Will an automatic car battery charger trip out at the correct point if the battery is left connected to the car?
I don't want my charger to keep pumping current into my battery if it is fully charged in case my battery suffers some sort of damage!
Thank you for any views.
Lem
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BACKGROUND ...
A thread last September in the uk.rec.cars groups called "Need to disconnect battery before charging?"
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seemed to generally conclude that it is alright to charge a car battery without disconnecting it first.
My battery charger is rated, by the manufacturer, at 11 Amps. It is probably not 11 Amps but it is bigger than I need for my old Mazda 1400cc car. It cuts out automatically when the battery is charged and the cutout has an selector for sealed batteries and non- sealed batteries. I think (not sure) it works at no more than 14.4 volts. This is it
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it ok to leave this charger connected until it trips out or will the trip point be delayed by the presence of the car's elctrics in the circuit?
On Thu, 03 Feb 2005 01:03:03 GMT, Lem strung together this:
Mine always seem to, I've done it a few times with a couple of nothing-fantastic-cheapo-chargers and the charge current steadily drops and tails off to 0A or thereabouts after a period of time.
If your battery is good, it should be OK If your battery develops a short, it could blow the top of the battery off. Cheaper batteries do this sometimes, they keep sucking the amps + never charge up. If your battery voltage is less than 10.5 volts, it probably will never charge
If the charger works correctly with the battery out of the car, it will work equally well with it in the car. The only thing left electrically connected to the battery is the clock in your radio! So there is no significant difference, in or out.
That is *extremely* unlikely. However, what you don't want to do is connect too large a charger. They virtually all adjust down to some minimal charge, but generally the higher the maximum charge the higher the minimum charge too. For example, any charger from 1 to 10 amps is probably absolutely safe. At about 10 amps, it starts getting iffy. I'm not sure I'd want to leave a 15 amp charger connected too long. I certainly would not leave anything connected that can put out 20 amps or more.
(Note that I've lived in the, ahh, cooler parts of Alaska for a few decades, and I rather like the idea of hardwiring a 1A charger into the system, along with a block heater and an oil pan heater, for winter use. Lots of people put a heat blanket around the battery, or put a heat pad under it; but that just keeps it warm and doesn't top off the charge. A 1A trickle charger keeps it warm and charges it, and doesn't use nearly as much electricity.
That might indeed be true, but if so it has absolutely nothing to do with whether the battery left connect to the car or not.
And... I haven't heard of anything like that in at least 30 years or so.
Dead batteries do that, cheap or otherwise.
Not true. But, if you put a charge on it for hours, and immediately after it is removed the voltage goes to 10.5 volts, the battery is a gonner.
Heck, I just left a dome light on in my truck the other day and ran the battery down so low that the clock in the radio actually stopped. (That must be down about 5 volts or less.) I'm not saying that is good for the battery (and trying to rapid charge it would certainly be worse than not), but a nice slow 5A charge for a couple hours put it right back where it was.
might be true for a 20 year old banger but prettty much anything younger will have the computer(s) connected, alarm etc. OK all in various states of "standby" depending on how long the car has been switched "off" but all still there. Some vehicles have a deliberate "sleep" mode so that the battery isn't flattened by all these devices before delivery or other known periods inactivity.
As for the OPs question, the battery will be fine so should all the, permenantly connected electronics. Indeed disconnecting the permenant
12v may well cause more problems as the computers may "forget" their settings or reset to basic defaults. Not to mention having to reset the time on your clock and enter the anti theft code into the radio...
However, if a battery is always needing charged and the car charging system is ok, the battery might well be on its last legs, and never reach a high enough voltage to cut out the charger.
The few times I've had to charge my car battery I've done so in-situ with no problems. HOWEVER most el-cheapo car battery chargers are NOT regulated and could seriously over-charge the battery if left connected for too long (they may well taper off the current but still end up over-charging the battery).
If you want to be sure, you can buy an external battery charging regulator that you connect between the charger and the battery. This not only prevents over-charging but some also have indications on them to indicate how flat the battery is and how the charge is progressing.
Most el cheapo chargers are also of low output, so if charging a well discharged battery will take a long time anyway. Most would simply use an overnight charge - not leave it on for days.
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