Science (Car) battery issues

[N_Molson]

Hello there :hello:,

I'm pretty sure there are some electrical engineers/techs here and people who have an extensive knowledge about electrical hardware.

So my issue is pretty simple : a few days ago I had my "Houston we have problem - Main A bus undervolt" moment when my car didn't start. I'm pretty sure it's the battery as I have all the symptoms of such a problem : dim lights, slow electrical equipement... and not enough power to run the starter of course.

I do have a cheap battery tester : it showed me nothing the first day (the battery was too weak to make it work).

Then I had the idea to jury-rig a battery charger with an unused TV decoder power supply and some extra wire. After several hours I have some results : the battery tester tells me that the Volts were between 11.5V (low) and 12V (medium). Before going further here are the specs of my hardware :

Battery : Leaded, 12 DC Volts (nominal, max 14.4V), 420 Amps, max output 44 Amps/hour, Maximum install date : 2010 (that's a bit old, no ?), made in Ukraine.

Power Supply : 220 AC Volts to 12 DC Volts, output 3.5 Amps/hour.

With the "low-medium" Volts level I got, all "minor" electrical systems of the car seemed to work fine : interior lights were bright, I heard the fuel pump power itself correctly, the interior fan was a bit slow but working. But when I tried to start the starter sounded very underpowered, and wasn't even close to provide enough torque to start the engine. Also it could barely perform 2 revolutions.

I suspect I had some Volts but not enough Amps at all. If I'm right in this scenario (when you have a near-acceptable level of Volts but a low level of Amps), "small" systems can work well, but anything big (typically like the starter) will fail.

So a few questions :

- I dismounted the battery (man, those things are heavy, I guess that's all the lead into it !) and I'm now trying again to charge it inside my flat this time, which is much more convenient (and also potentially dangerous but well I can watch it and I put it right under the smoke detector) and more humidity/temperature controlled. Given the specs above, do I have any luck to reach an acceptable charge level with my home-made "battery charger" ? Is it only a matter of time or is my "charger" far to weak / inefficient ? It doesn't generates any noticeable heat, so I suspect it isn't working that much.

- The power supply has a built-in LED, which simply tells it is powered on. If I connect the outputs to the battery, the LED switches on, even with the AC input unplugged. What does that mean ? The device "pumps" on my battery ? But it does something, as I managed to rise the charge a bit.

- What kind of power level requires a small (european) car engine (1100 cc only) starter ?

- Maybe the battery is simply too old and can't hold a sufficient charge anymore. Any simple way that could validate/invalidate that hypothesis ? Sadly I have no multimeter.

Again, all I want is enough charge to start the engine. After that, I'll drive at high RPM on the beltway for a couple of hours (that's fuel-expensive and not very funny given the noise level inside the car but oh well) and the built-in alternator will do its job. The alternator failed 2 years ago and was replaced with a brand new (expensive) one, so it should be above any suspicion.

 

[marcogavazzeni]

3.5 amps at 12 volts are very few, maybe you can light a bulb...
a small light bulb 40W ...

 

[Artlav]

Well, a 12V supply won't charge a car battery, you need one that can give 14.1V, that is a proper car battery charger (here you can get one at an auto shop for $5, not sure about over there). Or, any current limited device that can do over 13-14V.
Battery charging is a current limited process, not voltage-based one. For a car battery, you typically want to charge at no more than 0.1C, that is about 10A. Typical chargers use 4-6A, so the PSU is good on the "won't overheat the battery" side.
But for the current to flow, the voltage should be higher on the supply side, in addition to the current limit.

To start the motor, you need A LOT of current, in the 100A range. The car batteries are designed for just that - give a pulse of current for a short time, they can't handle repeated deep discharges in a "power a home overnight" kinds of scenarios.

A near-empty battery would have about the same voltage as a full one, but won't be able to source anywhere near the amount of current, so little stuff would work, but a motor won't crank.

What happened before the problem?
Have you left your lights on overnight, or did it just happen out of the blue?

If it just happened, you'll need a new battery.

If it's a case of accidentally getting it flat, then you need a charger.
Be aware that your car is a charger, so if you can borrow someone else's battery to start it, then you can put yours back in and it would get charged after a day of idling or driving (no need to rev it up - idling is enough).

Emergency shenanigans you can try is to get a bunch of AA batteries (10 of them) in series and connect to the car battery in parallel for 10 minutes. That would usually trickle in enough charge to start the engine once.
10 AAs have about 1/10th as much energy in them as a car battery, but are chemically incapable of delivering all that energy as fast as a lead acid battery can, so you would have to transfer the energy to one first.

 

[Urwumpe]

While charging a car battery, it gives off hydrogen. You should not do this in your flat without some ventilation. The explosion risk should be low from just one small battery, but well, its better to be safe than sorry.

BTW, even the starter of a small car has 1 kW of power, so you can do the math, how much electricity this needs at 12 V.

 

[Donamy]

You may have a bad starter.

 

[N_Molson]

While charging a car battery, it gives off hydrogen.

That's good to know. The smoke detector won't be of any help. :shifty:

 

[Urwumpe]

You may have a bad starter.

Yes, but that has also some other symptoms. Its important to not use the starter too often when a battery starts to age - they like to overheat and fail.

7 years is a pretty old age for a battery, usually you should consider changing it after 5 years.

 

[N_Molson]

7 years is a pretty old age for a battery, usually you should consider changing it after 5 years.

Yeah, I think this is the main cause. Needless to say this is an old car, and there is very little electronics under the hood, only the injector is regulated by a (primitive) calculator (and that's precisely why I don't want to change the car. Heard too many horror stories about cars full of chips and cards).

At this point I'm clearly not going to invest in a charger (more like 40€ here) to reanimate a battery on its last days. Especially given that my father, which is alas living 600 km away, has not 1 but 2 chargers. So I'll get a brand new 50 A/h battery which fits my car slot for 65€, that's going to be fine.

But anyways that's very interesting, I have a lot to learn about electricity. We use it so much, better to know how to deal with it...

 

[Evil_Onyx]

Keep the old battery, if it holds a charge and you have a charger and jump cables, you have a jump starter kit that is easy to handle. I take an old charged battery and cables with me on long trips and holiday, I usually use it once or twice a year starting other peoples cars.

 

[Thunder Chicken]

Check your alternator as well. Your alternator could be failing and providing just enough juice to run the vehicle but might be undercharging the battery. This happened in my Honda Civic last year. Thought it was a dead battery, replaced battery, drove home, and just as I got within a mile of home my radio, dashboard lights started blinking out and the car started running rough. I basically drove my car for an hour powered only by the battery - the alternator was dead dead dead.

Jump start your car and check the voltage across the terminals, should see about 14-14.5 V if the alternator is doing OK.

 

[Donamy]

Might as well check the belts too.

 

[Urwumpe]

Might as well check the belts too.

That is what one of my first cars had - not enough tension on the belt. Fixed this at home with a small 13mm wrench AFAIR.

Should the alternator not produce power to charge the battery, you will see a red battery symbol while driving in most cars I know. That red means: Stop.

 

[Thunder Chicken]

Should the alternator not produce power to charge the battery, you will see a red battery symbol while driving in most cars I know. That red means: Stop.

Good point. I didn't get this light until my radio and lights started to die. I should look into it and see if the sensor is defective.

 

[Urwumpe]

Good point. I didn't get this light until my radio and lights started to die. I should look into it and see if the sensor is defective.

Should mean "check charging system" on a Honda as well, just checked the manual to be sure.

 

[Notebook]

How is it progressing, have you got your car going? Have to say, the biggest killer of lead/acid batteries is age and temperature.
If your car has been outside during the Winter, that can finish it off.
Have you tried the "Jump-Start" technique from another car/battery as mentioned above?

N.

 

[MaverickSawyer]

Check your alternator as well. Your alternator could be failing and providing just enough juice to run the vehicle but might be undercharging the battery. This happened in my Honda Civic last year. Thought it was a dead battery, replaced battery, drove home, and just as I got within a mile of home my radio, dashboard lights started blinking out and the car started running rough. I basically drove my car for an hour powered only by the battery - the alternator was dead dead dead.

Jump start your car and check the voltage across the terminals, should see about 14-14.5 V if the alternator is doing OK.

Lemme guess... alternator failed high, and your Civic is from the 87-92 batch?

 

[N_Molson]

How is it progressing, have you got your car going? Have to say, the biggest killer of lead/acid batteries is age and temperature.
If your car has been outside during the Winter, that can finish it off.

First, I didn't managed to reproduce the Hindenburg incident in my small flat. Its badly isolated, and I can definitively feel some air flowing. And it is ventilated - which is mandatory here. It would take very serious H2 leaks for it to accumulate below the ceiling and ignite with a lightbulb. And I don't smoke. No gas cooking or heating, all-electric.

The issue was indeed the battery. I went to the nearest mechanic, which is luckily specialized in car electrics. The owner was out, and the last employee was closing, but still agreed to sell me a battery (luckily he had 3 left on a shelf, one of them was fitting my car perfectly). 44 Amps/hour, just like the old one. A small car battery in other terms. Still a very dense and upside-down sensitive box of 13.5 kilograms to carry back home. There is roughly what you imperials call a mile, it was quite a long one !

So asking myself if my lower vertebrae would fully recover, I inserted the new battery into the slot. Perfect fit, a few turns of key to secure it to the chassis, and voilà.

And then the drama. I realized that the battery terminals were simple cylinders. And that's not what I wanted, because on the old one battery you had a screw path around the negative terminal, and a thin rod that receives to cables that end with holed metal plates. So at the positive terminal, you have to fit the 2 cables "hole" interface through the thin metal rod. Once that done, you have a ceramic cap that can be screwed over the "holed plates" to firmly secure the whole.

I had some moment of despair, because I paid the new battery 75€. I even considered trying to jumpstart the old with the new, but such an interface problem was sooo stupid. Then I went back to the old battery upstairs and noticed after a close examination that the "custom" terminals were not soldered. And that below the screw path and thin rod thing, you had to standard cylindrical terminal, just like on the one I bought. So I took thick piece of cloth, and tried to pull the "custom interfaces" to free them from the terminals. It was reatively easy, and I didn't even electrocuted myself. Cool.

Now the last step was obvious : to take those to precious (and greasy) adapters, and put them back on the new battery on their respective terminals. THEN I could secure correctly the cables. First thing I did with some anxiety is a test of the new battery charge, with the car key still in my pocket. Bingo, I got the green led meaning full charge (more than 13v). Now a bit more confident, I pushed the clutch pedal (manual gearbox, needless to say) to the floor (father told me it diminished the load put on the starter, even at neutral). The starter high-pitch sound was the prettyest sound I heard that week ! The motor immediately ignitied, as usual the electronic injector boosted the ignition with some extra fuel and quicky stabilized to idle RPM in a very nominal fashion.

Excellent !

But I had another check to do. Engine running at idle RPM, I used my battery tester again. It doesn't only test the battery charge, it also can tell how the alternator is performing. The 'normal charge' (13.5V) led ignited, which seems in order given that the battery was fully (or almost fully) charged. The other leds were "Max charge" (14.1V) and "excessive charge (15V) - check the alternator limiter".

So I think I'm out of the woods ! Phew ! Public transportation is an adventure when you're not used to it, and is hardly cheaper the fuel I burn on my old car (but with a tiny gas (95 Octane index, unleaded) engine).

Now I wonder what to do with the old battery. I'm sure there is a procedure to charge it using the car alternator, even with the engine at idle. The alternator can easily deliver the 13-14 Volts I need to achieve a good charge. As expected, my 12 DC Volts adapter was never able to even reach 12V. The tester told me the battery voltage was between 11 and 12 Volts, which means you don't have enough charge left for the starter to work correctly.

And indeed I'd like the idea to convert that battery into a "emergency starter pack" able to allow at meast one good attempt to have the starter running, just in case, or to help friends/neighbors.

The parking is below the ground (below the 3-story buildings actually) so the climate inside can really be compared to a cave. The temperature tends to stay around 15°C, a bit more in summer, a bit less in winter. Humidity is the big issue. There are cracks in some walls and portions of the ceiling that let rain make it way through the concrete slabs. So yeah, after 7 years of use and a misclosed trunk with internal light staying on, conditions for battery failure were all there.

Thanks a lot for the quick support and the kind of expertise you can only find there. I'll soon ask your advice about a very different matter, as I'm going to have to buy a new PC (I just began a "network administrator" intensive training course in order to get qualifications for that kind of jobs, and the old one I have will simply die if I run complex CISCO network simulations on it). Lots lots of fun with those Network training session, very intensive too. Last day we worked on DHCP and how to make exclusions in pools of DHCP-managed IP adresses in order to relief busy servers... Now that was intense ! :lol: Good mood around, excellent and funny teacher, so yeah, that's great.

 

[Frilock]

Heh, was just talking about this somewhere else. Don't have much time right now, but for anyone that owns a car:

This and this (not necessarily those brands) is some of the best money you can spend. Keep your battery topped off and it'll last almost forever. Shame it doesn't work for cell phone batteries.

 

[Thunder Chicken]

Lemme guess... alternator failed high, and your Civic is from the 87-92 batch?

No, it is a 2005. System was at 12 volts with the car running and all electrical items switched off, which was pretty much the nearly-dead battery voltage.

 

[Fabri91]

This reminds me that I should probably start looking into replacing our Ka's battery, since lately after activating the automatic start-stop system the engine would turn on again automatically after 5 or so seconds, as if the system's logic would realize that the battery charge were lower than expected. It's still the original battery, now six years old.