Batteries drawn down over night
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Laughing Gas
Joined: Sep 2007
Posts: 869
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From: Near Shenandoah Valley
Batteries drawn down over night
'95 2X4 5 spd. Batteries go dead over night. Not complete but will not start. Removed both batt.'s recharged and reinstalled, load tested and both good. ,clean and tight. Removed alt. and had tested at Autoxxxx, tested good, charge, rectifier, diodes. not completely trusting them, I unhooked it at night and same thing, low batt's needing a boost to start. Just for grins I checked to see if GPR was energized but was not. Any ideas what to check? The key switch is a little flaky in that with key removed in rotates as much as you want to turn it. Between me and the guy I bought it from it's done that for years.
Senior User
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Sounds like the batteries are done to me....how old are they and what were the numbers (results) of the load test?
Assuming all the tests were done correctly and the alternator isn't involved, I'd suspect you have a significant current 'leak' and you need some equipment to find it. A clamp on amp meter is preferred though an 'in-line' type can be used. I always consider "normal" off current for an ECU equipped vehicle to be between 20 and 50 milliamps - anything more indicates an issue. (only exception is for the 'newer' designs where they have a timed sequence before they "go to sleep". until they "go to sleep [within one hour after key off] they may draw a few amps (1-4 depending upon equipment).)
Assuming all the tests were done correctly and the alternator isn't involved, I'd suspect you have a significant current 'leak' and you need some equipment to find it. A clamp on amp meter is preferred though an 'in-line' type can be used. I always consider "normal" off current for an ECU equipped vehicle to be between 20 and 50 milliamps - anything more indicates an issue. (only exception is for the 'newer' designs where they have a timed sequence before they "go to sleep". until they "go to sleep [within one hour after key off] they may draw a few amps (1-4 depending upon equipment).)
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Laughing Gas
Joined: Sep 2007
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From: Near Shenandoah Valley
I used an analog type of load tester that stayed in the high "good". I do not have a clamp on DC meter, AC only, but do have the inline type you lay along wire. Batteries are matched set as far as size, however, one is a replacement for an earlier bad one. One new in Dec. ,other almost three years old. Both batteries show same on load test. Also, starter is an Autoxxxx from Dec. as well.
FOREIGN GURU
Joined: Jul 2006
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From: Celaya, Gto. MX
If the batteries are fine, to look what circuit is causing the drain,
try removing both positive terminals tie one out of way so not to touch anything ,take other terminal and put a voltmeter or test light between battery post & terminal if you get more than 3-4 volts or light is on you have a drain. Make sure everything is off while doing this. If you find voltage or light start pulling fuses 1by1.When light goes out u have found the circuit that is causing you're drain, Good Luck..
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try removing both positive terminals tie one out of way so not to touch anything ,take other terminal and put a voltmeter or test light between battery post & terminal if you get more than 3-4 volts or light is on you have a drain. Make sure everything is off while doing this. If you find voltage or light start pulling fuses 1by1.When light goes out u have found the circuit that is causing you're drain, Good Luck..
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Lead Driver
Joined: Aug 2006
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From: Gambrills
If you are going to disconnect the batteries again tonight, I would also seperate the batteries. Then in the morning (if you have a multi meter)....see wich one is low. It has been my experience that 1 bad battery can drain the other even went it is not hooked to the truck (but still hooked to eachother).
lol, I hope that was understandable.
lol, I hope that was understandable.
Senior User
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So you don't know how much current was produced during the load test or what the measured voltage at the end of the test was???
I'd start by redoing the load test at a real auto electric shop, not one of the AutoxxxxBox stores.
I'd start by redoing the load test at a real auto electric shop, not one of the AutoxxxxBox stores.
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Laughing Gas
Joined: Sep 2007
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From: Near Shenandoah Valley
OK, when I did load test batteries showed 13+ before 10 sec. load , 12+ after. Since they never dipped into bad I assumed they were ok both tested the same. I know this isn't very accurate but has always worked. Perhaps I do need to take them to a real auto or battery shop. I think I will try the test you guys outlined here, first unhooking from each other and also checking for draining circuit. Thanks All!!
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Senior User
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The key to the load test is the "load" the battery get put under. Your voltage numbers are stellar for a spec test on a Group 65 HD battery but don't tell you anything if the load applied only draws 10 amps...and your started draws a bit more than 10 amps.
Lead Driver
Joined: Aug 2006
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From: Gambrills
If you want to read my bad battery thread....here it is--> https://www.ford-trucks.com/forums/8...batteries.html
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Laughing Gas
Joined: Sep 2007
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From: Near Shenandoah Valley
Well now, after unhooking just the suspect battery( in ya'lls mind)-older one- I redneck insulated it in an old rubber glove. I left the newer one hooked up, new one 12.5 volt, old one...7.9 volts. I have found out a few things, first, I need a more accurate way to load test and that you folks are some of the best. Thanks!! I will be heading off to Autoxxxx soon to haggle with them.
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Learning is a never ending process. This forum allows it to be a two-way process.
FWIW, the AAP stores around here have rolled out a new battery tester they keep behind the counter. The kid I spoke with claims they cost > $10K each. Looks like it is computer based. May want to see if they have one out there if you have an AAP store close by - second opinions, without financial bias, are always worth getting.
FWIW, the AAP stores around here have rolled out a new battery tester they keep behind the counter. The kid I spoke with claims they cost > $10K each. Looks like it is computer based. May want to see if they have one out there if you have an AAP store close by - second opinions, without financial bias, are always worth getting.
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