Has anyone successfully added a second 12 volt battery to their vehicle?

[metallicdan]

Hi all,

I am in the planning stages of a mild audio system (800w to sub), but I really want to make sure this is done the right way. It may turn wild later with more power, but for now, it will be only a single AudioControl LC-1.800 amp.

Prior audio experience tells me that on most ICE cars suffering from charging problems due to current draw (dimming of lights), adding a second battery and a battery isolating relay is often an affordable and reliable solution. Being that our cars are particularly sensitive to current draw, has anyone successfully added a second battery yet? The Stinger data sheet shows how to do this in an ICE car. Looks easily doable on our cars as well, assuming we grab switched 12v off the center console LED.

I've seen the 30amp solid state relay with parallel 2.4 ohm 100-watt coil solution, but I don't like how solid state relays can generate a lot of heat, not to mention 30 amps just isn't enough for a high-powered stereo. The mechanical Stinger relay would not generate any heat at all, and the amplifier(s) will draw all of their current from the secondary 12v battery, and that battery would be slowly charged by the primary 12v battery.

 

[Tam]

....that battery would be slowly charged by the primary 12v battery.

Tesla monitors its 12V usage so if you want to add loads, you should add them from one of those trackable sources such as a cigarette lighter outlet, OBDII, other wires in the cabin...

If you just simply add them to the 12V battery posts. That would bypass the Tesla monitoring system and there would be a discrepancy between the real total loads and what Tesla monitors as much fewer loads. That would kill your Tesla 12V battery very shortly (days or weeks).

 

[metallicdan]

Tesla monitors its 12V usage so if you want to add loads, you should add them from one of those trackable sources such as a cigarette lighter outlet, OBDII, other wires in the cabin...

If you just simply add them to the 12V battery posts. That would bypass the Tesla monitoring system and there would be a discrepancy between the real total loads and what Tesla monitors as much fewer loads. That would kill your Tesla 12V battery very shortly (days or weeks).

Unfortunately, those trackable 12v sources cannot provide enough amperage for a large amplifier. To add an amplifier that draws 80 amps is not uncommon for most car audio enthusiasts. Some even top 250 amps.

There doesn't seem to be a general consensus on the safest way to add a high-current device to the 12v system. Some are tapping the DC-DC penthouse, others are wiring directly to the 12v battery. Some have killed their 12v battery, others are still going strong. Some have received an error message on current draw, others have no issues after a penthouse reset.

The potential solution I'm talking about is adding an isolating relay in-line, and the second battery is connected to the relay. It is not wired directly to the existing 12v battery. The current draw to keep that battery charged, as it would go through the isolating relay, would be much lower than an amplifier constantly taxing the 12v system. And each time the amplifiers need juice, they hit the secondary battery instead of the main battery.

 

[jjrandorin]

You likely want to ask a company that designs aftermarket audio systems for teslas' like reus audio or something:

Reus Audio V.2

Reus Audio Systems | Car Audio Design Custom Audio for Most Luxury and Exotic Cars

www.reusaudio.com

Note, I have the stock system, and no interest in upgrading, so I am not specifically endorsing this company or any other. I am just aware of this company as I remember reading posts here from a few who have had them design something for their car.

 

[Watts_Up]

An issue is how to keep the secondary battery been charged?

Some systems with a secondary battery use a diode (but there is a voltage drop) or an isolator to protect discharging
the primary battery, this allows every time the primary battery getting re-charged, to have the secondary battery also getting re-charged.

No Diode Voltage Drop Effect!​

How To Install A Battery Isolator In Your Conversion Van​

Robust, inexpensive 12V 150+amp smart battery isolator and smart split charge relay​

How to Choose Between Battery Isolators and Separators​

I wonder if the Tesla inboard charger would complain if there is a secondary battery?

I noticed when not driving for several days, when the battery reaches 12.55 V,​

this trigger the inboard charger to generate 13.50 v for two hours.​

This process starts again about every 36 to 48 hours.​

 

[stopcrazypp]

Unfortunately, those trackable 12v sources cannot provide enough amperage for a large amplifier. To add an amplifier that draws 80 amps is not uncommon for most car audio enthusiasts. Some even top 250 amps.

There doesn't seem to be a general consensus on the safest way to add a high-current device to the 12v system. Some are tapping the DC-DC penthouse, others are wiring directly to the 12v battery. Some have killed their 12v battery, others are still going strong. Some have received an error message on current draw, others have no issues after a penthouse reset.

The potential solution I'm talking about is adding an isolating relay in-line, and the second battery is connected to the relay. It is not wired directly to the existing 12v battery. The current draw to keep that battery charged, as it would go through the isolating relay, would be much lower than an amplifier constantly taxing the 12v system. And each time the amplifiers need juice, they hit the secondary battery instead of the main battery.

I'm running a completely separate 12V battery system for my wifi USB security cameras in the car (not using sentry mode). I have two of these LiFePo4 30Ah batteries I got on sale off eBay in the compartment under the trunk. Note you may not want to use LiFePo4, given Lead Acid may actually provide higher current draw and is cheaper, but I chose it for my application to save weight/space.

lithium battery

The Page only can edit in LayoutHub Editor

www.eco-worthy.com

In my first iteration, from the wire I ran to the center console, I left a stub that could plug into the cigarette outlet to charge the batteries. The other part is just a standard 12V to USB adapter. Currently I have removed that stub and just use a dedicated 12V to 4-port USB adapter and added an inline toggle switch I got at home depot so that I can easily turn off the system at any time. I charge the batteries in the trunk weekly using a 12V battery charger instead (not using car 12V system at all).

I guess you can do something similar, just run your amp off a separate battery system that you can charge via the cigarette port. You would have to do a calculation however how big a battery system you need and if charging via the car is enough to replenish it. If your amp is in your trunk anyways, this may save you some wire losses too when running the amp.

 

[metallicdan]

Yeah, I don't think your solution is really feasible. I, and many others, would be far too lazy to charge the secondary battery every week, and there's no way the USB charge system could keep up. I don't think.

 

[stopcrazypp]

Yeah, I don't think your solution is really feasible. I, and many others, would be far too lazy to charge the secondary battery every week, and there's no way the USB charge system could keep up. I don't think.

Definitely, you won't use USB at all in your application, you'll use 12V directly. To clarify, the battery charger I am using is 12V that connects to the battery directly (can also charge while they are parallel), there is no USB involved. The USB is only there because my cameras run off USB power.

Amazon.com

In your case, you'll need to just run a wire and either use the cigarette port or tap into some other 12V in the car to do your charging.

 

[crazyrudy]

I installed an Ohmu battery in the frunk. I use a lot of 12v accessories including cameras, radios, monitors, etc. All non-standard equipment draws from the Ohmu. I have a RigRunner for distribution. You can see this setup in the attached photo. The Ohmu is directly connected to the standard 12v battery, and is charged concurrently with that system. I have had this installed for about 30 days, and it works well.