Comments by "Keit Hammleter" (@keithammleter3824) on "See How Truck Battery charger Made in Factory || Making Battery Charger" video.

  1. Gee, that design of battery charger goes back to the 1930's, except for the use of 1960's style stud rectifiers instead of selenium. Don't these guys know you can now buy potted silicon bridge rectifiers at much lower cost? It looks like they are cutting up regular passivated steel sheet to make the core laminations instead of using proper transformer-type silicon steel - as far as I know transformer steel is only supplied already punched into laminations, bonded into C-cores or toroids, or supplied in bulk in huge coils. Using regular steel would be a lot cheaper, but the energy efficiency will be low, due to considerable hysteresis and low permitted flux density. Efficiency will be lowered more due to burrs left during their guillotining, which will short the laminations. Normally, laminations are punched first and then passivated, which ensures good inter-lamination insulation. They are grouping the laminations instead of 1:1 interleaving, which is normally regarded as poor practice in the transformer industry, but given the above points, and that it is a high leakage reactance design (desirable in a simple battery charger) it may be a good thing.
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  2.  @mechanicd7562  : Only if they found a really HUGE burned out transformer. A burned out ordinary size transformer would not need cutting up - the laminations are already cut. No, they are doing a shonky - cutting up ordinary passivated mild steel sheet meant for making boxes, cabinets, and the like. Its a lot cheaper and more readily available. It would be far more profitable to rewind a burned out transformer to suit its original application anyway.
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  3.  @mechanicd7562  : I assume you mean heat, not head. I don't think eddy currents will be a problem - the sheets look thin enough. But the magnetic properties of ordinary steel are not very good. Saturation will occur at lower turns per volt, and hysteresis will be much higher, forcing them to use more turns - which in turn mandates using a larger core and/or having more copper loss.
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  4.  @mechanicd7562  : And me, most of the time ...
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