Jump started my car with the help of 6 Panasonic NCR18650A this morning...

Yesterday my car battery (an automatic) died on me, or rather it died with my wife while she was parked then could not start the car while she was running some errands.
A helpful soul helped her jump start the car and she managed to get back home.
Yesterday was Sunday and there was only a faint possibility for me to get a new battery, but I argued that using the battery charger, I could charge back the battery to be able to at least start the car this morning…

Left it on charge for 6 hours and tested the voltage… :frowning: big deception, it did not manage to keep a voltage above 12Volts, but still I tried to start the car yesterday evening just to know what to do and have a backup plan in case the worse happens. I could not start the car.

So, I thought what about using these unprotected panasonic cells that I have been accumulating all this time to start the car? Heck, if Tesla can use them to move a car, I can at least give a boost to start a car with these.
So I used the battery holders from an Acebeam and a BTU shocker, 3 cells per holders, connected the output from the holders in parallel, (pana were almost already charged, but I charged them to full capacity) output was 12.55 volts, and then to the car battery and asked my wife to start car…. Sure enough the car started and I was so satisfied but promptly disconnected the 18650 from the car battery. I was so pleased about my McGyver talent,… my wife not so much impressed.

So my question is,… I changed the old battery for a new one, but does it make sense to keep the old battery to be used as a booster when the new battery (its not a question of if, but when) needs a boost? Or is the old battery too worn out that it is useless?

COOL story bro!! Good idea if your in a pinch!

I'd take the battery in for the core charge and get what you can out of it. Not really worth keeping once it quits holding a charge. Once you hit 10.5V it won't start a car and it will cause the electronics to do some really weird stuff on newer models. If you tried to run it parallel with a good battery all that would happen is the bad one would pull power away from the good one.

You need to trash the old battery. If it’s gone that low and bad it wont be useful for jumping anything as it’ll never hold a charge to do any good with.

It wouldn’t cross my mind to use 18660’s. haha

I would just take the old battery to the recycle place if you have one. A new battery that doesn’t have to work hard in cold weather should last a good few year’s, that’s if it’s charging okay.

In the UK a car battery lasts around 7 year’s or so.

One of the cells in the battery is dead for sure, so just discard it.

“Left it on charge for 6 hours and tested the voltage… Sad big deception, it did not manage to keep a voltage above 12Volts”

Don’t know how many amps you pushed in it during those 6 hours but it sounds like it gave up the ghost, lead acid hate to be deep discharged even the so called deep discharge ones, the longer they stay discharged the bigger the damage, even if your battery maintained a good voltage after a charge doesn’t mean it’s healthy, the only way to know is to put a load on it (like starting a car), if it doesn’t provide enough juice it’s become a useless heavy environmental hazard that can’t store energy and need to be recycled.

Damn, there must be something wrong with my car then, I changed the batteries every 2 or 3 years for the last 10 years and I live in the tropics.

This’ll be the kiss of death but I’ve never had to change the battery on a car that I’ve owned. My volvo is coming on for 8 years old and it’s on the orignial battery. My car before that was on the original for a similar amount of time.

High heat is equally, if not more harmful to a lead acid car battery than extreme cold.

A properly charged and healthy battery generally will not freeze; but heat still has an affect no matter what. We all know what heat does to electronics. Batteries are no exception.

5-7 years is typical in most cases for the life expectancy of a normal car battery. I’ve had a few that made it to 10 years. Some, maybe only 6 months.

It’s in their DNA :stuck_out_tongue:

F*ck! nothing related to our hobby is enough to impress our wives! “it´s just a flashlight” “just a couple of batteries” they say… |(

There is nothing wrong with your car. Modern automotive batteries will only last two years in warm climates (sometimes three if kept in garage). Just discard that battery to avoid further damaging your car's alternator.

Just as an FYI, the biggest cause of alternator failures is due to bad batteries. Batteries now supplement the charging system and when a battery starts to go bad the alternator has to pick up the slack and leads to a failure. You best avenue is every two just throw the battery out but most will not do that if the vehicle still starts.

This is absolutely correct with regards to alternators.

Keep in mind modern vehicles, since the 80’s have had alternators, not generators.

The vehicles battery should be at a resting voltage of about 12.65v. The operating range is between 13v and 14.5v. So the alternator is energized by batt voltage, and then outputs between .50v to 2.0v over battery voltage to maintain the state of charge, as well as outputting current to run the accessories.

Take a slightly weak, or even partially dead battery that only can muster about 11.0 volts. Enough to possibly start the engine, but now to reach that regulated voltage of 13-14.5v, the alternator must now double or triple it’s output to reach those levels. This quickly results in a failed alternator.

Saw it all the time when I sold auto parts for 7 years… customer buys new alternator (not knowing that the battery was at fault), fails to replace failed battery, or properly charge good one that was discharged… comes back the next day or two because the new alternator I sold him crapped out. Gee, I wonder why?

Also, never disconnect battery terminals while vehicle is running as a test for anything. That means squat on any car built in the last 30 years. Plus, it may cause a voltage feedback that shorts out your ECM. Whether or not it stalls is not an indicator of anything other than your own ignorance about how modern vehicle charging systems work.

Throw the old battery out (take to recycling or return for core exchange).

Great post, Thanks!

So you should keep an eye on the battery voltage to avoid a hefty bill (battery + alternator + dealer hours)?

So that explains why the engine just stalled when I started the aircon with the old battery :open_mouth: . I always thought that the alternator was enough to supply all the current/voltage of the car even without a battery and that you could start a car then disconnect the battery and be ok driving without a battery…

Yes, keep an eye on batt voltage and also note for any changes when you turn on multiple accessories. Sometimes an alternator will output good voltage, but cant handle the current requirements of the load put onto it. You’ll see voltage drops, headlights will dim, weak radio output, on newer cars the tachometer or electric speedometer will start to go nuts, even an MIL (check engine light) can and often does illuminate.

So even if the voltage is good, you still need to be cognizant that other things may indicate a failing alternator. A failing alternator won’t always necessarily kill a healthy battery, but the opposite is certainly true. A failing battery can and will kill what used to be a healthy alternator (given the circumstances I’ve already outlined).


Back in the 1970’s and earlier, if it were equipped with a generator instead of an alternator, you would have been correct. Sometimes you still see this in older farm equipment.

The alternator itself cannot produce more than a few volts, and it does so based on the given input voltage (the voltage regulator handles this). It’s similar in ignition coils as well. They have a primary and secondary winding. The primary receives vehicle voltage as an input, 12-14v, and then steps it up like a step-up transformer in an old CRT tv to higher voltage, normally 15-30,000 volts, inside the secondary windings… this is what eventually is transmitted to the spark plug to ignite the air/fuel mix.

Assuming the vehicle does not stall/turn off when you disconnect the battery while it’s running (some cars do this intentionally, the ECM notes the massive drop in voltage and powers everything off to protect itself), the vehicle may only stay running at lower rpm when the ignition requirements are low (note what I said about how the ignition coil works. If the voltage is now only 20% of nominal on the primary side, no way you’ll get enough output voltage on the secondary side to fire the spark plug, resulting in a stalled engine).

So as soon as you turn on any additional accessories or put an electrical load on the system, the alternator cannot sustain this, and as you saw, will stall due to insufficient power (both voltage and current).

I once watched a guy not listen to this information, thought he could “test” his alternator on his 2000’s Chevy Cavalier by yanking the battery cable while it was running. It stalled of course, but also experienced a voltage feedback surge that shorted out all of the electronics, and then proceeded to ignite something on fire. Engine bay burned to ashes in the parking lot of the parts store.

I opted not to use my typical super-cynical reply and say “I told you so…” But he deserved it, nonetheless.

Not since 1983 on US cars and much earlier on European cars . Even though some cars stayed running there was always the risk of damage to the alternator or or on-board emission controls (ie - computers).

Even if a battery seems to be good it should still be discarded every two to three years in warm climates (depending on garage or no garage). I believe it is 5 years in the cold climates but Jason will know better than I about that (I left that stuff almost 30 years ago ). My analogy that I used to give customers was to think about meat. Cold preserves and heat spoils.

By the time one realizes a battery is getting weak there is already risk to the alternator. Another unknown is that an automotive battery gets severely damaged every time it falls below 80%. After a few times that battery must replaced.

so basically what you are saying is that I should baby-sit that damn battery and charge it with an external charger when I see that it is falling below 80% charge… :~
why is it that this is the first time i see this? it should have been common knowledge for every car owner…

but thanks guys, I have learned a lot about my car today.

To further what Jason is saying....A good rule of thumb is:

Bad battery = New battery and possibly new alternator when warm weather arrives

Bad Alternator = New alternator AND new battery

When alternators can now cost a person $500 - $600 for parts and labor (often even more) the battery is not worth keeping around. You never know until the vehicle will not start and that is always when you need to go somewhere.