Battery drain!

Stoney#1

Stoney#1

Stoney
Good Day
I seem to have an occasional drain on my battery. At times after sitting for a week or two the battery will be to drained to turn over. How can I test to find out what would cause this. Is there a way to use a multi meter to test this and how and where would I attach it? With everything turned off how much power should I read for the ecu?

Sorry, a lot of questions from someone who really doesn't know my amps from a volt
Any help would be appreciated

Thanks

Stoney
 
Standard technique is to put a multimeter in series with the battery, measure current flow if any, then pull and replace one fuse at a time, looking for stoppage of current flow when the "right" fuse is pulled and then current flow when put back. That narrows it down to which fuse circuit the drain is on, then you have to drill down on the functions/devices on that circuit.

https://www.popularmechanics.com/cars/car-technology/a5859/how-to-stop-car-battery-drains/

But yeah like Jefco said, the digital clock consumes a surprising amount of power. If you have a marginal battery, plus maybe too much resistance in the ignition switch, in a couple of weeks you might not have enough juice to energize the starter.
 
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A couple of things you can do.
Charge the Batt and write down the voltage at rest. It will show high 13+ right off the charger so take another reading about an hour later and write it down. It should be around 12.29.
let it set 12 hours and take a reading and another 12 hours after that. If you can let it set unhooked for a couple of days or more taking volt readings every 12 to 24 hours that is all the better. A good battery should self discharge about 1% every 24 hours. These voltages are from memory so your measurements may vary. The main thing is the battery should not self discharge much more than 1% in 24 hours.

A faster way would be charge the batt and if you do not have a load tester go to a car parts store and ask them to test it for you.
 
https://www.harborfreight.com/15-watt-solar-battery-charger-62449.html

I zip tied one of these on my dashboard (driver side above the gauges) and have it wired in. Should be able to keep up with the clock, cell phone charger and GPS (that is alway's on) but I also drive it almost every day so I don't know if it will keep up or not..(but for $14 not bad) have one in a 91 dynasty and loaded it out they commented they killed the battery and the solar charger charged enough to start the next day.
 
Dan Sarandrea (Phila) said:
Standard technique is to put a multimeter in series with the battery, measure current flow if any, then pull and replace one fuse at a time, looking for stoppage of current flow when the "right" fuse is pulled and then current flow when put back. That narrows it down to which fuse circuit the drain is on, then you have to drill down on the functions/devices on that circuit.

https://www.popularmechanics.com/cars/car-technology/a5859/how-to-stop-car-battery-drains/

But yeah like Jefco said, the digital clock consumes a surprising amount of power. If you have a marginal battery, plus maybe too much resistance in the ignition switch, in a couple of weeks you might not have enough juice to energize the starter.
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This will work, but make sure the meter is protected with a 1 A or smaller fuse (internal or external to the meter).
The way I usually do is put a digital VOM across the ground cable from battery negative - you need a good meter with sub mV resolution, but that way you do not need to disconnect anything. Might not work for everyone as I have a very good test equipment.
 
Dan Sarandrea (Phila) said:
Standard technique is to put a multimeter in series with the battery, measure current flow if any, then pull and replace one fuse at a time, looking for stoppage of current flow when the "right" fuse is pulled and then current flow when put back. That narrows it down to which fuse circuit the drain is on, then you have to drill down on the functions/devices on that circuit.

https://www.popularmechanics.com/cars/car-technology/a5859/how-to-stop-car-battery-drains/

But yeah like Jefco said, the digital clock consumes a surprising amount of power. If you have a marginal battery, plus maybe too much resistance in the ignition switch, in a couple of weeks you might not have enough juice to energize the starter.
Click to expand...
Old thread revival. Ever since getting the ‘74, the battery seems to drain easily. I read the article you posted, and one symptom, long crank times without starting, is definitely a symptom.
The WD folks put a 26 in instead of a 24. Also, the starter was replaced by a local X1/9 ‘expert’, in that he put in one of his ‘refurbished’ exxe starters, in December. Ever since, unless the car has been driven recently, starting from cold is the car’s weak spot.
Today, after a couple of long cranks and no starting, the battery was done. Hooked up the charger, and it’s back.
The only thing I did with the car today was occasionally have the door open for testing the trunk latch.
That tiny, rear interior light shouldn’t be enough for draining a battery.
Could the starter be killing the battery, or the other way around.
I‘d do your ‘in series’ test, but could you clarify how that’s hooked up?
It‘s possible the master mechanics made a wiring alteration that continually kills the battery, or maybe the alternator is under powered/dying?
Thanks

 
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There should be no drain from the ECU when the engine is off.

How old is your battery?

Your alternator can also cause a drain if the rectifier has gone bad, it can drain the battery.
 
Series means "knee bone connected to the thigh bone connected to the hip bone" 🤪

Start with a freshly charged battery.

Make sure everything is off, keys out of ignition, doors closed and remove any chargers from cigarette lighter plugs. The idea is that you want as little electrical "flow" as possible so you don't accidentally blow your multimeter fuse and then have to chase all over town to find a new one.

Disconnect the ground cable from the neg batt post.

Set the ground cable's batt post clamp onto something that will insulate it from the car (rags, cardboard, etc).

Set your meter to the highest amperage range. On most recent meters with a dial selector, the amperage choices are positioned at 1 o'clock thru 5 o'clock. Some of the newer digital meters want you to move the red test lead to different ports depending upon the amp scale, so if in doubt, see if there's a user guide or video on the meter maker's web site or YouTube on how to figure that out.

Now touch the meter's red probe point to the neg cable's clamp and then the meter's black probe point to the neg battery post. In this state, any electrical flow taking place is flowing thru the meter, so it will show up on the readout.

If you get a blip on the needle or readout, remove the probes, notch down the amperage range one notch on the scale and retouch the probes.

For a typical classic car situation, the most useful scale for battery drains is going to be the single amp range or the first milliamp range.

If you want to try the fuse-pulling test, it would be best to have a helper hold the probe points in place and look at the meter readout while you are under the dash pulling fuses. Or you could find some meter leads with alligator clips. Since all circuits are live during this test, take care to not short anything out while pulling fuses, one of those plastic fuse puller thingies (essentially a pair of pliers made from plastic) would be a good idea.
 
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myronx19 said:
There should be no drain from the ECU when the engine is off.

How old is your battery?

Your alternator can also cause a drain if the rectifier has gone bad, it can drain the battery.
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It looks like it’s about 14 months old. But remember, a Wheeler Dealers car, so no idea how many times it was in use without the engine being started, aka headlights, console testing, etc.
 
myronx19 said:
There should be no drain from the ECU when the engine is off.

How old is your battery?

Your alternator can also cause a drain if the rectifier has gone bad, it can drain the battery.
Click to expand...
Ok, after sending a couple of pictures to MWB, Matt thinks the alternator is the original, 33a Bosch. He has doubts adding stereo equipment/subwoofers, etc. would be a good idea, and suggested going up to a 65a with an internal regulator.
Are there plusses and minuses to internal regulators over the stock, external one I'm running now?

540E81F3-44C6-443D-8846-F583BBD03705.jpeg
4850B0D1-CA86-4BF6-9659-DB7DA5EA5C7F.jpeg
 
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There is no downside to internal regulators. They work well are about as easy to replace as external ones. If you change to an internally regulated alternator, you'll have to change the wiring accordingly, removing the external regulator from the circuit.
 
tvmaster said:
Ok, after sending a couple of pictures to MWB, Matt thinks the alternator is the original, 33a Bosch. He has doubts adding stereo equipment/subwoofers, etc. would be a good idea, and suggested going up to a 65a with an internal regulator.
Are there plusses and minuses to internal regulators over the stock, external one I'm running now?

View attachment 45625View attachment 45626
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The only minus I know of would be how heat has a tendency to work against older generation electronics. Since exxie alternators live right next to a cooling system pipe and the exhaust manifold, that's a thing.

Some where in the early 80s FIAT added a cooling duct that tapped outside air from the right side engine scoop and delivered it to a cowling attached to the backside of the higher powered alternators.

I have seen a specialty vendor that offers a "remote" electronic voltage regulator that in theory would address this issue, and might actually be something that someone converting from an external regulator might have interest in.

Dave's Volvo Page - Volvo Adjustable Voltage Regulators

Dave's Volvo page. Adjustable Voltage Regulators.
www.prancingmoose.com
 
Dan Sarandrea (Phila) said:
The only minus I know of would be how heat has a tendency to work against older generation electronics. Since exxie alternators live right next to a cooling system pipe and the exhaust manifold, that's a thing.

Some where in the early 80s FIAT added a cooling duct that tapped outside air from the right side engine scoop and delivered it to a cowling attached to the backside of the higher powered alternators.

I have seen a specialty vendor that offers a "remote" electronic voltage regulator that in theory would address this issue, and might actually be something that someone converting from an external regulator might have interest in.

Dave's Volvo Page - Volvo Adjustable Voltage Regulators

Dave's Volvo page. Adjustable Voltage Regulators.
www.prancingmoose.com
Click to expand...
So you're thinking the voltage regulator adds significant heat to the package?
 
The location adds heat to the package. My 74 came with an asbestos covered heat shield in between the exhaust and the alternator.
 
tvmaster said:
Ok, after sending a couple of pictures to MWB, Matt thinks the alternator is the original, 33a Bosch. He has doubts adding stereo equipment/subwoofers, etc. would be a good idea, and suggested going up to a 65a with an internal regulator.
Are there plusses and minuses to internal regulators over the stock, external one I'm running now?

View attachment 45625View attachment 45626
Click to expand...
How much power do you plan to be running? 33A @ 12 - 14V gets you 400W. A class B amp will give you 50+% efficiency and a class D 90+%. You can always turn the volume down if the lights get dim.
 
dllubin said:
How much power do you plan to be running? 33A @ 12 - 14V gets you 400W. A class B amp will give you 50+% efficiency and a class D 90+%. You can always turn the volume down if the lights get dim.
Click to expand...
I'd like to not have to change. At the moment, there's 16w x 4 single din installed. Everything else in the car is stock. Most I'd go is probably 50w x 4 plus a subwoofer - maybe 100w there? So, yeah, it's getting close...
 
tvmaster said:
So you're thinking the voltage regulator adds significant heat to the package?
Click to expand...
No, the heat from the exhaust and the cooling system pipe negatively affect the early electronics of the solid state voltage regulator in the alternator, which is going to run hotter by itself in the first place because it's around 55-65 amp as compared to the original which was 33 amp. More power almost always = more heat.
 
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