Honda Car Forum

Just wanted to ask:

Is the "light bulb" test (putting a 12v bulb in series with the battery
circuit) an accurate test for a parasitic drain? My ammeter only goes
up to 0.25A, and I don't want to risk overloading the meter.

How bright should the bulb light up, if it should at all, for a
"normal" drain? (clock, ECU, radio memory)

Thanks!

"sharx333" <emil.santos@gmail.com> wrote in news:1163212200.212648.320350
@k70g2000cwa.googlegroups.com:

> Just wanted to ask:
>
> Is the "light bulb" test (putting a 12v bulb in series with the battery
> circuit) an accurate test for a parasitic drain? My ammeter only goes
> up to 0.25A, and I don't want to risk overloading the meter.
>
> How bright should the bulb light up, if it should at all, for a
> "normal" drain? (clock, ECU, radio memory)
>


See the relevant page at Bill Darden's excellent Battery FAQ:
http://www.uuhome.de/william.darden/carfaq10.htm



--
TeGGeR®

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/

sharx333 wrote:
> Just wanted to ask:
>
> Is the "light bulb" test (putting a 12v bulb in series with the battery
> circuit) an accurate test for a parasitic drain? My ammeter only goes
> up to 0.25A, and I don't want to risk overloading the meter.
>
> How bright should the bulb light up, if it should at all, for a
> "normal" drain? (clock, ECU, radio memory)
>
> Thanks!
>
sure, but it depends on the bulb and the drain!!! if you describe your
problem, maybe we can address that question better?

In rec.autos.makers.honda sharx333 <emil.santos@gmail.com> wrote:
> Is the "light bulb" test (putting a 12v bulb in series with the battery
> circuit) an accurate test for a parasitic drain? My ammeter only goes
> up to 0.25A, and I don't want to risk overloading the meter.


I had a light bulb that was a parasitic drain, once.
I thought I just had a dying battery. It was a little sluggish starting
sometimes, and dead if I didn't drive it every day.
I bought a new battery, and that made things much better, and then it was
dead again after it sat for a few days.
I charged it up, got in, and noticed a strange glow on the floor. At first
I thought it was a street light, then I realized that the glove box light
was on. The switch had gotten knocked out of it's mounting. I didn't see
the dim light under daytime conditions, and only happened to notice it at
night.

> How bright should the bulb light up, if it should at all, for a
> "normal" drain? (clock, ECU, radio memory)

I would say that a dual filament 1157 bulb should glow dimly. If it is at
all bright, that is a pretty good load. At full brightness:

bright filament: 12.8V, 26.9W, 2.10A (R=V/I=12.8/2.1=6.1 ohms)
dim filament: 14.0V, 8.3W, 0.59A (R=24 ohms)

--
---
Clarence A Dold - Hidden Valley Lake, CA, USA GPS: 38.8,-122.5

Sure, jim. And thanks.

Last week, the battery drained overnight on my '95 Civic 1.6L. I took
the battery to be recharged at a shop, and we found that the water
level was low. But I suspected a "ground" somewhere, because I had just
sprayed the engine with a degreaser and rinsed it (low pressure garden
hose).

Since my ammeter only goes up to 0.25A (250 mA), and I read on some
posts that the current could go over 1A, I tried the bulb trick first.
I don't know the exact rating of the bulb (aftermarket dome/trunk
light), but it glowed brightly. (All doors/trunk was closed, key off)

I tried pulling underhood fuses and even disconnecting the alternator,
with no result. Then I tried pulling the cabin fuses, and I found that
it was the Pioneer head unit that was pulling most of the power (for
the preset memory, I guess).

When I disconnected the radio, the bulb was finally very dim. I tried
the ammeter and expected less than 80 mA (from the battery FAQ link,
thanks to TeGGer). But I still got 170 mA or so. I've checked all the
possible bulbs, and I think a bulb would pull more than that.

I finally concluded that there was no parasitic drain at all, but I'm
puzzled as to what could be making that extra load.

sharx333 wrote:
> Sure, jim. And thanks.
>
> Last week, the battery drained overnight on my '95 Civic 1.6L. I took
> the battery to be recharged at a shop, and we found that the water
> level was low. But I suspected a "ground" somewhere, because I had just
> sprayed the engine with a degreaser and rinsed it (low pressure garden
> hose).
>
> Since my ammeter only goes up to 0.25A (250 mA), and I read on some
> posts that the current could go over 1A, I tried the bulb trick first.
> I don't know the exact rating of the bulb (aftermarket dome/trunk
> light), but it glowed brightly. (All doors/trunk was closed, key off)
>
> I tried pulling underhood fuses and even disconnecting the alternator,
> with no result. Then I tried pulling the cabin fuses, and I found that
> it was the Pioneer head unit that was pulling most of the power (for
> the preset memory, I guess).
>
> When I disconnected the radio, the bulb was finally very dim. I tried
> the ammeter and expected less than 80 mA (from the battery FAQ link,
> thanks to TeGGer). But I still got 170 mA or so. I've checked all the
> possible bulbs, and I think a bulb would pull more than that.
>
> I finally concluded that there was no parasitic drain at all, but I'm
> puzzled as to what could be making that extra load.
>
well, first, you have to eliminate the battery as a problem - if it's
draining itself, it's no good.

after that, 170mA is a 2W bulb at 12V [hence bulb glow]. that drain
seems high for the ecu memory [what you'd have left after disconnecting
the audio.] i'd continue looking for leakage. check both sets of fuses
pulling each one individually and connect the meter probes between the
slots.

Ok. Thanks for the heads-up.

In rec.autos.makers.honda sharx333 <emil.santos@gmail.com> wrote:
> I don't know the exact rating of the bulb (aftermarket dome/trunk
> light), but it glowed brightly. (All doors/trunk was closed, key off)

That might be a low wattage lamp, and glow brightly at a low current draw.
A stoplight bulb is a better choice, perhaps. I could look at autozone.com
to find the dome light bulb number, and then sylvania.com for the bulb
specs, but I think you found your culprit.

> I tried pulling underhood fuses and even disconnecting the alternator,
> with no result. Then I tried pulling the cabin fuses, and I found that
> it was the Pioneer head unit that was pulling most of the power (for
> the preset memory, I guess).

I think you are indicating that 170mA made the bulb glow dimly, and the
Pioneer made it bright. That's not good. The pioneer should only draw a
few milliamps in standby. There should be a figure in the manual.
There should also be a standby control on the Pioneer.

A voltage supplied to the Pioneer that is always on is expected to be a
heavy current feed for the amplifier, that also draws a tiny amount of
power in standby. There should be another switched control that comes on
with the radio or ignition that cause the Pioneer to turn on its
amplifiers. I think yours is switched on all the time.

Or maybe not... ;-) Check the manual for some specs on the Pioneer.

--
---
Clarence A Dold - Hidden Valley Lake, CA, USA GPS: 38.8,-122.5

dold@XReXXParas.usenet.us.com wrote:
> In rec.autos.makers.honda sharx333 <emil.santos@gmail.com> wrote:
>> I don't know the exact rating of the bulb (aftermarket dome/trunk
>> light), but it glowed brightly. (All doors/trunk was closed, key off)
>
> That might be a low wattage lamp, and glow brightly at a low current draw.
> A stoplight bulb is a better choice, perhaps. I could look at autozone.com
> to find the dome light bulb number, and then sylvania.com for the bulb
> specs, but I think you found your culprit.
>
>> I tried pulling underhood fuses and even disconnecting the alternator,
>> with no result. Then I tried pulling the cabin fuses, and I found that
>> it was the Pioneer head unit that was pulling most of the power (for
>> the preset memory, I guess).
>
> I think you are indicating that 170mA made the bulb glow dimly, and the
> Pioneer made it bright. That's not good. The pioneer should only draw a
> few milliamps in standby. There should be a figure in the manual.
> There should also be a standby control on the Pioneer.
>
> A voltage supplied to the Pioneer that is always on is expected to be a
> heavy current feed for the amplifier, that also draws a tiny amount of
> power in standby. There should be another switched control that comes on
> with the radio or ignition that cause the Pioneer to turn on its
> amplifiers. I think yours is switched on all the time.
>
> Or maybe not... ;-) Check the manual for some specs on the Pioneer.
>
but the 170mA is /after/ the audio is disconnected! yes, the audio
needs to be addressed, but there's still unusually high residual drain.

jim beam wrote:
> dold@XReXXParas.usenet.us.com wrote:
>> In rec.autos.makers.honda sharx333 <emil.santos@gmail.com> wrote:
>> .... also draws a tiny amount of
>> power in standby. There should be another switched control that comes
>> on with the radio or ignition that cause the Pioneer to turn on its
>> amplifiers. I think yours is switched on all the time.
>>
>> Or maybe not... ;-) Check the manual for some specs on the Pioneer.
>>
> but the 170mA is /after/ the audio is disconnected! yes, the audio
> needs to be addressed, but there's still unusually high residual drain.

The obvious question is - can you see the Pioneer front panel lit up?


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