Testing a Car Battery - Page 1
Forum section: electronics / beginners

author: DW1961
author_rank: Frequent Contributor
timestamp: October 27, 2022, 08:11:16 am
content: My factory battery is 4 years old and this morning, it wouldn't crank the engine. No lights were left on. The only draw would be parasitic from the car's electronics.I charged it with a trickle charger on fast for about 20 minutes and it cranked right up. (Battery takes a charge)I tested voltage with the car running which provided 14.7V (Alternator good)After driving the car for around 2 hours, I let it sit for 30 minutes, and it tested 12.7vI let it sit for around 7 hours and the voltage was 12.37With the headlights on and engine off, voltage drops to around low 11.3V.If I knew what sort of voltage I should see with the engine off and headlights on, I'd know if the battery was bad or if I have parasitic load problems. I'm trying to test it best I can before taking it to the local dealer for a free load test so I'll know if they are trying to rip me off, which they have a reputation of doing. And, that's why I call them stealerships. It seems like every car shop and car dealership is constantly trying to break it off in my ass instead of just doing the necessary workThanks.

author: gbaddeley
author_rank: Regular Contributor
timestamp: October 27, 2022, 08:38:21 am
content: Check the leads to the battery and that connections are clean and tight. Is the weather cold?

author: SmallCog
author_rank: Frequent Contributor
timestamp: October 27, 2022, 09:33:02 am
content: Another common test is voltage whilst crankingIf your meter has a min feature it’s quite easy to do, I’d be looking for at least 10.5v4 years is not an abnormally short lifespan for a battery

author: MrAl
author_rank: Super Contributor
timestamp: October 27, 2022, 09:46:15 am
content: Quote from: DW1961 on October 27, 2022, 08:11:16 amIf you have an analog meter you can measure the voltage while cranking the engine. You can see how low it gets when you crank and that tells you something about the battery health.Unfortunately it is best to start doing this when you get a new battery, then watch it over the years. As you see it go farther down year by year you get to understand how it ages and get ready to purchase a new one at some point.A panel meter works good for this they respond fast. The top end should be 15 volts so you can read voltages from around 8v to around 15v.I dont know if it is winter where you are, but in winter it is a good test to just crank and watch the meter. If the battery is good then it will crank each time you try it day by day, but if you see the cranking voltage getting lower and lower over several days then you probably have to buy a new battery.Some batteries are guaranteed for 2 years, some for 3 years, some for 4 and some for 5 years. If your battery is guaranteed for 2 or 3 years it may be time to get a new one, and if for 4 years it may still be time. The cranking test over several days though is a good test. It's basically a load test with the most practical load you can find, which is the actual application load so you cant beat that.

author: CaptDon
author_rank: Super Contributor
timestamp: October 27, 2022, 02:51:15 pm
content: You need to have the probes on the lead battery terminals (if possible) and not on the connectors for the initial test of the battery. The terminals will add a bit of drop, quite a bit more if corroded!!! Try going to an auto parts store not a new/used car dealer. Most dealers are thieves. Auto parts stores will usually show you the 'cold cranking amps' available from your battery in its current condition and you can decide if it is acceptable. It sounds to me like you have a classic case of one single cell which is shorted from crud buildup under the plates. The cell takes a charge and provides current, but when left to sit it will self discharge and start to have high internal resistance to current flow. You can often get a sulphur smell coming from the bad cell during a heavy load or cranking.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: October 27, 2022, 07:35:45 pm
content: Most Autozones, Autoshacks, Orilely type stores will test for free right in front of you.

author: mjkuwp
author_rank: Unknown
timestamp: October 28, 2022, 12:45:31 am
content: what kind of car? and do you live in a really hot climate?depending on the type of car and conditions, batteries can last much longer but just one example, the 10th gen Civic seems to eat batteries.are all of the power electronics working normally? windows up and down properly, Moonroof open/close normal and do the doors all lock and is the way the car lights turn off all perfectly normal?if any of the door locks are broken, for example the car may not turn fully off and the drain would be higher than the sleep current.

author: Peabody
author_rank: Super Contributor
timestamp: October 28, 2022, 01:53:59 am
content: The 9th generation Civics too. In fact the Honda Dual Mode charging system is a disaster for batteries because it doesn't keep them fully charged, so they sulfate up and fail early.

author: DW1961
author_rank: Frequent Contributor
timestamp: October 28, 2022, 02:07:11 am
content: I started testing with everything clean and I used the post themselves for testing.I went to OReily's and had them test it -- bad battery. I had them install one of their Platinum Super Start AGM batteries. AGM is what it came with.After getting home tonight and letting the car sit for two hours, the voltage tested 12.87V.I'm still not sure if it isn't parasitic draw that is caused by some electronics not shutting off. I'll test it tomorrow to see what the overnight volts are.I hope it's good because I do not want to deal with Hyundai Dealer service. It's a shit show and I will never buy another Hyundai (Still has 12K on warranty is why I would take it to Hyundai to fix it). For instance, I learned that the guy fixing my car the first time it had a warranty problem wasn't even a certified Hyundai technicians. I called corporate and talked to Hyundai corporate and they said anyone working on a Hyundai has to be a certified Hyundai technician. Anyway, due to warranty work dealer shit show, this was the first Hyundai I have ever bought, and the last. I'll stick to Toyota like I have most of my life. that. and Hyundai cars are just junk (bad suspension, defective electronics), and Hyundai tries to get out of their factory warranty anyway they can.I did some battery research and found Johnson Controls manufactures almost every battery, and even though they 'can' be differences in quality, they all come with 3 year warranties. Even Wallmart batteries are manufactured by Johnson Controls and look exactly the same as the OReilly battry, except the sticker. The OReily's employee who installed it confirmed that, saying the only difference is the sticker on them. Even interstate batteries use to be made by Johnson Controls, at least the majority of them.I checked Costco Interstate: 180.00 (No installation and no battery check) Must bring back core for 22 dollars.OReily's: 239.00 rip off price (free installation, but easy as hell)WallMart: Doesn't carry my Hyundai Accent battery. I called all of them in my town. The OReily employee said that was strange because that battery is really common.I could have played musical battery by going to Costco, then to Wallmart for installation (10 bucks) or have done it myself, then back to Costco for the core. I would have saved 50-60 bucks. But, what happens if the battery goes bad in the 3 years? OReily is everywhere and just swaps them out any time 7 days a week. Since I am my elderly memory impaired mother's 24 hour care giver, I decided to just do OReily. It goes against my grain to pay 60 bucks more for a similar battery with exactly the same warranty, but I think it was probably the best option given my situation.Anyway, I'll post back and share the overnight voltage.

author: DW1961
author_rank: Frequent Contributor
timestamp: October 28, 2022, 02:08:20 am
content: Quote from: Peabody on October 28, 2022, 01:53:59 amThe OReily guy today said the same thing and that's why car batterie4s are moving to Lithium.

author: DW1961
author_rank: Frequent Contributor
timestamp: October 28, 2022, 02:08:53 am
content: Quote from: JustMeHere on October 27, 2022, 07:35:45 pmThanks. Went to Oreilys today.

author: DW1961
author_rank: Frequent Contributor
timestamp: October 28, 2022, 02:10:13 am
content: Quote from: CaptDon on October 27, 2022, 02:51:15 pmHow do you get a sulfur smell on sealed batteries?

author: CaptDon
author_rank: Super Contributor
timestamp: October 28, 2022, 02:42:02 am
content: Well two things about that smell, some aren't as 'sealed' as you may think with the exception of the all position type batteries and most of my experience is with batteries that can still be topped off including the one I replaced in springtime in my tractor. It has a transparent case and you could see the obvious problem in one cell and it made a sulphur beer fart smell when cranking or charging. It was toast with a shorted cell. Leave it sit for a week and it reads 10.8vdc, barely turns the engine over. Charge it for 1/2 hour and you would swear it was a new battery.

author: mikerj
author_rank: Super Contributor
timestamp: October 28, 2022, 10:34:31 am
content: Quote from: DW1961 on October 28, 2022, 02:10:13 am"Sealed" lead acid batteries still have a vent, but controlled through a pressure relief valve hence VRLA (valve regulated lead acid). If a bad cell outgasses too much then the valve will open to prevent possible catastrophic failure of the battery housing.

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: October 28, 2022, 04:50:45 pm
content: Quote from: DW1961 on October 28, 2022, 02:10:13 amThe interface between the plastic case and the terminal post is rarely a lasting seal. It's a reminder to be very careful when slipping the connector on or off. Do it gently.

author: DW1961
author_rank: Frequent Contributor
timestamp: October 28, 2022, 04:51:48 pm
content: As stated above, last night after I got home and let the battery rest for about two hours, I tested its voltage:12.87VJust tested the battery today. It has been sitting for 15 hours.12.66V12.6 is considered 100% charged, so I'm happy with that. The residual 0.21V was probably higher than normal since I didn't let the battery sit long enough to become "normal" voltage.Thanks to everyone.

author: BeBuLamar
author_rank: Super Contributor
timestamp: October 28, 2022, 08:04:22 pm
content: Quote from: DW1961 on October 28, 2022, 02:08:20 amCars that run on battery all have Lithium battery. As far as gasoline powered car the lead acid are fine. I have them failed from time to time but never bother me as much as other problems with the cars and they should go when the gasoline engines go.

author: radiolistener
author_rank: Super Contributor
timestamp: October 29, 2022, 03:47:20 am
content: Quote from: DW1961 on October 27, 2022, 08:11:16 amWhen you turn on headlight at max and all onboard electronics, the current consumption will be about 100 Amps for a usual ordinary passenger car. It is close to a load test fork which performs measurement at 100 Amp load.But different car can have their own current with all powered-on electronics, so it's better to measure actual current with a current clamps. So, it's impossible to say what Voltage you should see exactly for your own car, because it's current is unknown.And you're needs to charge battery to 100% before testing. If a fully charged battery Voltage drops below 10 V at 100 Amp load, you're needs to think about replacement.

author: Vovk_Z
author_rank: Super Contributor
timestamp: October 29, 2022, 12:42:21 pm
content: Anyway, 11.3V is too low for an ordinary car. This voltage means a battery is empty or close to its end-of-life (possibly have only small fraction of its rated capacity).For example, my car (with LED headlights) has about 30 A with most powerful loads on (w/o engine fan and a/c compressor on).

author: radiolistener
author_rank: Super Contributor
timestamp: October 29, 2022, 02:13:02 pm
content: Quote from: Vovk_Z on October 29, 2022, 12:42:21 pmThis is not open terminals Voltage, this is Voltage under high load (about 100 Amps for 60 Ah battery). As I know 11.3 V after 5 seconds with load is acceptable.Quote from: Vovk_Z on October 29, 2022, 12:42:21 pmTry to turn on long distance headlight and fog lights, all interior lighting, A/C fan, and radio with a loud sound. It should increase power consumption.

author: Vovk_Z
author_rank: Super Contributor
timestamp: October 29, 2022, 04:34:57 pm
content: Quote from: radiolistener on October 29, 2022, 02:13:02 pmI have H4 headlight lamps, so all headlight is LED. I don't have fog lights (the main headlight is ok with fog), and all my interior light consists of one LED lamp, A/C compressor is dead and removed.The only two main power loads I found are the rear window heater (about 13-14 A) and the interior air fan (13-14 A at full speed). I haven't checked the radio because it is not a constant load (the radio consumes about 0.5 ADC when turned on silently).

author: radiolistener
author_rank: Super Contributor
timestamp: October 29, 2022, 06:09:48 pm
content: Quote from: Vovk_Z on October 29, 2022, 04:34:57 pmyes, just forgot it, they have significant current consumption