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Still Having Power Issues


Guest mcramsay

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Guest mcramsay

So after a few drives and setting the cooling fan up I am still having power issues, basically after a few journeys and the car idling for a while with the fan cutting in and out the battery resting voltage is 12.3 volts with the rad fan struggling to start, turn the engine and fuel pumps off and fan kicks into life....

 

So I did a bit of testing tonight, with ignition on and engine off ( but both hp and lp fuel pumps running) the amp draw was 17 amps, this peaks at 39 with the fan starting but settles at 32 amps but obviously the fan doesn't run all the time. full load with the lights on main was 28 amps. Add the fan to this full load on the electrical system is 43 amps with everything turned on.

 

 

Started the car, with all lights off and fan off battery showed 6A flowing in, alternator output was around 23A. I then manually turned the fan on and current draw drops to -6 amps ish... so the battery is draining with the fan on as I thought might happen, also if I put the headlights on when the fan is running it cuts out.

 

All belts are new and tight on the alternator. I gave the engine a little throttle and amps going into the battery jumped to +6A.

 

Alternator pulley diameter is 53mm with crank pulley being 128. This should give an alternator speed of 1950 rpm with the engine idling at 800. Which is what the m3 sits at and is non adjustable.

 

Battery is an extremely small odyssey pc680 which looking today is a 16AH battery... standard 063 battery is 44Ah in comparison,

 

I have not had time to hook a charge light up, I am running 12v straight into the excitation post on the alternator but I have been told I need a light in the circuit for the alternator to spence load?

 

I can't find a smaller 5 groove pulley to make the thing spin a bit faster

 

What are my next steps going on the results above?

 

Bigger battery, bigger alternator ( currently a gxe2297 70 amp)

 

Last piece of my kit car puzzle, everything else works fine.

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Guest mcramsay

I think the odyssey batteries are made for racing when you just want to start an engine and nothing more.... only problem is the only spot for a bigger battery is in the passenger side footwell or in the boot

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Guest mcramsay

I did think along those lines, part of the issue is I never expected the cooling fan to cut in as much as it does, I can't get a bigger radiator so the fan has to stay, the alternator is a version on the classic mini 17acr but uprated to 70A, but I don't think you see any where near this output until 4000 rpm alternator speed.

 

The m3 alternator just wouldn't fit, no matter where I put it.

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Guest mcramsay

I agree but surely the alternator should increase its output when it sees the load of the fan.... unless it's output is maxed out at the speed it's rotating at

 

I don't know I'm stumped, personally I think changing the battery is a good starting point, the only thing different with my set up is the battery...

 

it's just a lot of work to move the battery location, lots of cables to extend... etc

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I might of misinterpreted your post, and I don't know how you are testing this.

 

But you mention that you have a 28 amp draw with lights on, four side light bulbs and two headlight bulbs should be about 12.5 amps plus a little for your dash illumination say 15 max. so why 28 amps?

 

before you start pushing more into the circuit, I would check you do not have a resistance somewhere, giving you these readings.

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Re-reading post 1 -- I would install the charge lamp ( needs to be around 5watt tungsten not led ) although not certain why direct 12 volt shouldn't work & check & double check all earth points -- some of your comments sound like there is insufficient earth path to take all the return current. Is there a potential difference between battery negative (earth ) & fan earth return when all systems running? Should be very near or at zero.

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Guest lotusPaul

I have the pc1100 on Sophie. One thing to remember is these batteries need to be kept on tiptop condition, so get a good battery conditioner and keep well topped up. Aldi or lidl do a great version and less than £15,i have and use one too.

 

Im not a sparky as ive said before so to me you have to make sure the cables are correctly sized and all components are earthed correctly.

 

You say you have a 70amp ACR alternator. Thats big enougth for your load if your max is 28Amps. Even adding into the fan pulling more.

 

You will find that on initial startup the fan motor will pull a bigger load then normal running. This is normal.

 

The Acr needs that little charge lamp in because it acts as an excitor and allows the alternator to start charging. If its not loading its not charging.

 

So, ensure your cables are big enougth to take the load.ensure all earths are fitted and are on clean metal.

 

Thats about as far as my memory goes.

Edited by lotusPaul
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