How To Verify A Faulty Battery (Page 1/1)
billybacon AUG 11, 02:57 AM
I recently got an '87 SE as a first project car. I'm almost certain it has a battery issue, but I don't know how to verify it. What I DO know is that some electric components (headlights and windshield sprayer) will sometimes not turn on right away, but will after a while, after it's presumably running off the alternator . I know it has an aftermarket radio (Kenwood KMM-bt32bu) from the previous owner, but I don't know to what extent that would change how it behaves. Again, I'm still pretty new to all this and trying to figure it out as I go. I would prefer to go through my options before I buy a new battery, because they look expensive. Is there a way to check for sure and figure out what's wrong?
NOTE: I have also noticed that my phone will still connect to the radio, even when my car's off, and has been off. I don't think it plays sound though. I don't think it is, but If the radio is draining the battery, the previous owner provided the original.

[This message has been edited by billybacon (edited 08-11-2021).]

Xenoblast AUG 11, 03:39 AM
Take it to autozone or advanced auto or stores like it, they should have a battery tester. the radio should be hooked up to switched power, meaning that itll turn off if the ignitions off. it might just be your phone messing up with the connected to the radio.
theogre AUG 11, 01:12 PM
battery full charge is 12.6 to 13v and will stay there when not connected.
Dead Cell or leaches will drain them in hours to days.

Yup first take to AZ Wmart etc.
Walmart w/ service bays not stores w/o them have "computer testers" for car batteries.
Many computer test can test a "dead" battery w/o charging.
"Dumb" load testers can't do that and charging a dead battery is a big safety problem.

If battery is good...
See my Cave, Battery Leaches
Get Small DC Amp Clamp to find faster and w/o pulling/cutting wires.
Example: https://www.amazon.com/Uni-...itance/dp/B00O1Q2HOQ

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

reinhart AUG 12, 06:37 PM
Easy way to diagnose without removing the battery from the car. You can disconnect one of the two terminals overnight and see what the voltage is before and after. It should start at 12.8V and still be pretty close to that 12 hours later when one terminal is disconnected. If it is the same voltage the next day you have a parasitic leach you'll need to track down. If it has dropped more than say 0.05 volts overnight then the battery is dying and should be tested/replaced.