Battery Info Page

General Miata battery recommendations:

  1. AVOID Westco!  Short life.  2-3 years is typical life and are usually wimpy batteries in general.  I've had 2; no more.  Weighs 24 lbs.
  2. Optima Yellow top model D51R fits well w/ little modification (need longer J bolt from autoparts store - easy to get).  Has 625 CCA and deep cycle, meaning that you can discharge the battery to a low voltage w/o damaging it.  Great for super-stereo cars.  Weighs 26 lbs.  Short warranty: 1 year full replacement warranty + 1 year prorated replacement warranty.  About $140 from 1st OptimaŽ Battery Sales or
  3. Optima Red top model 35 is a little fat but not hard to make fit w/ longer J bolt and hold down bracket modifications.  Has 910CCA which is more than enough.  Is not as good for deep cycling as the yellow top but not necessary if you don't need to drain the battery much.  Weighs 33 lbs.  Long warranty: 3 year full replacement warranty + 3 year prorated replacement warranty.  About $140 from 1st OptimaŽ Battery Sales or
  4. Optima Red top model 75/25 is similar to the Red top model 35 but the posts are on the wrong side which requires the battery to be installed by flipping it around.  The battery cables have to stretch a bit.  Weighs 33 lbs.  910CCA.  Warranty is 3 + 3.  It is about $25 cheaper than the 35.

Optima redtop 35

I ended up with a Optima redtop model 35.  It required a bit more modification than I expected to my car for it to fit, but it wasn't hard and turned out well.  Starts the car very well!  It masked/fixed my ignition/starter problem too.

Here is my modification procedure:


IMG_3743.JPG (203752 bytes) Starting with the old Westco battery.  Out with the old...  3 years and it finally wouldn't hold much of a charge more than 24 hours in sub 40 degree F weather.  This battery is poo!  Jump starting every morning is getting old.
IMG_3751.JPG (177325 bytes) Here is the Optima redtop model 35 next to the Westco.  Yep, it's a bigger battery in every way, but it will fit... oh yes, it WILL fit.
IMG_3745.JPG (220152 bytes) Once the battery is pulled, the area looks like this.  I have a few extra wires there for an amplifier and a trunk release solenoid.
IMG_3758.JPG (191405 bytes) Remove the following:
1) Black plastic tray under the battery
2) 'L' shaped bracket that supports the bottom inward side of the battery from moving.
3) 'A' shaped bracket that the 'J' hook attaches to (to hold the battery down).
4) Black rubber hoses that were used to vent the Westo or original battery gases.

I placed the Optima in position at this point to get an idea how it would fit.  I removed the battery after this picture as it was in the way for future steps.

IMG_3757.JPG (140928 bytes) Cover up the two existing bolt holes that were used to hold down the 'L' bracket.  The bracket will be relocated and those holes need to be covered to keep water from coming into the trunk.  I just used ordinary electrical tape.  Here is one pictured.  You'll also see two other pieces of tape already covering two other holes.  Those will be used in the next step.
IMG_3762.JPG (134409 bytes) Those pieces of tape placed at the factory are covering holes already properly positioned to reposition the 'L' bracket.  How convenient!  In this picture, I indented the tape over the holes so it could be visible in the picture.
IMG_3765.JPG (176853 bytes) Here is the 'L' bracket now bolted down in the new position.  Again, I put the battery in place as a test fit.  Snug so far, left to right but not front to back.
IMG_3766.JPG (168593 bytes) Now add the 'A' bracket back in, but turn it around 180 degrees.  This gives more room for the wider battery while providing an attach point for the 'J' hook.  Test fit the battery then remove it.
IMG_3768.JPG (183559 bytes) Next, drill a 1/4" hole in the metal stop to prove a place for a new 'J' hook to attach to.  Notice that I drilled it off to the side a bit so that the hole was actually centered with the battery.
IMG_3775.JPG (176799 bytes) I bought a universal battery hold down bracket (it adjusts in width to any battery) and a package including two 8" 'J' hooks w/ wing nuts and rubber washers.
IMG_3770.JPG (178554 bytes) Here is one of the new 'J' hooks in position.
IMG_3778.JPG (196366 bytes) The rest is really easy.  Put the battery in place, position the hold down bracket over the battery, slip the new 'J' hook into the hold down bracket, washer and attach the wing nut.  Reattach the original 'J' hook to the 'A' bracket and slip it into the hold down bracket, washer and attach the existing 10mm nut.
IMG_3782.JPG (126719 bytes) Here's a close up shot of the hold down bracket.
IMG_3784.JPG (178710 bytes) Here's another nice trick Mazda did for us.  When you position the battery cover back, there will be two unused snaps.  Position the cover on those instead of the two they used to be attached to.  Viola!  It's a great fit over the battery.  Only problem is that crams against the tail light housing a little, but I can live with that.
IMG_3787.JPG (218754 bytes) All done!

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