Troubleshooting the Battery and Load (long at first)
#1
04-13-2012, 06:40 AM
Troubleshooting the Battery and Load (long at first)
We have a challenging electrical problem that went sideways at first. This is where things got back on track, so I'm posting this to get to the point quicker.
I'm getting a better understanding of what happened with the readings and it sounds like you have the meter hooked up correctly now. PM me if you want a more detailed (boring) explanation of why you need to move the meter lead to measure current.
I'm not sure what was going on with the high voltage reading you saw while driving. How long did it last? Did it coincide with anything else electrical happening? Has the voltage ever dropped low while driving? I'm assuming it went away by the time you got to AutoZone.
Speaking of AutoZone, your choice of the word idiot was right on. A load test does just that, it puts a load on a charged battery and measures the amount of current it delivers before the voltage drops below a specified value. The resulting product of current and time (that's where the term amp-hours comes from) is the battery capacity. You cannot accurately load test a battery if it is connected to anything else. If it is still connected to the vehicle any parasitic loads (which is what we are concerned with here) will alter the results. If it is connected to another battery (as it is in dual battery tucks) the second battery will contribute its own current and alter the results. That's the long way of saying you could still have a bad battery and the AZ manager is an idiot.
When you had the no-start this afternoon at 2:45 the truck had only been sitting for about 2 hours. Assuming your batteries were fully charged from the driving you did in the morning, that's one hell of a draw. Perhaps your batteries are not getting charged. I know the alternator is new, but maybe there is a separate intermittent problem that causes them not to charge while driving.
When you get a chance, do the following voltage tests. First, move the meter lead back to the regular voltage position. This is VERY important to avoid blowing the internal fuse in the meter. Disconnect both batteries and measure the voltage of each. Depending on the level of charge they should be anywhere from about 12V to 12.8V. The exact voltage isn't important, but they sould both be within about 0.1V of each other. Then reconnect the batteries and measure the voltage with the key off and engine off. You should see about the same voltage as when they were disconnected. Then start the engine, wait a few minutes to make sure the GPR is off, and measure the voltage at idle. Depending on the level of charge, you should see something between 13.8 and 14.2V. Then start to add load (headlights, heater, wipers, etc.) and measure the voltage. You may need to bump up the RPM's to about 1200, but the voltage should not drop below 13.8V with all of your electrical accessories running.
Sorry for getting long winded. Keep me posted.
Chris
I'm not sure what was going on with the high voltage reading you saw while driving. How long did it last? Did it coincide with anything else electrical happening? Has the voltage ever dropped low while driving? I'm assuming it went away by the time you got to AutoZone.
Speaking of AutoZone, your choice of the word idiot was right on. A load test does just that, it puts a load on a charged battery and measures the amount of current it delivers before the voltage drops below a specified value. The resulting product of current and time (that's where the term amp-hours comes from) is the battery capacity. You cannot accurately load test a battery if it is connected to anything else. If it is still connected to the vehicle any parasitic loads (which is what we are concerned with here) will alter the results. If it is connected to another battery (as it is in dual battery tucks) the second battery will contribute its own current and alter the results. That's the long way of saying you could still have a bad battery and the AZ manager is an idiot.
When you had the no-start this afternoon at 2:45 the truck had only been sitting for about 2 hours. Assuming your batteries were fully charged from the driving you did in the morning, that's one hell of a draw. Perhaps your batteries are not getting charged. I know the alternator is new, but maybe there is a separate intermittent problem that causes them not to charge while driving.
When you get a chance, do the following voltage tests. First, move the meter lead back to the regular voltage position. This is VERY important to avoid blowing the internal fuse in the meter. Disconnect both batteries and measure the voltage of each. Depending on the level of charge they should be anywhere from about 12V to 12.8V. The exact voltage isn't important, but they sould both be within about 0.1V of each other. Then reconnect the batteries and measure the voltage with the key off and engine off. You should see about the same voltage as when they were disconnected. Then start the engine, wait a few minutes to make sure the GPR is off, and measure the voltage at idle. Depending on the level of charge, you should see something between 13.8 and 14.2V. Then start to add load (headlights, heater, wipers, etc.) and measure the voltage. You may need to bump up the RPM's to about 1200, but the voltage should not drop below 13.8V with all of your electrical accessories running.
Sorry for getting long winded. Keep me posted.
Chris
Man, we need to back up the bus again. There is another way to do this:
Fret not... there is a plan and methodical steps will prevent wheel-spinning.
- Make absolutely certain all your battery cables are clean, well seated, and tight (can't rotate the cables by hand when tightened).
- Leave the meter in Volts and touch the black probe to some un-painted metal in the engine bay, with the red probe on the positive cable - not the battery post.
- Engine off, no charger hooked up - about 12 -13 VDC and stable for a minute. If the meter shows a constant drop, note how far and how fast, then we'll deal with that later.
- With a cool engine, have the meter connected to the same locations and turn the key to "Run". You only have a few seconds to check the voltage to make sure it's above 10 VDC, 11 VDC would be better. If you have enough time, check the battery post too and make note of any voltage difference between post and cable.
- If there's enough juice, start the truck and make sure the volts get up to at least 13.7 VDC - then watch for a couple of minutes to see if it climbs. Check the battery posts of both batteries and both positive cables. No 13.7? We need to talk.
- Put the meter on AC and make note of the voltage there as well.
Fret not... there is a plan and methodical steps will prevent wheel-spinning.
Just a confirmation of what was already noted above: we still don't know that both batteries are good. There's either 1) a bad battery, 2) the batteries are good but aren't being fully charged during operation (do you have a battery charger and has it been used to fully charge the batteries?), or 3) the batteries are good but there's one serious parasitic power draw in the trucks electrical circuitry.
As I noted above, when my good battery was being drained by a shorted battery at a similarly high rate of current draw within a 24-hour period of time, I could literally see (melted anti-corrosion grease on battery terminal) and feel the heat generated due to the prolonged high rate of current flow. Such high rates of current flow generate significant heat.
As I noted above, when my good battery was being drained by a shorted battery at a similarly high rate of current draw within a 24-hour period of time, I could literally see (melted anti-corrosion grease on battery terminal) and feel the heat generated due to the prolonged high rate of current flow. Such high rates of current flow generate significant heat.
You need to do a load test on the battery's separate. there has to be a dead cell in one for it to drain that fast. if there both hooked up during any test, Sure it's going to read good. one battery has to over compensate for the other. Im sure the bad battery will hold a charge, Not a full charge but a charged enough to work for a start or two.
Im Sure if you disconnect them over night they work the next morning. this is because it's not hooked up and has no kinda draw on it. Now with the good battery hooked to it it becomes a charged circuit and the bad cell will pull from the good battery.
I accidentally left my truck turned on " not running " over night and it still started the next morning.
Im not saying this is your total problem or is the fix for you.
But i have had a similar experience on my toyhauler with a dead cell battery.
It has two deep cycle 12V Battery's in series
Maybe you need to find another place to test your stuff at. Then tell AZ what you found to be bad and replace it.
Im Sure if you disconnect them over night they work the next morning. this is because it's not hooked up and has no kinda draw on it. Now with the good battery hooked to it it becomes a charged circuit and the bad cell will pull from the good battery.
I accidentally left my truck turned on " not running " over night and it still started the next morning.
Im not saying this is your total problem or is the fix for you.
But i have had a similar experience on my toyhauler with a dead cell battery.
It has two deep cycle 12V Battery's in series
Maybe you need to find another place to test your stuff at. Then tell AZ what you found to be bad and replace it.
OK, just a heads up. I have to drive the truck to St. Louis tomorrow morning with a couple of associates. Hopefully not going to embarrass myself (any further) so, after 8am, I'll be gone for the weekend. (with jumper cables behind the back seat). Besides that, and trying to remember the past 4 days. I actually did go to work one day. I think. Really wonder about one battery being bad, but, they both held a charge individually overnight. OR was that still a bad scenario because the to negatives were still connected? Is it possible that my tensioner could be causing all of my problems?? LMFAO!!! AAARRRGGHH!!
At one point, I left the batteries disconnected. By disconnected, I mean the neg was still hooked up, but both pos disconnected. Before going to bed 12.74 both. In the am 12.68 approximately (both) The alt spike was at this point a one time thing. otherwise, it's kicking 14.4 all day, every time I check it. Which has been pretty often. Tonight I was trying to duplicate the problem of my rapid drain. Starting and stopping checking if at any time the draw got any worse or spiked. And using what appears to be not quite as accurate clamp meter, it did vary, but never much over .80A. But then it dropped back down.
At one point, I left the batteries disconnected. By disconnected, I mean the neg was still hooked up, but both pos disconnected. Before going to bed 12.74 both. In the am 12.68 approximately (both) The alt spike was at this point a one time thing. otherwise, it's kicking 14.4 all day, every time I check it. Which has been pretty often. Tonight I was trying to duplicate the problem of my rapid drain. Starting and stopping checking if at any time the draw got any worse or spiked. And using what appears to be not quite as accurate clamp meter, it did vary, but never much over .80A. But then it dropped back down.
Both batteries being at the same voltage is a pretty decent indicator that you don't have a bad battery discharging a good one, but they still should be individually load tested to make sure.
Since you're reading around 14V with the engine running the batteries should be charging (assuming that's 14V at the batteries). A wiring problem (corrosion, etc) could give you a 14V reading on the dash but less at the batteries. That same type of wiring problem could also cause a voltage spike if the bateries were being intermittently removed from the electrical system. Hmmmm.
One last thought. When your truck doesn't start I'm assuming it has all the signs of low battery voltage; dim headlights, slow blower motor, weak horn, etc., not just a slow/no crank.
Enjoy your weekend, keep those cables handy. Hope you don't have to use them.
Chris
Since you're reading around 14V with the engine running the batteries should be charging (assuming that's 14V at the batteries). A wiring problem (corrosion, etc) could give you a 14V reading on the dash but less at the batteries. That same type of wiring problem could also cause a voltage spike if the bateries were being intermittently removed from the electrical system. Hmmmm.
One last thought. When your truck doesn't start I'm assuming it has all the signs of low battery voltage; dim headlights, slow blower motor, weak horn, etc., not just a slow/no crank.
Enjoy your weekend, keep those cables handy. Hope you don't have to use them.
Chris
LOL. thanks. Yes, very first thing. Cables pulled off, cleaned, reinstalled and tightened. The 14.4 is at the batteries. When its low charge. You can watch on the guage as the fuel pump kicks on and watch it drain from approx 10v to 8. you can hear the pump slow down. the radar detector gives a low voltage warning and turns off.
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