RX7 FC S4 Battery killer
 

Good Day everyone.

So my car has killed a few RED TOP Ultima batteries now. So I am trying to figure out the issues. Here is what I have done

Alternator testing. Single cable connected to the top has 12V all the time. The other 2 wires in the other connector read 12v when ignition switch is on. Battery voltage is 12.5v on a newly charged battery. So I crank the car and the battery voltage is now 13.4v. I then turn on my electric fan and battery is 12.9 v. So when I check the alternator voltage under the black boot at idle it is 14.3. So it appears I am losing a volt from alternator to battery. So is this the problem here? What do you guys think. My battery is sitting in the rear cargo bin now instead of under the hood.

I also checked for parasitic draw on battery. I disconnected the negative cable and the amps showed .02 amps. I opened the car door just for a test and it went up to .08. I think this is acceptable correct?

One last thing to add to the mix. So at times when I am troubleshooting my car won't start after running for a while. At times this could be the temp is to hot and not allowing it to start. I wasn't check that at the time so I am not sure. But I have repeatedly tried to start the car and it not start I know this will definitely kill my battery. So maybe this is the big culprit of course. But I would think the car should charge it back up if all is well.

Based on the picture, I'd say your cables are original and that is the problem. Under the mountain of electrical tape, the Alternator output cable is STAPLED to the Fuse box input cable. This junction corrodes and burns juice as you are experiencing. The simple solution is to de-tape and separate the two cables from each other. Put a fresh ring terminal on the fuse box cable, toss the old alternator cable out in favor of some fresh 4awg stuff. Solder lugs on per Aaron Cake's grounding guide.

Now that you have three cables for the positive terminal (Starter, Alternator & Fuse box), this is where Marine Battery Terminals come into play. Grab a pair from Walmart or Autozone for $4, put them on your battery and call it a day. Now your alternator can work without being held back.

However, the other half of your issue is simple: S4 alternators suck, even on a stock car. S5 ones suck slightly less, but are still inadequate for a car with an E-fan. A FD Alt is okay, but still gets pushed too hard when paired with a thirsty fan like the 2-speed Taurus fan. My personal recommendation is to jump straight to a 130A Taurus alt.

Trust me on this, there's no such thing as too much power from your alternator. When the voltage regulator on mine failed, it put out enough power to trip a 150A breaker through 20 feet of 4awg cable. Replaced the regulator and it acted like the all-out session never happened.

:lol:

Thanks Akagis_white_comet. I think I have the issue resolved!

can you tell the rest of us your secret if you solved it????

Well I am not completely done. I cleaned up a big mess that I made in the past and I reran the wires directly from battery to alternator and also the starter. I cranked the car and was receiving 15v now. This was a huge improvement over the 13.4 and 12.9 at some tests earlier. My next phase will be to see if I can clean up the fuse box connection and put the wires back on there like it should be for safety and not lose to many volts still. I have only started the car once to check the voltage at battery. I usually have 1 day a week I try and mess with it some. Now I know it is just a cable issue as Akagis_white_comet had stated and I figured since I measured voltage directly off the alternator last time.

I don't think you should be receiving 15 Volts under any conditions. Maximum should be 14.4.

Here off the OPTIMA website on charging. It says 15v max. Yeah that is kinda high, but within spec for the Optima REDTOP I have in it. I had looked at the website when I was curious about what it should be. I always thought 14.4 as well until i read this. So I think I should be good. Especially when I change it back to coming off the fuse box I am sure there will be some drop.


The following charging methods are recommended to ensure a long battery life. Always use a voltage-regulated charger, with voltage limits set as described below.

REDTOP Type: 34 & 34R - 34/78 - 78 - 25 & 35 - 75/25

These batteries are designed for engine starting applications. They are NOT recommended or warranted for use in deep-cycle applications.

Recommended charging information:

Alternator:
13.3 to 15.0 volts, no amperage limit.

So turns out my EBAY alternator that I had bought a year ago or so that was marked at 150-160 amps was 55 amps. So that really sucks. I went to am alternator shop and now i have a 90 amp alternator. My voltage is pretty good , but still not overly satisfied with my results.