Lead acid battery testers?

[SUNRAY]

At least a couple of the ones I still have pre-dated silicon diodes, at least in applications like this, instead having (massive, with fins) "metal-oxide" rectifiers

I still have several such chargers, at least 4 that I can think of but I think 2 or 3 more inherited. Only one of them has silicon diodes and second time I replaced them I used a 25A block...
I managed up to 16 car batteries for about 40 years with those for portable work (and yes it was quite hairy sometimes getting them all ready for the busy summer weekends. Occasionally I still have to use one to raise the voltage high enough to use a 'smart' version.

 

[SUNRAY]

The Lidi Smart charger seems to have evolved, early one no display 3.8 amp, then came with a volt meter, also 3.8 amp, and then a 5 amp version.

The early versions would not return to 3.8 amp or even 3 amp, think from memory would flit between 0.8 amp and 0.1 amp for high AH range and to zero with low AH range so it would charge to 14.4 volt (14.8 in cold mode) then drop to 0.1 amp until voltage dropped to 12.8 volt. The problem was if the battery would not reach 14.4 volt at 0.8 amp, when it could hold the battery at a high voltage for an extended time.

The 5 amp version would return to a higher amps, so unlikely to hold at a high volts in the same way. But they were cheap, around £14 I seem to remember.

I have 2 each of ULDG 5.0 A1, ULDG 5.0 B1 & (ULDG 5.0 D2 as yet unused). I believe this means are all 5A the B1 & D2 manuals mention dropping back to 'trickle' when fully charged but no mention of returning to a higher charge current. I can't find my manuals for the A1 version and a very quick www search brought up the B1 version

 

[Harry Bloomfield]

I'm not sure what distinction you're making here, oor what sort of thing you're talking about - "a transformer and rectifier only" is surely gives an essentially "fixed voltage output", doesn't it ?

Really? Those old chargers, would output a very raw, oc dc voltage of up to 20v. Much higher, than needed to charge the battery, hence the need to closely supervise such a charger. The actual voltage output, was also related to the mains voltage. How can you possibly describe that as a fixed voltage output charger?

 

[Harry Bloomfield]

At least a couple of the ones I still have pre-dated silicon diodes, at least in applications like this, instead having (massive, with fins) "metal-oxide" rectifiers

Selenium? I got rid decades ago, have never suffered the smell, when one failed?

 

[JohnW2]

Really? Those old chargers, would output a very raw, oc dc voltage of up to 20v. Much higher, than needed to charge the battery, hence the need to closely supervise such a charger. The actual voltage output, was also related to the mains voltage. How can you possibly describe that as a fixed voltage output charger?

It's about as "fixed voltage output" as was the case with the dozens, if not hundreds, of PSUs I build back in the 60s and 70s - the actual voltage output was, as you say, dependent both on load and on mains voltage.

It being in the pre-zener days (at least, for my pocket!), on occasions where I really needed a 'stabilised' output voltage, I tended to use things like neon stabiliser tubes - or, occasionally, 'proper' stabiliser circuitry (using valves, of course ).

 

[JohnW2]

Selenium? I got rid decades ago, have never suffered the smell, when one failed?

You're taxing my memory, but I have a feeling that 'metal oxide' and 'selenium' ones were two different things (different materials), although they obviously both did the same job.

 

[Harry Bloomfield]

One charger I had for many years, had a button to start the charge, which pulled a little relay in. Once the battery voltage got to fully charged, it would release the relay.

A charger I designed myself, was a pulse charger - it could source up to 40amps. It would pulse a charge into the battery, switch off, sample the voltage. It included reverse connection, and under voltage protection. It had the same problem, of refusing to charge, if the battery voltage was too low, so I included a button to bypass that problem.

 

[SUNRAY]

Really? Those old chargers, would output a very raw, oc dc voltage of up to 20v. Much higher, than needed to charge the battery, hence the need to closely supervise such a charger. The actual voltage output, was also related to the mains voltage. How can you possibly describe that as a fixed voltage output charger?

They are crude and you are not far off correct, however they are not as bad as you describe. For a start the saturated forward biased votlage drop of the metal oxide rectifier is often around 1.5-2 V and with 2 in circuit potentially 3-4V. My own experience of such transformers is around 8 & 13V, after recticication 11.3/18.4V and under load; potentially 7.3-8.3/14.4-15.4V. The other thing to bear in mind is the deliberately poor transformer voltage regulation so the output drops off as the current increases.

Affectively they self regulating to some extent. I think it's fair to say that the very elderly 4A charger my father purchased from Woolworths before 1966 (before we built a garage) never showed more than 4A on the moving iron meter regardless of the state of battery charge. I remember trying to run a headlight bulb on it and didn't understand why it showed well below the expected 4A or 12V across it whereas it would charge at close to 14V. I doubt any of them (one of mine is 12A) can exceed, or even reach 15V across a usable battery although generally 18-20V open circuit.

 

[Harry Bloomfield]

You're taxing my memory, but I have a feeling that 'metal oxide' and 'selenium' ones were two different things (different materials), although they obviously both did the same job.

A selenium rectifier, was a metal rectifier.

 

[JohnW2]

A selenium rectifier, was a metal rectifier.

I know it was, but my vague recollection is that selenium ones were usually called selenium and metal-oxide ones were usually called metal or metal-oxide!

Having just asked Mr Google, so see how good (or bad!) my ageing recall is, he sayeth ...

In some countries the term "metal rectifier" is applied to all such devices; in others the term "metal rectifier" normally refers to copper-oxide types, and "selenium rectifier" to selenium-iron types.

 

[SUNRAY]

I've always known of Metal Oxide or Selenium devices but the actual make-up I know not. MO types generally had a higher forward voltage (1.5 - 2V for a typical 12V battery charger) as they had more elements than Selenium (~1V), I guess for reverse breakdown voltage reasons but again I know not. My impression is Selenium had a shorter lifespan than MO.

Externally there was little to indicate the technology (until the smell, oh yes that sweet but pungent smell) other than the number of elements which was frequently difficult to see as they didn't always provide a heatsink for all elements.

They were generally lumped into the category of "Metal Rectifier" despite Selenium not being a metal .

 

[JohnW2]

I've always known of Metal Oxide or Selenium devices but the actual make-up I know not. MO types generally had a higher forward voltage (1.5 - 2V for a typical 12V battery charger) as they had more elements than Selenium (~1V), I guess for reverse breakdown voltage reasons but again I know not. My impression is Selenium had a shorter lifespan than MO.

Whilst I was aware of them, I'm not sure that I ever knowingly used selenium ones - all mine seemed to be called 'metal oxide', which refers to copper oxide.

They were generally lumped into the category of "Metal Rectifier" despite Selenium not being a metal .

True but, to be fair, selenium is right on the borderline between metals and non-metals - and you'll often see chemists referring to ut as a "metalloid". I think there were only three (or, at least, three main) types of 'metal rectifier' - copper oxide, selenium and early germanium ones (although the latter obviously went on to have a much wider career ).

 

[ericmark]

I had not considered what was a metal

and yes your right, Selenium not a metal.

My first look at batteries and charging from the mains using a cheap battery charger was likely when working on Sizewell 'B' and living in a caravan. The propriety battery eliminators/chargers were expensive, so I tried a 7812 chip with a red LED on the common, but the problem was the standard battery charger of the day, was not a high enough voltage to work with the IC chip.

So I built a device using a 2N3055 transistor and a 36 watt bulb which would start to conduct at 13.8 volt, and put it across the battery, so if I saw the light on I knew the battery was fully charged, and the unit was stopping the battery from over charging, long time ago, can't remember exactly how I made it, but it worked.

The Lidi chargers are so cheap, it would likely cost me more for the components now to make a regulated battery charger, and the 12.8 to 14.4 volt on and off voltages are likely better for the battery to a single set voltage.

I will look on my other laptop for the Lidi instructions, sure I have them somewhere.

 

[morqthana]

At least a couple of the ones I still have pre-dated silicon diodes, at least in applications like this, instead having (massive, with fins) "metal-oxide" rectifiers

They're the only ones I remember.

why would anyone buy this View attachment 382134 load of rubbish?

Because that's what they've always bought and they don't trust the new fangled ones? Particularly if they once tried a 'smart' one on a dead or not-alive-enough battery.

 

[Harry Bloomfield]

So I built a device using a 2N3055 transistor and a 36 watt bulb which would start to conduct at 13.8 volt, , a 78and put it across the battery, so if I saw the light on I knew the battery was fully charged, and the unit was stopping the battery from over charging, long time ago, can't remember exactly how I made it, but it worked.

When designing my high-current, pulse charger - I used a large toroid, and a triac, to do the switching. at the zero crossing point. From memory, a 7812 was limited to 1amp.