This is a follow-up to Is there a mathematical relationship between the battery AH rating, and that of the transformer in the charger

Since that post I've uncovered a vintage battery charger (Manufacturer: Philips Model: PK-5000) in the old house itself. The device looks good, albeit it has probably not seen service in easily 3 decades ... or so; certainly not since I was a little boy.

It has a 2-point supply (without a ground point); what should be done to ground the device so it may be powered by a proper 3-point plug?

Battery Charger Front Charger Back-cover Innards ...

  • \$\begingroup\$ The previous question OP linked to talks about charging lead-acid batteries. \$\endgroup\$ – AndrejaKo Dec 12 '11 at 12:54

If this charger has metal case, then you can connect ground wire to the case. However, first measure that there is no connectivity between case and any line right now. If there is connectivity, then do not connect ground and do not use it at all.

  • \$\begingroup\$ If there is connectivity on GND (negative terminal) and the case and you insist on using Earth(yellow/green) you would need to install an Earth Leakage Breaker inside the transformer. Just connecting Earth to the case wont do anything and only increases the chance of somebody getting hurt during a leakage. It used to be an OK standard to GND to the case back in the day but TODAY it is very wrong - because of many deaths/injuries. Earth is a modern day safety feature. \$\endgroup\$ – Piotr Kula Oct 24 '12 at 8:59

Nothing. AC doesn't need ground to function if it has neutral line. You can just put a 3 pin plug and not connect anything to ground pin if you must use a 3 pin plug.

If you want to implement the ground yourself for say additional safety, post pictures of the insides of the charger (In fact post pictures of the insides in any case! We may identify some component that may have failed over time with them). Most such devices I've seen just have the ground wire connected to the case of the device.

If you find electrolytic capacitors somewhere inside, do change them! They tend to wear out with time.

  • \$\begingroup\$ Wilco. I'll photograph, and upload first thing in the omrning \$\endgroup\$ – Everyone Dec 12 '11 at 19:45
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    \$\begingroup\$ Uploaded. This looks like an air-dielectric multi-plate capacitor; look to the right of the photograph \$\endgroup\$ – Everyone Dec 13 '11 at 5:22
  • \$\begingroup\$ @Everyone For far so good. I don't see anything that could go bad over time in here. It would be nice if you could post pictures of the other side of the device and how the connections going to the transformer actually look like. Hopefully you have a small enough camera to fit inside... \$\endgroup\$ – AndrejaKo Dec 13 '11 at 5:57
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    \$\begingroup\$ That "capacitor-looking component" (dark green colour) is a rectifier; probably not silicon, not even germanium, but selenium. There's one diode between any two metal plates. (For the high currents a charger operates at, an air-dielectric capacitor would be quite useless because you would need much more capacitance than can be achieved with an air dielectric type.) \$\endgroup\$ – zebonaut Dec 13 '11 at 7:39
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    \$\begingroup\$ ... just in case: If the rectifier blows (or is not intact anymore due to a failure that has already occured), keep in mind that selenium and most of its chemical compounds are toxic. You would not want to have selenium dust in your vacuum cleaner's bag and run it in your house afterwards. Use venitlation while cleaning or go outside while blowing it off to be extra sure. \$\endgroup\$ – zebonaut Dec 13 '11 at 9:05

If a device has exposed terminals and is supposed to be 'free floating' relative to earth ground, but you have doubts about its electrical safety, perhaps you should wire a GFCI/RCD into the plug? That should avoid the possibility of a lethal shock hazard in the event that something becomes live that isn't supposed to.


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