How much current?

Geo-TH,In

Well-known Member
I don't have a DC ammeter to measure large currents. I realize my question has many variables like size of engine, speed of golf cart, trolling speed, weight in dump trailer, so I'll ask my question this way. What is the average or range of DC amps have you measured for the following?

1. Lawn mower starter
2. trolling motor
3. golf cart
4. car starter
5. diesel starter
6. dump trailer
 
I retired from the class 8 truck shop in 2010. At that time the M-11 Cummins and series 60 Detroits ran from 600 to 900 amps when new and occasionally 1100 amps. My ammeter read up to 2000 amperes. I had two trucks that pegged the ammeter and still started the engines. One on a Cummins the other one a Detroit. They would loose the memory on the radio. The starter was shorted internally on both. When the starters were replaced both dropped back to the normal range.
 

1. Lawn mower starter 75 to 100 amps
2. trolling motor dunno but low depends on speed setting
3. golf cart dunno
4. car starter 125 to 200 depends on engine
5. diesel starter don't do much if any diesel I spec to see in the 400/600 range up on dodge pick up 5.9
6. dump trailer it uses a car starter I would spec it to be in the low range as it would be a constant load unlike a car/diesel that has to overcome pushing the starter to get it to move then fight every compression stroke as it works.

https://www.youtube.com/watch?v=kWvII9Vsdpw

Are google relative compression test with scope to father your education.
 
Hello Kito,

600 to 900 Amps is correct! Two good group 31 batteries would start the engine on a warm day. How many CCA capacity did your trucks had?. Ours had 3 group 31 which made the CCA at 1875,

Guido.
 
I have a little DC induction type ammeter I bought years ago, when I was a "wrench turner". I can't remember the last time I used it. It has two different size clips on the back, for sliding over different size cables. Kind of crude, but if you could get hold of one of those, you could do a lot of experimenting.
 
Measurement is easily done George. Get a slab of low resistance material, brass, copper, aluminum 10+ times the area of your conductor. This is the sort of thing meters use for high current applications, called a "meter shunt" and commercially have the resistance stamped thereupon with terminals at each end for an accurate connection point. Accurately measure the resistance which is pretty easy with today's digital meters, as is the voltage drop. Use ohms law and get your answer.
 
All depends on how hard the engine is turning over. Starters are rated at "no load" and "locked max load."

Starter in my 7.3 Ford diesel draws around 275 amps @ 9.4 volts in normal starting. It can draw up to 500 amps.

Here are a few specs from old tractor starters.

Delco 1107905 6 volt starter, no-load - 65 amps @ 5 volts, max - 600 amps @ 3 volts
Delco 756 12 volt starter, no-load - 75 amps @ 11.3 volts, max - 700 amps @ 5 volts
Delco 806 24 volt starter, no-load - 115 amps @ 23 volts, max - 800 amps @ 4.4 volts
 
Just too many variables to venture an accurate guess, engine size,,,,,,,compression,,,,,,,,,,,temperature,,,,,,,,,oil viscosity,,,,,,,friction,,,,,,,,,starter motor HP,,,,,,,,starter motor design,,,,,,,,loaded versus unloaded and how much loaded etc etc etc. An ammeter will tell you the answer

John T
 
(quoted from post at 21:39:20 03/06/17) All depends on how hard the engine is turning over. Starters are rated at "no load" and "locked max load."

Starter in my 7.3 Ford diesel draws around 275 amps @ 9.4 volts in normal starting. It can draw up to 500 amps.

Here are a few specs from old tractor starters.

Delco 1107905 6 volt starter, no-load - 65 amps @ 5 volts, max - 600 amps @ 3 volts
Delco 756 12 volt starter, no-load - 75 amps @ 11.3 volts, max - 700 amps @ 5 volts
Delco 806 24 volt starter, no-load - 115 amps @ 23 volts, max - 800 amps @ 4.4 volts

I never took time you use that info useful I check it under operating conditions. I guess it would vary depending on the application.

If he had a real load tester instead of a toy tester he could build his own library.
 
My lawn mower has a 240 CCA battery. It might use 40% of those CCA's to start the motor but it could have a short bursts where it would use 48-50% of total CCA's available. The battery is in slight state of discharge after sitting all winter so it will not have all the CCA's available as it's rating says. Some factors are unknown to give exact answers. The oil is 30W with several hours on it with some dissolved solids in it and the compression is 8 or 9 to 1,but has six years wear on the motor. So compression could be down from new. Then there is some line loss in the wiring from the key to the starter and to the battery as it sits under the seat, the starter motor is in way out in front of the operator by the engine. More wiring line loss. Have no gauges like ammeter on the dashboard to give any closer answer, the mower price was cheaper that way.
 
I haven't been able to find the old kind. Newer ones are pricey that's why I'm asking what others have measured.
 
https://www.amazon.com/TekPower-TP2108A-Voltage-Current-Frequency/dp/B019G9QC5W/ref=sr_1_67?s=hi&ie=UTF8&qid=1488835213&sr=1-67&keywords=dc+current+clamp+meter
https://www.amazon.com/ZIBOO-ZB-UT204A-Handheld-Multimeter-Voltmeter/dp/B0144B2PH6/ref=sr_1_73?s=hi&ie=UTF8&qid=1488835363&sr=1-73&keywords=dc+current+clamp+meter
https://www.amazon.com/ZIBOO-ZB-UT204A-Handheld-Multimeter-Voltmeter/dp/B0144B2PH6/ref=sr_1_73?s=hi&ie=UTF8&qid=1488835363&sr=1-73&keywords=dc+current+clamp+meter
http://www.ebay.com/itm/UNI-T-UT203-Digital-Clamp-Meter-AC-DC-Current-Volt-Multimeter-Ohmmeter-new-V2Y1-/302025458293?hash=item46521ec275:g:lasAAOSwSv1XmE9O
http://www.ebay.com/itm/LCD-Digital-Clamp-Meter-Multimeter-AC-DC-Current-Voltage-Resistance-Test-D1H0-/172556353598?hash=item282d29003e:g:-oQAAOSwhlZYtpLg

have not used any of these
used to use a Fluke clamp on DC amp meter way more money, had to leave it behind when I was laid off

let us know if you get one how good it works
Ron
 
You find those little goodies with the "tool" vendors tables at your local big flea market. I have four or five of them . They made a low amp as you described, and a 600 amp one for starters. I have both.
 
(quoted from post at 08:35:29 03/07/17) You find those little goodies with the "tool" vendors tables at your local big flea market. I have four or five of them . They made a low amp as you described, and a 600 amp one for starters. I have both.

Like the guy in the video said low amp clamps are a little complex for me. I need both and have both... I could make do with just a low amp probe its the jaws that limit what you can do with it.
 
We had 4 group 31 batteries on nearly all the trucks. In the early 2000's Kenworth only used 3 in the T-600 style trucks. They rode stacked on top of each other under the driver's side step. You had to remove the top one to load test the bottom ones.
 
We had 4 group 31 batteries on nearly all the trucks. In the early 2000's Kenworth only used 3 in the T-600 style trucks. They rode stacked on top of each other under the driver's side step. You had to remove the top one to load test the bottom ones or clean the cable connections.
 
Hello Geo,

Lawnmower, believe it or not. 235CCA BATTERY,4 INCHES from the starter. Engine did start, it drew a little less the second time around,

Guido.
a153550.jpg

a153551.jpg
 
Guido,

I can't find anyone selling your antique ammeter. I wonder just how accurate they are.
BTW, don't remember who,( was it Hall?) discovered the relationship between electricity and magnetism, but I do remember how much fun E&M class (Electricity and Magnetism) was in college. There are some cheap clamp on electronic dc ammeters using the Hall effect, but they are made in China. Debating on should I spend $25 just to find the answers to my questions above.
geo
 
It should be as far away from the Starter as possible. and against the wire. The starter is an electro magnet, and will make a fan out of the needle on that meter. Jim
 
Hello janicholson,

You went and spoiled it! I was just answering his question HE!HE!....

Guido.
 
Hello Geo

I left the Dodge dealer in 1965. I had the meter then. Used to be floor displays with all kinds of hand tool at the parts store in blister packs. Did you notice the amp reading? CRAZY HIGH or what?

Guido.
 
Yes it was crazy high. That's why I questioned it's accuracy. However many motors have crazy lock rotor amps when they first start so it's possible.

It's hard to measure with conventional meters, but even an incandescent light bulb has a crazy cold starting amps.

I have a friend who was a VW mechanic back in the hay day of VWs. He has a meter like yours, just can't find it.

I would like to know the amps my dump trailer uses. My 10k dump trailer is used often and the marine battery has a short life. It takes 70 seconds to dump and 50 seconds to come back down. I'm thinking the marine battery is the wrong battery. I read my electric pump can use up to 250 amps under max load. That's a lot of amps for 70 seconds.
 
Hello Geo,

I thought you would see right through my post.4" from the starter is NOT were Amp draw is taken!. Lots of magnetism generated by the starter to make the draw appear that crazy. Just funning with you.
Here is the normal draw picture from the same garden tractor. That dump trailer battery belongs in a boat. Also you should actually double up on CCA with that kind of draw. There are many clap up amp testers out here. 5 minutes on Ebay and I found one,

Guido.
a153619.jpg

a153620.jpg
 

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