Battery

amandstu

I sat in with my car yesterday for an hour and the lights were on (I think)

The car wouldn't start and the mechanic told me the battery was flat but ,after a really quick charge (about 10/20secs) it started and restarted on its own.

Is that the sign of a battery that needs replacing or (as the mechanic suggested) normal for any battery.?

Ie is an hour too long to leave the lights (dipped ,I think) on and expect it to start then?

I have mistakenly let it on in the past for maybe 40 minutes and it started OK .

Was I running my luck?

Atlantic Dawn

An hour would drain most batterys to empty if lights were left on, I wouldn't see it as needing replacing, however with limited driving opportunities because of Covid it will need a good bit of driving to get back to fully charged. Hooking it up to a battery charger if you have one would be best.

amandstu

Atlantic Dawn wrote: »

An hour would drain most batterys to empty if lights were left on, I wouldn't see it as needing replacing, however with limited driving opportunities because of Covid it will need a good bit of driving to get back to fully charged. Hooking it up to a battery charger if you have one would be best.

Thanks.Actually I was a long way from home (So fairly alarming at the time )as I had a medical appointment and so there was no problem getting it charged.

So the parking lights would be much less draining?

I wonder how long they would last(esp if the battery was not fully charged)

punisher5112

amandstu wrote: »

Thanks.Actually I was a long way from home (So fairly alarming at the time )as I had a medical appointment and so there was no problem getting it charged.

So the parking lights would be much less draining?

I wonder how long they would last(esp if the battery was not fully charged)

Why would you be leaving lights on?

Drive on and if you find it starts getting hard to start then that would be a sign it's on its way out.

You will most likely be grand.

If doing this again start the car every so often so you're not draining the battery.

kirving

Parking lights would be approximately 5W, while the dipped beam would be around 55W.

So Parked with your dipped beam on, you'd be using 55+55(dipped)+5+5(front parking)+5+5(tail lights) = 130W

On Parking lights alone, this would be 20W or so. So you could expect to last 5 times longer or so on parking lights alone.

This power usage would be much less using LED, but may be slightly more if your car uses double rear tail lights.

amandstu

Kevin Irving wrote: »

Parking lights would be approximately 5W, while the dipped beam would be around 55W.

So Parked with your dipped beam on, you'd be using 55+55(dipped)+5+5(front parking)+5+5(tail lights) = 130W

On Parking lights alone, this would be 20W or so. So you could expect to last 5 times longer or so on parking lights alone.

This power usage would be much less using LED, but may be slightly more if your car uses double rear tail lights.

So you can't leave parking lights on overnight,it seems.

I left the lights on by mistake. It was daylight and I wasn't even aware I had been driving with them on when I parked and waited for an hour or so .

biko

Years ago I sat in my car chatting to someone on the phone for about 45 mins/hour with lights on and engine off, and it wouldn't start.
Luckily I had jump cables in the back so a friendly motorist helped me.

punisher5112

amandstu wrote: »

So you can't leave parking lights on overnight,it seems.

I left the lights on by mistake. It was daylight and I wasn't even aware I had been driving with them on when I parked and waited for an hour or so .

Nothing wrong having lights on but turning them off is what's needed.

Leaving anything on will drain it.
Why on earth would you leave side lights on all night? I understand by mistake but you sound like what you've been saying you think it's ok.

amandstu

punisher5112 wrote: »

Nothing wrong having lights on but turning them off is what's needed.

Leaving anything on will drain it.
Why on earth would you leave side lights on all night? I understand by mistake but you sound like what you've been saying you think it's ok.

No I have never done it but I just assumed you could leave them on (parking lights) quite a long time .And I could imagine leaving them on in the evening and coming back to the car next morning

Won't be doing that now!

kirving

amandstu wrote: »

So you can't leave parking lights on overnight,it seems.

I left the lights on by mistake. It was daylight and I wasn't even aware I had been driving with them on when I parked and waited for an hour or so .

Say 30W (5W x4 at rear + 5W X2 at front)

30 Watts / 12 Volts = 2.5 Amps

Take a 40Ah Battery (the first one I found on Micksgarage). It can in theory supply 40Amps at 12V for 1 hour straight. In practice it can't really as it will never be fully charged, and it won't be able to maintain the 12V as it goes out of charge, and it degrades with age. I don't know by how much, but say it has 50% that capacity in the real world.

40Ah x 50% = 20Ah

20Ah / 2.5A = 8h

You could expect a battery to run side lights for about 8 hours before going fully flat. But remember too that below a certain voltage, it won't be able to start the car anyway, and the lights could be on and drawing current but not be bright enough to see.