I think the OP and the response here are talking about the headlights, not an accessory light.
VW PSA, Nissan, MB all have some current vehicles with 48v systems or scheduled for 2019.
48 volt systems.
With increased hybridization, I expect all automakers to develop or contract for 48v systems.
yes, but 48 volts is strictly for the hybrid/mild hybrid feature. the rest of the car is still on 12 VDC.
I think Crafter-Man has it right. batteries have gotten smaller and more powerful (cranking amps). They don’t last as long but provide better starting power. The only way this can occur is to have more plates in them spaced closer together.
Older batteries used to slowly fade away. Engines would slowly turn over. Newer batteries start hard and then self destruct quickly. I’ve had batteries turn an engine over like they were brand new and die in the middle of a start. I don’t know if the plates short out or what the mechanism is but it’s a dramatic ending without any warning.
If the op plans on leaving headlights on for 8 hrs at a time then the battery of choice is a deep cycle marine battery.
Most cars have a headlight buzzer but if it’s broken have someone rig up a relay and a buzzer to the headlight circuit.
A few weeks ago I got in the car to go to the gym, and when I started the car, I noticed it cranked slower than normal. There was no previous indication of a problem. I thought “uh-oh, bad battery,” but decided to risk getting stuck at the gym. Sure enough, the one start was all it had, when I tried to leave, all I got was the dreaded starter-clicking. I got a jump, drove home and went with my truck to get an (absurdly expensive) replacement battery.
This is typically the way they tend to fail, a few slow starts if you are lucky. 1st time I get a slow start I head for a battery.
If you think it’s shot after you start the car turn on the radio to a weak AM station and rev the engine. If you hear a whining from the alternator the battery is probably toast.
That was your problem. When I needed to replace the battery in my old car I got the absolute cheapest one I could, because I knew I would be getting rid of the car soon. I left the lights on parked at work, and got a call from parking services around lunch time letting me know. I’m guessing the lights were on 3-4 hours. I didn’t try to start the car until it was time to go home, because I didn’t know how many starts it would have in it, but it started fine.
Ain’t like the old days. Back yon, battery plates were of heavier construction for the same amp rating, and would last longer… notsomuch now. Cheaper manufacturing techniques now result in shorter service life.
Yeah, trickle draining of brand new cars with brand new batteries that don’t get started much sitting on a dealer lot is definitely a thing due to the passive electronics that continue to operate while the vehicle is not running.
Nothing more confidence inspiring to a potential customer than to have them see you having to jump box a brand new car they are considering buying…
It’s more than just the “evils of cheap manufacturing”. The biggest killer of batteries is heat (ironic that you only discover that when it’s freakin’ cold out, though)and vibration. AGM (Absorbent Glass Mat) batteries don’t like heat and don’t handle overcharging well, and both can significantly shorten their lives.
More reading and such:
FWIW I have a 2006 Honda Shadow that still has the original battery. Garage kept, and I keep it on a Battery Tender when I park it for more than a few weeks. I should probably ore-emptively replace that battery. I believe it’s a Yuasa AGM.
Oh, and I had an Optima Redtop in my truck that was almost 10 years old. What finally killed it was leaving my lights on, wouldn’t take a charge after that. Discharging batteries and leaving them discharged for long at all is a sure way to kill them in my experience. A lightly used and always charged battery tends to last a long time for me.
Can you imagine an MG or Triumph with a Lucas 48v system? :eek:
You know, if the voltage is high enough, the electricity will arc and jump over the bad connections. They might actually work better. 
Yeah, I know, cheap shot at Lucas.
I have a Prius that’s coming up on ten years old and it still has the same battery. And I was away for 3 solid months earlier this year. I asked my wife to turn it on now and then but I’m quite sure she didn’t. And we live in Southern California where it gets quite hot.
Maybe I’ve just been lucky.
PS, I’m referring to the 12v battery, not the hybrid battery. But I haven’t had problems with that either. I hate the car but it’s paid for, cheap to run, and it never breaks.
Designing car batteries to run the lights for hours at a time is a lot more wasteful than designing cars that make it really hard to leave your lights on. Which pretty much every car made in the last 20 years does.
I agree that batteries haven’t gotten worse. They’ve gotten more appropriately specced.