Results of testing old batteries which have been desulphated

[mael]

[Amr]

[SeaMonkey]

What you're experiencing is the nature of
the high frequency switching inverter welding
machine. They're programmed to provide a
higher voltage at 'no load' in preparation for
'striking' the arc. The initial high voltage makes
the arc easy to strike and easier to maintain
while welding.

Once the arc is 'struck' and current flows
through the arc, the welder's current control
adjustment takes over and limits arc current to
the pre-set maximum. It's all very efficient and
good for welding.

In order to decrease the 'no-load' voltage and
assure that it remains low, and adjustable, it will
be necessary to alter the 'programming' of the
controller circuit inside the welder.

I haven't been able to find the details for your
model of welder so I'm unable to say exactly
how it need be done. However, if you know of
anyone who is skilled in electronics and/or
computers, they may be able to figure it out
by studying the circuit board and the control
circuitry. It is basically just a very high power
switching power supply very much like what
is inside every computer.

It simply needs to be slightly 'modified' to
operate in Voltage Mode rather than Current
Mode. Once that is done then it'll be very useful
for you. Because it operates at a high frequency
the transformer in the welder will be much smaller
than a welding transformer which operates at
50/60 Hz., but still able to produce nearly two
hundred amperes.

If you're not able to find someone to make the
necessary 'modification' to your welder then
it would be best to find a conventional transformer.

In fact, it is very easy to re-wind the large transformers
found in the inexpensive microwave ovens. Try to
find an old microwave oven that is no longer working.
In most cases the transformer secondary winding
which produces high voltage for the magnetron will
be shorted. The primary winding will still be good.

Remove the secondary winding by cutting it away
carefully, then replacing it with a suitable number of
turns of heavy wire to obtain the lower voltage you
desire. There are instructions on how to do this on
several web sites. A re-wound microwave oven
transformer (MOT) is nearly indestructible.

[Amr]

Thank you SM for explaining how this SMPS works; now it makes sense.‎

But do you guys think that as I now managed to make the starting V as low as 46 along ‎with the high output Amps and I have the pulsar in serial with it, then do I need to make ‎any modifications in the control area of the welding machine? I mean dont I now have ‎enough power to pulse the batteries with no need for capacitors? I'm too chicken to play ‎in it, I paid 200 USD for it and neither I nor my friend has enough knowledge to mess ‎with it.‎

I can of course try to connect the capacitors again but this time, after the machine starts ‎and see if V will go up again,‎

[mael]

Well I think 46V is way too high as your minimum voltage.

46V is OK for a few individual batteries. Some batteries are so badly sulphated they need a high voltage to start the desulphation process within a reasonable space of time. BUT you will likely never pulse with 46V into a single battery if the battery is anywhere approaching being servicable.

Another case you might use 46V is when you desulphate two or three 12V batteries in series ... but you'll most likely blow your fuses or your output if you hook 48V to one battery.

* Yes you can get the voltage lower than 46V. You can get the cap bank down to practically zero if you use a suitable resistor between them and your DC supply.

Out of around three hundred batteries I've put through my desulphators, only around three had bad connections between the cells. These batteries can read OK on a voltmeter, but when put under a load, an internal connection breaks. These batteries, if low in electrolyte, can explode because of the arcing/heating effect where the poor/intermittant connection is.

Blown-up batteries = BAD.

At 46V on a 10% duty pulse you can expect problems of an explosive nature - and at 46V and an instantaneous extremely high amperage, you might very well create an open circuit by melting the connections. Yeah! I've done pulsing with highly unsuitable voltages and currents ... but it is nerve-racking and expensive in time and replacement semiconductors.

* On your system, from what I understand, just hook the leads to the battery and switch the pulser on but with NO input.

* Then slowly allow the caps to increase their average charge through lightbulbs.

*** But I'd say you wouldn't be able to safely leave it, as if the battery was not pulsed for a few seconds - for any reason, then the caps' charge may be increased to 50 or more volts. - And so when the pulsing starts again, that first pulse will likely be more than your semiconductors can handle, and even if the semiconductors survive, the connections and the battery might not. - At very high amperage in the pulses I use woodworking clamps to press the copper clips on the battery terminals.

A sturdy transformer is certainly likely to be less troublesome than a SMPS. And as your SMPS has been designed for a particular application, I would be expecting all sorts of 'surprises.'

When I suggested using a small welding transformer, I had it in mind that all there was, were transformer-type welding transformers. The last thing I was expecting was that you would find yourself a SMPS welding unit.

SeaMonkey's links to sites detailing how to re-wire a microwave oven transformer are great. You can put a new secondary in a M.O.T. easily enough, and the transform is good for several hundred Watts - which is just what you want.

[mael]

Sorry etc... about the confusing 46/48 volt references ... I'm dead-tired.

[Amr]

Humm, to be honest, I don’t feel comfortable using this high output SMPS in works that ‎involves a lot of hand modifications along with water and alike (I usually submerge the ‎battery in a water bath few mills below the poles to help cooling it down and prevent it ‎from over heating) especially that last night, and although using a lamp in parallel, I ‎started the system without connecting the caps and was at 46 V, but the moment I ‎connected the caps V went up to 101V (too dangerous to work with let alone the effect on ‎batteries). So, I disconnected the caps and emptied them, started up the system and ‎hooked it up to the pulsar, every thing was fine and v at 46 and stable (I use 5 X ‎IRF540N in parallel to deliver the pulse to the battery). So, I shut it down and connect the ‎wires to one poor battery and started the system, then and as you guys expected, ‎something blow up almost instantly that I didn’t know from where the sound came, I ‎don’t know what it is yet I only noticed that the lamp became much brighter. But that was ‎it. A welding machine will be used later on only for welding (I’ve always wanted to have ‎a welding machine and now I have it ). At least I still don’t look like those mad ‎scientists that always come out of their labs with burned hair (I’m bold any way) and balk ‎faces

So back to square X, either finding a transformer or modifying one. I will try to make it ‎with thick secondary winding to get high amperes and will also try to keep it with maybe ‎‎20 – 25 V (about 30 + few volts rms). Will start by visiting SM’s links.‎

[mael]

Yes. 25 to 30V is probably fine.

If you are immersing the batteries in water because they need to be cooled down then you are doing the pulsing in a way I don't understand.

So are your pulses making these batteries hot? If so, then you are using way too much power and/or the pulse width is too long.

Set the pulse-width to 1/100 th of a second.

Those microwave oven transformers are good because they can handle several hundred Watts. People say they aren't hard to re-wire, so you could try that. - I've never rewired a microwave T, but I'm confident I could do it.

* My batteries never get hot. The warmest they get is a few degrees above room temperature. - I can make them hot if I want to, but I think heat is bad for batteries. I'll certainly never let a battery get so hot that I couldn't keep my hand on it.

[mael]

Oh!

And don't put a lamp in parallel with the battery. The bulb should be in seriesb between the rectified output and the cap bank.

If you have a bulb in parallel with the battery then one thing it will be doing which you don't want is that the coil of the lamp will be taking the sharp edge off your pulses.

You'll have to come over here and then I'll show you.

[Amr]

Mael, if you are pulsing at 1/100 of a second width, and you pulse 100 times a second, ‎doesnt that make it as a DC continuase current? (100 X "1/100 / S" = 1 S ? I try to keep it ‎at 1/10 pulse time, if I'm using 100 Hz, then pulse width would be 1/1000 s (1 ms).

I ‎suffer from some batteries being heated up (not to the extend of not being able to touch it - but more ‎hot than it should), this usually happen with sealed batteries, so last night it was time for ‎‎3ed explosion , I wanted to check the water level of one of these beasts, I started ‎drilling holes in one of them, I was as careful as I could but it was my dog who hates the ‎sound of the driller, he think it is harming me so he jumped over me (I think he wanted to ‎push me away from what he though a threat) doing so, the driller went in too deep and ‎touched the plates of a cell and here I am: experiencing my first battery explosion that every one talks about !!! but ‎what the heck, I always wondered what it will be like and now I know and I found ‎the battery to be low in water (below plates top level with at least 1 cm, so now I can ‎relate batteries that heat up with at least one reason, low water level, shorts could be ‎another reason but I’m trying to read about symptoms of shorted cell and cant find a rule ‎that every one accepts.‎

I agree with you for not having the lamp in parallel, but wouldnt having it in serial ‎‎"strangles" the pulse going to the battery? I know that you are using it and that you are ‎getting good results but it looks mysterious to me. I will add a lamp in serial to my ‎configuration.‎

Yesterday after work, I had a tour looking for transformers, I found 750 VA and 1000 ‎VA ones (multi out put V 12, 24, ....) . I need a 24V X 30 Amps = 600 VA, but I prefer to ‎over rate it to avoid any heat coming out due to bad materials used in them, I will also use ‎two big pc fans in serial to cool it down. I think I will get the 1000 VA one to be in the safe ‎side.‎

I also found a huge Capacitor: 80 V 33000 mf and it is rated 40 Amps (whatever that ‎means - I think it might be something to do with the current that the terminals would ‎handle).‎
I hope to get them today. I forgot to look for a Variac, I will have a second look before I ‎buy, if I found a good one, May be I will get it instead of the transformer.‎

But my friend the electronics engineer keeps pushing me to try 2 identical PC power ‎supplies in serial, 450 W each, each can give me 12 V at 37.5 A. It seams a good idea, low ‎cost, built in fans, less space, cleaner connections, no need for bridges and I can use their ‎‎2 X 5v outputs in serial to drive the rest of the circuit (555, transistors, frequancy meter display, leds...). I already have ‎the 100V/1000mf capacitors so I might also try this idea out.‎

[mael]

[Amr]

[Amr]

[Amr]

[SeaMonkey]