Sealed lead-acid battery suspicious deaths - Page 1
Forum section: electronics / projects

author: thexeno
author_rank: Regular Contributor
timestamp: December 15, 2019, 04:21:11 pm
content: Hi,forgive me if there is the same topic somewhere, but I have not found it.I'm just curious on why certain type of modern lead-acid car batteries dies "instantly". I heard stories by many people, in the recent years, so I guess is a pitfall of the modern batteries, and the other day happened to me as well.Interestingly, I bought an OBD Bluetooth monitor for my car just few days ago, and I used it on my mother's car to see the parameters ecc. The battery, with no engine running but ignition turned on, was well above 12V and all electronics of course was working (ok, I could have used the multimeter for that). The next day I used the car for about 200km (a travel of 100km x2), and on the way back the electric system, while cranking the engine, failed by dropping the voltage, so I tried again, and all went ok. It seemed like a "bad contact", because there were no loss of power on the next crank.The day later: car is dead. Battery measures 12.5V ish with all shut down, but when I turn on the small interior light or even worse turn on the ignition (NOT cranking, it just does nothing if I crank), drops to 4.5/5V. Seem that the internal impedance grew enormously in the last 2 days.After additional 20 hours of the car staying parked, when all is off, I measured with my multimeter and battery is now 3V. I jump started with emergency cables, drove for 30 minutes at high rpm, battery settled at 9V. Drop again to 3-ish V when attching a load, like ignition.Reading about it on batteryuniversity and other sources on line, the chemistry should not be that sharp in dropping power, regardless the conditions. I will change the battery, but this still puzzle me. Is true that the car was used for short distances, and is not the best use case, but how could it fail so quickly, and why?

author: trevatxtal
author_rank: Contributor
timestamp: December 15, 2019, 04:55:38 pm
content: Possible a shorted diode in the alternator Bridge!

author: trevatxtal
author_rank: Contributor
timestamp: December 15, 2019, 04:58:13 pm
content: take the battery of the vehicle charge to full with a charger then leave 3 days if the voltage drops much then it is the battery, if it stays then look at the alternator.

author: rstofer
author_rank: Super Contributor
timestamp: December 15, 2019, 04:58:49 pm
content: The internal intercell connection fails over time. It is pretty normal, especially for less expensive car batteries. Once the connection starts to fail and it's impedance rises, this go downhill in a hurry.If you get 5 years out of a car battery, you're doing pretty good. Where I live, it gets HOT and heat is not a batteries best friend.The autostore can test the battery and help determine it's mode of failure. You could also take in the alternator and they can test that as well. No point in installing a new battery if the alternator is going to kill it.

author: SeanB
author_rank: Super Contributor
timestamp: December 15, 2019, 05:01:52 pm
content: The manufacturers are going to thinner and thinner plates and connectors, to save on the amount of the expensive lead that they have to use in the plates and connectors the slightest stress ( not helped by the Antimony added to make it stiffer, and thus more brittle)can result in the connections to the plates fracturing, and then corroding because of the acid. Thus you can go from a battery that is still able to provide peak voltage, but with only a small section of one cell actually providing power. then you draw power, and this tiny plate sulphates, and does not recover, and with each cycle gets worse, not helped by the small cell then being grossly overcharged, and boiling off the limited water in the sealed cell.Had this happen to me as well, battery responded to a charge, but went flat soon after, and needed to be replaced. At least I was able to drive to the battery centre, and there they tested it, and it was close to stone dead, barely able to supply 20A for 10 seconds.

author: David Hess
author_rank: Super Contributor
timestamp: December 15, 2019, 06:53:29 pm
content: Quote from: thexeno on December 15, 2019, 04:21:11 pmThat is nothing new; old starter batteries did it also. The automotive environment is harsh with vibration and temperature changes. If the battery lasts long enough, then a cell will crack and present a high impedance to the series string of cells so the battery voltage reads almost normal with a light load but cannot provide enough current to operate the starter.