Dual Battery Question

Alright just a bit of background before I ask my questions: I'm no electrical expert but I did pay attention in my science classes. I currently run a Die Hard Platinum Marine PM-2 battery in place of my stock battery that 'mysteriously' died on me at 25k miles (long story). I liked this one because I knew I would be adding a lot of extra power sucking devices and this particular battery had 4 terminals. I now will be adding a lot of extra lighting (3 hellas on an avid off-road light bar and 2 whelen landing lights behind the grill) which will majorly suck battery life when all in use. To add to that, I already upgraded my stock stereo and added bed speakers and run my CB almost all the time when I’m in my truck. I'd also at some point like to add a viair on board air compressor too, so I'm thinking with all this, I should probably run dual batteries. Now for the questions. What I would like to do (not sure if this is the best way to go about this, please feel free to drop your two cents! ) is run a Die Hard Platinum Automotive P-1 in a parallel circuit. I thought the P-1 would be best because it had identical specs as far as reserve capacity and cold cranking amps. Am i correct in that the batteries have to have the same specs, or do they not?, or do they literally have to be the exact same battery? Next question, if I run my set-up this way, will I have to upgrade my alternator as well? Sorry for the mini novel, but thanks for taking the time to read and reply!


And just a disclaimer so I can avoid hate posts...i will NOT be one of those obnoxious drivers who blinds on-coming vehicles, I just like a lot of light when off-roading, or making new roads to find new places to camp etc.

 

If I were to do dual batts I wouldn't run them in parallel because what if you wanted to use an accessory without the car running? Then you would still risk killing both batteries. I believe what you want is an isolator such as the national luna kit. Or in the spirit of marine electrical you could get a simple switch that has 1-2-both-off.

Here's some good reading about dual kits http://www.expeditionportal.com/forum/showthread.php?t=35667

If you plan to use the accesories only with the truck running then maybe what you need is a heavy duty alternator such as one from mean-green
http://www.mean-green.com/

Also to help reduce the load you could get the lights in hid

 

Good point! though, I forgot to mention, on my PM-2 I have a PriorityStart ProMax hooked up which would stop whatever was running before the battery was so empty it wouldn't start. I also got it because it extended the length of my positive cable to my battery since it didnt have reverse leads...two birds with one stone!


And I use the accessories a lot when the truck is off too. Especially the bed speakers and sound system for drive ins and such. And camping...a lot of camping.

 

Nice. I learned something to. I didn't know there was something like that. Thanks.

 

Yup, most emergency vehicals use them (ie police cars, ambulances, fire trucks, etc...) And thanks for the website for mean green alternators. I've been trying to find a decent brand of high output alternator.

 

So...since I would not have to worry about killing the batteries...would running in parallel make the most sense, or at least cost effiecent sense?

 

Yeah I was just reading about how they are used on fleets. What a good idea.

 

haha i thought so. Im looking at the mean green site...they dont have an alternator listed for the 2.4L 2005+ tacomas...would the 4.0L 2005+ fit in the 2.4L?

 

I wouldn't have a clue. Maybe shoot them an e-mail or wait for somebody to chime in.

Isn't the 4 cylinder the same from first to second generation Taco?

 

Haha totally already emailed them...I'm a bit impatient...or just superly bored with nothing to do at work waiting to close haha

thanks for your help!

Any other two cents are certainly welcome! current total of loose change... $.02

 

Lol! No problem. Also if your truck is a 2nd gen and a 4 cylinder you have the 2.7. The 2.4's in the Taco's stopped after 04.

 

Whoops, haha, thanks (just had to send another email correcting my error...)

 

x2...they make isolators for the RV industry. They are designed to charge your "accessory" battery only after your primary battery is charged. You can get away with your normal alternator, but obviously a high-output upgrade will keep things charged up.

 

hm good to know.

So does anyone know whether in my case, running two batteries in parallel is probably my best option, and if the batteries have to be identical or not to do so? Thanks very much!

 

Ok, after massive amounts of research, talking to our electrians at work, and having some random guy who works on golf carts? walk in...I think my best option would just be to run a parallel circuit with 2 batteries. No one was sure if I needed identical batteries or not...but they said I should *try* to get ones made around the same month. To play it safe, I'm going to get the diehard P-1 since it has the same specs as the PM-2, only having 2 terminals and not 4. I will then connect it's terminals, to the the extra set of terminals on the PM-2. I'm not worried about killing both batteries off by leaving a light on because I now have the priorty start promax device hooked up. I am curious about getting a HO alternator though. I like the mean green ones, but am still waiting to hear back from the company as to if it will fit the 2.7 L 4 banger 2009 access cab because it's not one listed on their website. If anyone knows the answer to this please feel free and chime in. I do have concerns about putting in the alternator myself...has anyone does this before? Is it hard/safe/doable, or should I have someone do it for me. Also, will the alternator be able to charge both batteries even though technically its only connected to the one? Or how does that work? Sorry for all the questions...I like to figure out everything before I go start spending large sums of money and realize stuck up a creek without a paddle. Thanks for all the help thus far!

 

I thought if they were in parallel the batteries will live and die together in other words charge and drain at the same rate. I've never installed an alternator but from what I see it doesn't seem to hard. How's the accessibility to the alternator on the 4 banger?

 

If you run two batteries in parallel without an isolator, you can burn out the regulator in the alternator.
Use an isolator and run your accessories off the aux battery. When aux dies, you can still start on the main battery.

 

It would die even with a HO alternator? I was under the impression that it would be fine with the HO alternator...and I'm not worried so much about batteries dying...that won't be an issue. I just will have a lot of juice being sucking while the car is running, so I'd want to have a HO alternator to keep up. Is that correct in my logic?

 

I wouldn't run it without an isolator. HO alt or not.

 

Any particular reason why? I'm not afriad of draining both batteries to the point of not being able to start my truck, i've got that covered. As far as killing my alternator, a HO alternator is rated to be able to put out an intense amount of juice, thats what is is for. Don't think of the parallel circuit as 2 batteries sucking the alternators life, think of it as one big battery, that has the same amout of juice pull. think of it like two buckets of water, when you have one bucket of water, and you need to fill a container, it takes the given amount to fill it. when you have to buckets of water that are connected that are both full, you will only use half of each. It will take the same amount of water to replenish either senario. With two batteries in a parallel circuit, you have the same volts, but twice the reserve and twice the cca. As far as the alternator...it wouldn't be burnt out from that. it could burn out with just one battery, with the same amount of juice being sucked out becuase it can't keep up with it. 2 batteries would kill it quicker becuase its that much more that can be sucked out and it has to fill up both, but thats the purpose of the HO alternator, at least thats what i've come to the conclusion of from all the research i've found and what all i've been told. does that make sense or am I completely wrong? lol