How do I connect two car batteries together to charge them both?

Question

I have one 12v battery in the car. I want to add another 12v battery to run accessories from. I want them both to charge from the alternator.

Answer 1

You have to run them parallel, pos to pos / neg to neg. If you run them series pos to neg / neg to pos, then you just effectively turned your car into a 24 Volt system, not good, will blow every light in the car and probably fry the PCM.

This wont be very effective for running accessories. The cars alternator produces the power, the battery just stores it, if your alternator is good then you dont even need a battery once your car is running.

You might want to check into a high output alternator. These work as follows:

# a replacement for a standard, low-output automotive alternator in work, service, emergency, or off road vehicles, or
# as an auxiliary / secondary alternator installed in a vehicle electrical system in addition to an existing alternator -- dedicated to large nonstandard electrical loads, or
# to function in a service vehicle as an ultra high output, heavy duty, high current battery charger, or
# as part of an onboard DC secondary power source for high current demand accessories such as exotic automotive sound systems, marine electrical systems, mobile communication systems, high power radio transmitters, and/or emergency/medical equipment.

Hope this helps you out, Good luck.

Answer 2

You simply need a battery isolator. It will allow both batteries to be charged while your accessories only draw from one. If you run down that battery you still have your original battery to start the engine with. If you only need accessory power for a short time (like a winch) there is no need to upgrade your alternator, but if you plan on running lots of lights or a high powered stereo you'll need more charging amps. Good luck!

Answer 3

Tie the + posts of the two batteries to the + submit of the charger and the -'s to a minimum of one yet another and the - submit of the fee and you have a parallel equipment. The batteries will take longer to fee, because of the fact they are splitting the fee being presented by using the charger, whether it works. My 18 wheeler has 4 - 12 volt batteries in parallel being charged by using a unmarried alternator. the only element to look at is the amp hour score of the two batteries. in case you have an computerized shutoff variety charger it ought to close off while the smaller of the batteries reaches finished fee and not fee the different to finished potential.

Answer 4

Why? What accessories would you run and for what purpose? If you are needing more power for extra accessories you may simply need to install a high capacity alternator that will provide more amperage. Check with an aftermarket dealer.

Answer 5

this can be done but it is not a very good thing to do ----the best battery will be dragged down by the other and you will need to get a high output alternator and change your present battery cables to the gauge/cable ought two (heavy duty cables are in your local auto supply) I did this to a limo awhile back and it never seemed to work like the idea of more power....probably you need to talk to your stereo buddy and get the scoop from him also____

Answer 6

++ - - but check w. a mechanic that your car is suitable.

Answer 7

don`t know