Backup battery Installation

[Yehuda]

Hey, guys!

I want to install a backup battery in a vehicle so that I may use one battery to run the radios and other electronics all the time and not drain the primary battery.

I've looked through the forums but haven't found any information on how to achieve this.

I'd appreciate it if someone could explain how I can hook this up.



I also read some tutorials like the batteries tutorial, but I still don't know what to do.

 

[pollenface]

You can use a simple Voltage Sensing Relay with another "cranking" or "marine" battery

I would recommend using a proper dc-dc charger for an AGM or lifepo4 deep cycle battery.

You can also use a small inverter and a mains ac charger with some efficiency losses.

 

[kenryan]

It depends upon your vehicle, specifically the charging system. If it is a newer vehicle with a smart alternator, you will need to use a B2B (battery to battery) charger. If it is an older vehicle, one that does not have a smart alternator, you can just use a battery combiner, which is a voltage sensing relay that connects the two batteries together when it senses that charging voltage is present. You can also use a B2B on an older vehicle, so if you are not certain whether or not you have a smart alternator, that is the way to go.

A B2B charger has another advantage in that it limits the charging output. You need to be careful not to have too much charging amps because you could damage your alternator, your battery, or both.