how to charge batteries?

[5abelsons]

We have a 2002 gmc 2500 duramax. Went to start the truck and it is completely dead. I have a charger but no idea how to hook it up. Hubby is deployed and usually does it. I know how to hook up to a battery but wasn't sure if this was different being diesel and having two batteries. Help please?

Thanks!

[DmaxMaverick]

Welcome aboard!

Battery charging (or jump starting) is no more complicated with 2 batteries than one. There should be a red plastic box (size of a deck of cards) on the left side of the engine, near the top. Pop it open and there'll be a large stud/nut inside. Clamp the Positive there. Above the box should be a silver metal tab, approximately 1" x 3". That's for the ground. If you don't get good contact (sometimes they just don't), I suggest grounding on the rear A/C compressor boss (just inboard from the "box", where the A/C compressor bolt passes through). If that isn't simple enough to figure out, you can charge/jump directly from either battery. They are wired parallel, so + and - on either battery is the same for both. The passenger side battery is a little further to reach, but the terminals are easier to access, with fewer obstacles. WATCH for the fuel lines, etc. when connecting the + clamp there. Make sure you don't short to ground, or it can burn right through the metal lines. Make your + connection first, ensure it's clear, and it should be OK. If the terminal caps are still on the batteries, they just pop off.

[5abelsons]

Thanks. How do I make sure not to short to ground? I"m not exactly sure what that means.
If I'm reading right, it's like hooking up jumper cables? I've done that before.

Thanks, again!

[DmaxMaverick]

It's just like hooking up jumper cables, except there's a box on the other end instead of another vehicle.

"Short to ground" (short circuit) merely means contacting a grounded component with the Positive cable you are connecting. This is only a factor if there's power to the Positive connector, and the other clamp (ground, often the black cable/clamp) is connected to the vehicle ground (frame, negative battery terminal, engine, or other "grounded" part). It causes an arc, like a welder, and will burn or melt metal if there's enough current (like an automotive battery).

[5abelsons]

I get it. I just need to make sure the neg end doesn't touch any other part of the truck once i've hooked up pos end.


Thanks a ton!!!

[DmaxMaverick]

I get it. I just need to make sure the neg end doesn't touch any other part of the truck once i've hooked up pos end.


Thanks a ton!!!
Um...No.

Make sure the Negative end doesn't touch any part of the truck UNTIL AFTER the positive is connected. Red/Positive clamp to Battery Positive. Once that is connected, Black/Negative clamp to truck ground (any large bolt on the frame or engine is usually good). If both aren't connected, positive to positive, and negative to negative, no charging (or jumpstart) will occur. Connecting the Positive first helps prevent a short circuit.

Place the charger on an insulated surface away from the truck (not touching the truck), like on a box, stool, or milk crate.

AFTER the cables are connected, THEN connect the AC (house) power to the charger, make sure it is selected to 12V (if it has a selection). You may also have to select a charge rate. 10 amps will normally charge both batteries overnight (about 12 hours). 40-50 amps should fully charge in 2-4 hours. I recommend the slower charge, unless you must drive sooner. In either case, leave the hood up to prevent gas buildup (batteries vent gas when charging, and can be explosive if enclosed). This is also why we don't (normally) make both connections to the battery terminals, as this can cause sparks too close to the battery. If you "fast charge", watch it closely. If the charger has a "meter", the needle should normally start high, and lower as charging continues. If you are connected to "dead" batteries and get no needle movement (once connected, properly selected and powered), you have a bad connection or the batteries are bad. If the vents bubble liquid or vapor, leak or do anything that doesn't seem "normal" (like get very hot, enough to soften plastic or clamp insulators/wires), STOP the charging (exact reverse order). You probably have bad batteries, and it needs to be checked before trying to charge. A "wet" spot around the terminal connectors normally means the battery is leaking (bad), and need to be replaced.

I'll be here for a while. Just holler if you need more help (or confusion).

[Kennedy]

My trucks have historically been hard on batteries. Well actually it is I who has been hard on them. Leaving accessories plugged in and forgetting them is what gets me.

A battery tender is an excellent tool to have at your disposal. It's not going to get you going quickly, but it will keep the system happy while parked. I like the waterproof 800 units. Tough as nails and lots of cord between teh long AC cord and teh long 12v output cord.

My 2002 sits for weeks or even months or longer. I recently purchased a 12 lighter plug end for my Tender. Now I can plug in and maintain charge through the lighter circuit with no need to have the hood open. I've found that this works pretty darn slick, PLUS it is said to be good for maintaining radio presets etc when batteries are disconnected. Because it's such a low current output accidental shorting is not a hazard.

Back to the batteries at hand, charge as slowly as you can unless there is some sense of urgency. Also it is preferrable to charge completely with the wall charger rather than relying on the alternator to do the heavy lifting.

[More Power]

My dad doesn't drive much now, just some short in-town trips. During the winter, aside from a couple of times per week town trips he will warm up his car once in a while. This isn't enough to keep the battery charged. A brand new DieHard went flat in just one year.

I gave him a set of jumper cables and a 2-amp trickle charger to get him out of a pickle, but suggested he either use the charger more often going forward, or drive the car for longer distances once a month or so - say 20 miles or so.

Jim