WesBrooks
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| posted on 14/3/16 at 02:04 PM |
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Current Estimation for Rover V8 Starter Solenoid & Starter
Afternoon All,
The starter motor for my '95 Rover V8i engine is listed as a 1.8kW unit. I'm presuming this is an average power when under peak load which
would result in a current of around 150A. I'm assuming peak currents could be 200-300A without significant issues.
The solenoid is protected by a 60A fuse. The readings I get of the coil vary from between 0.5 and 1.2 ohms, but I have little confidence in these
readings as a little contact oxidation could have a big effect at those sort of readings and the reading itself is probably outside the best accuracy
range of my Clarke meter. If anyone has good figures for the resistance of the windings of the solenoid and starter I'd appreciate them as I
guess that gives a maximum inrush/stall current for the devices.
Anyone got any decent figures on what current the solenoid will draw?
If I supply a decent gauge wire to the solenoid and ensure the voltage drop is 10% or less (assuming battery isn't the limit here) could I be
risking supplying too much current to the solenoid? Could the donors length of wire from the relay in the cabin, though the bulkhead and down to the
starter be designed to protect the solenoid from over current?
Cheers,
Wes.
http://doctrucker.wordpress.com
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HowardB
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| posted on 14/3/16 at 02:48 PM |
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hmmm,
I feel that you are over thinking that,. the solenoid is a low (relatively) current device and will pull in the starter which is a high current
device.
I have fired the solenoid on the car with a bit of thin wire, and also by jumping it to the full time 12v on the starter. On the Landy the solenoid is
switched in with a 10A microswitch without any issues.
hth
Howard
Fisher Fury was 2000 Zetec - now a 1600 (it Lives again  and goes zoom)
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Chris_Xtreme
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| posted on 14/3/16 at 03:11 PM |
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mine has a thin bit of wire, thinner than 20amp thinwall cable, and I doubt it is thinwall. I would suggest 15amp wire with a 10amp fuse, or try with
a big wire and drop the fuses down till one pops.
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britishtrident
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| posted on 14/3/16 at 03:22 PM |
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Don't worry about it not significant.
The a big chunk of ressistance is internal the battery if you dead short a brand new fully charged premium grade type 096 battery the most current
it can produce is about 800 amps and the 096 is a very big battey rated at 74+ AH 700 to 780 CCA
At a 100 amps current draw a full charged brand new battery of this size drops about 1.6 volts internally , at 200 amp it will drop 3.2 volts
internally, and older or smaller batteries will drop more volts iinternally.
Normally on big Yankee v6 engines of the size of your engine 9.6 v is regarded as thet mimium cranking voltage for battery testing which is a 3 volt
drop from the no load battery voltage so you are looking at a normal load of less than 200 amps.
A geared permanent magnet starter will only draw about half the current of an old style starter.
[Edited on 14/3/16 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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gremlin1234
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| posted on 14/3/16 at 03:27 PM |
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quote:
Could the donors length of wire from the relay in the cabin, though the bulkhead and down to the starter be designed to protect the solenoid
from over current?
no, they would use a fuse for that
as far as I know the only wire ever used as a resistor in a car, used to be the 'pink' wire to the coil
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WesBrooks
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| posted on 15/3/16 at 01:03 PM |
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Just after I posted a similar thread on a Land Rover forum I found this thread:
http://forum.landrovernet.com/showthread.php/230666-Land-rover-200tdi-starter-motor-broke
Gives the following specs:
Main winding 0.145 - 0.165 ohms
Hold winding 0.46 - 0.56 ohms
Both of these are used to begin with for a fraction of a second, then the holding only. This means Inrush current will be based on a resistance of
0.110 ohms, and a main current through the 0.46 Ohms. So inrush of 109A settling to 26A.
30A-60A Fuse looks about right then!
This is for the 200tdi starter though. The solenoid may be different on the 3.9 V8i.
[Edited on 15/3/16 by WesBrooks]
http://doctrucker.wordpress.com
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britishtrident
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| posted on 15/3/16 at 04:15 PM |
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quote:
Originally posted by WesBrooks
Just after I posted a similar thread on a Land Rover forum I found this thread:
http://forum.landrovernet.com/showthread.php/230666-Land-rover-200tdi-starter-motor-broke
Gives the following specs:
Main winding 0.145 - 0.165 ohms
Hold winding 0.46 - 0.56 ohms
Both of these are used to begin with for a fraction of a second, then the holding only. This means Inrush current will be based on a resistance of
0.110 ohms, and a main current through the 0.46 Ohms. So inrush of 109A settling to 26A.
30A-60A Fuse looks about right then!
This is for the 200tdi starter though. The solenoid may be different on the 3.9 V8i.
[Edited on 15/3/16 by WesBrooks]
The solenoid is normally just fed off the main ignition fuse
I think you will find tintop that has a fuse link on the main starter link will have at least 120 amps usually 150 amps --- a 1.8 rover engine
cranks at 80 amps in normal ambient conditions. For Rover V8 you will need a fuse link rated at 200 amps
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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