MX5 Miata Tech Forum

Miata eats batteries

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Sundancer270 Paul Smith
Knoxville, TN, USA   USA
I have a 2009 Miata retractable hardtop. It has never been on a wet street and I keep it immaculate. I have a pretty serious issue as it goes through batteries. I have had a total of eight and the last three were Optima's in two years. Just replaced the new one under warranty yesterday. Some thing is going on. I took it to Advanced Auto and they checked alternator and it checked out. Any body have any ideas? Every time I park it, I check to see all lights are off and top is locked down.

Paul E. Smith
Knoxville, TN

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Lotoy Jason Morgan
Newmarket, TN, USA   USA
Do you have any aftermarket ad ons? Does the car sit for a long period?

Sundancer270 Paul Smith
Knoxville, TN, USA   USA
Zero after market stuff. The car does sit a lot, sometimes several weeks without a start. It has eat three of these in two years.

Paul E. Smith

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gravymeister Dwight S.
San Tan Vallwy, AZ, USA   USA
The method is to get an automotive ammeter. Disconnect the + cable from the battery and hook the + probe to the battery terminal and the - probe to the cable end. Flip the trunk latch to closed or remove the trunk light bulb. You should read no current flow. If read more than 250 ma, pull fuses one at a time until the draw goes away. The last fuse is on the circuit that has the draw. Check everything on that circuit.

davzway David W
Fort McCoy, FL, USA   USA
FIRST OFF, I would BUY a different battery. Went through THREE Optima batteries in less than six months,, under 3k in driving, on my 2001 Nissan Truck. Dealer kept saying it was TRUCK, testing and finding NO drain from truck, LONG Story, but BAD battery. Nothing wrong with truck, different battery that was a 'LESSER' battery than their most expensive OPTIMA junk,, as Paul Harvey says ,, rest of story was getting rid of Optima for a new battery, resulted in NO MORE BATTERY problems, Today, it's been 3-years plus before a 5-year battery needed replacing.

MIATA? The current (third Miata) is an NC like yours, a 2011 PRHT, which I'd NEVER sell unless Miata's ND comes out with another PRHT version,, not sure about the FS or whatever, BATTERY drain,, one of two issues,, #1 - battery is bad. or #2- Miata has POWER drain, taking away charge while sitting. Too long, it won't start. Too many total discharges,, if batter wasn't BAD it soon will be. Most work on Miata requires battery to be disconnected. At Moss Miata
( ) for a $10 part, green color on battery terminal, giving easy turn knob and battery.disconnected. Battery Drain should show when Miata is OFF. Need to take one item at a time, working to find gremlin. Car Alarm,, disconnected, still have drain. Car stereo, amp disconnected still have power drain,, etc. etc and etc. Also, can be wiring short, NOW THOSE are difficult to trace, finding where a wire is broken in wiring harness,, someone install something, running a screw into a wire.. Go to a mechanic who is KNOWN for being Miata expert, and check his credentials.

(WHY? Avoid nightmare, like the 1992 NA, DREAM deal Miata that PO sunk $20k into, using best of everything to set up for racing, got that, best of everything (from MOMO steering wheel, to sound system worth $1700-2000 depending on his shopping, , found out he had cancer and sold to doctor for song to have enough to see daughter in California (long way from Florida). MY mistake, taking to dealer who's good old boy been here forever, doing 'preventive maintenance, replacing belts (one squeak 3x in month) and do timing belt since date was unknown (Paul Harvey on that deal, mechanic was an idiot who had an even dumber kid doing work- ruined engine, year half later after engine pulled six times replacing Head fourth time, having to sue him and another year half to collect SOME of money)

Sure would replace that OPTIMA,, regardless of what they say on it still being good,, and LONG before I would remotely consider spending money to trace a battery drain that in all likelihood doesn't exist. just davzway

davzway David W
Fort McCoy, FL, USA   USA
Follow t his guy's advise, will save a lot of time finding a battery drain, STILL would buy a new battery to REPLACE the OPTIMA battery FIRST,, Only then would be concerned there was a battery drain.

samsonsg303 Avatar
samsonsg303 Stanley Samson
Victoria, BC, Canada   CAN
1992 Mazda MX-5 "Red Lady"
1998 Chrysler Sebring "Converti"
2004 Kia Amanti "Monty"
2012 Lexus ES "My Hybrid"
Sounds like a battery drain to me. Something must be pulling energy from the battery when the car is parked and turned off. Replacing batteries is not the cure as batteries can last for years even with the occasional charging for sitting too long.

Yes, the first thing they do is to check the alternator to make sure that it is charging the battery.

Good luck!

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