.

If you're trying to overload the generator not constantly but just for a few songs here and there, then a second battery over a larger alternator would seem to be fine. A battery will be smaller than a cap, a battery will be cheaper than a cap. But a battery won't provide that burst current like a cap. And since you should have a cap anyway, why add both if the cap alone covers it. But if you've been there done that with your playback style and already know a cap is just not enough for your overload duration, then so be it. Cap+battery :-) Though I wonder if these Stinger carbon cap 5F and 10F hybrids would be a two in one solution. My car audio days, what's those first few words in Star Wars?

You're going to have a battery isolator, that's a given with two batteries. Not a topic I ever needed to bother with. Addressed my needs with generators and caps and that's all I needed. Looking at http://www.bcae1.com/battiso.htm, it appears if you go the diode route, you might have some concern over voltage level that makes it to the batteries, a little lower than original. Will slow the charging process. If you go the solenoid route, then things look normal. No messing with the negative, so the BEM will just sit there and see it's own normal battery; the second battery is just an additional consumer out on the grid.

Note the J367 BEM has four wires on it, and it functions as a voltmeter across the + and - posts of the factory battery and as an ammeter between the - post of the factory battery and the chassis ground point at the battery. So long as whatever you do you attach outside of those points, not directly to the posts on the factory battery, then the new additions are just additional electrical components. When you look at "fuse panel A", the big block on the + post, the BEM connects to B/1, there's three big fuses for most of the car's term 30 on C/1, D/1, and E/1. And the alternator charge comes in on the massive wire at F/1. I don't think I'd add load to the fuses SA1, SA2, SA3. I'd try to connect to F/1 or the massive wire coming to F/1. Just be cautious of the battery interrupt igniter that is in that block. The two pin plug goes to the airbag system. The F/1 in goes through the igniter that's controlled by that airbag connection.

The other end of that F/1 wire is TV22, the terminal block in the middle of the plenum chamber, back in the engine bay. So not helpful. Somehow tapping F/1 is what I would figure out. Or if you can figure out if you have spare capacity on SA1, SA2, or SA3.

The flashlight example is not really relevant; the flashlight doesn't have a charging system, which is the crux in this scenario.

[AllLowd]

Thank you!!
Where did you find this info on the battery fuse block? I was looking for this, and couldn't find anything. Is there a picture somewhere online that shows where c/1, d/1, e/1, and f/1 are located on the battery fuse block, and what they power? So are you suggesting i connect to the alt in aka f/1 before or after the air bag fuse? I was just thinking of hooking up to the unused spot closest to the battery + post, where audi gives you a spot to add a fuse. This is the same spot where my airride is hooked up https://cdn.shopify.com/s/files/1/08...81818194608761
As far as a battery isolater, i thought that was only if you plan on playing your stereo with the vehicle not running, so you dont drain your starter battery.

[Smac770]

I was just reading the wiring diagram. You can get it along with all the other Audi produced documents for your car at erwin.audiusa.com. Pay for a day and grab all the PDFs for your car.

Take the pic you linked. The horizontal fuse to the right is SA1 (110A, car and engine stuff). The vertical fuse in the middle is SA2 (110A, car and engine stuff). The missing fuse on the left would be SA3. Haha, ok, SA3 would be either: *driving school option 40A; *rental car option 50A; *council car option 110A; *80A for ABS control module fuses S123, S124, S137, but only in right-hand drive cars (?). So that's why we lack the SA3 fuse. So yeah, that would be mint for you to hook into. And then ground it at the same ground point the main battery uses.

C/1 is where the big red wire connects to SA1. D/1 is where the wiring connects to SA2. E/1 is where the wiring connects to SA3 (once you add it). F/1 is the massive connection there at the right end of the black box with the Audi rings on it (that's the interrupt igniter), just above the C/1 connection in your pic. The BEM B/1 connection is that small wire with the black torx or hex screw.

You'd know better than I about battery isolators. It was not something I ever needed to bother with in my systems. If it is to prevent recharging of the secondary battery by the primary battery after you've drained it engine off, then ok, I see how that would work and it would seem unnecessary in your expected use. Every time I do a search for car audio dual battery, they always bring up the isolator so I assumed it was something to do with managing the charging system view of the dual voltage sources.

[Novarider]

Yea, they are both agm batteries. I wanted to go lithium, 6 banks of Yinlong 40ah LTO cells, but id have to change the whole system to lithium, and that is just not feasible at the current $$$ of large lithium starter batteries, and would most definitely open a whole can of worms with the battery monitoring that the car does. As far as running multiple batteries, i have done it many times, as well as larger alts that add more parasitic drag to your engine, and it helps out a lot better than any cap i have ever ran, a cap store voltage for low bass hits, but takes too long too charge if your planning on playing your system for long periods, for something like quick constant hitting techno. An extra battery will add more amperage. Take a flashlight for example, the bigger and brighter the light the more batteries are needed to power it, not extra capacitors. A cap will rob the power from your amp as it charges, size for size a cap would be larger than the same amperage agm battery. Caps are more expensive, caps have to be charged every time you turn off your car before they are useful, while batteries store amps long term. An extra battery can also be used by the car, while a cap can not. A cap is defiantly a step up, but not as good as adding more store-able amps imo.
I should be fine with the stock alt for now. Our alts are 180amp alts, and our stock battery is 140ah, so adding a 35ah battery makes the total battery capacity 175ah on a 180amp alt.

You need to do some research on caps and electricity in general

First, A larger flashlight uses more batteries to increase voltage which is NOT what you need to do.

Second, a cap is not going to "rob the power" from the amp. That's not how electricity works. If what you're saying were true any time you turn on your headlights you'd loose power to something else.

Third, a car audio cap stays charged for a long time. It does not drain when you turn the car off. If it drained every time you turn the car off it would have to be charged slowly like the first time you charge it. They also recharge almost instantly after a big draw, you're not going to drain one by just listening to music.

Forth, your amp does not put out its full capacity all the time, most of the time you use a fraction of the rated watts

A cap is designed for your exact situation, no need to fool with another battery if it's not a compitition system like your neighbors.

[AllLowd]

You need to do some research on caps and electricity in general

First, A larger flashlight uses more batteries to increase voltage which is NOT what you need to do.


Second, a cap is not going to "rob the power" from the amp. That's not how electricity works. If what you're saying were true any time you turn on your headlights you'd loose power to something else.

Third, a car audio cap stays charged for a long time. It does not drain when you turn the car off. If it drained every time you turn the car off it would have to be charged slowly like the first time you charge it. They also recharge almost instantly after a big draw, you're not going to drain one by just listening to music.

Forth, your amp does not put out its full capacity all the time, most of the time you use a fraction of the rated watts

A cap is designed for your exact situation, no need to fool with another battery if it's not a compitition system like your neighbors.

Actually voltage x amps = wattage, so I don't see your point here. Voltage is a measurement of pressure, while amperage is a measurement of volume, and a larger flashlight needs more juice which can be achieved with either more amps, or more volts. Math is hard. :D

Second and third, a cap does loose power and does rob the amp, when first turned on and when charging, cause the alt power is going to the cap before the amp, at the end of the circuit.

Here is a very good read with proven tests showing a cap is pretty much useless.
https://forum.realmofexcursion.com/accessories-electrical/17919-why-you-dont-need-capacitor.html

[Novarider]

Actually voltage x amps = wattage, so I don't see your point here. Voltage is a measurement of pressure, while amperage is a measurement of volume, and a larger flashlight needs more juice which can be achieved with either more amps, or more volts. Math is hard. :D

Second and third, a cap does loose power and does rob the amp, when first turned on and when charging, cause the alt power is going to the cap before the amp, at the end of the circuit.

Here is a very good read with proven tests showing a cap is pretty much useless.
https://forum.realmofexcursion.com/a...capacitor.html

LOL, OK buddy.