Lombay

Bought vehicle brand new in 08/2004, replaced battery w/brand new at Sears in 09/2010..vehicle would not start on Dec 21, 2012...Sears says battery is good, I may have a bad alternator...Lexus dealer says battery is too big (cold cranking is 770, should be 560) and that is the problem...alternator may or may not be bad....what do you (the readers) say. Is it possible to have a bettery that is too big??...Thanks.

salimshah

I would go to sears and ask why they put the large battery and if needed offer them the option of you connecting them to the Lexus tech. [This advice is strictly to help you get a new battery at reduced cost ]

Now the long answer:

Think of the battery as a tank of water. Now think of two tanks which are maintaining the same hight (head or level ~~ voltage) ... the difference is that one tank has smaller surface area of water and the the other has much larger area [the bigger the difference, it will help me make my point]. As you drain the tank the larger area tank can maintain flow for a longer time. That is the battery and CCA for you.

Now let us consider the fill (recharge). The pump required to fill the smaller area will have less demand and the one needed to fill the larger area can strain if it is not designed for it. That is what Lexus tech is telling you.

Now the complexity ... The drain and charge balance depends upon how frequent and the duration of drain is and how long the charge cycles are and also the status of the battery and to be fair the condition of the alternator. I have had no problem with a larger CCA battery but your case may be different.

So how do you proceed:
The only thing you can go with is what are the specs and which item is outside of the specs and hope that Sears will come to your assistance.
You can augment your set up by using a battery charger every 15 days.

Salim

carguy07

"Is it possible to have a bettery that is too big??..."

No (at least at those specs) complete BS!

tfischer

Is it possible to have a bucket too big for your hose to fill?
Eventually it will get filled to the top.

RX330inFL

Ask the Lexus dealer to put that in writing. Get it framed. Will always be good for a laugh.

My Duralast Gold 24F is rated at 750 CCA.

You can have an undersized battery. You can have an alternator which overcharges or undercharges your battery. However, I have never heard of a case where the proper sized battery for your vehicle was too big. Is the Sears battery a 24F? If so, then you are good no matter the CCA rating. How are the battery terminals? Clean? Has this problem happened a second time?

Perhaps you left a light on inside the vehicle, a door left ajar or something else was drawing power to drain the battery. Would not worry unless it happens again. Sometimes, stuff just happens.

BTW, you state that your RX would not start. There are a lot of reasons why a vehicle will not start. What were the symptoms? When you turned the key, what happened?

pauljcl

+1
You could ask your Lexus service manager if your turn indicator fluid is leaking?

jfelbab

Assuming the vehicle didn't sit unused for several weeks, I'd say the Lexus dealer failed to properly diagnose the issue. Take it to another Lexus dealer, auto store or to a Toyota dealer. You can have the battery load tested at a number of places. If you had the car in storage for a few weeks you should buy a Battery Tender to maintain the battery over long periods of inactivity.

Sounds like one of a few possibilities...
• The charging system is malfunctioning
• The battery is defective.
• The battery connectors could possibly be in need of cleaning.
• A power using component is drawing down the battery when the vehicle is not in use. (Aftermarket alarm systems are notorious for this.)

That statement from the dealer is BS. Your battery is NOT too big.

tfischer

Be careful about that fluid check.
The last time I had my dealer check the turn indicator fluid, he also said I needed the air in my tires changed.
However, I am a big fan of the Battery Tender (as I don't run my SC for months during the winter), but a battery should not show any problems after only a few days or even weeks of inactivity. As noted above, however, for a few months of inactivity, a Battery Tender (brand name) is absolutely the best and will pay for itself many times over. Highly recommended.

Rainbird

Have the new battery load tested at Sears. I had a brand new battery that was defective.

LEXRX04

I agree I would go with getting it load tested...

gusar

Cranking amperage (770 in your case) is NOT the battery capacity. Usually when cranking number is bigger, capacity is bigger as well, bit not necessary.
Cranking amperage has nothing to do directly with car charging system (or alternator).
The battery capacity will be around 70 AHrs (+/-). The higher capacity battery can put more load on the charging system, when heavily discharged (and may require longer charging time), but in normal use it will work just fine.
Don't be confused with cranking amperage and battery capacity.

Bottom line - it's defective battery, but if you often heavily discharged it, you could damage charging system of your car and consequently the battery (very unlikely though).