amperage for starters

[lakespirit]

Anyone know how many amps required to crank a qd1003c starter for KAMA TS254?

 

[greg_g]

Anyone know how many amps required to crank a qd1003c starter for KAMA TS254?

It's a 2200w starter. Ohms Law says a 2200w starter should not pull more than 167 amps from a fully charged (13.2v) battery. That's on a healthy system. On an unhealthy system, it will probably try to pull more.

//greg//

 

[SPYDERLK]

It's a 2200w starter. Ohms Law says a 2200w starter should not pull more than 167 amps from a fully charged (13.2v) battery. That's on a healthy system. On an unhealthy system, it will probably try to pull more.

//greg//

Due internal resistance of batt it would be more accurate to use around 11.5V as the hard source voltage from a healthy batt - unless its a pretty big one. This would predict 191Amps. In the cold, with thick oil, the voltage would not hold as high and current would go even higher.
larry

 

[Reg]

Due internal resistance of batt it would be more accurate to use around 11.5V as the hard source voltage from a healthy batt - unless its a pretty big one. This would predict 191Amps. In the cold, with thick oil, the voltage would not hold as high and current would go even higher.
larry

Errr, no.
If the voltage drops and the resistance of the starter remains the same the drawn current will also drop. {Ohm's law}.

OTOH, if the starter's resistance drops due to stalling - by which time the battery's terminal volts might have dropped to 9 or so - the current is unpredictable as the battery's internal resistance also rises.

The 2200 watts is a spec, for which there are defined conditions - that we are unaware of. It is likely a nominal "3 HP" motor.

 

[SPYDERLK]

Errr, no.
If the voltage drops and the resistance of the starter remains the same the drawn current will also drop. {Ohm's law}.

OTOH, if the starter's resistance drops due to stalling - by which time the battery's terminal volts might have dropped to 9 or so - the current is unpredictable as the battery's internal resistance also rises.

The 2200 watts is a spec, for which there are defined conditions - that we are unaware of. It is likely a nominal "3 HP" motor.

Yes. Motor resistance is very low. If you applied Ohms law to the actual motor resistance you would predict extremely high currents. This resistance doesnt change as the motor spins, but as the motor spins it generates a counter V [opposite from the batt V] called Back EMF. As the motor goes faster so rises BEMF until current limits. - So the resistance of the motor appears to vary with speed. Slow the motor with a load, BEMF drops and current rises. As current rises there is more V lost due to the internal resistance of the batt so the V remaining to feed the motor goes down. The current to a starter is way high at low cranking speeds in cold engine starting applications regardless that the battery may be consuming 2V internally and only delivering around 10V to the starter.

Very few tractor sized 12V batteries will hold up to deliver 12V to a 100+ Amp load-NONE will deliver 13.2V . Thats why I used the 11.5V figure for predicting current consumed by a 2.2kW starter.
larry

 

[greg_g]

Very few tractor sized 12V batteries will hold up to deliver 12V to a 100+ Amp load-NONE will deliver 13.2V . Thats why I used the 11.5V figure for predicting current consumed by a 2.2kW starter.
larry

Hmmmm. So that means that if my $120 Interstate Group 93 shows a measured 13.2 cranking volts - I shouldn't believe the the multi-meter?

If one can't believe a real-time voltage reading, what good are the derivative numbers obtained when applying Ohm's Law mathematics?

//greg//

 

[SPYDERLK]

Hmmmm. So that means that if my $120 Interstate Group 93 shows a measured 13.2 cranking volts - I shouldn't believe the the multi-meter?

If one can't believe a real-time voltage reading, what good are the derivative numbers obtained when applying Ohm's Law mathematics?

//greg//

That is high even for a rest V, much less one shown under load. Fully charged rest voltage of all nominal 12V batteries that have been off the charge long enuf to dissipate surface charge effects is in the 12.8V range. A V higher than that indicates a battery that has not been off charge very long. The only way I can imagine what you describe [under load] is with a huge [200+ pounds]battery taken straight off a good long float charge. Or else an optimistic meter. If its digital there is another consideration - some update the reading only once every few seconds and you can miss a short dip in V.
larry

 

[Dave_Lilly]

A 12V battery needs a charging system higher than 12 Volts, usually around 13.5 to 14.5 Volts. If you measure the battery voltage while the engine is running you will get a 13.5 to 14.5 Volt reading. If you turn off the engine and then check battery voltage, you should get a reading of 12 to 12.5 Volts. A battery that registers 13.2 Volts while cranking the engine is overcharged.

 

[Soundguy]

Alot is going to depend on load vs battery capacity.

A very large battery driving a small load ( warmed engine, or very good starter , or smaller engine.. etc..) Is going to maintain a higher output voltage longer that a battery with a smaller reserve.

The battery in my ford 1975 5000 is a huge 4DLT.. Actually a larger battery than my NH 7610s. the 7610s has a similar sized engine.. the 5000 is a 256ci , and the 7610s is a 304ci w/turbo. As long as I am not in a hard start scenerio.. like cold weather.. or it has sat along time.. the 5000 usually bangs on about the 3rd rev. I've had a good analog and lab grade meter on that 4DLT.. It don't drop under 12v cranking, unless you make a few attempts. The 7610s on the other hand will get the battery into the 11v range on the first attempt. I was going to refit the battery box int he 7610s to take the bigger battery.. but then figured that if it does ok on the smaller 80$ one.. then why stick in the 120$ one! Plus.. that 4DLT is about as much abttery as i want to lift.. it's dern heavy..

soundguy

 

[Creekman]

Anyone know how many amps required to crank a qd1003c starter for KAMA TS254?

Why do you need to know how many amperes are required to crank your KAMA TS254? On your previous post about your starting problems you stated that disassembling and cleaning your solenoid and replacing the starter brushes solved your problem and your tractor started like new.