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View Full Version : Whats the smallest battery you can DD in a SC?



275hptbirdsc
03-16-2011, 07:04 PM
I had my car in storage and being dumb I didnt trickle charge the battery so it died and stayed frozen over the cold iowa nights. Anyway the battery wont hold a charge so I need a new one. I heard that the recommended battery size is to big and that our cars dont need that large of a battery so what sizes/brands work best but still keep the car daily drivable in the summer?

BLOWN38
03-16-2011, 08:16 PM
The 95 miata one fits in the tray sideways. I think Ricardoa1 has run one for awhile. I've had one in my dads marauder but only for one year and its not a DD. So I not sure if it lasts yet.

ricardoa1
03-16-2011, 08:42 PM
I an attempt to fix my starter issues I took it out and went back to a full size one to find out that the starter problems were still there. I had already relocated the Alky pump to the frame rail on the passenger side so I did not go back to the miata.
The starter problems ended up being the remanufactured starter and aftermarket flywheel not jiving and a shim spacer resolved the issues.

My miata battery is now on my MazdaSpeed 6

Some notes on it. It works well on daily driven cars. But if your car has the smallest drain or you tend to start it once a week or so. The battery does not have alot of reserve to deal with it. It has enough power though to start and operate an SC. But running the radio for long periods of time while the car is off, it will leave you stranded. Also no big stereos either I dont think it will handle it well.

I wish I had solved the issues with my starter prior to doing a changeover But my mazda can use the weight redux also anyways.

davec73
03-16-2011, 09:50 PM
Optima red top and your done for good.

275hptbirdsc
03-16-2011, 10:14 PM
The miata one sounds pretty good and I wont have to worry about big stereos or letting it sit as its my DD in the summer. Thanks guys

Mercutio
03-16-2011, 10:44 PM
I have a Braille 14115 in my SC, but I don't DD the car.

stangerbanger
03-17-2011, 09:11 AM
Optima red top and your done for good.

x2 mine has never let me down

David Neibert
03-17-2011, 12:02 PM
Optima red top and your done for good.

I must be doing something wrong, because I can't get the Optima red top in my car to hold a charge for more than a week if not kept on a battery tender.

David

ricardoa1
03-17-2011, 12:08 PM
I must be doing something wrong, because I can't get the Optima red top in my car to hold a charge for more than a week if not kept on a battery tender.

David


I dont think Optimas carry alot of reserve, It sacrifices that for cranking power.

rzimmerl
03-17-2011, 12:20 PM
I had my Optima in my car last year, which maybe gets driven once or twice a week with out a battery tender and had no issues.

David it sounds like you have a drain somewhere. I had this problem years ago when I thought my first Optima was junk, and come to find out the armrest door was broke not letting the light shut off. Simple to check by putting a multimeter in line checking for amp draw.

90coug
03-17-2011, 12:25 PM
+1 for the Optima red tops

Plus it's a Colorado battery ;)

David Neibert
03-17-2011, 01:16 PM
I had my Optima in my car last year, which maybe gets driven once or twice a week with out a battery tender and had no issues.

David it sounds like you have a drain somewhere. I had this problem years ago when I thought my first Optima was junk, and come to find out the armrest door was broke not letting the light shut off. Simple to check by putting a multimeter in line checking for amp draw.

Ryan,

I've checked for a drain and not finding anything more than what would be normal. I think it was something like .04 amps, but not sure.

I think that at least part of the problem is with my alternator not putting out the voltage it should. When first starting the car it shows 13.8 volts, then after the car is up to full operating temp voltage is down to about 13.0....then when idling at 1000 rpms it will sometimes get as low as 11.9 volts.

Battery charging isn't my main concern, it's the negative impact to the injectors at warm idle that I'm most concerned with. If the car sits at a stoplight idling for more than 15 or 20 seconds it starts going very lean, then fuel trims go real high trying to correct it back to 14.7 or whatever to keep it from stalling, and then when you go to take off from the light it's pig rich and stumbling until you give it enough throttle to clear it out.

We originally thought it was the o2 sensor location (long tubes) causing them to cool off at idle and stop switching, but after digging deeper we discovered the sensors were working fine, so now we suspect the low voltage is fouling up the way the injectors function at idle. Dave has adjusted the tune to quickly trim the fuel both to richen and lean it back out, so it's not that big of an issue. With short term fuel trims turned off, you can barely keeping it running. I also found that if I increase the idle to 1300 rpms by holding the brake and giving it a little gas pedal, everything works fine.

Since swapping to a new alternator didn't really change anything, I had a smaller pulley (2-5/8") made to replace the 3" diameter one that came with the March underdrive set. I expect the smaller pulley to increase voltage about to where it would be now if idling at 1250-1300 rpms. If that doesn't correct the problem, I'll try switching to a low maintance acid filled battery that has more reserve capacity than the Optima. Plan C is a 6G alternator built to make more voltage at idle using the 3" underdrive pulley.

David