Quick battery question

[dmasini]

Noticed for the past couple days I would go and start the X only to have everything go dark for a second or two and then start up. My first thought was the starter but I have never gotten the usual solenoid click when this happens. Just put a volt meter on the battery and with the ignition off it reads about 10.5v and at idle it's running around 14.5v. Let it run for a couple minutes and turned it off to watch the reading go back into the mid 10's. Isn't the battery supposed to be reading around 12.5v with no load? Or is that pretty close to normal. Thanks guys...

 

[David in NC]

How old is your battery? Charge it over night and check it again. If you get the same kind of readings, my guess is it's shot. If it fires up and operates fine for a few days but then gives problems, I'd question the alternator. If you charge it, and let it sit for a few days and it is hard to start, I look for a voltage leak or back to a weak battery.
Check the charging volts and amps to see if your alternator is putting out. Check the voltage drain with everything switched off. Check the voltage when the starter is on. Check the battery after it has been fully charged then put under a load. You should be able to isolate the problem. AutoZone can cut through a lot of this with their gizmos if you get them to check it when it has had a good charge. But remember, they sell batteries.
I used to be in the parts business and it was funny when guys would come in and buy a battery when the problem was the alternator was not putting out. Everything was great for a few days till the battery went down again. They'd come back mad as hell that the new battery failed. We'd check the system to find the battery was dead beacuse the alternator wasn't charging.

Sorry for the long reply.

 

[BrooklynBay]

If you are getting 14.5 volts at idle, then your system is charging. Are your battery contacts corroded? Clean them, and use an anti-oxidant. It should make a difference. If the battery is weak, put a charger on it for a few minutes, and try to start it after it is completely recharged.

 

[ma96782]

Simple way:

You suspect that your battery is at fault and it is old.

So, take it out........clean up those cable connectors..........if you have a trickle charger you could charge it up...............if you have a specific gravity tester you could do that test too...............or you could just take it down to the auto parts store and have them bench test it under load.

If you end up buying a new battery............you've already brought in the core.

Aloha, Mark

PS.........If you wanna put in the extra effort..........take out your alt. and have it bench tested too, while you're at the auto parts store.

 

[dmasini]

Thanks for the replys guys. I'll work through these suggestions and tell you my results. Don't have an over-night charger so I may have to just take it into Pep Boys or something.

 

[dmasini]

Oh, what is the normal voltage supposed to be coming from the amp?

 

[glfredrick]

Your alternator SHOULD be charging at around 14 volts. That is normal. Below 13 and it is not working correctly.

The CHEAPEST and EASIEST battery test is with the hydrometer. Go to any auto parts place and look for a little glass eye-dropper thing with a rubber bulb. It is used to test cells on a battery. Just pull the caps (please work with rubber gloves and safety glasses -- that stuff in the battery is powerful acid!) stick the little dropper into a cell, suck up the acid and watch to see how many balls float. The more, the better the life of that cell. It will all be explained on the package that the hydrometer comes in anyway.

Test each cell. One will likely be lower than the rest. That will be your bad cell. At 10 volts, you likely have a bad cell (one that has enough gunk that has fallen off the plates from use to short it out on the bottom of the battery) as each cell produces 2 volts (6 cells = 12 volts). If they are all low, it is either time for a new battery OR time for a total recharge using a quality charger like those from Snap On or some other major manufacturer. They condition the battery to take a full charge, unlike the little cheapy buzz boxes you get from K-mart or some place.

 

[Papa]

Ok so you are this far along and I will assume you have a digital volt meter 14.5 VDC with the engine running. Yes hydrometers work and I used them for years before the digital meter was invented but I learned the if you take a charged battery and turn the engine over for fifteen seconds (or use a load tester) the terminal voltage should not drop below 9.5 VDC... Yes if it can not make it fifteen seconds before the voltage drops below 9.5 VDC the battery needs to be replaced or you need to invest in a portable jump battery to carry around with you because the battery will not serve you well. In addition if you take your DVM and place one lead on any post of the battery and take the other lead and start testing anywhere on the top of the battery ( we are checking to see how clean the top of the battery is and this will equate to battery discharge) the voltage read should be near 0 VDC. Any voltage over that is suspect and the battery needs cleaning. I have seen 12.5 VDC to any where on top of the battery so clean it. Selection of batteries-if it does not say bla bla cranking amps at 32 degrees run don not walk to the nearest exit of the store!!! In other words bla bla cranking amps at 80 degrees = a crap battery. I have had excellent luck and warranty from Champion Batteries sold at Sam's Club and other places they even installed a new battery under warranty and gave me $20. back the last time around. Yes 13.5 to 14.7 VDC is the norm for a good alternator but a failing battery can fool you. Treat the problem not the symptom...

 

[ma96782]

I had a hard time figuring out what you were saying:

Selection of batteries-if it does not say bla bla cranking amps at 32 degrees run don not walk to the nearest exit of the store!!! In other words bla bla cranking amps at 80 degrees = a crap battery.

Till I remembered this (Johnson Control's battery site):

Be careful of products that display only ratings such as Hot Cranking Amps (HCA) or Cranking Amps (CA).

Products that display HCA or CA ratings are tested at higher temperatures, in the case of HCA -- 80 degrees -- so the resulting numbers appear higher. (CAs are tested at 30°F.) Since these batteries are not as powerful as you might think, what looks like a "bargain" may end up costing you money. Make sure you are comparing apples to apples when looking at ratings. The CCA and RC are the best measure of a battery's true power.

For other tips on choosing a battery, read here:

http://www.johnsoncontrols.com/bg/BatteryBasics/bb_right_battery.htm

Aloha, Mark