krnpimpsta

Hey everyone,

My battery is almost dead - at this point I can't let the car sit for over 12 hours without it dying.

I want an Optima red top, but I'm not sure what size to get. Do I need to mess with any of those expensive optima brackets to make it fit? Also, are the yellow-top sizings any different?

I searched through the forums extensively for information on this and all I could find was debate/bickering on whether or not Optima batteries are worth their price, or whether they're actually better than standard batteries. Can anyone with optima red or yellow top batteries please list the battery size you have and if you had to do anything to make it fit?

If I get an answer soon I might even just drive over to autozone in the next hour and pick up a new battery instead of trying to save money online.. thanks guys.

krnpimpsta

(and I checked optima's website. They recommend a size 35, but I read of someone using a 34 yellow top, so I'm interested in knowing if there's a certain size that fits well.)

metroplex

The Optima batteries are not a direct replacement for many trays. You might get by with their "brackets" but the best way to go is with a custom made tray/bracket.

I'd recommend against an Optima battery. They're overpriced and have less capacity than the same-sized flooded lead-acid counterparts. AGM batteries don't have very good performance in cold weather, although you're not likely to experience these temperatures driving the Mustang.

Most people incorrectly associate Optima batteries as "high performance" batteries for their high performance cars. The only genuine reasons to use Optima/AGM batteries:

1). You live in a high temperature environment where traditional flooded lead-acid batteries (FLAB) easily overboil and last less than 1 year.

2). You need to mount the battery upside down, sideways, or at obscure angles and normal FLAB's would leak/spill.

3). You need to mount the battery inside the cabin area and do not want acid spilling all over the place.

4). You need to ship the battery via airplane and due to IATA regulations, you cannot ship FLABs w/ the acid already filled in the case.

Overall I'd recommend just buying a quality replacement DieHard Gold. If your batteries are getting completely drained in 12 days, there is something wrong with your electrical system. I can park my Stang or any other Ford (uncharged/unmaintained) in the winter for 6 months and not have a dead battery in the spring.

To check the parasitic current draw on your vehicle, park the car, prop open the hood, arm the alarm systems and check the current in the positive cable after waiting a few hours (sometimes the SJB/LCM modules draw up to .30A for 15-30 minutes before it automatically deactivates). There is also a relay that allows power for 15 minutes after the key is pulled. There should be less than 0.03A of current draw even w/ the active alarm engaged! Assuming linear performance, that's a minimum stand-by life of about 2.5 months.

krnpimpsta

Hey, thanks. I drive my stang daily in the winter, so winter performance matters for me. Also, my car drains after 12 hours - not 12 days, so I'm sort of desperate for a new battery ASAP.

I already ordered an Optima Red Top from Amazon.com for $137 including shipping last night. I have alot of junk that draws current that I don't really want to unplug (XCal2 constantly plugged in for example), so I need something that can handle the occasional drain from a long weekend without driving. Assuming changing my power-consumption habits or changing anything about the idle current draw is off-limits, would you still recommend that I get a traditional battery - and if so why? (I should have a day or two to cancel my order...) -- My main reason for choosing Optima was because I heard they were better at dealing with the occasional drain w/o losing too much of their capacity. Is that true?

Thanks for the advice.

metroplex

If your battery is draining within 12 hours, something is definitely wrong or you have an excessive amount of load on the system.

The Optima Red Top is intended for SLI (starting/lighting/ignition) applications like traditional FLABs. If you want something for deep cycle purposes, consider the Yellow Top. They can handle discharge/recharges better.

AGM's have a tendency to stop working properly at extremely cold (As in Alaska winter temperatures) temperatures.

Can you install a float charger/maintainer when you don't drive the car? It's a PITA to do on a daily basis but that is the only sure-fire way to get around the 12 hour discharge problem or at least slow it down.

The DC metro area won't see the cold temperatures I was talking about, but discharging your Optima isn't good for the battery either. I would try to fix or reduce that parasitic draw and just replace it with a DieHard Gold or Motorcraft.

krnpimpsta

My car does discharge a bit more than the typical car, but my battery really is dead, because I let it fully discharge too many times.

About 8-10 months ago, I could let it sit for 5 days at the airport with the alarm enabled and the battery plugged in, and still be able to start it. A few months ago, it would die if I didn't drive the car all weekend (friday 5pm to monday 8am). Now I have to drive it every 12 hours. For the next battery, I'll just have to make sure to drive the car at least once every weekend.

Amazon isn't letting me cancel my order yet.. CSR said to try again tomorrow. My main concern at this point is the fitment. If I can get the order cancelled, I'll get a Diehard gold just so there's no guesswork in making it fit.

mustangjack

Why do you have the XCal2 plugged in constantly?

metroplex

I bet he's using it for datalogging, and he might have a power inverter for a laptop as well. I highly recommend you shut off all accessories when the engine isn't running.

krnpimpsta

You got it.. datalogging/watching "real" engine temp/etc.. no inverter though. Just a 300W DC-DC power supply that uses <5mW when off.

I don't power accessories when the car is off, except for the Xcal2. The computer takes about 30 seconds to shut down after the ignition is killed, so my batteries are taxed for about 30 seconds @ 15-18A every time I turn the car off.. I'm sure that doesn't help. Any opinion on whether an optima or a regular battery would handle this better? Would there be a difference?

97svtgoin05gt

My battery is dead again. Sucks!!!!!

Silverback

I have Optima Red Tops is both my DD's and am very happy!

After this winter the Bullitt gets one too.

metroplex

The Optima/AGM battery won't handle this better because something in your electrical system is drawing an excessive amount of current when the alternator is not charging. Even if you used an Optima Yellow Top, it would have a finite lifespan. The Optimas have less capacity than the same sized FLA battery due to the voids in-between the spiral cells. Your best bet is to get a higher capacity battery, FLA or AGM, it just has to have a larger capacity (ampere-hours), eliminate that massive parasitic draw, or use a maintainer/charger during your off hours.

The higher the capacity, the longer the battery lasts when there is a load connected to the supply. A 50A-h battery won't last as long as a 70A-h battery assuming they have the same loads.

krnpimpsta

Well.. it's not constantly drawing 18A. It's drawing it for 30 seconds after the car is off, so that's 0.15Amp-hours according to my math. Theoretically that shouldn't really hurt a healthy battery right? I think the reason my battery is dead right now is that I allowed my battery to discharge completely about 10-20 times already - and I park my car on the street so I can't really use a maintainer.

krnpimpsta

Do you know what size you're going to get and how you plan on mounting it?

metroplex

In that case, your best bet (if you're dead set on getting an Optima) is to swap it for the Yellow Top since it is designed for deep cycling. Can you measure the current draw with your engine off, having armed the alarm system, and waited 30 minutes+ ? I'd be interested in seeing how much of a parasitic draw there is when the car is off. If I were you, I'd just go to Sears and get a replacement DieHard Gold and try not to have so much stuff connected to the car when the alternator isn't charging the battery.

krnpimpsta

Yeah, unfortunately the red top has already shipped and the Amazon CSR was extremely unhelpful. "No returns accepted on batterys."

Eh. I'm interested in the current draw too, what do you do to measure the current? Voltage across a shunt resistor? I have a cheapo $30 radioshack multimeter and I'm pretty sure it won't be able to handle the over a few amps through it. Or do you connect the ammeter while the car is off? (And in that case, wouldn't that be somewhat inaccurate because the car is now in a "power has just been restored, but the car has not been started" state, instead of the "engine has been turned off" state"?)

metroplex

I use a Craftsman clamp ammeter. It can read up to 400A DC or 400A AC (watch out, most of the cheap clamp ammeters only read AC) and was something like $60 with discounts.

I just clamp the lobster claw over the positive cable leading out of the battery and into the power distribution box. There are 2 other positive leads from the terminal, one goes to the alternator and the other leads to the starter solenoid. The power distribution box positive lead is the one you want to measure, but do this only after waiting at least 30 minutes so the power relay(s) shut off (there's a relay that keeps stuff alive for 15 minutes after you pull the key) and for other stuff to go on standby. I measured my 07 GT to draw about 0.01A-0.02A with the active anti-theft armed and activated.

Shunts and the old fashioned way of measuring current are fine, but I find the clamp to be the most convenient method and it offers somewhat decent precision. It won't offer the precision of a Fluke, but it will get the job done.

Since the Battery Tender provides 20mA of float charge current, that is more than enough to overcome self-discharging and the parasitic draw.

Silverback

The Optima site recommends for a 2008 Mustang:
Red Top
35 (8020-164) RedTop®; Battery; Group 35; Cold Crank Amps 720; Crank Amps 910; Reserve Capacity 90; Ampere Hour 44; Top Terminal; L-9 5/16 in.; W-6 3/4 in.; H-7 5/8 in.;

Yellow Top
D35 (8040-218) YellowTop®; Deep Cycle Battery; Grp. D35; Cold Crank Amps 650; Crank Amps 810; Reserve Capacity 98; Amp Hour 48; Top Terminal; L-9 5/16 in.; W-6 3/4 in.; H-7 5/8 in.;


And don't forget your $25 rebate!:
http://www.optimabatteries.com/save25_promo/save25.htm



I will mount using the adapters that ship with the battery. They have worked great on the other 2 cars.

P.S. Sam's Club sells Optima batteries now.

krnpimpsta

Oh yeah, duh. I'll look out for one one ebay/CL. Thanks.

krnpimpsta

I went with a 25/75 - same dimensions but also has GM side terminals. ..just to keep my options open in case the battery terminals I'm using are too tall.

I wish I knew Sams club had them earlier.. right now they're scheduled to arrive late next week.

Thanks for the rebate link.