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How to track down what's draining my batteries?

LagunaH1

Well-Known Member
Messages
3,703
Location
Lake Forest, CA
Hi guys,

Something in my truck must be drawing current from the batteries because it is completely dead and the batteries are almost brand new.

I have had my CB radio disconnected for a while and in an attempt to locate the source of the current drain, I have had an am-meter inline in the circuit powering my HAM radios. With the HAM radios off, there is 0.0 amps going through that circuit so I think I can pretty much rule out the radios as the root cause.

Are there any common things that are known to be causing battery drain on a '97 TD?
 

Sierra H3

Well-Known Member
Messages
150
Location
Central Sierras
I had this problem for a couple of years with my old F-250. Batteries lasted a shorter and shorter amount of time. To check the alternator, I found out the normal charging voltage range at the battery when idling or at 2000 RPM. An ammeter check showed it to be good. I Also checked resistance to chassis for the starter cable coming off of the battery, that also checked good. I pulled the starter and had it bench tested at a local parts store - it passed. But, measuring voltage at the starter cable while cranking showed an intermittent drop below specs. I decided that it was the starter shorting out when hot. A new starter did the trick. I don't like to buy rebuilt starters, they never see to last most likely due to weakened wiring insulation. Different vehicle and different age, but hope this experience is of some help.
 

f5moab

Mr. Beretta
Messages
1,986
Location
Hiding in a potato patch in Idaho
Sounds more like a parastic drain. One way to check is to connect an ammeter in series with the battery (ENGINE NOT RUNNING), and read the amps, and then pull fuses one at a time until the large drain is removed. However, you might need a hefty ammeter. If you connect it inline and the draw is larger than what the ammeter is rated for it will blow the ammeter's fuse.
Also, can't speak for an H1, but with the 2 and 3, you need to wait about twenty minutes to allow the computers to go into sleep mode.
Once in sleep mode, the computers will draw milliamps, but again, I have no idea what the NORMAL drain would be on your 1.
But it takes many many days for milliamp parastic drains to draw down a good size battery and in your case I believe you have two. So if it is draining overnight, you have a big parasitic drain.
You can purchase shunt kits at some auto part stores. These are basically resitors put in line with the body and the battery, and you in turn use the voltmeter to test voltage across the shunt, then divide the voltage by the resitor and that gives you an amp reading.
Some auto parts stores have some heavy duty machines such as VAT or ARBS testers that if they will connect, you can then start pulling fuses.

Look for a large draw and when it goes away with the fuse being pulled, that is the circuit causing the problem. Make sure to check any add on accessories that are fused in the fuse panel, but (hopefully) inline very close to the point where they draw their power from (i.e., near the battery).

Disconnect the battery cable and install a 100 ohm resistor inline between the battery and the cable. Wait about twenty minutes (sometime disconnecting/reconnecting cables will wake up computers). Then, using a voltmeter, measure the voltage across the shunt.
For example, if you show 30 volts on the meter, take that number and divide by the resistance of the resistor, in this case 100 ohm. and you will show it as a .3 amp draw.
 
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LagunaH1

Well-Known Member
Messages
3,703
Location
Lake Forest, CA
Thanks for your input guys. Like Doug I think this is a parasitic draw. The truck had been sitting for a few weeks before the batteries were down so my first thing will be the ammeter & fuse pulling. If nothing else, it will be pretty interesting to see how much of a draw it is in the first place.

It was kinda funny: It took the AAA battery service truck PLUS one of these additional little battery booster things before there was enough amps to start the truck. If I recall correctly, the AAA tech's computer gadget said 550 "CCI's" whatever that is. I know this because he blurted out "wow , that is a REALLY high capacity battery!"

Anyways, once the truck was up and running, everything seemed to work great. I'll go check the battery voltage later tonight but it sat right at 13 volts when we got home after a 2 hour drive.
 

LagunaH1

Well-Known Member
Messages
3,703
Location
Lake Forest, CA
I don't think anything is wrong with the batteries, they are practically new. The AAA tech used a gadget to "test" the batteries and alternator, but I have my doubts about the accuracy and usefulness of those types of devices, I have seen them be wrong in the past.

Edit: Maybe it's time to look into a battery tender
 

hummech

Well-Known Member
Messages
123
Location
huntington beach ca.
i am running a draw test on it while it is here, we will get it pin pointed at no charge to you.... i am teaching my guy's how to properly do a parasitic draw test on your Hummer. i will let you know what we find.
 

alrock

El Diablo
Staff member
Messages
10,442
Location
Scottsdale
Mike, do you wanna teach your guys how to rebuild leafs, add a leaf, straighten UCP, replace rear shocks, and detail an H3? :giggle:
 

Hunner

Well-Known Member
Messages
2,334
Location
Arkansas
I worked on a boat at one time that kept draining the batteries and traced that to a bad diode in the alternator. Sort of like pulling the cork out once the juice was in the battery when the engine was shut off.
 
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