How many amps dose a mini starter draw?

mopar56

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The battery box and battery on my 56 Dodge pick up are mounted on the frame under the cab so I thought for added protection I would add a inline fuse, as a work at a marine shop I used a good quality blue seas fuse block , it mounts directly on the battery post and the cable mounts to it, the fuse blocks are available in many different amps, I thought a 90 would be good, I got 1/4 revolution and it popped, previous to the fuse install it cranked fine, I realize the starter draws many amps at crank but not sure what to go to next, thinking 200? Pictures below.

Screenshot_20210917-204446_Gallery.jpg


Screenshot_20210917-204452_Gallery.jpg
 

toolmanmike

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The battery box and battery on my 56 Dodge pick up are mounted on the frame under the cab so I thought for added protection I would add a inline fuse, as a work at a marine shop I used a good quality blue seas fuse block , it mounts directly on the battery post and the cable mounts to it, the fuse blocks are available in many different amps, I thought a 90 would be good, I got 1/4 revolution and it popped, previous to the fuse install it cranked fine, I realize the starter draws many amps at crank but not sure what to go to next, thinking 200? Pictures below.

View attachment 1715792229

View attachment 1715792230
:rofl::rofl: Most starters draw 200-500 amps. Bad starters much more.
 
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pishta

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They are rated at 1.4kW so >116A?
Power Rating (KW) 1.4
 

my68barracuda

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They are rated at 1.4kW so >116A?
Power Rating (KW) 1.4
I know just enough about electrical stuff to be dangerous, but doesn’t the current draw on a device like an automotive starter depend upon how difficult it is for the starter to turn the motor over.
For example, the same starter on a 7.5:1 compression motor will draw fewer amps than that exact same starter on a 11.5:1 compression motor.
And isn’t also true that the current draw in either case listed above will not be a stable flat line. The initial current draw just to get the starter motor to begin to turn the engine over will be much much higher than the current draw to keep the motor spinning.
 

toolmanmike

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I know just enough about electrical stuff to be dangerous, but doesn’t the current draw on a device like an automotive starter depend upon how difficult it is for the starter to turn the motor over.
For example, the same starter on a 7.5:1 compression motor will draw fewer amps than that exact same starter on a 11.5:1 compression motor.
And isn’t also true that the current draw in either case listed above will not be a stable flat line. The initial current draw just to get the starter motor to begin to turn the engine over will be much higher than the current draw to keep the motor spinning.
Exactly! That 116a. Is probably on a test bench and not under load. Every situation would be different there.
 

Needswork

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I was planning to use the exact same fuse from Blue Sea. But, I just did a quick search and it looks like 300A is the max you can get. That might might be borderline OK. For my project I was thinking in the range of 350-450 amp fuse. You have to consider a "hot start" as well. Once the starter is hot more current is required. I think Toolman's numbers are a reasonable guide.
 

pishta

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They also rate them about 1.9HP...saw a diagram on the output of these type starters...if anyone can read it?
Figure-1-Performance-graph-of-the-serial-wound-starter-motor-1-kW-12-V.png
 
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mopar56

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Well damn, guess I'll try the largest one and if it won't work I'll scrap the idea, I only wanted to add it just in case the battery were to ever get hit in a accident and short, I do also have a battery disconnect and may have to just rely on that? Thanks for the info as usual, I'll let you know how the larger one works.
 

67Dart273

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My personal feeling is that it may cause more problems than cure. You can however MEASURE a starter draw, you need to beg borrow or steal a battery load tester using an adjustable carbon pile, AKA "old school"

What you do is, disable the ignition and hook up the load tester. Crank the starter about 10 seconds and just before releasing, carefully and accurately note the voltage.

Now without cranking the starter, turn on the load and crank in load until the voltage reading matches the reading you took on the starter. Quickly read the ammeter and that is equal to the starter draw.

This demos battery test, not the starter test




Some newer VAT meters have a clamp on ammeter which directly measures starter current
 
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Joey4speed

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My 12V battery is rated for 550 CCA, (cold cranking amps).
Keep going higher on the fuse, until it holds.
 

Syleng1

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My question is why a fuse? Why not a resettable circuit breaker like found on lift gates for big trucks. 200amp should be fine dependent on length of cable and diameter of cable run from battery to cable. Remember that the smaller diameter the more resistance (load) especially when hot.
7F299FCE-F35B-495E-8CF8-CB41014F4329.jpeg
 

mderoy340

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My 10:1 340 pulls 180 amps according to my fluke clamp on. Motor lights off instantly.
I measured my current draw because of wire size; battery in the trunk. I would securely mount the battery in a steel vented box and press on.
 

Dana67Dart

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Any fuse is there to protect the wire not a device. So determine the guage of the wire, and fuse accordingly.

Also there are slow blow fuses and cir brakers, they can sustain a higher than rated load for a longer time than a standard fuse. This allows for inrush current of a motor.


THE REAL QUESTION...
why are you worried about the wire from the battery to the starter?
Not sure if even BMWs protect that wire.

The shorter it is and the heavier the guage, the more currant carring capacity it will have and not be over loaded.
 

mopar56

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Ok, all good questions and ideas, I do actually own a carbon pile load tester at my shop we use them for boats all the time, mine is a smaller, portable Napa brand so we can take it in and out of boats, but same idea so I could try your idea 67dart273, as to WHY I decided to add this is simply because the battery is on the frame on a bracket mounted on the passenger side of the cab, the four gauge cable goes into the engine compartment and across the firewall down to the starter, probably a run of 8 feet? IF the truck were to ever to be hit on the passenger side and stuffed in about 6 inchs then the post could contact the door, OR if at any time the positive cable were to rub through at the firewall, same result, in marine the wire running from the Stern of the boat where the batteries are to the front is always protected by a fuse in case the feed wire going up front is comprised . I am just adding some safety against electrical shorting. So as far as a heavy duty breaker goes I did think of that to but thought on the off chance this thing would ever trip I would be fine with a fuse.....I was wrong, but now that I already have the fuse maybe I'll upgrade to the bigger amp and try it then if it works and know what size I need I'll get a breaker, thanks for the help and ideas.
 

cudamark

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If it's going to take a crash that hard to short the battery out, fusing the system is the least of your worries IMO. Why not just install a rubber barrier around the battery or relocate the thing to a safer spot? I hate having fuses or circuit breakers on a vital circuit. Just adds one more junction to fail.
 

Dale Davies

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Ok, all good questions and ideas, I do actually own a carbon pile load tester at my shop we use them for boats all the time, mine is a smaller, portable Napa brand so we can take it in and out of boats, but same idea so I could try your idea 67dart273, as to WHY I decided to add this is simply because the battery is on the frame on a bracket mounted on the passenger side of the cab, the four gauge cable goes into the engine compartment and across the firewall down to the starter, probably a run of 8 feet? IF the truck were to ever to be hit on the passenger side and stuffed in about 6 inchs then the post could contact the door, OR if at any time the positive cable were to rub through at the firewall, same result, in marine the wire running from the Stern of the boat where the batteries are to the front is always protected by a fuse in case the feed wire going up front is comprised . I am just adding some safety against electrical shorting. So as far as a heavy duty breaker goes I did think of that to but thought on the off chance this thing would ever trip I would be fine with a fuse.....I was wrong, but now that I already have the fuse maybe I'll upgrade to the bigger amp and try it then if it works and know what size I need I'll get a breaker, thanks for the help and ideas.
Many vehicles have their battery mounted just in the engine compartment against the radiator header. Now remember that most crashes involve the front end. GM pickup trucks have the + post close to the inner fender. If it gets hit that hard, which with crumple zones now is not that much, the battery gets crushed. A better place in my mind would be against the firewall as the crush zones get stiffer as the damage gets farther in. This is designed to absorb the impact in a controlled manner. Older vehicles did not have these controlled crush zones and with seat belts the impact was transferred to the occupants.
Considering side impacts are by far the minority of crashes, I would not be undully concerned. Just insulate the connections with rubber by the + batt post and the cable going to the starter be in good grommets where it passes through a panel.
Keep the battery and cables away from fuel lines.
 

72Duster440

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I plan on redoing the electrical portion of my starting system this winter. Instead of going with a fused lead from the battery to the starter, I plan on running a Ford style starter relay mounted next to my battery in the trunk. It'll leave that wire to the starter electrically dead, except for when cranking. The relays are ~$25 only as well, and just need the trigger wire from your ignition switch routed to them.
 

Demonx2

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I plan on redoing the electrical portion of my starting system this winter. Instead of going with a fused lead from the battery to the starter, I plan on running a Ford style starter relay mounted next to my battery in the trunk. It'll leave that wire to the starter electrically dead, except for when cranking. The relays are ~$25 only as well, and just need the trigger wire from your ignition switch routed to them.
That's how my battery in the trunk is wired too. Seems to work very well.
 

LO23M8B

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My personal feeling is that it may cause more problems than cure. You can however MEASURE a starter draw, you need to beg borrow or steal a battery load tester using an adjustable carbon pile, AKA "old school"

What you do is, disable the ignition and hook up the load tester. Crank the starter about 10 seconds and just before releasing, carefully and accurately note the voltage.

Now without cranking the starter, turn on the load and crank in load until the voltage reading matches the reading you took on the starter. Quickly read the ammeter and that is equal to the starter draw.

This demos battery test, not the starter test




Some newer VAT meters have a clamp on ammeter which directly measures starter current


You could also use one of those small/cheap inductive thing of migs
 

mopar56

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Update....installed a 300 amp fuse block, so far problem solved, motor cranks fine, havnt started it yet but should be fine after cranking is finished.
 

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