Car Stereos: 12v to 24v, 12v batteries, voltage regulators

Question
hi sir
i have a radio system that i want to install in a car with normal 12 v battery
this system is 24v and for this i will install 2 (12v) batteries in series
but the problem is how i will charge those two batteries while not effecting the car battery or drain it

i thought about installing another alternator but i found it hard to install in the car
another solution i thought about is to install an inverter (12/24v) for charging the 2 additional batteries and to install a protection that disconect the inverter when main battery voltage drop below 12 v ,but for this solution the two batteries may not charge if the protection disconect the inverter also the protection may be not reliable,also i am not sure if it is ok to charge 24v from 12v battery using inverter

please advice and if ther is better idea

thank you for your time and waiting for your advice

Answer
Sorry for the delay. It's been very busy at my job!

I have to ask where you're finding 24V equipment? I know it's illegal in  most competition sanctions, so I'm curious why you are doing a build including it. Were your amplifiers modified?

Converting to a 24V system would be just like a 16V conversion. You had both of the options correct, so it's just a matter of getting them completed.

Option 1:
You need to get an alternator built with a 24V regulator.
-This is a must if you plan to charge your system sufficiently. You would also have to use the conversion factors on your amplifier clamp read outs to determine max amperage being pulled so you can choose your alternator(s) appropriately. Contact Powermaster, Mechman, or DC Power Engineering for help with this.

You need external regulation for your alternator.
-The alt charges based on input voltage from your PCM using ambient voltage as a reference. The PCM defaults to 13.4-14.5 for a 12V system. Most aftermarket voltage regulators have 6-12-14-16V options. I haven't yet seen 24, but you can contact MLA, Mechman, or Powermaster to see if they can make one for you.

You need a 24V battery bank.
-You had the right idea with series 12V batteries. Just make sure you understand ampacity tables and run the correct amount of wires between the series batteries (and paralleled banks)

You need one or two 24V/12V stepdown modules.
-Stepdowns will run your engine and fuse blocks to operate your car. They generally output around 50A sufficient to run a car, but they are also a strain on the alt/batteries installed. Contact Powermaster for their stepdowns, as they are the best on the market.


Option 2 (no alternator):

You will need an inverter. I've seen 12/16V inverters floating around, but I've never seen 24V. This conversion is going to cause a lot of stress to your electrical if you're not replacing the stock alt already. While Ohm's Law states that increased voltage drops amperage, this is not quite the case in car audio due to losses and sympathetic variations in certain components since conditions change on a load. If you manage to find one, it will likely be a low output current and you would have lacking power downstream. If you're running very powerful equipment (>4000W@14.4V clamped) then this option is not good.


I personally choose option 1, but I feel the need to warn you again that it's illegal in any sanctioned competitions (IASCA, USACI, MECA, etc..)

I do, however, like the idea. I can help you more if you need it, and give you guidance on how to accomplish it. Let me know if this helps you out man!