I have an Optima battery that is 4 + years old and has served me very well. However, Last week it was dead as a doornail even though I have a switch for the battery and it was disconnected.

I charged the battery today until it was only taking about two amps. (might not have been fully charged) I put my multi meter on it and it showed 12.9 volts. Which I thought was great. Two hours later it is showing 12.3 volts.

So is the battery toast or is this inconclusive?

Thanks,

Ken

 

Sounds like self discharge from an internal short. An old time remedy is to turn it up-side-down and shake. Will sometimes shake loose the sediment causing the short.

 

The time has come. Replace the battery. Do not invert!!!!!

 

I've had really good luck with Duralast batteries from Autozone....good price and they last a LONG time....sharky's is 5 years old and running great...even starts after sitting for a MONTH.....(I know I know)

 

If the time has come then I probably will end up with a light weight battery, since a majority of my use is track work. Does anyone have any experience with these ?http://braillebattery.com/index.php/batteries/b2317r/

As for inverting the battery, I know this kid who works at Sherwin Williams who is a couple of bubbles off plumb. I think I'll stop down there tomorrow morning before his boss gets in and have him put the battery in the paint shaker upside down.

I'll let you know how it turns out.

Ken

 

Ken
I have an even smaller one

http://braillebattery.com/index.php/batteries/b14115c/

In my track shark....works great.....no issues so far, but the race shark doesn't draw much current either since everything is GONE

 

thats really funny, thx

 

That is a concern, I need to run the ignition, the intercooler pump, the radiator cooling fans and the brake duct fans. Of course the alternator should be up to that.....


You are welcome !!!

Ken

 

I get the hints. I have no problems with just being a reading member. PS: the world really is round despite what many naysayers insist.

 

I'll go with 'inconclusive' with what you've done so far. With the battery still disconnected from the car, go get a terminal voltage reading now, and see if it has decayed much below the 12.3V you measured yesterday.

When you put a charge on a battery, the charger needs to use a voltage somewhat higher than the resting terminal voltage to get current to actually flow through the battery. If you test voltage immediately after you remove the charger, you'll see some residual of the charging voltage. If you sit there a bit with the meter connected, you can watch the voltage drop down some. It usually rests somewhere around 12.2 to 12.5, so your 12.3 isn't something to worry about. If the voltage has dropped down to 12.2 or less after an hour of resting, it's time to go to the battery store.

The Optima is touted as a spiral-wrapped cell array, probably with glass mat in between the wraps. This type of battery is a lot more physically durable than common flooded plates, hence the claims that it can withstand more punishment than a normal car battery. How much punishment? I wouldn't put it in the paint shaker. For most of us commoners, the value is that it can deliver more amp-hours per pound of battery, and in a smaller space. There still isn't enough room to put more than a box of Kleenex in the battery well with it though.

For those of us with normal flooded-plate batteries, the easiest test for battery condition is taking a sample of the fluid in each cell of the battery using a specific-gravity tester. Sounds complex, but in reality you can buy a simple tester at most any auto parts place for less than $2. Eye dropper with colored plastic ***** in it. Draw a sample up in the dropper, look at which ***** float, and you have a reading. You need to test the battery at full charge and not the float charge voltage, so charge the battery if it needs it, rest a while after charging and before testing. As part of your annual electrical maintenence, this fits in nicely after the terminal cleaning and battery well inspection/refurb, while the battery is out of the car. Wally Plumley has a great annual electrical maintenance task list, something that should be included in every 928 owners arsenal. I don't know if it's on the 928 Specialists website, but do know that you can get it by requst from them or directly from Wally P if you PM him with your e-mail.


Back to the original question on the Optima-- Does it start the car again, now that it's been charged and had the terminal connections cleaned? That's pretty much the definitive test. Batteries in my '89 warn me of impending doom when the digital dash resets on start-up a couple times. I've been using the Duralast batteries, and get about four reliable years from them. My car sits for weeks at a time with a maintainer attached, so it's never run down to critically low levels. Car lives a luxurious life in a temp-stable low-humidity garage for the most part. Problem may be that I don't drive the car hard enough to really sock it to the battery when charging. It seldom sees much over 3000 RPM in my normal driving regimen. Good news is that batteries are pretty cheap in the big picture. Less than $2/month in rental fees the way I figure it.

 

Damn Dr Bob, you one smart cookie!! Thats good stuff.

 

I keep being tempted to buy/build one of the desulfator circuits to add to my battery maintainers.

 

Dr Bob,

It has been about 14 hours now since I pulled the charger off. The voltage is down to about 12.15 volts setting in a 45 degree garage. The car is in storage several miles away, so I haven't committed to a reinstall to see if it will start the car. Would it be benficial at this time to take it to an auto parts store for a load test....

+1 on the design and benefits of the Optima.

Thanks for your input.

Ken

 

Well he did say they're nothing to sneeze at...
just sayin

 

IIRC, the definative test to determine whether your batter is servicable or not is to take the battery to a good battery store or an auto electrician and have a CCA, cold cranking amp drain test done. This test is done on a machine where a load, (amphere drain) is applied to your battery to its design specification and the voltage drop is measured taking the temperature into account. When the battery is new it should be able to hold the CCA for a specific time and maintain a voltage across the terminals above a minimum voltage.

If the cells are clogged up with lead sulphate, with age, then when the fully charged battery, via rested voltage reading or with specific gravity reading showing a good charge, is loaded and the voltage drops significantly and below the designed minimum voltage, then the battery is unservicable.

Voltage is a measurement of the "Electro Motive Force", so when the voltage falls below a certain level, as the load is applied there is insufficient EMF to crank the engine via the starter motor, the starter motor solenoid will/can drop out (clicking), as the magnet field is insufficient to hold the starter motor spur gear in the ring gear on the flywheel and the voltage could also be insufficient to supply a good spark in the ignition circuit to ignite the fuel. This is a degenerative process as the battery dies.

As stated previously when the digital dash cars start to reset during starting due to low voltage when the battery is starting load it can be taken as a sign it is on the 'way out'.

Tails 1990 928S4 Auto