Lidl charger

Is it some kind of intelligent charger? In which case the ammeter may be playing with it's mind.

At worst take it back and ask for another.

Lee D

Check the voltage while it's switched on and hooked up to the battery. It should be within the range you'd expect from an alternator - ie something around 13.8 volts, depending on state of charge of the battery.

Trouble with these clever chargers is they may not work with a knackered battery that a crude type manages to kick into some sort of life.

Of course it may be faulty and IIRC has a three year warranty. But you'll probably either have to take a refund or wait months 'till they're on sale again.

I'm well pleased with mine - although I keep an old basic one to attempt to kickstart an absolutely flat battery if this ever happens.

In message , "Dave Plowman (News)" writes

Its gone dark now and falling rockets are all around us, so I'll wait for a new day. iirc, the battery voltage on no load when I started was approx 12.5, and the Lidl charger took it up to about 13.1, and seemed to be rising. At that stage I switched the multimeter into the ammeter mode and that's where it was sitting in series with the battery when I observed the drop in charging current to 0.06 amps. I assume this was the trickle charge rate that cut in, but, if so, I'd have expected the charger lights to indicate that the battery was charged.

Before I take it back, I'll try it on a known good battery like the one in the Landie. (Had to get the AA out on the way back from Wales yesterday when the alternator started to fall apart - luckily we heard the merry tinkle of the alternator fan hitting the bolts).

Maybe its its "battery buggered mode" - what was the initial current in the first seconds of charging ?

Steve

I don't appear to have Bills post so I'll follow up with this bit quoted.

That seems ball park correct.

Did you really break the circuit and put the meter in series before switching to "ammeter mode"? If not when you switched to ammeter mode you will have effectively shorted the charger and come to think of it the battery but as you mention no magic smoke escape or a failure of the meter to measure any current I don't think you did that.

That is certainly a possibilty but I doubt that there is more than one chip that does this intelligent lead/acid battery charging and they normally detect and indicate reverse battery, knackerd battery, full/float charge etc.

Just for the record, I followed the instructions - in other words connected the charger to the battery, applied power to the charger, measured volts across the battery, disconnected power, disconnected the charger-to-battery negative lead, switched the meter to the 10Amp range and connected it in series with the negative lead. I did once work in sort of electronics. The battery still has the car hanging across it in all of this, but only the clock (I think) takes any current all the time.

What I'm not sure of is what this meter (a cheapo thing from Maplin) presents to the circuit in its 10A range. Presumably it puts something like an ohm in series with the 10A socket and measures the volts across it. I'm never really confident about these digital meters, and I don't own a proper Avo or anything with a real meter that isn't full of electronics, but I'll try to measure it with another meter..

Isn't the trouble that things like a battery charger will have a standard chip inside, but only use the connection points they can afford? So, if the box has 6 led's, only 6 things can be indicated. If the chip indicates the phase of the moon, but the box has no room for the phase of the moon dial, then it just isn't shown.

Anyway, if it doesn't rain tomorrow, all may be light. I am grateful for all the moral support!

More like .05 Ohm - 10A into 1 Ohm = 10 W.

I'm never really confident about these digital meters, and I don't

An AVO does it the same way, there is a shunt resistor and the AVO takes a fraction of the current.

Steve

It is quite possible/probable that the volt drop across the digital ammeter is enough to make the charger think the battery is charged, and so go into trickle mode. 0.5 volts is not much to drop across a meter, but a lot when looking at battery voltages. You are better off using a clamp type ammeter, but beware that not many work on DC and those that do are more expensive than AC ones. The traditional AVO, or other moving coil meter, probably has a lower voltage drop than a digital meter.

Gordon

I'm not aware of clamp ones that are accurate at low DC currents. They might exist but most are designed for high currents - like starter motors

- where using a shunt type is impracticable.

Hmm. They all work in the same way.

A very low value high current resistor called a shunt (usually a lump of metal ;-)) is inserted in series with the load. This is why most meters have a separate terminal for high current - a switch would introduce resistance. The meter 'movement' then measures the voltage drop across this resistor and reads it as current. A moving coil meter has a lower basic resistance than an electronic type and this is likely to make things more difficult in making an accurate reading one as it has to be taken into consideration at the design stage.

I have an AVO Model 8 which I bought many years ago - but is really only for show these days. A couple of quid DVM from Maplin is actually more accurate on most measurements - and my Fluke much more so on all, at a cost of about a third of an AVO these days - you can still buy them. I think they cost about 600 quid. ;-)

Of course a cheap DVM won't be very accurate on all ranges - but then again neither will the ammeter fitted to a battery charger. It's only there as a rough guide.

The 'failing' of a moving coil meter with its relatively low input impedance is actually quite useful for many domestic tasks. The fact it draws some current when measuring prevents those phantom readings you can get with the more usual very high impedance DVM across mains circuits that are actually not supplying any current at all as they are switched off.

Same principle on a car. Using a DVM to check for 12 volts is a fairly useless test on a faulty circuit unless that circuit is under load. A high resistance switch or relay contacts, poor connector, etc will simply not show up using a simple voltage measurement off load. A small bulb - say 6 watts - is a better one. Where the DVM scores is to measure accurately the voltage drop across each leg - positive and ground - of that circuit under load which a moving coil one can't do anywhere near as well.

I don't think you'll get anything like 1/2 a volt across an ammeter with say 10A FSD, that half a volt means 5W of heat has to be got rid of...

I also suspect that a moving coil meter will require a larger drop than a digital one as the moving coil does require some current, say 100uA, were as the digital jobbie has input currents probably measured in nA or pA.

As Mr Plowmans says shunt "resistors" are more often than not quite hefty bits of metal. Take your typical moving coil meter with a 1k5 coil and

100uA FSD that gives a voltage across the shunt of 150mV at FSD or for a 10A FSD meter the shunt resistance is 0.015 ohms.

I don't know how to test it but in my experince modern "smart" chargers often won't charge old knackered batteries where an older and cruder model will bully some life into them.

On or around Mon, 05 Nov 2007 21:56:02 GMT, snipped-for-privacy@btopenworld.com (Tim Jones) enlightened us thusly:

too clever by arf, some of 'em. The other thing to try is to jump-start it from a big battery and then see if the vehicle alternator will charge it once it's up and running.

So, between showers, I've had to replace the battery. Even the traditional charger, left for 6 hours, wouldn't put enough juice in to start the car.

A second digital meter only resolves to one decimal place, but the first meter on the 10A range measures between 0.1 and 0.0 ohms.

The Lidl charger on the new battery sends 0.8 amps, but with an occasional burst up to 2.6 amps.

What has happened to the price of batteries? It's a bottom of the range old Fiesta, with a cheapo battery. Halfords wanted £60, but I had to pay £48 elsewhere. A friend said they had wondered about the sudden increase in thefts of lead from the church roofs in the villages around, and this might explain it.