Originally Posted by crazzydiamond85

ok, number one rule here: keep it simple,
stupid. in other words, always start with the easy stuff, then think about the hard stuff.

note: all these tests are quick checks we are taught to do with a volt meter w/amp clamp, they are essentially the same as the tests is the 95,96, and 97-99 m/y factory service manuals. they are not the exact procedures, because the FSM assumes you have a battery charger and a load tester/charging system tester.


first things first when ever you have an electrical issue, always visually inspect your cables, clean them with a terminal brush and make sure they are tight. this is the cause 75% of the time, it will cause a dead battery, and can even have enough resistance to keep you from starting.



next, if your battery has removable caps, remove them and make sure that the electrolyte (water) is up to the ridge at the bottom of those little tubes. it should look a little like a fish eye. only put distilled water in a battery.

now, with your car running, put your volt meter across the terminals. gator clamps rock. you should be reading 13.75-14.25 volts, or really close to that. (if you just jumped the car, drive it around for 15 minutes or so, try to keep the rpms up around 3k).

if you don"t show 13.75-14.25, you have a problem for sure.

now, you should turn the car off to hook this up, but make sure you can start it again.

clip one end of your volt meter to the nut on the back of the alternator that holds a fat cable, thats your output. make sure you won't melt the wire or catch it in a belt. start the car. put the other volt meter lead on the pos (+) terminal on the battery. this is checking the voltage drop in the + circuit.

with someone holding the engine at 2400 rpm, you should have 0.6 volts or less. this is the difference in voltage between the 2 ends of the cable, and is an indication of its condition. if you have over .6 volts you have too much resistance.


now we are going to check for voltage drop on the ground side. this will tell us is there is a bad ground strap keeping the battery from charging. so, put one lead on the negative terminal, and clip the other end to the alternator case (or anything else you want to check the ground on) on this one, if you see 0.3 volts or more, you have a problem.

if you read over the limit on either of these, find the problem by testing at each connection, starting at the battery and working down the line, until you isolate the faulty wire, then replace it.

i know these testing procedures may seem confusing, but if you make notes, and go do it on your car, you will get it and then it only take a minute. everyone should know this stuff. you can also use these to test other things, like your starter, your ground straps, pretty much any wire or system.

now, if you pass those tests, its on to battery testing.

the hydrometer.

this is the only way to truly check the charge of a battery. basically it tells you the specific gravity of your battery's electrolyte. you can pick one up for a few bucks at napa or maybe autozone.

make sure its for batteries, don't get the one for coolant. make sure your water is full first, fallow the directions and always wear glove and safety glasses. battery acid burns. if you get some on you, put baking soda on it, with alittle water, pat it around and rinse. repeat till it stops burning. this is because baking soda is a base, and a base will neutralize an acid.


load test.

make sure the battery is at least 3/4 charged, hydrometer comes in handy. unplug the coil pack so your car cant start put a volt meter across your battery terminals, turn on your lights, radio, flans, fog lamps, high beams, rear defrost, i mean EVERYTHING. now have some one start the car while you watch the volt meter. your magic number is 9.6 (if its cold, you may get lower readings, but should be no lower than 8.8 and thats if its like -10*f outside) if your voltage is low, either your battery isn't charged or it has one or more shorted cells. DO NOT CRANK THE CAR MORE THAN 15 SECONDS! its VERY bad for the battery.

3 minute test:
this is a quickie test to tell if a dead battery will take a charge. if your battery fails the hydrometer or load test this is your next step. you can do this first if your car wont start but if you can start it the other tests are easier to do IMHO

you need a digital volt meter for this one, and a battery charger capable of 40 amps. if possible, use an amp clam to see how much current your battery is actually taking.

IMPORTANT: you MUST NOT perform this test on a maintenance free battery. batteries produce hydrogen gas when they charge, and when you charge with 40 amps it can make a lot of hydrogen. because of this, you must remove the caps over the cells, like you would to add water to the electrolyte. maintenance free batteries are permanently sealed, so doing this test is dangerous. also don't smoke, nothing sucks like burning hydrogen and flying battery acid. its happened to others, it can happen to you. there, you are warned, don't blame me when your girl dumps you cause you look like the joker.

so, charge the battery at 40 amps with the volt meter on the terminals for 3 minutes. if you go over 15.5 volts your battery is almost certainly bad. if it spikes but comes back down before the end of 3 minutes, then you can try trickle charging the battery, but its hit or miss. if i could afford to i would pitch it.