How To Test For Parasitic Draw On Car Battery

Battery Drain
Parasitic Draw Testing

Electric current Bleed Article
Battery Article

© Copyright 2000 - 2006 Chuck Kopelson 12/01/2003
Updated

March vi, 2010

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by Wayne O. Wenzlaff and Chuck Kopelson 4/15/2007

What is parasitic describe? All vehicles draw some ability from the batteries when the car is shut off. Sure accessories such as clocks, radios remote door openers and alarms ever demand power. The normal power used is called parasitic draw. Information technology is always a very low draw so information technology doesn't run the battery down. If you install accessories like shortwave radios or plug things like invertors and portable refrigerators into the accompaniment socket and operate them too long without the engine running yous can drain your batteries to the betoken where the engine won't start. If at that place is an electric short in the vehicle or a malfunctioning accessory it could be drawing much more than than its normal load causing a drain on the batteries. If you lot leave your door open and the inside lights stay on all night you lot could drain the battery down till the automobile won't start. My 98 draws iii.five amps with the front end door open. Ordinarily what happens is the truck is dead when you first go to start it.

The first thing to do is a test for a major short. Remove the positive and negative cables from the batteries. Put an Ohm-meter across the positive and negative cablevision. If your reading is close to 0 Ohms then you lot accept a straight brusk. I read 150 ohms on my stock 98. Y'all need to trace the curt earlier yous can perform the following tests.

In social club to check for parasitic describe, you demand to be conscientious then y'all don't ruin your meter. At the risk of sounding like an uncomplicated instructor, here'due south what y'all demand to do.

1. If you don't already have one, go a digital meter capable of reading upward to 10 amps DC. Sears sells them for less than $l - I bought one on sale for $14.99 that I leave in my truck.
2. Your battery must have a reasonable charge for this test - it won't work if your bombardment is expressionless. Quick proof - if your dome light operates normally, you're fine. My truck wouldn't start and the batteries were downward to 5.5 volts so I put a charger on the batteries overnight. They are now 12.2 5. When I started the truck the voltage went to 14.3 V so the alternator is working.
3. Cheque to make sure ALL loads are turned off. Unplug annihilation you may have plugged into the cigarette lighter. Remove your keys from the ignition. Close all doors so the dome lights are off.
4. Disconnect the thick positive (Ruby) cable that goes down to the starter.
5. To get-go make certain your meter is ready to the x amp DC range. Some meters have a special connector for the cerise probe when you lot are reading electric current. The meter pictured on the left has one jack for high amps and one for low amps. If yours does, make sure the meter cease of the probe is in the right connector. Y'all can either practice this next step by but holding the meter probes to their corresponding contact points (you won't get a shock from 12 volts) or you can use probes with alligator clips to snap them in identify then your easily are free to practice something else.
6. Connect the positive probe to the battery - either battery is fine, electrically speaking, since they are connected together by the negative (Blackness) wires. Polarity on digital meters doesn't matter because they are autosensing.
7. Connect the negative probe to the ruby-red cable that is still connected to the vehicle. Make sure this cablevision and your probe do not bear upon ground.
8. If in that location is a severe current describe (more than than 10 amps) it will either popular a fuse in your meter or destroy it outright. That's why you need to examination for a short, otherwise, your meter should now be reading the current drain on your battery.
9. If your vehicle has an alarm system or remote locks, the current depict may be around 2-3 amps for a few minutes after yous last close the door. This is normal. If yous're not sure, wait at least 20 minutes after you concluding open or close a door earlier you take a reading.
10. If everything is normal, you will read less than 35 milliamps, or .035 amps. If the current drain is higher than that, you need to find out what is draining your batteries: You tin can start by pulling fuses until the load goes away. If that doesn't reduce the draw, you demand to look for a wire that is corroded or frayed.

Happy Hunting!

Measuring Current Draw

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Information technology took awhile to figure it all out over several YEARS. I kept replacing batteries, with the trouble much worse in the winter than summer, when information technology was rainy than dry.

I had several shorts in my truck.

• the winch
• the light organisation to all gauges
• a hot wire to an amplifier

When yous do a parasitic depict test in a dual battery system and you have an electric winch, you should rewire the truck temporarily as two dissever circuits, one to the winch and i to the truck. Each should be checked independently from the other.

If you are drawing also much current in the truck, my first steps would exist to check engine compartment components. Disconnect the hot wire to the alternator to rule out diode backdraw in the alternator itself. Then, disconnect the master engine cable connection to the electric block.

Disconnect all add-on components wired directly to the battery or positive main engine block terminals. Look for elimination of the excessive amperage draw, one item at a time. Disconnect the starter motor, bank check the draw.

Once the engine compartment is ruled out, I would go to the fuse box nether the dashboard and disconnect all add-on components wired to the fuse box or extra hot leads (1 always hot, one ignition controlled hot) that AMG supplies for add together-ons. Do this one at a time, looking for correction of your excessive current describe.

Finally, I would pull all fuses one at a time.

In my case I had corrosion on the winch manus controller connection that immune for a constant low electric current menstruation. Even the wires to the winch were blackened inside their insulation. The winch itself never activated spontaneously. I moved that connectedness far abroad from the winch and abroad from salt spray from the road.

I had a short in the shifter that ultimately acquired a curt to ground and blew fuses when I turned on the lights which activates the console lights. I replaced the shifter (evidently, more than to this story).

I had a big aftermarket hot wire to the amplifier (continued to the battery with a fuse) that rubbed the insulator glaze off and grounded to the body when it was moisture or metal of the torso contracted in the cold and completed the circuit.

Source: https://flashoffroad.com/electrical/Batteries/BatteryDrain.html

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