How many amps does a 152 starter pull?

[Mastiff]

I'm considering my options for a dual battery setup on my Scout 80. I've been running a group 25 battery in the factory tray. The ones I've had are around 550 CCA rated. I have no heater, so I'm eying the top of the inner fenders as possible battery spots, but the group 25 would be tight there. I notice Odyssey has a lot of options for slightly smaller batteries in the 325 CCA range. The setup would be slick, but it's essential that I be able to start with one of the batteries dead. Any thoughts?

I'd also like to know the current draw for sizing my isolator relay. The one I use in my Blazer is good for 1000 amps short term. I assume this is way overkill for the Scout. If it never pulls more than 150 amps I could save money and space.

[Eric VanBuren]

The standard rule of thumb for determining the CCA for a 4cyl is to double the engine size then add 100a for a cushion.

The dual battery isolator sizing depends on the alternator (or generator) output. The cranking power should not be going through the isolator, only the charge and running current should go through it.

[Mastiff]

Originally Posted by Eric VanBuren

The standard rule of thumb for determining the CCA for a 4cyl is to double the engine size then add 100a for a cushion.

The dual battery isolator sizing depends on the alternator (or generator) output. The cranking power should not be going through the isolator, only the charge and running current should go through it.

I like to set mine up so I can use either battery to start, I don't use an isolator. It's all preference. I know it's common to have a starting battery and an accessory battery.

My Blazer setup has saved my butt on numerous occasions. I run both batteries to a boat switch and the output goes to everything that uses power, including the starter. I put the big relay across the inputs of the switch and run it from ignition power. This way the battery not selected by the switch is completely disconnected from everything when the vehicle is off, but they both start and both get charged all the time. With an isolator setup I guess you have to jump yourself with jumper cables from your accessory battery if the starting battery goes out, but this only works as long as the starting battery isn't totally fried.

Anyway, sounds like you are saying about 400 amps is the number.

[George Womack]

You got me wondering about this, so I just checked the starter draw on two of my 152 Scouts with my clamp meter. Both drew around 150 amps.

[Mastiff]

Originally Posted by George Womack

You got me wondering about this, so I just checked the starter draw on two of my 152 Scouts with my clamp meter. Both drew around 150 amps.

Good data point. Was that a cold engine? I expect it would draw more hot? Even so, maybe 350 CCA would cover it...

[Mastiff]

I'm liking the Odyssey PC925.

http://www.odysseybatteries.com/battery/pc925t.htm

Less than 6" high and roughly 6" square footprint. Could easily fit on the inner fender. Could even fit both on one side, and they have these cool trays.

Of course by the time it was done I'd be about $450 into it.

[Jay Tabor]

bigger is better when it comes to batteries, get one or two group 27 or 31 batts with 1000++ cca. then you wont worry.
the starter pulls 150 amps on a good day, those are same starters as V8, which pull 200 a.
well if the starter has a dragging armature, or the engine has some resistance to turning the crank, a toasty awg 8 battery cables [ to save space mind you]
and a hundred other resistance causing amp draws, and those tiny batteries wont do any good.
might as well put 8 Dura cell D size batteries in there.

[Mastiff]

Where am I going to put monster batteries like that? Besides, this is a little 4 banger, not a V8 diesel. Why carry a bunch of weight around that's not needed? The Odyssey specs 925 amps for the first 5 seconds.

[pokemont17]

Originally Posted by Mastiff

I'm considering my options for a dual battery setup on my Scout 80. I've been running a group 25 battery in the factory tray. The ones I've had are around 550 CCA rated. I have no heater, so I'm eying the top of the inner fenders as possible battery spots, but the group 25 would be tight there. I notice Odyssey has a lot of options for slightly smaller batteries in the 325 CCA range. The setup would be slick, but it's essential that I be able to start with one of the batteries dead. Any thoughts?

I'd also like to know the current draw for sizing my isolator relay. The one I use in my Blazer is good for 1000 amps short term. I assume this is way overkill for the Scout. If it never pulls more than 150 amps I could save money and space.

Thanks you for the post.

[Will Marsh]

Originally Posted by Mastiff

Where am I going to put monster batteries like that? Besides, this is a little 4 banger, not a V8 diesel. Why carry a bunch of weight around that's not needed? The Odyssey specs 925 amps for the first 5 seconds.

What if it doesn't start in the first 5 seconds?

You might note that the Reserve Capacity is only 28 min. I'd suspect using those you'd get about 2 30sec. crank cycles out of it before it was done. I don't know about your truck, but even on good days mine don't usually fire that quick.

The group 24 I typically use fits just fine in the stock battery trays. 720 Cranking amps and ~120 min reserve capacity. I wouldn't put anything smaller than that in one of mine.

YMMV,

Will Marsh