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Old 20th-April-2017, 10:45 AM   #1141
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Quote:
Originally Posted by Tarantula View Post
Remember, I don't have any problems with starting the car and the drop in voltage has no effect on starting her up or even cranking her for more than 10 seconds. In fact I can crank for a good while or several times with no lag on the starter.

All I'm trying to do is create a scenario where the EFI ECU gets 12 volts all the time. Which is why a second battery and combiner was the initial idea.

As for the Alternator, it really has nothing to do with what I am trying to accomplish. Because I am seeking voltage before the alternator begins to operate. But to answer your question I have a Powermaster with a 2 wire plug. According to the spec card that came with the alternator, it has a max of 116 amps with idle being at 83 amps.

Its not like I have an issue starting the car in its current state. I'm merely trying to improve the ECU's functions by trying to give it 12V all the time even while cranking.
My question regarding the alternator wire size, has to do with recharging and overall system voltage.

Stock, Gm connected the battery and alternator through a 10ga wire going to the starter. While easy for manufacturing, it is not the best for a fuel injected electrical system. Compounding the problem is the fact that your battery is 20 feet away from it. I asked because if you are running the stock 10 ga wire (hell or even 4 ga) you'll have 15% or more voltage drop from the alternator to the battery. The alternator may output 14 volts, but your battery may only ever charge to 12V, and remember dropping system voltage is your main problem here. It is all related. The bigger the wire from the alternator to the battery, the less voltage drop.

If you minimize the voltage drop throughout the system (maximize system voltage), it will take less current to start the car and run functions, this will give you less draw down when starting. You will also create less heat.

For example, in my car I have a 140 amp alternator, battery in the stock location, 2/0 going from the battery to the starter lug. 2ga going from the back of the alternator to the battery and fuse box. My static system voltage is around 13.5 volts. Car starts instantly, with very little to no voltage fluctuation.

I also have 2/0 ground wires.

With the car off, what is your voltage reading at the battery?


For fun (not taking inrush current into account):

To illustrate the difference voltage drop makes.

Your starter= 3Hp

1 hp = 746 watts.

your starter = 2238 watts.

P=VI

2238=12volts(I)
I=186.5 amps

But your voltage drops while cranking so:

2238=10volts(I)
I=223.8amps.

Now if you had 13.5 Volts steady with a cap in the engine bay for example.

2238=13.5volts (I)
I=165 amps.
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Last edited by romancommander; 20th-April-2017 at 10:58 AM.
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Old 20th-April-2017, 01:25 PM   #1142
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I have 2 questions, isn't the ECU supposed to be connected to the battery directly? (where are you installing the ECU?)

And instead of spending the money on the cap, would it make sense to upgrade the wires from the batt in the trunk to the front instead? (that would fix a lot of the issues)

BTW isn't the vol 13.0-13.2V for YELLOWTOPs
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Old 20th-April-2017, 11:21 PM   #1143
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Quote:
Originally Posted by romancommander View Post
My question regarding the alternator wire size, has to do with recharging and overall system voltage.

Stock, Gm connected the battery and alternator through a 10ga wire going to the starter. While easy for manufacturing, it is not the best for a fuel injected electrical system. Compounding the problem is the fact that your battery is 20 feet away from it. I asked because if you are running the stock 10 ga wire (hell or even 4 ga) you'll have 15% or more voltage drop from the alternator to the battery. The alternator may output 14 volts, but your battery may only ever charge to 12V, and remember dropping system voltage is your main problem here. It is all related. The bigger the wire from the alternator to the battery, the less voltage drop.

.
I definitely am not using stock wiring. All was renewed. The wire size is 2 Gauge. When car is on, The highest I have seen is 14.5v (when cold). Average is 14.1v. When electric fan is on its 13.8v

Quote:
Originally Posted by romancommander View Post
With the car off, what is your voltage reading at the battery?.
I have not used the car in almost a week and I do have an alarm light that stays on all the time when the car alarm is active. I just checked and its currently 12.85V at the battery. At the front posts its 12.8V.


Quote:
Originally Posted by EdyJun View Post
I have 2 questions, isn't the ECU supposed to be connected to the battery directly? (where are you installing the ECU?)
Yes. The ECU is connected directly to the battery posts in front. There are two connections.

Quote:
Originally Posted by EdyJun View Post
And instead of spending the money on the cap, would it make sense to upgrade the wires from the batt in the trunk to the front instead? (that would fix a lot of the issues)
Not practical. And though I would like to have 12V to the ECU while cranking, Its not a big enough reason to justify redoing the wiring from 1/0 to 2/0.

Quote:
Originally Posted by EdyJun View Post
BTW isn't the vol 13.0-13.2V for YELLOWTOPs
Correct. When I placed battery in the car it was at 13.1 Volts. The Redtops fully charged are at 12.8v
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Old 20th-April-2017, 11:35 PM   #1144
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When the car is running, you are reading alternator voltage at the point where your gauge is hooked in, which your numbers point to a healthy alternator. Voltage drop increases as current demand increases (which is what you are seeing when your voltage dips below 12v).
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Old 20th-April-2017, 11:40 PM   #1145
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What I may do is add in a capacitor but not for the starter or battery. I can use the cap for the ECU since it would draw much less power therefore drain the cap much slower. The cap would be powered by a battery combiner this way it would get charged up again once alternator starts charging.

I only need power for the ECU while the car is cranking. Once it starts, the alternator takes over.

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Old 20th-April-2017, 11:47 PM   #1146
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Since the Ecu draws so little, you maybe money ahead with a separate small 12v Agm. Something from a power wheels would work, like an 8 amp hour. Then just connect it with a small "run hot" not "start hot" lead to charge it. I don't think you'd even need a battery isolator as it would be separate from the starting circuit. I buy these type of batteries from my local Batteries Plus.

https://www.walmart.com/ip/Universal...&wl13=&veh=sem
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Old 20th-April-2017, 11:57 PM   #1147
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Originally Posted by romancommander View Post
Since the Ecu draws so little, you maybe money ahead with a separate small 12v Agm. Something from a power wheels would work, like an 8 amp hour. Then just connect it with a small "run hot" not "start hot" lead to charge it. I don't think you'd even need a battery isolator as it would be separate from the starting circuit. I buy these type of batteries from my local Batteries Plus.

https://www.walmart.com/ip/Universal...&wl13=&veh=sem
I actually bought one (along with the combiner). But I wanted the battery to be charged and found that my alternator would damage the tiny battery because it needs a max of 1 amp to charge. Its 50CCA AGM and 3Ah.

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Old 21st-April-2017, 10:58 AM   #1148
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From my understanding of capacitors, they lose voltage (discharge) over time. There are times when I have the car sitting for a couple days and if the cap is a temporary source of power, then that would be bad.
So I asked about it...

Quote:
Originally Posted by romancommander
So there are two factors that cause a capacitor to discharge. 1. Internal leakage (known as desulfating in a battery)
2. External Current draw, (memory wires, alarm, etc)

If you buy a good cap, then it should have minimal internal leakage and stay charged a long time, but it will also be connected to the battery so it would at minimum maintain the batteries level of charge. I would not try to use a cap that wasn't connect directly to the battery, I don't think it would work.
.
So I came up with this Concept.



The Capacitor would receive power from the battery always when the car is off via a NC relay. This would keep the capacitor charged at all times. When I turn on the car, the NC relay would open and cut power from the battery to the capacitor. This would prevent the capacitor from discharging by starting the car. The Capacitor would then slowly power up the ECU giving it 12v.
When car starts and Alternator starts to charge (over 13v), the capacitor would once again receive battery power via the battery combiner/isolator.

Starting the car would take seconds so it is my understanding that the capacitor would be able to power the ECU for a little while (while the car is cranking) before being completely drained because it would only be consuming less than 10 amps. I chose a 2 Farad Capacitor which in my understanding would be equivalent to 166 amps of storage power.
There are 2 connections for the ECU. One in which is specifically for the ECU to turn on. The other for all the sensors of the ECU to get power. This connection would be connected to the battery. The ECU connection goes to the Capacitor.
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Old 21st-April-2017, 12:18 PM   #1149
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Quote:
Originally Posted by Tarantula View Post
From my understanding of capacitors, they lose voltage (discharge) over time. There are times when I have the car sitting for a couple days and if the cap is a temporary source of power, then that would be bad.
So I asked about it...



So I came up with this Concept.



The Capacitor would receive power from the battery always when the car is off via a NC relay. This would keep the capacitor charged at all times. When I turn on the car, the NC relay would open and cut power from the battery to the capacitor. This would prevent the capacitor from discharging by starting the car. The Capacitor would then slowly power up the ECU giving it 12v.
When car starts and Alternator starts to charge (over 13v), the capacitor would once again receive battery power via the battery combiner/isolator.

Starting the car would take seconds so it is my understanding that the capacitor would be able to power the ECU for a little while (while the car is cranking) before being completely drained because it would only be consuming less than 10 amps. I chose a 2 Farad Capacitor which in my understanding would be equivalent to 166 amps of storage power.
There are 2 connections for the ECU. One in which is specifically for the ECU to turn on. The other for all the sensors of the ECU to get power. This connection would be connected to the battery. The ECU connection goes to the Capacitor.

A couple things.

1. I originally suggested a cap to attenuate your voltage drop when installed in the engine bay and help your starting, to alleviate having to change out your 1/0. I still think this the best idea because it fixes a systemic problem, but I understand the engine compartment lack of space problem, and the fact that its only an issue during cranking. It was merely a thought I had, there are tons of wasy to skin this cat.

2. The scenario you are outlining would probably work, but is a little expensive and a little complicated, and technically not the best use of a cap.

Since the ECU draws so little, a simpler system would be to go with what you originally intended, involve a small 8ah-ish battery mounted in the trunk, relatively large wires going to the ecu to negate voltage drop (12ga? 10ga?) and instead of battery combiners or isolators a simple charging relay/trickle charger that only energized when in the "run" position. It would be a completely separate system, cheap, easy, small.
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Old 21st-April-2017, 06:25 PM   #1150
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Originally Posted by romancommander View Post

A couple things.

1. I originally suggested a cap to attenuate your voltage drop when installed in the engine bay and help your starting, to alleviate having to change out your 1/0. I still think this the best idea because it fixes a systemic problem, but I understand the engine compartment lack of space problem, and the fact that its only an issue during cranking. It was merely a thought I had, there are tons of wasy to skin this cat.

2. The scenario you are outlining would probably work, but is a little expensive and a little complicated, and technically not the best use of a cap.

Since the ECU draws so little, a simpler system would be to go with what you originally intended, involve a small 8ah-ish battery mounted in the trunk, relatively large wires going to the ecu to negate voltage drop (12ga? 10ga?) and instead of battery combiners or isolators a simple charging relay/trickle charger that only energized when in the "run" position. It would be a completely separate system, cheap, easy, small.
Actually its not so expensive. That's where ebay comes to play. And if it works to get me to my small goal than that's all that matters in the end. Regardless if its not the way capacitors are used normally. In this case one normally used for smoothing out ripples of current for amplifiers. Capacitors are used in practically every electronic device no matter what's it purpose. So technically I am creating a new purpose for the audio capacitor.

In reference to the small batteries which are meant for Power Sports, Motorcycles, Go carts and Scooters...
I have asked a battery manufacturer about them (such as the one you describe) and they said that 83/116 amps (which is the output of my alternator) would over charge the small battery which would cause it to overheat and swell.

Quote:
Thank you for the information. 83-116 amps would be too high for the battery as it only has 3 amps. The max amps would be 3 amps. But we recommend using 12V .5 or 1 amp. The slower you charge the battery, the longer the battery lasts. If the alternator outputs too many amps, it can damage the internal cells of the battery and cause it to swell. Overcharging the battery or inputting too many amps can damage it.

Best Regards,
ExpertBattery
The small battery idea is unsafe which is why I don't want to use it. Connecting it anywhere in the electrical system would allow the alternator to get to it putting in too many amps. Of course I learned about this after I bought the small battery. But it was cheap so I can find a use for it one day .

Let me clarify. I don't have a starting problem. Nor do I have a voltage problem when it comes to getting the car started or when in use. I'm trying to get 12v for one simple ECU while cranking. That's it.

The reality is that no matter what battery or high end wire installation I was to put or do to the car, it will still not have 12v while cranking. That is not possible in any car.
I'm merely making an improvement. It's more of a challenge in general to me.

To get 12v for the ECU "ALL THE TIME" means a separate power supply away from the biggest amp draw in the entire electrical system...The Starter.

But even if I was to fail with anything other than installing a real auto battery (which is the Optima Red top that I currently have or getting the smallest factory installed automotive battery which is the Mazda Mx 5 from my research) the car still starts up and drives beautiful. All electronics work great and the battery maintains fully charged by the alternator plus gives me 1600 watts of stereo pleasure without dimming lights and powers my big electric fan to cool my car for a 15 degree drop in coolant temps and cycles on and off frequently (at 60+ amps of draw per startup of fan) when I have the AC on.

The suggestions are helpful and bring light to other ideas. But there are no real problems to solve.
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Last edited by Tarantula; 21st-April-2017 at 07:12 PM.
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Old 24th-April-2017, 01:04 AM   #1151
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I have not given up on the idea of having a separate electrical system. All weekend have been on it on the internet with hours upon hours of research and ideas.
I'm confident that I finally have a solution. My car is still down while I wait for my ECU and tablet to come back and that has given me full dedication on playing with options.
Keeping my eye on the prize!
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