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Voltage drop
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DRR Sportsman
Picture of Matrix
posted
Just curious to see what some of you all are seeing at the starter. Im running two golithiums spinning over a 582. I havent put a voltmeter on it yet but its spinning slower than I think it should and the first time I went to spin it the racepak blanked out for a second (IQ3). Ill be checking my grounds again today


Daryl Pinder

Dynasty Motorsports
www.dynastymotorsports.com


 
Posts: 456 | Location: Ft. Washington, MD USA | Registered: March 05, 2001Reply With QuoteReport This Post
DRR Top Comp
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I’m sure that some people love their lithium batteries but I’ll stick with my XS-D1600, it has been flawless for 8 years. I do plan to replace it at the end of this season unless it dies before then. It just seems like I’ve seen too many with issues with their lithium batteries. Good luck!


Clowns to the left of me, Jokers to the right. Here I am.......
 
Posts: 5326 | Location: stuck in the middle with you! | Registered: March 11, 2002Reply With QuoteReport This Post
DRR Trophy
Picture of NC3x58
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The lithium batteries seem like they need to warm up for a hot second before they actually work to turn over a motor. There was a post on here a while ago about it, and the battery manufacturer actually told people to turn on say your water pump for a couple seconds before going to spin the motor over to get the batteries warmed up. I've heard it works, but I do not have a lithium to confirm this.


Nick Craig

1971 Camaro Split Bumper
376ci LS3
 
Posts: 410 | Location: Ohio | Registered: December 28, 2013Reply With QuoteReport This Post
DRR Pro
Picture of rusty
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no more than 4 volts on mine,it almost seems you are only on one battery.check cables ect an both batterries,and starter.on two go lthiums mine will spin like a top anytime,those chargers can be tricky may have to unplug and plug back in to get the charge started


honesty is the best policy,insanity is a better deffense
1.036, 6.16@ 224

 
Posts: 1441 | Location: texas | Registered: February 17, 2006Reply With QuoteReport This Post
DRR S/Pro
Picture of Eman
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Posts: 1498 | Location: E TN | Registered: February 13, 2009Reply With QuoteReport This Post
DRR Pro
Picture of rusty
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the voltage drop i am seeing is on gauge in the dash.this other test looks to much more defining


honesty is the best policy,insanity is a better deffense
1.036, 6.16@ 224

 
Posts: 1441 | Location: texas | Registered: February 17, 2006Reply With QuoteReport This Post
DRR S/Pro
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To check real voltage drop you need to check it at the battery and then the at the starter while cranking! Need to have the current flowing!

At the starter the more the better but 9v is a good min for 12v batteries. Too many cars out there are wired with too small wire and bad ground choices, both cause too much voltage drop. For grounds, using the chassis which many cars do, is a source of voltage drop, steel is not a good conductor as compared to copper! So running a short ground cable to the chassis, especially when the battery is a good distance from the motor is a source of voltage drop, lengthen the cable a see for yourself. Using small cable gauge wire is another common issue, usually in an effort to save weight, and going from #2 to 1/0 is about a pound for about 18 feet! No brainer here.

Voltage drop is a function of resistance in the wiring and current draw. For a given system, the higher the current draw the more voltage drop you will see. That is the reason 16v systems help, more voltage means less current to do the same amount of work.
 
Posts: 2161 | Location: Tewksbury, MA,USA | Registered: November 03, 2000Reply With QuoteReport This Post



DRR Trophy
Picture of 1leg
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You need to check at the battery post on the starter while cranking with a digital multi meter.

On a 12v system we like to see 11 or more volt while cranking. You get below that performance drops off. A 16v should see over 12-13 volts.


Meziere Tech.
Make sure your water pump is on whenever you check your coolant level.
 
Posts: 255 | Location: Escondido | Registered: July 01, 2011Reply With QuoteReport This Post
DRR Sportsman
Picture of sr4440
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I wrote a how to a few years ago, this is my bible when it comes to electric gremlins.

Voltage drop testing is one of the simplest tests in the world to do, but often is over looked. Here is a detailed explanation of how to perform the test.

You will need a volt meter, preferable a digital one. The help of a friend will make testing a lot easier as well. And possibly a set of booster cables if the circuit you are going to test is really long.

A few things that you should know first. When you use a volt meter it displays the difference in voltage from one lead to another. So when you place it across the battery on the + and - posts, and it reads 12.79volts, it means that the difference in voltage between the two posts is 12.79volts.

All the circuits in your car complete themselves at the battery, specifically between the + and - plates inside the battery. So any extra resistance outside the battery, any where in the circuit is a bad thing.

Industry standard for automotive production cars is a .5 total voltage drop in any system. Except maybe your starting system, as the old style starters just draw a ton of amperage. The .5 is divided up as .3 positive and .2 negative. So when we are testing the positive leg of the circuit we will want to see less than .3 of a drop, and less than .2 on the negative side. This is while the device is in use. i.e. if you are checking your lights, they need to be on while doing the check.

So here is how to do the test. Put one lead on one point of the circuit, and the other lead at another point. Say at both ends of a wire. The meter should read zero. Now turn on the device. The reading on the meter is how much the voltage drops between the two leads. If it is on both ends of a wire, then it is how much the voltage drop down that wire. If it is over .3 + or .2 - it needs to be replaced.

Here is an example testing the starter system on an older Ford. It is slow cranking, with a new starter and battery, so we will check for voltage drop issues. First thing we do is put one lead on the positive terminal of the battery, and the other lead on main post of the starter. Try starting it and we get a reading of 1.5volts. So we know there is a 1.5 volt drop on the positive side of the circuit.

So leaving the lead on the battery, we move the other lead up to where the main battery cable from the starter goes to the fenderwall solenoid. We repeat the start, and still get a reading of 1.5volts. So we know that cable is not the problem. (Could have also put the leads on each end of the wire to determine this, but takes longer to do the test).

Next you put the lead on the solenoid's post, and try the test. Still 1.5volts, so we know the connection between the post and the starter cable) is good. So we move the lead to the other post of the fenderwall solenoid, and repeat the test. Now we get a reading of .5 volts on the meter, instead of the 1.5volts. So it would appear that we are losing 1 volt through the solenoid. To confirm that we can put a lead on each post of the solenoid, and try starting it. In this case it does confirm that we dropping 1 volt through the solenoid.

But we still have .5 volts drop. So now we check the cable end at the solenoid, to the battery post. It reads .5volts still. So we then go to the battery post to the cable end at the battery itself. We get a reading still of .5 . So that would mean that between the battery post and the cable end we are losing .5volts, in other words, we have a bad connection.

So you replace the solenoid, clean the battery cable end at the battery. Also preventive clean the solenoid cable ends too. Test the complete system down to the starter again, and get a reading of .2 volts. So we are happy. Moving over ot the negative side. You move one lead to negative post of the battery, and another lead to the body of the starter.

You start the motor and getting a reading of .7 on volt meter. Now you just follow the ground path back every where there is a connection. So first you would go from the negative post to the bell housing, then block, then the ground strap clamp at the block, then to the frame rail, etc, etc. Where ever the drop goes away, then the what ever is between your last point and the new point is likely where the drop is. Always double check it by actually putting the leads on both ends of the item being tested (both ends of a wire, between a clamp and bolt, two posts on a solenoid or relay, two posts on a kill switch, etc).

It should take less than a couple of minutes to check a complete circuit. If the circuit is really long, say with the battery in the trunk. You can clamp a booster cable to the battery, and then to the one lead of the meter, thus extending the lead's length. You can use a small wire even, just booster cables are readily available.


Without data, you’re just another guy with an opinion.
 
Posts: 1301 | Location: TEXAS | Registered: February 07, 2003Reply With QuoteReport This Post
DRR Sportsman
Picture of Matrix
posted Hide Post
quote:
Originally posted by rusty:
no more than 4 volts on mine,it almost seems you are only on one battery.check cables ect an both batterries,and starter.on two go lthiums mine will spin like a top anytime,those chargers can be tricky may have to unplug and plug back in to get the charge started


It definitely seems like it's on one battery. I have their first gen charger that will flash at 100% but never go steady green. I wonder if the batteries aren't fully charged even though it reads 17v on the racepak dash


Daryl Pinder

Dynasty Motorsports
www.dynastymotorsports.com


 
Posts: 456 | Location: Ft. Washington, MD USA | Registered: March 05, 2001Reply With QuoteReport This Post
DRR Sportsman
Picture of Matrix
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So after going over everything I did find two loose grounds. I also discovered that 2 gauge wire isn't gonna cut the mustard. Replaced everything with 2/0 wire and she spins like a champ now. Only problem now is when i turn on the master disconnect it turns everything on lol. It was an old switch any way so its time for a new one.


Daryl Pinder

Dynasty Motorsports
www.dynastymotorsports.com


 
Posts: 456 | Location: Ft. Washington, MD USA | Registered: March 05, 2001Reply With QuoteReport This Post
DRR S/Pro
Picture of Lenny5160
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quote:
Originally posted by Matrix:
So after going over everything I did find two loose grounds. I also discovered that 2 gauge wire isn't gonna cut the mustard. Replaced everything with 2/0 wire and she spins like a champ now. Only problem now is when i turn on the master disconnect it turns everything on lol. It was an old switch any way so its time for a new one.


I don’t see how the master switch going bad would enable it to power items that it didn’t power before when the switch was turned on.


Tony Leonard
 
Posts: 3185 | Location: Inver Grove Heights, MN | Registered: March 18, 2004Reply With QuoteReport This Post
DRR Sportsman
Picture of Matrix
posted Hide Post
Me either. All I did was change one of the cables out on the master cut off. Went to turn it back on then everything powered up


Daryl Pinder

Dynasty Motorsports
www.dynastymotorsports.com


 
Posts: 456 | Location: Ft. Washington, MD USA | Registered: March 05, 2001Reply With QuoteReport This Post
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