Parasitic Battery Drain

[TomH]

I’ve had a parasitic drain on my battery for probably 5 years now. I killed a Optima battery in less than two years and it looks like my Sears Platinum is heading down the same path, although it has a far better warranty.

My Land Cruiser will sometimes sit for weeks without being driven. I got tired of having a dead battery every time I wanted to use it so I installed a dual battery system. Well, this wasn’t the only reason for the dual battery, but it solved the need to get a jump. I’m running all the accessories off the main battery, a Sears Platinum 65 that is rated at 75 Amp Hrs. The second battery is a Costco group 35 and does nothing but supply power if the main dies. I use a Blue Sea 9112 automatic charging relay.

Last summer I installed a Datel voltmeter using the Gamiviti dash bezel so I could monitor both batteries during a two week camping trip. This meter shows that I’m getting about 14V to the batteries during normal driving. Voltage normally starts about 14.5 then falls to about 14 after everything is warmed up. Alternator brushes were replaced a few years ago. During this trip, I bought two new Costco deep cycle batteries and used one Costco battery to power the fridge back at camp during the day while the other charged in the second battery location. At night I powered the fridge and lights from the main battery. The main would barely last overnight and the Costco batteries I swapped out every other day. The Costco batteries outperformed the Platinum battery.

I think I've finally gotten to the point where I want to get this resolved. A week ago my wife went to drive the truck after it had sat for about two weeks and the battery was dead. She drove it and I drove it some more to get the battery charged. Saturday I greased my window runs to try to improve performance and probably cycled the window about 15 times per side. Sunday morning, dead battery. Decided it was time to measure current draw.

I connected my meter inline with the negative battery cable and started pulling fuses with the following results in milliamps. The fuses listed are the only ones that showed any difference in the base reading:
Base 21.3
EFI 19.2
Dome 10.3
ECU-B 19.0
FL Power 18.7
AM1 18.5

I’m running the following accessories:
Fog lights, wired through a Slee harness. No draw in the headlight circuits
12V outlets for fridge, kids games, and misc. No draw in this circuit.
Seat heaters, two circuits. No draw in either circuit.
Automatic charging relay switch. No draw in this circuit.
Voltmeter. No draw in this circuit.

The only thing that jumps out is the dome light circuit, pulling more than 10 mA. I was going to try to locate the relay and check it to see if that is the source of the drain, but it started raining, so I gave up for the day.

Everything I’ve read suggests that any drain less than 25 – 50 mA is probably ok so it would seem my 21.3 mA draw shouldn’t be a problem. I decide to use a little math to see what this type of draw would do to the battery.

So 21.3 mA is 0.021 A. I have a 75 Amp Hr battery so that should give me about 3571 hours, 148 days, or about 5 months before it drew the battery down to 10.5V, which I think is how this is measured. This assumes I understand amp hour rating correctly. Even so, at 21.3 mA, the battery shouldn't go dead in a couple weeks.

I’m stumped on this. I’m probably going to take the battery back to Sears and have them check it, but I really don’t think that is the problem. It seems the charging system is functioning adequately. If the battery is good, the charging system is good, and there is no obvious drain, then my battery shouldn’t be dying on me.

Any thoughts?

 

[NLXTACY]

Finding a short, partial short, or battery drain

Here is what I have on a sticky on my laptop for just such issues (I was going to do a "how to" but can't seem to find the time):

TO FIND A SHORT or battery drain, first switch off and disconnect the obvious devices (eg. taillights if blowing taillight fuse) to see if the fuse still blows or the battery current drain disappears. Also try disconnecting everything that is or may be on that fuse’s circuit or anything suspicious or recently worked on that’s electrical or not stock (eg. aftermarket alarm or radio). Disconnect anything electrical that doesn't work since it may be the problem. Examine and wiggle the wiring and connectors on the things you disconnect to see if they are frayed, broken, melted, wet, or touching other wires or metal (and while you’re disconnecting a connector this is a good time to check if it’s pins are all still locked into place). Also check wiring on anything that was added, changed or tied into for power (eg. stop light, radio, and cigarette lighter are typical aftermarket power sources). Probably 95% of the time you will find the short or battery drain using the above techniques which is also the quickest method. Lastly, if all else fails, try unbolting the engine fuse box (disconnect battery first) and examine the cluster of wires underneath. Some may be melted, broken, or shorting against others.

If the fuse still blows you will have to use a tougher technique. Replace the fuse that blows (temporarily and only for testing purposes) with an actual 12 volt incandescent light bulb like a sealed beam headlight, tail light, automotive tester light, or dome light (don't try to start the engine with it in if it’s an engine circuit). If you don’t have a tester light put a bulb in a socket that has wires (or you can solder wires on a bulb). Then insert the wires into the slots where the fuse was. Try to use a light that draws between 3 and 8 amps. More than that can melt wires. Less than that may leave the test light on even after the short is eliminated should there be other lower resistance loads (eg. lighting) that are normally on and drawing power on that circuit. Using a test light drawing between 3 and 8 amps it will go from bright to dim when the short is eliminated and you have other lower resistance loads present on that circuit. Don't use an LED as this will glow even when you only have 30mA of current flowing which is normal for ECU and radio memories. LED’s also only conduct in one polarity so it’s misleading if it’s backwards.
[Note: Instead of using a bulb you can use the ammeter part of a multimeter if the current draw will be less than 10 amps. More than that can damage the meter (check it's maximum) or possibly the car's wiring or blow an internal ammeter fuse if it has one (warning: not all do). You should use a 10A scale if possible since lower scales will add enough resistance to affect the circuit's current draw giving a misleading reading. If you don't know if it's going to be over 10A (which often is the case) you may want to start with the bulb method. Also the bulb limits the current flow to safe levels - the ammeter doesn't since it’s basically a dead short].

This paragraph is not really for a short but I feel it’s useful and can be the problem many people who read this article are hoping to find. If you have very weird symptoms (eg. headlights never go off, or turning on/off one device causes another device to turn on/off), check for open grounds on the devices affected (also any isolation diodes that are an open or short circuit in both directions). Without the device ground the current will find another way to ground, often through another unrelated device which can cause strange happenings! Also check all fuses as sometimes a device may be getting power through a different fuse when its one is blown. If the problem involves an exterior light (headlight, taillight, turn signal, brake light) check to see if any dual filament bulbs have their filaments shorted together (or a single filament bulb is where a dual one should be). This can cause back feeding the other circuit (eg. taillights on backfeeds brake circuit cancelling cruise control). Just removing the bulb will identify this situation (weirdness stops). If an aftermarket radio or alarm power was tapped into a not true power source, strange things will happen. A not true power source is one where you measure +12V but it’s because you are on the load side of something that’s turned off (ie. open circuit voltage). As soon as the device is turned on there won’t be +12V there anymore since it causes a voltage drop. Often using a light bulb in addition to a voltmeter is a good way to find true power sources if you don’t have wiring diagrams (light will be dim on not true sources).

FOR THE CASE OF AN UNKNOWN BATTERY DRAIN, disconnect the negative battery cable terminal and connect the test light (or ammeter but read precautions above) between that cable terminal and the negative battery post.
[Note: Some aftermarket alarms have a surge current when battery is first connected so if using an ammeter instead of the light, connect a jumper between negative battery cable terminal and negative battery post first. Then connect ammeter in parallel to jumper and finally remove jumper. This will prevent any damaging surge from going through ammeter.]
Be sure the light is the only thing connected to the post - all other battery negative cables go on the other side of the light. The light is now the only thing connected to the battery in series with the rest of the car's electrical (don't try to start the engine with it in). The bulb will limit the current so you now don’t have to worry about any short melting the wires. Don't use an LED as this will glow even when you only have 30mA of current flowing which is normal for ECU and radio memories. LED’s also only conduct in one polarity so it’s misleading if it’s backwards.
[Note: If you are also going to be measuring voltages to ground you may want to use the positive post for the test light instead so you don’t "raise or float the ground" for the measurements (there will be a voltage drop across the light if it’s on, of course, to consider). Just be careful not to touch any metal when working with the positive battery terminal.].

THE LIGHT WILL GLOW BRIGHTLY if there is a full short. An open door will appear as a full short so it should either be closed, or it's door switches disconnected, or the fuses removed that operate items (eg. dome/foot lights) caused by an open door (if the test light goes out when removing these fuses, that is the circuit with the short).
THE LIGHT WILL GLOW DIMLY if either you have a partial short or normal devices are turned on (which you should turn off to then see how it glows).
THE LIGHT WILL NOT GLOW AT ALL if nothing draws any significant current (30-40 mA is an acceptable draw to power the ECU memory, radio memory, etc.).

THEN START DISCONNECTING, and removing fuses/relays, and switching off, one at a time (1) things that don’t work, (2) suspected things, and (3) everything on that circuit. When you disconnect, or switch off, the item that is causing the short, the light will go out (so it's a great detection device). Keep in mind the short may be in the wiring or fuse box which is harder to find, but first check all the easier, more obvious devices and places. If the light always stays on no matter what item you disconnect, you probably have a short in the wiring. In that case switch off all devices one at a time to see if light goes out. If it does, then the short is between the switch and the device. If you still can't find the short, try removing all fuses and relays in both the engine and inside fuse boxes. If the light goes out then start replacing the relays and fuses one at a time until the light goes on (identifying the circuit with the short). If the light is always on, you will need to get a circuit diagrams manual to start tracing and disconnecting wires and unplugging harnesses until the light goes out or, without the light connected, start measuring voltages and circuit continuities.

 

[bsmart82]

Toyota spec is 50ma max, so 21 is fine and not killing your battery.

 

[TomH]

Toyota spec is 50ma max, so 21 is fine and not killing your battery.

Yeah - I know 21 mA is fine. I also know if I let the truck sit for three weeks, the battery will be dead.

Just as a baseline, I checked my Tacoma after work today - 13.2 mA. This gives me confidence I'm measuring correctly.

Like I say, I'm stumped on this one. Maybe it's something pulsing intermittently, like the alarm. I'll have to look up how to disconnect it since I never even use it.

 

[blkprj80]

How much current is drawn by your aftermarket voltmeter?

If you're going to let it sit for a couple weeks, try measuring the voltage daily and see how fast it falls.

 

[TomH]

How much current is drawn by your aftermarket voltmeter?

Voltmeter is toggle switch controlled. It's only on when I flip the switch.

If you're going to let it sit for a couple weeks, try measuring the voltage daily and see how fast it falls.

I was thinking this would be the next thing to do. Drive it for a few days to make sure the battery is fully charged and take daily reading. I checked it when I got home today and it was sitting about 12.1, so I don't think it has gotten fully charged since last week when it was dead.

 

[mick085]

I had a similar problem to this and it was my central locking where the alarm and immobilizer was hooked it it would constantly pulse to stop the doors re locking if they key wasn't put in the ignition after a certain amount of time. I killed two big exide batteries before I could find the problem.

 

[TomH]

I had a similar problem to this and it was my central locking where the alarm and immobilizer was hooked it it would constantly pulse to stop the doors re locking if they key wasn't put in the ignition after a certain amount of time. I killed two big exide batteries before I could find the problem.

Thanks - I've been leaning towards the alarm for a while now. You got me wondering if the control module is bad. A couple months ago, not sure when, but the auto-unlock of the doors quit working. The doors used to unlock automatically when I shut the truck down and now it doesn't.

Guess I'll need to start looking for an RS3000 schematic so I can figure out the easiest way to disable.

 

[thestunts]

Ive been having this same issue and happento have a sears platinum as well. However, only one battery.

I've disabled my factory alarm system by selecting disabled on the "brain" of it under the drivers seat. But if my 80 sits for even a day. Next morning, won't start.. BUT the wierd thing is if I hook the battery to a charger, it shows it at 90% or better charge ? but wont get her to crank unless I jump it.

I've taken mine into Sears and they said it checked out fine ... although its my second one.

Subscribed to see what you end up with.

 

[mick085]

Because I had mine hooked in but not to the ignition feed it wouldn't stop the pulse from the system to the locking module and would just be powered all the time. Central locking worked fine but after you lock or unlock it mustn't close and keep running a constant stream of power.

 

[TomH]

Because I had mine hooked in but not to the ignition feed it wouldn't stop the pulse from the system to the locking module and would just be powered all the time. Central locking worked fine but after you lock or unlock it mustn't close and keep running a constant stream of power.

I think the alarm is going to be my primary focus for now. My tentative plan is to hook my meter up to measure current draw, then shut everything down and let it sit. Check the readings every half hour or so to see if I can find the pulsing. I'd really like to verify the problem before I just start disabling systems.

How much current is drawn by your aftermarket voltmeter?

If you're going to let it sit for a couple weeks, try measuring the voltage daily and see how fast it falls.

OK - followed up on this a bit since I left the voltmeter on overnight - 13mA max current draw.

Now for some seat of the pants calculations, the type of calculations you wouldn't give a lot of value because there are some pretty big assumptions.

Yesterday at 4:00 I checked the voltage - 12.1 somewhere around there.
This morning at 5:00 I checked the voltage - 12.02/12.03.
So that is about 0.07V/13hours.
Let's call that 0.1V/day.
A fully charged battery is 12.6V but I've seen 12.8V on my gauge so I'm going with that.
Pretty sure my Land Cruiser needs a solid 12V to start, but let's say 11.8V is good.
That's a 1.0V drop from good to bad at 0.1V/day which gives me about 10 days. A little faster rate than I'm seeing, but something to think about.

 

[blkprj80]

How about a battery tender?
Letting any lead/acid battery sit at less than full charge is bad for it.

 

[e9999]

I think the alarm is going to be my primary focus for now. My tentative plan is to hook my meter up to measure current draw, then shut everything down and let it sit. Check the readings every half hour or so to see if I can find the pulsing. I'd really like to verify the problem before I just start disabling systems.



OK - followed up on this a bit since I left the voltmeter on overnight - 13mA max current draw.

Now for some seat of the pants calculations, the type of calculations you wouldn't give a lot of value because there are some pretty big assumptions.

Yesterday at 4:00 I checked the voltage - 12.1 somewhere around there.
This morning at 5:00 I checked the voltage - 12.02/12.03.
So that is about 0.07V/13hours.
Let's call that 0.1V/day.
A fully charged battery is 12.6V but I've seen 12.8V on my gauge so I'm going with that.
Pretty sure my Land Cruiser needs a solid 12V to start, but let's say 11.8V is good.
That's a 1.0V drop from good to bad at 0.1V/day which gives me about 10 days. A little faster rate than I'm seeing, but something to think about.

haven't reread everything but something here doesn't sound right to me. 13mA max of leakage is not much at all. Should not do your battery in for a long time. Is your number OK on leakage or is there something else going on? And why is your battery only 12.1V, that's very low. Is it not charging right? (Btw, you can't compare absolute voltage at different temps so your 5am voltage should be corrected for the -I assume- lower temperature.)

 

[TomH]

How about a battery tender?
Letting any lead/acid battery sit at less than full charge is bad for it.

Battery tender isn't really an option. I live in the city and park on the street so running an extension cord out to the truck won't work. Plus, I think this would be a band-aid to the real problem.

Assuming a maximum 50mA draw with a 75 AmpHr battery, I should have 30 days until I drop to half the battery capacity - 37.5 AmpHrs. It's rare that the truck sits for 30 days without being driven. I just need to find the source of the draw and fix it.

 

[TomH]

haven't reread everything but something here doesn't sound right to me. 13mA max of leakage is not much at all. Should not do your battery in for a long time. Is your number OK on leakage or is there something else going on? And why is your battery only 12.1V, that's very low. Is it not charging right? (Btw, you can't compare absolute voltage at different temps so your 5am voltage should be corrected for the -I assume- lower temperature.)

OK - maybe you should read everything because your facts are mixed up.

The measured draw is 21.3 mA. The 13 mA is what the voltmeter draws if I leave it on.

The battery is at 12.1V because it hasn't fully charged since it was last drained - I think. I drove the truck today to work and back, about 15 miles each way. Still sitting at about 12.1V. So it may partially be a charging problem, but while driving I'm reading 14V on the voltmeter.

I think once the battery is drained, I don't drive it enough to get back to full charge and the problem magnifies as a result.

And I said my numbers weren't anything to bank on - just some quick seat of the pants calculations. Nothing I'd put a lot of weight on.

 

[blkprj80]

How about a solar charger on the dash?

It sounds like your charging system is right if you see 14 to 14.5 at the battery. Batteries don't like deep discharges, so yours may be compromised already.

 

[Stevesnj]

You need to AMP charge the battery not Volt charge the battery. Take it someplace to have them AMP charge it to get the plates inside back to operating condition.

 

[e9999]

OK - maybe you should read everything because your facts are mixed up.

The measured draw is 21.3 mA. The 13 mA is what the voltmeter draws if I leave it on.

The battery is at 12.1V because it hasn't fully charged since it was last drained - I think. I drove the truck today to work and back, about 15 miles each way. Still sitting at about 12.1V. So it may partially be a charging problem, but while driving I'm reading 14V on the voltmeter.

I think once the battery is drained, I don't drive it enough to get back to full charge and the problem magnifies as a result.

And I said my numbers weren't anything to bank on - just some quick seat of the pants calculations. Nothing I'd put a lot of weight on.

No desire to. 21 or 13mA, it doesn't matter. That should not kill a good battery. (I assume that is measured with all the wires disconnected from the battery.) 12.1V is unacceptably low. If your alternator puts out a real 14+V and full amps, it should recharge a good battery a great deal in 30 miles.

 

[TomH]

How about a solar charger on the dash?

It sounds like your charging system is right if you see 14 to 14.5 at the battery. Batteries don't like deep discharges, so yours may be compromised already.

Agreed, the battery may be compromised by now. This is one of the reasons I bought the Platinum battery - 36 month replacement warranty and 100 months pro-rated. I think it's been less than three years since I bought it.

You need to AMP charge the battery not Volt charge the battery. Take it someplace to have them AMP charge it to get the plates inside back to operating condition.

I'm a little confused, isn't the alternator providing current to charge the battery? I could pull the battery and put it on the charger but I'm trying to get a look at the whole system to see how it is performing. I believe something isn't working right and I'd really like to find out what so I can fix it.

No desire to. 21 or 13mA, it doesn't matter. That should not kill a good battery.

Agreed. Yet something is killing my battery. This problem has been going on for years. Like I said, I’m going to focus on the alarm and see if it is drawing current when it’s not supposed to be. Not sure what else to check.

(I assume that is measured with all the wires disconnected from the battery.)

I thought the purpose of measuring current draw was to keep everything hooked up. To do the test, I disconnected the negative battery terminal and connected my meter in-line with the negative post and negative terminal.

12.1V is unacceptably low. If your alternator puts out a real 14+V and full amps, it should recharge a good battery a great deal in 30 miles.

Agreed, 12.1V is too low. I checked voltage a couple hours after I got to work today and it was reading 12.2V. Maybe it’s slowly getting charged. I have no idea how long (miles) it should take to get a fully discharged battery back to 12.6V.

I’m pretty confident in the meter I’m using to measure voltage. It’s rated as follows:
Accuracy @ +25°C: ±0.01V (typ.), ±0.03V (max.)
It’s not calibrated but I think it’s pretty close to reality. When I left home this morning, voltage was reading 14.75. By the time I got to work it was down to 14.2ish. It typically runs right about 14V after everything is warmed up. At low idle, traffic lights, it will drop below 13V but pretty sure this is normal.

I do not know how to verify the alternator is putting out full amps. Can I just measure DC Amps across the battery terminals or do I need some fancy tester or process?

 

[blkprj80]

Uh, don't try to measure current across the battery terminals! More DMM fuses get blown this way.

I have a clip on current probe, but it would only tell you what is flowing to/from the battery. Probably show a few hundred amps while you start it, going out, and then show 10s of amps going back into the battery at first, then tapering as it charged.

I've been told that today's DMMs have excellent voltage accuracy, even the el cheapos from Sears, etc. Something about the chip that they use nowadays.

I'd say take it to Sears and have them check your battery. I had a 2 year old battery recently that went south, probably from lack of use. One morning it barely started, and when they checked it they said it was bad.

Then, put a solar charger on it and never worry again.