Am I understanding this about charging car batteries correctly?

[kamesama980]

you don't need a fully charged battery to start the car. period. barebones 500 cca batteries are twice what even the biggest engines need (well maybe not some of the diesels and 8l+ ones) most starters, once the engine is spinning, draw well under 200 amps. the other how-many-hundred CA the battery has is extra for when you leave your lights on at the supermarket or 5 years down the line when the battery's only working at 60% of it's original capacity so it can still start the car.

Academically speaking, no the alternator won't push the 15+ volts to shove every last milliwatt into the battery but practically speaking who gives a hoot.

as far as not charging at idle, I haven't seen a car made in the last 25 years that couldn't maintain 13.5v at idle (unless something was broken). In all actuality it's been longer since they converted to alternators but I haven't worked on much older than mid-80s. The reason city-drivers replace more batteries is more starts and shorter trips.

[imzjustplayin]

Well part of the reason you want to keep a battery fully charged is because they get sulfated if you don't do that.. Also because of the electronics and alarm systems cars now have, I'm starting to see people replace their batteries every 4 years instead of something like every 10 years+. Batteries can easily last a decade or more if they're taken care of but by the looks of things, that's not happening and I feel the cars are to blame.

[add|ct]

Originally Posted by *************

Sounds like you need that buzzer to remind you to turn off your headlights like the civics come with.. Also just because you can start the car just fine, doesn't mean the battery isn't discharged. 10.5V is the minimum voltage needed to crank most cars but 11.7v is generally considered a fully discharged battery and to charge a battery from 11.7v to 12.7v (full charge) requires quite a few amps, something you can't normally do with your car since it would take several hours of highway driving. What your car was likely doing was charging the battery just enough so that you could drive around with it but that doesn't mean the battery wasn't discharged.

My civic needs one added!

[theholycow]

I too would like a headlight buzzer.

I searched the12volt.com thinking I'd find it in their DIY relay projects, but then I found this:

They sell tiny headlight warning buzzers at local autoparts stores. I've bought one before and it came with little clips to plug it right up to the fuse box. You hook the hot to the headlight fuse, and the ground to any ignition fuse. Simple 5 minute installation! And it only cost like 2 or 3 bucks. That less than the price of one relay!

I can't find one for sale, so from that same thread:

Your headlight wire should have +12v on it and your Ignition line from steering column should be at Ground when the car is off, so those would be the wires to hook up to the coil of the relay. Then get yourself a little buzzer, Ground the black lead and use the relay to switch +12v to it. 30=+12V, 87=to buzzer red wire, 85=Headlight wire, 86=Ingnition wire.

[bobc455]

With regards to temperature, I know of at least one OEM whose voltage regulators will charge a higher voltage when cold than when hot. For example, when you first start the car you'll get about 14.6V, then about 13.7V when everything is hot. Obviously this recharges the battery faster, then drops the system voltage for improved efficiency.

By the way, you won't find any kind of temperature compensation circuit in the regulator, they just take advantage of the effect of temperature on resistance (generally hotter items have higher resistance) in their circuit design.

One time we were on a long trip in my brother's truck and the regulator failed (external regulator), we measured 18.5 volts while running. (We noticed because the turn signals were kinda blinding, and we'd burned out two light bulbs within an hour of each other)

-BC

[Jay2TheRescue]

HC, your Buick doesn't already have a headlight buzzer? They were stock on the Century and Regal. It replaces the seat belt buzzer on the fuse block, and has a wire that you tap into the dash lights. I even took one out of a Junk 1980 Century and put it in Rusty years ago. Just plugged right in.

EDIT: The Buick headlight "buzzer" is actually a chime unit

[Jay2TheRescue]

HC, what you need is a chime unit similar to this one:

http://cgi.ebay.com/ebaymotors/1984-...Q5fAccessories

The chime plugs into the fuse block instead of the stock buzzer. You may need to break the connector off the pigtail harness attached to it. The gray wire is spliced into the dash lights, and the other 2 wires connect to the fuse block. I'm sure if you went to a u-pull-it yard you might get it for $1 or $2.

[add|ct]

Speaking of headlight buzzer/chime mods, I believe a fellow VX owner on the forums mentioned they did that as a 'mod'. I also liked the idea of a WORKING wiper switch, but that's another story. I'd like to get intermittent ones, but I'm not sure if it requires other work than just replacing the existing original switch.

[JanGeo]

Charging a lead battery fully takes many more hours than you would normally drive the car. From overnight to a few days of time to as much as a week of properly applied charging voltage.

[theholycow]

Jay, I may have the chime/buzzer already, I'm not sure. I've been working with the repair manuals trying to identify all the stuff at my fuse block and make sure everything is plugged in correctly. I have good documentation on the headlight warning circuit, I just need to check for existence and functionality of all the wiring and see if I have the right unit.