ive never had a truck with duel batteries before and i am going to be installing a hydraulic liftgate, so should i be installing the wiring on the main battery(the posts look pretty full) or can i use the second one? also when i start the truck she turns real slow for a couple seconds then seems to crank faster is that a problem? ??? thanks, <br><br> dan<br>

 

if the lift gate requires a lot of power go with the main if not the other will work. it also sounds like either a terminal is loose or the batteries are going and when one goes the other will follow

 

A quick way to check if you have a loose or corroded terminal is to immediately after starting place a finger on each battery post and see if it is warm. This is only a rough guide but ANY heating at any electrical connection is an indication of a problem that requires correction.<br>Wash your hands after you do this.

 

Find someone who has a load tester. Disconnect all cables from each battery and test the batteries individualy. This is the only way you will know for sure if you have a battery that is bad or going bad. If you plan on installing a lift gate, have the batteries checked first.<br>Rich

 

There is another way to test if one battery is draining the other, and that is to remove both positive terminals, and connect an DMM with an ammeter function (suggest starting with the highest range first -- usually 10 amps) between the two positive posts. Ideally, there should be zero current. Anything more than about 50 mA can possibly be a problem. There is no spec for this that I know of, but it's the same effect as having a load on a single battery. If it's in the hundreds of mA or amp range, the battery that the black meter lead is connected to is the &quot;sucker&quot; if the current reads positive, and the one on the red lead if the current reads negative.<br><br>As far as the liftgate power connection, as long as the cables between the batteries of of sufficient size (like 2 gauge or bigger), it does not matter which battery you connect it to. <br>

 

I run anything with a sizeable load, like stereo amps, from the right battery since it seems like it gets little use and has gone bad three times first in two of my trucks. Can't really say if it makes a difference or not but it also gets some of the clutter off that left battery terminal and the already cluttered up area. Other than personal preference though, it does not really make a difference.<br>Check your batteries like stated above, individually and disconnected from each other. The right one (passenger side) usually goes bad first and drags the left one down with it. Make sure you use a good breaker somewhere close to the battery when you run power to that lift gate.

 

From my reading, the passenger side battery cranks the truck and then the truck maily runs off the other battery. The passenger side also gets more charging power than the other one. I run all of my stereo equipment off the passenger one and my headlights just barely dim. Running off the drivers side, there was a noticeable dim everytime the subs would hit.

 

Not to start a war, but Gary is absolutely right. The batteries are in parallel with a rather large cable connecting the two. That means that there would be no difference between connecting to one or the other -- unless there is a poor connection between the positive posts or from the batteries to ground.

 

I don't disagree here but why does the right side (passenger) always go bad first?

 

Is that true? My driver's side battery went belly-up first. Other circumstances that may affect one battery differently are environmental, like heat, the presence or absence of a thermal sensor on one battery, or vibration.<br><br>In a perfect world, batteries in parallel are ok, but in reality no two batteries are exactly alike, and the environment that they are exposed to is not exactly the same. It's really not a very robust system. It would make more sense from a power standpoint to have them in series, doubling the voltage, and thus doubling the power with the same amount of current. This is, of course, very impractical because of all of the 12 volt systems and components on the vehicle that would have to be adapted to 24V. If you could run two alternators and only parallel the batteries during starting, that may be a better solution, but the added expense for the manufacturer is prohibitive. There are many ways to &quot;skin that cat&quot;, and the system in use is likely the best overall pragmatic solution for the manufacturer. There are 42V initiatives and standards in development right now that may see actual use in the next few years.<br>