The charger says it's running at about 3 amps. When can I consider the battery properly charged?
The manual for the charger is unhelpfully vague, merely saying in poor English that when the pointer is "in the left part of" the scale that charging is complete.
Daniele
On Fri, 9 Oct 2009 13:40:27 +0100 someone who may be snipped-for-privacy@apple-juice.co.uk (D.M. Procida) wrote this:-
Lead-acid batteries are best left being trickle charged. Of course that implies that the charger is capable of doing that, which many cheap ones are not.
On some battery chargers - when the amp meter drops to zero (on the old one that I use anyway) When the batter hydrometer says so (if you can get at the individual cells)! When a voltmeter says so! When any indicator on top of the battery says so - usually turns green (on the battery on my car at least)!
Or when you can start the car on a chilly morning using battery power alone.
Cash
When its terminal voltage is about 13.5 V off load.
When it reaches a certain voltage. The voltage varies slightly by battery temperature, battery type, and if this is a cyclic charge (almost certainly what you're doing) or a standby charge (where it's left permanently connected to the charger).
If your charger is properly voltage regulated, the charge current will drop to almost zero when charged. If it's not properly voltage regulated (and many aren't), the charge current won't drop to zero ever, and you may wreck the battery by leaving it charging too long.
You also need to be careful about the max charging current, again depending on battery type. Charging at 1/7th of the battery capacity is safe with just about any type. Some batteries (e.g. car) can safely be charged at significantly higher rates. This is the max current though when the battery is pretty flat. As it charges, the current will drop.
Since you haven't said exactly what type of battery or charger, can't be more specific.
I'm not sure. The instructions warn that it doesn't automatically stop charging, but the current does diminish as it charges - whether this is through regulation or the effect of the battery's increasing charge I don't know.
It's a car battery.
Daniele
Ouch no!! That's the best way of wrecking a lead acid battery, especially if the sealed types. Any current after it's fully charged will dry out a battery.
The best charger has always been a constant voltage charger. This matter has been discussed ad nauseum before in the NG.
"D.M. Procida" wrote in message news:1j7bn2j.1ee7orr2z34j3N% snipped-for-privacy@apple-juice.co.uk...
For a cheapie charger, the best indication is terminal voltage. When it's more that 14V, I'd disconnect the charger. 13.5V is too low, and the battery won't have been fully charged.
Which is a lot of help if the battery if for a non-vehicle application. R.
Sounds like it isn't a proper voltage regulated one then, so you need to be careful not to overcharge the battery.
If it's been taking 3A for a few hours, it will have 9Ahrs (less a bit for inefficiency) added to it, which is plenty enough to start a car many times, unless there's something wrong. The car will then charge it properly, and much faster, whilst you do your regular driving (don't sit on the drive reving the engine, as that's pretty pointless).
It's a 60Ah battery. The terminal voltage isn't yet up to 13V.
It's a fairly new battery, yet either there is something wrong with it, or there is something wrong with the car (that is draining it rapidly while it sits on the driveway).
The other day it was flat, so I charged it for an hour or so, it started up right away, then later that morning it was flat again.
Daniele
Oh dear that doesn't bode well. One thing that car batteries hate is having a deep discharge. A fairly new one should survive but one a year or three old may not.
You need to find out if the car has a fault that is taking more than a few 10's of mA when just parked up. You may need to measure this up to half an hour after switching off and locking the car to allow it to fully "go to sleep".
Had a Daewoo (yes I know but ...) and it had a known feature where the bracket holding the brake light switch got tired and bend slowly out the way so eventually the brake lights stayed on -> battery flat next morning.
Not saying it is but ...
leave the battery on the car overnight again, but this time disconnected. Then you'll know
NT
Generally most home chargers are pretty weedy and car batteries are fairly tolerant. All you really need to do is charge it sufficiently to start the car and then let its charging system worry about topping it up. Overnight is usually good enough for this.
Incidentally, Lidl have their rather fine chargers on sale again from next Monday. They can be left on indefinitely since they switch to a maintenance charge when the battery is 'full'. They've gone up since last time - now 15 quid - but still very worth it. Enough output to charge most batteries overnight.
On Fri, 9 Oct 2009 15:05:18 +0100 someone who may be "Fredxx" wrote this:-
I have been charging a set of sealed lead acid batteries in that way for the best part of a decade. So far they remain fine. Obviously if the charging voltage is set too high then it would indeed dry out the battery, but I did a lot of research before deciding on that form of charging to get the charging voltage right.
On Fri, 9 Oct 2009 15:57:07 +0100 someone who may be snipped-for-privacy@apple-juice.co.uk (D.M. Procida) wrote this:-
I would suspect a fault in the car wiring and track this down. More and more things are being connected directly to the battery, sometimes without even a fuse, so are able to gently drain the battery. If one of these has gone wrong then it will be able to drain the battery more rapidly than designed to do. It may take a while to track down what it is, but things which are available even when the ignition is not turned on are where I would start looking.
5 minutes charge with one of those was enough to get one start, when a family member flattened their battery with lights left on. IIRC, they charge at just under 4A.
I bought one for £12, IIRC (Aldi or Lidl, can't recall, a year or two back). When I went back later, they were reduced to half price, so I bought 2 more. They are very nice units. Elsewhere, they could be found for around £40.
What would be _really_ nice is if they had a switch setting to automatically start charging when mains is applied. That could be the basis for an effective automatic emergency supply. Sadly, they don't do this.
A car where the brake lights work without the ignition switched off? Mine will when in the accessory position - but not when off totally.
If it's discharging overnight and nothing is obviously on one possible cause is a failed diode in the alternator rectifier pack. They can fail short circuit resulting in a permanent discharge of about 6 amps. Feel if the alternator back is warm when the engine is cold, if you can't measure the quiescent current.
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