Something i've sometimes wondered about. How much power does each glow plug cycle use? In other words: How many times could someone theoretically cycle the plugs before the battery goes flat?) (Of course the numbers would vary with different engines and battery's.)

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1982 300GD Carmine Red (DB3535) Cabriolet Parting Out
1990 300SEL Smoke Silver (Parting out)
1991 350SDL Blackberry Metallic (481)

"The thing is Bob, its not that I'm lazy...its that I just don't care."

I can't say.
When I tested some Glow pugs with dashboard type Amp Meter the gauge pegged at 60 amps; as high a that gauge would go for a really long second or so and then as the Glow Plug got hot settled down to about 16 Amps and stay that way.

The term "battery going flat" is too subjective because that could imply until the Battery is ruined. I say that because the Battery still has to Crank the Engine and during the Cranking your Gow Plugs are on.
As Voltage drops you start to cause some damage; especially if it is not charge up quickly after wards.

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84 300D, 82 Volvo 244Gl Diesel

I have glowed 3-4x plus 20-30 seconds of cranking before with no ill effects on the battery....the 100A batteries can put out quite a lot of power before being damaged. Key to is to have it on long enough to recharge adequately.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Theoretically if you had a 100 amp-hr battery and were glowing plugs pulling 50 amps, you could glow for 2 hours. Of course you'd have nothing left to crank the engine, but that's the theoretical. In reality, there are just too many variables to know for sure, and what would it mean in practical terms? Probably nothing. Perhaps a better way to think of it is for every minute of glow, you're using about 1-2% of your battery

I elected to go with a manual glow system on my conversion. This allows me to glow for only the amount required to start, and if the engine is warm, not glow at all... and after glow only if needed. This extends the life of the glow plugs and the battery significantly.

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Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

What does "100A" mean?

Looking at some aircraft batteries which have advertised amp-hour ratings and extrapolating for size/weight, I would conclude that the typical MB diesel battery would have at least an 80 amp-hour rating. That would suggest that no reasonable amount of glow plug operation would pose a problem for a battery in good condition.

when having difficulties starting I have tried along with glowing and cranking probably 20 times before the battery falling off. I don't recommend it but a good strong battery will take a huge abuse and keep on cranking. I don't recommend it for the starter either but again, they are very very rugged as well.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

There is no correct answer but we can guesstimate. It all depends on how many cylinders in the car, 4, 5, 6 or 8 and AH of battery.

Assume 1 GP is about 125watts. Most GP wattage is between 100-150watts. Amperage drawn by all GP: m = 125/12*n where n = # of GP.

Total minutes of glow time possible with a Y AH battery: Y/m * 60 minutes. So a 5 cyl car with a 100AH battery will glow for 115mintes in theory. So it is safe to say you can glow the car for a long time, 60+minutes and still have enough juice to crank the car.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

I have an inductive Amp Meter and applied it to the Battery Cable and My Starter Pulls about 150 amps when it is cranking. That includs the amperage the Glow Plugs are pulling as they are also on during cranking.

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84 300D, 82 Volvo 244Gl Diesel

.........and what do you think the battery voltage will be after 115 minutes?

How about after 60 minutes?

How about after 30 minutes?


Once the battery voltage drops from the fully charged point of 12.5V to somewhere around 11.8V, you're not starting the engine anymore.

If I had to make an educated guess, I would say that you're toast after about 10 minutes (about 20 glow cycles).

the bottom line is this. attempting to glow a motor until the battery is too weak to start is very very unwise. a battery is NOT designed for this purpose. it's designed to have juice to glow, and start, then rapidly be recharged by a good quality alternator. deep discharging of an automotive battery will RAPIDLY rush the demise of the battery.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

And, at what temperature?

I know that is what the say on Gasoline Engines because the Coil has to have a certan amount of Voltage to get a good spark but on Diesels I a not so sure.

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84 300D, 82 Volvo 244Gl Diesel

Temperature also plays a significant role. At very cold ambients, you might not get 10 minutes of glow time.

The starter on a diesel needs a certain voltage to get sufficient current to allow sufficient speed of rotation to allow sufficient compression to allow a start. It doesn't take much voltage drop in the battery to slide below the speed requirement, especially with older engines.

With the exception of Deep Cycle batteries of course. (Although they generally aren't used for automotive purposes)

__________________
1982 300GD Carmine Red (DB3535) Cabriolet Parting Out
1990 300SEL Smoke Silver (Parting out)
1991 350SDL Blackberry Metallic (481)

"The thing is Bob, its not that I'm lazy...its that I just don't care."

Don't know

Don't know

Don't know

I doubt it.

As I have said, there is no correct answer. It is all theoretical guesstimate. There is so many factors, like temperature, battery AH, GP wattage, GP # that it is not worth my effort to post anymore. If you glow 10 times and it does not start then you are done for.

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Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

Previously, ambient temp had been mentioned. It IS a factor, which is why I put the block heater on when the temp gets down to 5 degrees F, like it was last night.

The block heater also heats the engine compartment, keepoing the battery warmer.

What amazed me (I tried this too) is how much a hillbilly hotbox keeps an engine compartment warm, and even heats the oil pan and oil a little bit.

I tried the HHB when I had a battery which I suspected was losing its ability to keep a charge.

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Strelnik
Invest in America: Buy a Congressman!

1950 170SD
1951 Citroen 11BN
1953 Citroen 11BNF limo
1953 220a project
1959 180D
1960 190D
1960 Borgward Isabella TS 2dr
1983 240D daily driver
1983 380SL
1990 350SDL daily driver alt
3 x Citroen DS21M, down from 5
3 x Citroen 2CV, down from 6