Dual battery questions

I have a lot of light mods and other mods on my to do list for my taco, all that require hooking stuff up to my 12V battery. Of course, I don't want to hook everything up to my only battery. If a relay or something were to not work properly, It might drain the battery that starts the truck. That would suck. So, my dad has some nice batteries sitting in his shop he's not using, a bunch of heavy wire (some stuff from the oil field. More than capable of running any power those batteries can produce), and I have a good understanding of DC electrics, but I've never done this exact mod before. Could I just rig up the batteries in parallel to the alternator (with an inline fuse of course), or would I need a solenoid or some strange device?

 

You want a device that isolates your main battery from all your auxiliary add ons once a set voltage is reached so that the 2nd battery gets drained and not the first. I forget what the device is called, but any dual battery tutorial should lead you to it.

Also as I understand it, you generally want 2 batteries of the same make and model, preferably bought at the same time so the manufacturing date is the same if not very close so the 2 batteries dont beat each other to death.

 

Yeah, so it's called a dual battery isolator.

 

How much do they cost?

 

Let's be real dude, this is the part where you gotta start doing your own research.

 

Fair enough. Just seeing if you had an estimate, but I found a good one online. Thanks for the help man

 

the thing with batteries is they will equalize

That is why the idea of having two batteries the same is a good idea.

Have you figured out just what the extra load is going to be ??

LED lights have very low draw

Are these lights going to be used long term like for a whole weekend of drain on the battery .

If your not getting into adding a Winch maybe a deep cycle battery might be an option.

Just what sort of batteries are sitting around??

What sort of wire fell off the truck ??

 

T

They look pretty new. Not sure what brand exactly, but they look nice. Yellow top with 6 cylinder things. Not sure how he ended up with 3 of them. Lights will be used frequently but not 24/7. I will have an in cab switch. A winch is also something i will use every omce in a while. And im using an isolater that will let me hook up my alternator to charge both of them

 

You probably wont need dual batteries for your application to be honest. The people who run these complex dual battery setups are usually overlanders.

 

You could run them in parallel but both batteries need to be identical in type, amp rating, and maybe even voltage (to the tenth fraction) because a weaker battery will always drain the stronger battery. With a battery isolator, it does not matter that the batteries match. When the isolator is engaged, both batteries get charged by the alternator. When the vehicle is off, the isolator disengages (or isolates) the batteries from each other. There are two types of isolators, a diode and solenoid. A diode isolator is easier to install and self engaging, but it robs about half a volt and they are pricier. A solenoid isolator is mechanical and will eventually wear out. They are more affordable but require a switch to engage, unless you get a pricier 'smart' model.

 

Main reason I want to run dual battery is because of the large amount of electrical mods (lights, subwoofer, amp, etc.) and also a powerful winch for using on my ranch

 

But all those things won't be running together all the time. Plus you said you have LED lights. You're alternator will keep the battery charged. The only time I've seen a battery drain was from 40 mins of constant winching. We were literally packing the the winch with snow to prevent over heating as we winched 4 guys 500 ft up a icey trail in the mountains.

 

Yeah, none of those reasons require a 2nd battery. The winch runs off the battery with the car running so the alternator is providing power along with the battery. You don't need a 2nd battery for that. A 2nd battery is generally installed for one or both of the following: to use as a backup to the primary battery such as for those that offroad into the boonies or do solo excursions (me); or those that run accessories with the car off such as overlanders, audiophiles, work trucks, etc... who may drain the 2nd battery but not the primary battery because it's isolated.

But, it's your truck and you are can certainly do to it what you want. We are just pointing out your proposed electrical demands do not require a 2nd battery. You're better off getting a high output alternator.

I remembered a third way of isolating a 2nd battery that's the most affordable but requires lots of user attention - using a battery on/off switch to isolate the batteries, such as a Blue Sea 6005 on/off switch. You have to remember not to leave the switch on when you turn off the veh or you'll shorten the battery life.

 

Well, if I don't need a second battery, then I'm not spending money on an isolater and wiring. Thanks for the info, guys

 

Compare the batteries your dad has to yours, if any of them have a higher capacity get it tested and swap it. Thats probably the cheapest "upgrade" you can do here.

 

With the winch power demands, I would recommend a Big 3 Upgrade - bigger cables: battery to ground/chassis; engine to ground/chassis; and battery to alternator. However, in Tacomas, the alt wire goes to the fuse box, then to the battery, with the fuse in between. So, an upgrade here would be to add a fused 2awg wire from alt directly to the battery. Or upgrade the alt to fusebox to battery wires, but upgrade is limited if you don't increase the fuse amp rating. 140 being the biggest fuse I can find, which is what comes with the tow package models.

 

Look at Blue Seas MCR. Also @HeliMed makes some nice kits https://www.tacomaworld.com/threads/off-grid-engineering-dual-battery-trays-wiring-kits.420680/.
Also check out https://www.tacomaworld.com/threads...-batterys-thread.295653/page-56#post-12440297