How many amps does a 2H starter motor pull?

[new45]

Hi all,

Im installing a battery isolator on my primary starting battery on my new HJ47 build, and I am going to add a circuit breaker to it as well, with everything running through both the isolator and the circuit breaker.

How many amps does a 2H starter pull? so I can get the right circuit breaker? will 500A be fine?

Thanks for any advice.

 

[lostmarbles]

Hi all,
Im installing a battery isolator on my primary starting battery on my new HJ47 build, and I am going to add a circuit breaker to it as well, with everything running through both the isolator and the circuit breaker.
How many amps does a 2H alternator pull? so I can get the right circuit breaker? will 500A be fine?
Thanks for any advice.

Hi New45

You say "starter motor" in the title but accidentally say "alternator" in your post.

Anyway ...........Your starter has a 2.5kw power rating (same as mine).

So that means it draws around 200A.

However I question the logic of putting any circuit-breaker in this big cable.

In a factory installation, this cable (between battery and starter solenoid) is not very long and highly unlikely to develop any short-circuits (to body or frame).

If your starter refuses to disengage (which is the only serious not-uncommon starter-motor-destroying fault that comes to mind), then your planned circuitbreaker (even if it is rated at say 250A) will offer no protection (because the starter probably still won't draw more than 200A before it destroys itself in this scenario).

And if 250A were to flow in any other circuit (other than the one through your starter motor), you'd have a vehicle fire well before the circuitbreaker would trip.

 

[new45]

My plan was to keep everything together, and keep it simple. This is going to be a special rig, where I can isolate entire battery systems. there is going to be 4 total batteries and Id like to be able to totally isolate the starter so i know its going to stay fully charged.

I will grab a 250A circuit breaker and a 500A continuous switch and see how it goes, if the circuit breaker keeps flicking I will uprate it/

 

[lostmarbles]

My plan was to keep everything together, and keep it simple. This is going to be a special rig, where I can isolate entire battery systems. there is going to be 4 total batteries and Id like to be able to totally isolate the starter so i know its going to stay fully charged.

I will grab a 250A circuit breaker and a 500A continuous switch and see how it goes, if the circuit breaker keeps flicking I will uprate it/

I think you should be fine with a 250A breaker but I can't recall anyone having done this before so it'll be interesting to see if it ever trips..

 

[bj40green]

I subscribed to this thread. Curious to see how this develops.

Rudi

 

[new45]

Its a ways of rudi,

I have done i before on an old hilux, that we set up as a radio truck, this one is being setup as a HF radio transmitter and long term fridge for foot trek hunting trips.

240W of solar panels and 2 100 series LC alternators with 4 big deep cycles should be good for up to 14 days with the right weather.

 

[bj40green]

......Id like to be able to totally isolate the starter so i know its going to stay fully charged.

Do you want to isolate the starter motor or 1 battery for the starter? Worse case scenario: 3 empty batteries but 1 full for starting the engine?

Rudi

 

[Dougal]

I added isolators to each battery on my 12/24v 4bd1t setup. But these are entirely manual with no circuit breaker function. They have sustained over 500A without problems.

It has been quite convenient to use them for isolating batteries on many occasions. I will keep that setup in future.

 

[new45]

The primary battery (starter and winch - not much else)

The bank of three deep cycles,

These will be treated as separate isolatable supplies. and each of these supplies will be isolatable and have a circuit breaker.