So for about 6 months now, i've been dealing with this dead battery issue. Originally I was told by the dealer it was a drain, so i finally resolved that issue. For a while everything was great, but now the battery is dying again.

Today it wouldnt crank, and before jumping it... i tested it and it read 11.8 Volts. This should have been enough to crank. So I am thinking it maybe a problem with the starter. Here's my question... if it was a problem with the starter... how come it cranks when jumper cables are attached???

Oh, and I''ve already had the battery/starter replaced a few months back. I was thinking i just would need a new battery since the one that is in there now has been "jumped" dozens of times and has been weakened.

If anyone has any suggestions... i'm all ears.

-hS

 

Any conventional car battery that's needed to be "jumped dozens of times", probably has one foot in the grave and the other on a bannana peel. Most car batteries are not designed to be deeply drained, and will suffer a significant loss in overall capacity each time that happens. You might be getting 11.8 volts with a meter, but as soon as you put a load on it --- pfffft!

If, as you say, you've finally identified and fixed the problem that was draining the battery, then a replacement should set you right again. If you're under warranty I'd think the dealer should pick up the cost, or at least the majority of the cost and supply you with a proper replacement (the 640 CCA version, as specified in the TSB). If you really want some peace of mind and don't mind spending some of your own money, I really like the Optima Yellow-top group-35 battery for this application

- it's a deep cycle battery and can tolerate an occasional, or even repeated, deep discharge with no damage

This is a good thing if it turns out you still have some current drain or charging issue, your battery will still be fine after a jump or recharge. On top of that, all cars nowadays drain some current from the battery at all times. If you leave the car sit for extended time, say a few weeks, you are deep-discharging the battery.

- it will supply higher voltage, even when partially discharged

This is good news for the RX-8, since it helps get you started even though the battery may have experienced a partial drain. It's also good insurance if you ever do have a flooding incident, it will stand up to extended starting attempts and retries and still give you good cranking rpm -- essential to starting a rotary especially after a flood. Whereas a standard auto battery will gradually weaken and give fewer cranking rpm with each attempt.

- it is sealed and practically leak-proof. Say goodbye to corroded battery terminals and mounting hardware. And you never have to mess with adding water.

I've had mine for almost a year and a half. I opened the battery case the other day and aside from a bit of road dust, everything looked absolutely brand-new. No corrosion on the terminals or brackets, and no crud on top of the battery case other than dry road dust. Conventional (wet) batteries tend to form a film on top of the battery case, which is conductive. The battery will actually self-discharge across the top of the case. So if you do stick with a conventional battery, good maintenance includes cleaning off the top of the case regularly, in addition to keeping the electrolyte topped off.

 

so you made the 3 hour tour...

excellent... the one thing that comes to mind is if you have the navi system... a couple of people have had it drain the batt... dont remember the fix...

hope this helps.

beers

 

Thanks Nubo,
You were right. When we tested it "under load" the voltage dropped dow to less than 8.
I'll change the battery out tomorrow and report back with an update.

Swoope,
Yes it did survive the 3 hour tour. LOL!!
Oh and no NAV system for me... thats where my guages sit

 

Close the trunk, pull out the pass through, and make sure the trunk light is out.

 

11.8V on a lead-acid battery is DEAD. It has almost no capacity left at that voltage.

12.8V is a fully charged "12V" battery.

 

Already checked that.. thats not the case. Thanks ThoughWord, that seems similar to what Nubo said. I'll let yall know how things go after i get the new battery.

-hS

 

Make sure you read the TSB on the battery. It shows you how to install correctly.

Make sure you don't block the air passage way!

 

I think i took the air vent to the battery out a while back. Most of those air vents had to be removed to install the intercooler.
thanks though

 

Your battery is overheating from the lack of vent air. That's what's killing it, especially if it's marginal to begin with. Mazda put that vent in because the engine compartment is HOT.

 

check your dome light that the switch is in the correct position for it to turn off with the rest of the lights.

 

If that were the case, wouldn't a majority of the owners of turbo'd 8s have that same problem?
The drain was related to something completely different. The drain was found and has been rewired... so it shouldnt be an issue. Also, my dome light bulb is in the always off position. Thanks anyway.

 

and the drain was???? you tease!!

beers

 

i can't say... cuz it'll cause too much public histeria and rumors. All i can say it was one of my mods (and thats why the dealer wouldnt fix it), but its been reinstalled and is fine now.

-hS

 

I had this problem for a while with the stock battery. I then upgraded to a Optima YT, still had the problem. I measured the current drain on my battery with my datalogging DMM over a couple hours to make sure it wasn't some odd intermittent problem. Everything was within spec. Next step, I replaced the battery terminals and problem solved. My battery used to die whenever I left the car off for more than 2-3 days. Now I've left it for over a week and it starts fine.

 

I never thought about replacing the terminals. If this one dies... I'll definetely look into that.

Thanks!

 

Well, i changed the battery today, and while doing so i noticed the ground terminal was loose. After putting in the new battery i tightened the termnals all the way but they still weren't very sturdy.

Went to the auto shop today but they didnt carry the right terminals for this car. Rkostolni, where did you get your replacement terminals from?

-hS